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FRESH-WATER 
BIOLOGY 


BY 

HENRY  BALDWIN  WARD,  Ph.D. 

Professor  of  Zoology  in  the  University  of  Illinois,  Special  Investigator 
FOR  THE  United  States  Bureau  of  Fisheries,  Etc. 

AND 

GEORGE    CHANDLER    WHIPPLE 

Professor  of  Sanitary  Engineering  in  Harvard  University  and  the 
Massachusetts  Institute  of  Technology 


WITH   THE   COLLABORATION  OF  A  STAFF 
OF  SPECIALISTS 


FIRST   EDITION 


NEW    YORK 

JOHN  WILEY  &   SONS,  Inc. 

London:    CHAPMAN   &   HALL,    Limited 

1918 


Copyright,  1918 

BY 

HENRY  BALDWIN  WARD 

AND 

GEORGE  CHANDLER  WHIPPLE 


Stanbopc  iprcss 

F.    H.GILSON    COMPANY 
BOSTON,  USA. 


COLLABORATORS 

Edward  Asahel  Birge,  Dean  of  the  College  of  Letters  and  Science  in  the  University 

of  Wisconsin 
Nathan  Augustus  Cobb,  United  States  Department  of  Agriculture 
Wesley  Roswell  Coe,  Professor  of  Biology  in  the  SheflSeld  Scientific  School  of  Yale 

University 
Herbert  William  Conn,  Late  Professor  of  Biology,  Wesleyan  Uhiversity 
Charles  Benedict  Davenport,  Director  of  the  Station  for  Experimental  Evolution, 

Cold  Spring  Harbor,  Long  Island,  N.  Y. 
Charles  Howard  Edmondson,  Assistant  Professor  of  Zoology  in  the  University  of 

Oregon 
Carl  H.  Eigenmann,  Professor  of  Zoology  in  Indiana  University 
Herbert  Spencer  Jennings,  Professor  of  Zoology  in  Johns  Hopkins  University 
Edwin  Oakes  Jordan,  Professor  of  Bacteriology  in  the  University  of  Chicago 
Charles  Dwight  Marsh,  United  States  Department  of  Agriculture 
John  Percy  Moore,  Professor  of  Zoology  in  the  University  of  Pennsylvania 
James  George  Needham,  Professor  of  Limnology  in  Cornell  University 
Edgar  William  Olive,  Curator  of  the  Brooklyn  Botanic  Garden 
Arnold  Edward  Ortmann,  Curator  of  Invertebrate  Zoology  in  the  Carnegie  Museum, 

Pittsburgh 
Arthur  Sperry  Pearse,  Associate  Professor  of  Zoology  in  the  University  of  Wiscon- 
sin 
Raymond  Haines  Pond,  Late  Professor  of  Botany  in  the  Texas  Agricultural  College 
Edward  Potts,  Late  of  Meadville,  Pa. 

Jacob  Ellsworth  Reighard,  Professor  of  Zoology-  in  the  University  of  Michigan 
[Richard  Worthy  Sharpe,  Instructor  in  Biology  in  the  Dewitt  Clinton  High  School, 

New  York  City 

[Victor  Ernest  Shelford,  Assistant  Professor  of  Zoology  in  the  University  of  Illinois 
Frank  Smith,  Professor  of  Zoology  in  the  University  of  Illinois 
Julia  Warner  Snow,  Associate  Professor  of  Botany  in  Smith  College 
Caroline  Effie  Stringer,  Head  of  the  Department  of  Biology  in  the  Omaha  High 

School 
Bryant  Walker,  Detroit,  Mich. 
Robert  Henry  Wolcott,  Professor  of  Zoology  in  the  University  of  Nebraska. 


PREFACE 

For  the  ordinary  student  and  teacher  on  this  continent  fresh- 
water life  has  a  significance  heretofore  greatly  underestimated. 
In  most  parts  of  the  country  it  lies  at  one's  very  door,  readily  ac- 
cessible, and  is  indeed  the  only  type  of  aquatic  existence  which  can 
be  studied  Uving  and  at  work.  This  fact  gives  to  fresh-water  life, 
once  the  student  has  been  introduced  into  its  domain,  an  appeal- 
ing interest  that  fetters  his  attention  and  stimulates  his  desire 
to  know  something  more  of  it.  Among  the  most  remarkable  of 
early  works  that  followed  hard  upon  the  first  use  of  the  micro- 
scope are  some  great  classics  which  represent  work  in  this  very 
field. 

Various  European  countries  possess  elaborate  monographs  on 
fresh-water  organisms  as  a  whole  and  on  single  groups,  but  no 
attempt  has  been  made  heretofore  to  deal  with  North  American 
fresh-water  hfe  in  its  entirety,  and  few  treatises  have  essayed  to 
cover  completely  any  group  of  fresh-water  organisms.  American 
workers  in  general  have  accordingly  avoided  this  field  and  the  few 
who  have  attempted  to  engage  in  its  study  have  found  their  prob- 
lems very  difficult  to  solve. 

The  preparation  of  the  present  work  was  undertaken  many  years 
ago  with  the  purpose  of  stimulating  the  study  of  the  material  so 
easily  obtainable  and  of  aiding  workers  of  all  grades  to  acquire 
some  definite  and  precise  knowledge  of  the  organisms  met  in  such 
study.  Each  chapter  has  been  handled  by  a  specialist  on  the  group 
and  the  results  achieved  by  this  method  have  a  significance  that 
could  not  have  been  attained  in  any  other  way.  Conditions  en- 
tirely unavoidable  led  to  the  completion  of  the  different  parts  of 
the  work  at  somewhat  different  dates.  It  is  believed  that  this 
will  not,  in  fact,  impair  the  value  of  the  work  as  a  whole  and 
will  find  an  excuse  in  the  magnitude  of  the  task.  Individual 
chapters  represent  a  survey  of  the  group  treated  that  is  complete 


vi  PREFACE 

for  this  continent  up   to   the   time    at   which   the   chapter   was 
closed. 

The  first  few  chapters  are  devoted  to  a  discussion  of  general  bio- 
logical factors.  Evident  space  limits  prevented  extended  discus- 
sion of  many  most  interesting  biological  topics,  which  are  at  best 
only  outHned  here.  The  exact  citation  of  sources  at  the  close 
of  these  chapters  will  aid  the  reader  to  pursue  such  topics  further 
if  desired.  Not  all  discussions  on  general  questions  have  been 
confined  to  the  introductory  chapters.  The  chapter  on  Rotifera, 
by  Jennings,  presents  an  admirable  description  of  Ufe  processes, 
which,  altho  written  specifically  for  that  group,  appHes  with  ap- 
propriate modifications  to  all  groups  of  many-celled  organisms. 
In  the  chapter  on  Copepoda,  Marsh  has  treated  with  some  detail 
the  general  question  of  distribution  as  illustrated  by  this  group; 
yet  the  very  factors  which  he  shows  to  be  operative  in  it  are 
those  that  lie  at  the  basis  of  the  distribution  of  most  if  not  all 
other  groups.  The  discussion  of  the  aquatic  vertebrates  by  Eigen- 
mann  is  purely  biological  and  the  systematic  outhne  is  omitted 
entirely,  since  that  of  itself  would  demand  an  entire  book  for  its 
adequate  presentation.  The  same  is  true  of  the  chapter  on  Bac- 
teria, by  Jordan,  and  of  that  on  the  higher  aquatic  plants  which  are 
treated  by  Pond  in  the  physiological  (chemico-physical)  aspect 
primarily. 

Apart  from  those  just  mentioned  all  chapters  conform  to  the 
same  general  plan.  Each  is  devoted  to  a  single  group  of  organ- 
isms and  opens  with  a  general  account  of  the  occurrence  and  his- 
tory of  the  group.  The  description  of  the  anatomy  of  the  forms 
treated  is  very  brief  and  deals  chiefly  with  such  features  as  are  of 
special  value  in  the  key.  Similarly  the  life  history  is  given  in 
condensed  form.  More  attention  is  devoted  to  the  biological 
relations  which  at  this  point  are  discussed  with  reference  to  the 
entire  group,  whereas  individual  features  are  left  for  later  record 
under  individual  species  except  as  they  are  needed  for  illustrations 
of  general  questions.  Care  has  been  exercised  to  include  descrip- 
tions of  special  methods  for  collecting,  preserving,  and  studying 
the  organisms  of  each  particular  group. 

Special  details  both  biological  and  morphological  regarding  genera 


PREFACE  vii 

and  species  are  included  under  a  synoptic  key  which  comes  at  the 
close  of  each  chapter  except  as  noted  above;  in  some  cases  it  is 
carried  to  species  but  in  others  only  to  genera.  The  form  utilized 
for  the  keys  has  been  in  constant  use  for  many  years  at  the  Uni- 
versity of  Illinois,  having  been  applied  to  many  aquatic  types  by 
Professor  S.  A.  Forbes  and  his  associates.  The  introductory  num- 
ber of  each  key  line  is  followed  by  an  alternative  number  printed 
in  parentheses  and  on  reaching  a  decision  that  this  line  is  not  ac- 
ceptable, the  student  proceeds  at  once  to  the  line  introduced  by 
the  alternative  number;  in  case  a  given  alternative  is  accepted  the 
further  course  of  the  inquiry  is  indicated  by  a  number  at  the  close 
of  the  line. 

In  order  to  achieve  maximum  ease  in  use  and  perspicacity  in 
grasping  the  facts  presented,  all  the  information  on  a  given  form, 
viz.,  the  illustration,  the  description,  and  the  biological  features  with 
the  frequence,  range,  and  other  special  data,  are  included  between 
the  key  line  which  introduces  the  name  and  the  key  line  next  fol- 
lowing. The  total  information  on  a  single  type  forms  thus  a  solid 
panel  and  appeals  promptly  and  as  a  whole  to  the  eye  and  mind  of 
the  student.  Each  chapter  closes  with  a  brief  list  of  the  most 
essential  references  to  the  topic.  No  textbooks  are  cited  and  only 
such  works  are  noted  as  may  be  considered  indispensable  for  pres- 
ent-day study  of  North  American  forms.  The  student  is  cautioned 
not  to  regard  any  such  list  as  in  any  sense  a  bibliography  of  the 
subject. 

To  encompass  such  a  mass  of  material  within  the  limits  of  a 
single  volume,  even  tho  it  be  generous  in  size,  has  necessitated 
brevity  of  treatment  at  every  point.  Technical  terms  are  defined 
or  discussed  only  once  and  no  glossary  is  introduced.  The  index 
includes  important  terms  and  all  of  the  scientific  names  used  in 
the  keys  so  that  the  reader  can  find  every  item  promptly. 

A  serious  effort  was  made  to  attain  uniformity  in  the  use  of 
names  thruout  the  entire  work  but  the  worker  will  find  that  this 
end  was  not  fully  achieved.  The  most  conspicuous  failure  in  this 
particular  obtains  in  the  citation  of  host  names  for  various  para- 
sitic species.  In  all  such  cases  that  name  is  employed  which  was 
used  by  the  authority  from  which  the  record  is  cited.     It  was  felt 


viii  PREFACE 

that  in  the  absence  of  monographic  revisions  of  the  species  of 
parasites  noted  any  other  method  would  have  been  indefensible 
in  a  brief  treatise. 

Abundant  use  has  been  made  of  figures  to  illustrate  the  forms 
described.  Most  of  the  illustrations  are  new  and  many  of  them 
drawn  by  the  author  of  the  chapter  especially  for  this  work. 

In  chapter  II  certain  figures  and  tables  are  taken  with  modi- 
fications from  Shelford's  American  Communities  in  Temperate 
America  by  courtesy  of  the  Geographic  Society  of  Chicago  and  the 
University  of  Chicago  Press. 

It  would  be  impossible  to  acknowledge  all  of  the  aid  which  has 
been  extended  during  the  progress  of  the  work.  Valuable  sugges- 
tions from  many  sources  have  been  freely  extended  us  and  as  freely 
utilized. 

To  all  of  our  colleagues  who,  in  spite  of  multitudinous  difficulties 
and  seemingly  interminable  delays,  have  worked  so  generously  to 
perfect  their  individual  chapters  the  sincerest  thanks  of  the  editors 
are  due.  Especial  mention  should  be  made  of  the  numerous  help- 
ful suggestions  and  criticisms  given  outside  their  own  chapters 
during  the  preparation  of  the  work  by  Professors  E.  A.  Birge  and 
Frank  Smith.  Grateful  acknowledgement  is  also  due  E.  C.  Faust 
and  H.  G.  May  for  aid  in  reading  and  checking  proof. 

Finally,  it  is  a  pleasure  as  well  as  a  duty  to  express  our  apprecia- 
tion of  the  work  of  the  publishers.  Their  forbearance  and  continued 
kindly  assistance  during  the  long  and  difficult  period  of  preparation 
has  made  possible  the  completion  of  the  work  and  its  presentation 
to  the  scientific  worker  in  attractive  form. 


CONTENTS 

Chap.  Page 

I.   Introduction,  Henry  B.  Ward i 

II.    Conditions  of  Existence,  Victor  E.  Shelford 21 

III.  Methods  of  Collecting  and  Photographing,  Jacob  Reighard 61 

IV.  Bacteria,  Edwin  O.  Jordan go 

V.   Blue-Green  Algae  (Cyanophyceae) ,  Edgar  W.  Olive 100 

VI.   The  Fresh- Water  Algae  (Excluding  the  Blue-Green  Algae),  Julia  W. 

Snow 115 

VII.   The  Larger  Aquatic  Vegetation,  Raymond  H.  Pond 178 

VIII.   Amoeboid  Protozoa  (Sarcodina),  C.  H.  Edmondson 210 

IX.   Flagellate  and  Ciliate  Protozoa  (Mastigophora  et  Infusoria),  H.  W. 

Conn  and  C.  H.  Edmondson 238 

X.   The  Sponges  (Porifera),  Edward  Potts 301 

XI.   Hydra  and  Other  Fresh- Water  Hydrozoa,  Frank  Smith 316 

XII.   The  Free-Living  Flatworms  (Turbellaria) ,  Caroline  E.  Stringer :i2^ 

XIII.  Parasitic  Flatworms,  Henry  B.  Ward 365 

XIV.  The  Nemerteans,  Wesley  R.  Coe 454 

XV.    Free-Living  Nematodes,  N.  A.  Cobb 459 

XVI.    Parasitic  Roundworms,  Henry  B.  Ward " 506 

XVII.   The  Wheel  Animalcules  (Rotatoria),  H.  S.  Jennings 553 

XVIII.    Gastrotricha,  Henry  B.  Ward 621 

XIX.   Aquatic  Earthworms  and  other  Bristle-Bearing  Worms  (Chaetopoda), 

Frank  Smith 632 

XX.   The  Leeches  (Hirudinea),  J.  Percy  Moore 646 

XXI.   The  Fairy  Shrimps  (Phyllopoda) ,  A.  S.  Pearse 661 

XXII.   The  Water  Fleas  (Cladocera),  Edward  A.  Birge 676 

XXIII.  Copepoda,  C.  Dwight  Marsh 741 

XXIV.  The  Ostracoda,  R.  W.  Sharpe 790 

XXV.   Higher  Crustaceans  (Malacostraca) ,  A.  E.  Ortmann 828 

XXVI.   The  Water-Mites  (Hydracarina) ,  Robert  H.  Wolcott 851 

XXVII.   Aquatic  Insects,  James  G.  Needham 876 

XXVIII.   Moss  Animalcules  (Bryozoa),  Charles  B.  Davenport 947 

XXIX.   The  Mollusca,  Bryant  Walker 957 

XXX.   The  Aquatic  Vertebrates,  C.  H.  Eigenmann 102 1 

XXXI.   Technical  and  Sanitary  Problems,  George  C.  Whipple 1067 

ix 


i 


I 


CHAPTER  I 
INTRODUCTION 

By  henry  B.  ward 

Professor  of  Zoology  in  the  University  of  Illinois 

On  the  surface  of  the  globe,  water  and  life  are  intimately  asso- 
ciated. As  water  grows  scantier  life  becomes  more  restricted  until 
with  the  total  failure  of  water  life  also  disappears.  In  regions  where 
water  is  very  scarce  the  few  organisms  that  exist  have  learned  to 
store  water  or  to  discharge  vital  functions  with  a  minimum  supply 
and  thus  to  meet  the  natural  defects  of  the  situation. 

The  hydrosphere,  or  the  total  water  mass  on  the  globe,  forms  the 
subject  of  study  for  hydrography  which  is  readily  subdivided  into 
(i)  oceanography,  that  deals  with  the  vast  continuous  mass  of 
salt  water  in  the  ocean,  and  (2)  limnology,  which  treats  of  the  vari- 
ous fresh-water  units.  The  term  limnology  is  sometimes  re- 
stricted in  its  application  to  the  more  stable  bodies  such  as  lakes 
and  ponds,  in  which  case  rheology  is  used  to  cover  various  types  of 
flowing  waters.  All  fresh  water  is  distributed  over  the  surface  of 
the  land  and  variably  grouped  into  separate  series  of  systems 
connected  with  each  other  only  through  the  ocean  to  which  each 
system  is  joined.  The  rare  desert  systems,  such  as  terminate  in 
the  Carson  Sink  or  the  Dead  Sea,  are  exceptional  in  having  no 
present  connection  with  the  ocean. 

Fresh  water  is  deposited  on  the  land  in  the  form  chiefly  of  rain 
or  snow,  and  tends  ultimately  to  reach  the  sea,  though  first  and 
last  a  considerable  part  is  taken  up  by  evaporation  and  goes  back 
directly  into  the  atmosphere.  Much  of  the  precipitation  soaks 
into  the  ground  to  reappear  elsewhere  in  springs  or  by  seepage 
to  feed  ponds  and  streams.  Activity  or  rate  of  movement  dis- 
tinguishes two  classes  of  water  bodies:  the  flowing  water  of  streams 
and  the  temporarily  quiet  water  of  lakes.  The  latter  almost 
always  form  parts  of  stream  systems  and  have  thereby  an  inti- 
mate connection  with  the  ocean  that  is  of  fundamental  importance 
in  determining  the  origin  of  fresh-water  organisms. 


2  FRESH-WATER   BIOLOGY 

The  more  or  less  actively  flowing  waters  appear  in  the  form  of 
springs  or  rivulets,  then  increase  and  unite  to  make  brooks,  creeks, 
and  rivers.  The  transition  is  ordinarily  gradual  and  size  has  only 
a  secondary  influence  on  the  biological  character  of  the  stream. 
The  rate  of  flow,  and  the  physical  and  chemical  character  of  the 
soil  over  and  through  which  water  drains  into  a  stream  and  by 
which  its  banks  and  beds  are  formed  are  the  chief  factors  in  de- 
termining its  life. 

From  the  tiniest  rivulet  to  the  mightiest  river  one  may  find 
every  possible  intermediate  stage,  and  between  the  swiftest  moun- 
tain torrent  and  the  most  sluggish  lowland  stream  there  exists 
every  intermediate  gradation.  Biologically  considered,  the  torrent 
imposes  on  the  development  of  life  within  its  waters  evident  me- 
chanical Hmitations  which  are  not  present  in  the  slow-flowing 
streams.  Ordinarily  the  biological  wealth  of  a  stream  varies  in- 
versely with  its  rate  of  flow,  and  anything  which  stops  or  checks 
the  flow  makes  conditions  more  favorable  for  the  development  of 
life.  Flowing  waters  are  thinly  inhabited  and  also  present  con- 
siderable difficulties  to  the  student;  hence  they  are  relatively  un- 
explored territory. 

Waters  of  the  static  type,  characterized  by  lack  of  flow,  form  an 
equally  continuous  series  from  the  great  lakes  or  inland  seas  pro- 
gressing by  insensible  gradations  through  lake,  pond,  and  pool  to 
the  morass  or  swamp.  In  the  first  group  size  permits  more  wind 
action;  it  also  pro\ides  greater  stability  in  level  as  well  as  in 
thermal  and  chemical  conditions.  Possessing  only  limited  com- 
munication with  the  ocean  these  bodies  of  water  constitute  biolog- 
ical units  of  great  definiteness.  The  lake  is  a  microcosm;  a  minute 
repHca  of  the  ocean,  it  responds  more  quickly  to  changes  in  its  en- 
vironment, is  simpler  to  grasp  and  easier  to  study.  Yet  it  is 
withal  the  most  complicated  of  inland  environments  (Shelf ord). 

The  distinction  between  water  bodies  of  different  size  is  often 
indefinite.  Puddle,  pond,  and  lake  form  in  fact  a  continuous 
series.  Yet  in  a  strict  sense  lakes  are  characterized  by  a  central 
region  deep  enough  to  exceed  the  Kmits  of  growth  of  the  flora  in 
the  shore  zone.  Ponds  are  shallow  lakes,  usually  insignificant  in 
area,  yet  still  of  relative  permanence.     They  constitute  distinct 


INTRODUCTION  3 

units  of  environment.  These  more  nearly  stable  units,  the  lakes 
and  ponds,  are  often  rich  in  life.  They  are  exceptionally  favorable 
for  study  and  have  been  extensively  investigated  both  in  Europe 
and  in  this  country. 

The  temporary  water  body,  a  puddle  or  pool,  whatever  its  area, 
affords  only  conditions  for  transient  existence  that  are  sometimes 
irregular  in  their  recurrence  and  sometimes  present  themselves 
with  considerable  regularity.  They  are  fitted  for  organisms  that 
reproduce  very  rapidly  during  the  favorable  season  and  also  have 
special  means  of  tiding  the  species  over  the  unfavorable  period. 
Purely  temporary  water  bodies,  such  as  pools  that  form  in  hol- 
lows after  a  heavy  rain  or  in  a  wet  season,  develop  little  if  any 
life.  Such  places  on  poor  soil  are  most  barren  of  all;  the  aquatic 
life  increases  with  the  fertility  of  the  soil,  the  age  of  the  water  body, 
and  the  consequent  accumulation  of  organic  debris.  Residual 
ponds,  water  bodies  in  which  the  drying  out  is  more  gradual  and 
often  incomplete  and  in  which  a  central  area  may  be  protected  from 
complete  desiccation  by  vegetation  or  proximity  to  the  general  water 
level,  afford  conditions  at  the  opposite  extreme.  The  wide  stretches 
of  lowland  subject  to  periodic  overflow  from  great  inland  rivers  like 
the  Illinois,  Missouri,  and  Danube  in  certain  regions,  develop  a  rich 
flora  and  fauna  which  equals  or  exceeds- in  abundance  that  found 
under  other  circumstances  (Antipa,  Forbes).  Similarly  among 
ponds  adjacent  to  a  lake  basin  the  permanent  are  poorer  than 
those  which  dry  out  for  a  time  (Shelf ord). 

The  smaller  water  body  presents  nearly  uniform  conditions 
throughout  and  therewith  also  a  single  series  of  inhabiting  organ- 
isms. The  entire  area  falls  within  the  shore  or  shallow  water 
zone  which  is  hmited  to  such  parts  as  support  fixed  plants.  In 
this  general  region  are  readily  distinguished  two  zones,  (a)  that 
of  the  emergent  vegetation  where  the  larger  plants  reach  conspicu- 
ously above  the  water  level  and  constitute  the  dominant  feature 
to  the  eye,  and  (2)  that  of  submerged  vegetation  in  which  the 
plants  rarely  project  at  all  above  the  surface  and  in  consequence 
the  water  itself  dominates  the  view.  Both  of  these  regions  may  be 
subdivided  on  the  basis  of  the  particular  form  of  vegetation  which 
is  common  in  a  given  portion.     In  a  swamp  these  regions  are  often 


4  FRESH-WATER   BIOLOGY 

the  only  ones  that  are  present.  But  in  a  pond  one  can  usually 
determine  the  existence  of  a  third  zone  in  which  the  fixed  vegeta- 
tion is  lacking. 

With  increase  of  the  water  body  in  size  or  more  especially  in 
depth,  new  conditions  are  presented.  The  littoral  region  passes 
over  insensibly  into  a  deeper  bottom  region  with  its  own  biological 
series  and  to  a  free  open- water  area  known  as  the  limnetic  region. 
The  corresponding  region  in  the  ocean  is  designated  the  pelagic 
and  this  term  is  also  used  by  some  for  the  fresh- water  area.  The 
plants  and  animals  in  this  region  are  characteristic;  they  constitute 
what  is  called  the  plankton,  the  floating  life  of  the  water.  Such 
organisms  remain  suspended  in  water  during  their  entire  existence; 
they  Kve  and  die  ''on  the  wing."  In  the  larger  lakes  the  shore 
zone  loses  in  prominence  whereas  the  pelagic  and  bottom  regions 
gain  in  distinctness  and  relative  importance. 

Lakes  vary  widely  in  character  and  abundance  in  different 
regions.  They  are  infrequent  in  areas  that  are  physiographically 
old  and  most  abundant  in  glaciated  territory,  where  they  occur 
in  eroded  rock  basins,  in  partially  filled  rock  valleys,  in  hollows 
over  the  moraine,  and  more  rarely  at  the  margin  of  the  ice  sheet. 
Sometimes  lakes  are  found  in  old  volcanic  craters,  in  the  depres- 
sions of  a  lava-covered  area,  or  behind  a  lava  flow  dam.  They 
occur  regularly  in  streams  as  mere  expansions  in  the  course  or  are 
formed  by  the  inflowing  delta  of  a  lateral  tributary  or  when  the 
stream  breaks  through  a  narrow  neck  and  leaves  an  ox  bow  or  cut- 
off lake  at  the  side.  One  finds  them  often  on  low  coastal  plains 
some  distance  from  the  shore,  more  commonly  close  to  the  sea 
and  even  on  the  same  level  with  it.  Old  lakes  without  an  outlet 
become  strongly  alkaline  or  saline  and  develop  aquatic  Hfe  of  a  type 
pecuHar  to  each.  Most  lakes,  however,  are  fresh  and  shelter  organ- 
isms of  the  same  general  type. 

Taken  together  lakes  compose  one-half  the  fresh  water  on  the 
surface  of  the  globe.  They  present  an  infinite  variety  of  physical 
features  in  rocky,  sandy,  swampy  margins,  in  steep  and  shallow 
shores,  in  regular  and  broken  contours  with  no  islands  or  many, 
with  shallow  water  or  depths  that  carry  the  bottom  far  below  the 
level  of  the  sea. 


INTRODUCTION  5 

They  vary  in  the  chemical  character  of  the  soil  in  the  lake  basin 
as  well  as  in  their  banks  and  bed,  in  the  degree  of  exposure  to 
wind  and  sunshine,  in  the  relative  inflow  and  outflow  in  ratio  to 
their  volume,  in  their  altitude  as  well  as  in  geographic  location. 
All  of  these  and  many  other  factors  modify  and  control  the  types  of 
living  things  and  their  abundance  in  the  waters.  Lake,  pond, 
and  swamp  are  successive  stages  in  change  from  the  water-filled 
hollow  to  the  terrestrial  plain  that  ultimately  occupies  the  same 
location.  Along  the  margin  of  the  lake,  especially  at  the  points 
where  tributary  streams  empty  into  it,  the  inflowing  water  brings 
detritus  of  all  sorts  that  builds  out  the  shore  and  forms  a  shelf  on 
which  the  littoral  vegetation  gains  a  foothold.  As  the  lake  grows 
old  this  region  increases  at  the  expense  of  the  pelagic  and  bottom 
areas,  until  the  latter  disappears  and  the  former  persists  only  in 
reduced  amount.  Finally  the  entire  area  is  conquered  by  deposits 
of  silt  and  growth  of  vegetation.  The  swamp  comes  and  is  made 
over  into  dry  land  traversed  in  winding  channels  by  the  stream 
system  that  is  responsible  for  these  changes.  In  other  cases  the 
outflowing  stream  cuts  down  the  level  and  ultimately  drains  the 
lake. 

Lakes  are  thus  in  a  geologic  sense  only  temporary  features  of 
the  river  system  to  which  they  belong.  Similar  influences  direct 
the  evolution  of  the  stream  from  the  violent  instability  of  its 
youth  to  the  sluggish  stability  of  its  age.  During  this  process  of 
evolution  the  life  in  the  waters  undergoes  parallel  changes.  At 
first  the  fauna  is  scanty  but  increases  in  numbers  and  variety  as 
new  habitats  are  created.  Unstable  and  intermittent  conditions 
indicate  paucity  of  life;  but  when  the  aquatic  environment  be- 
comes more  permanent  organisms  more  easily  invade  the  territory 
successfully  and  its  life  grows  increasingly  complex  as  time  goes  on. 

Lakes  influence  noticeably  the  life  of  a  stream  system  in  that  they 
act  as  filters  or  settling  basins  for  inflowing  waters  and  also  regulate 
the  volume  of  the  discharge;  thus  the  outflowing  stream  is  free 
from  sediment  and  approaches  constancy  in  level.  This  greater 
permanence  militates  against  the  development  of  certain  types  of 
life  but  favors  others.  The  continued  dilution  of  the  stream  by 
the  addition  of  water  free  from  life  and  the  removal  of  such  organ- 


6  FRESH-WATER    BIOLOGY 

isms  as  are  produced  at  a  given  point  by  the  constant  flow  of  the 
water  make  the  river  plankton  scanty  in  amount,  but  many  fresh- 
water lakes  produce  an  immense  number  of  plankton  organisms. 
These  have  been  much  studied  in  recent  years  and  about  them 
alike  in  ocean  and  fresh  water  has  grown  up  a  new  study,  Plank- 
tology,  the  Planktonkunde  of  the  Germans. 

Among  the  forms  of  the  open  water  are  some,  primarily  the  fishes, 
which  manifest  indi\idual  power  of  movement  adequate  to  make 
them  independent  of  water  movements,  storms,  and  distances. 
They  can  thus  determine  their  own  distribution  in  an  active  fashion 
and  stand  in  marked  contrast  with  the  plankton,  for  the  latter  is 
unable  to  regulate  effectively  its  location,  and  is  dependent  upon 
the  winds  and  waves  for  its  dispersal.  Typical  plankton  organ- 
isms, in  fresh  water  known  together  as  the  limnoplankton,  are 
found  only  in  water  bodies  of  some  size,  whereas  in  small  lakes  or 
ponds  the  circumscribed  open-water  area  contains  life  which  con- 
sists of  migrants  from  shore  and  shallow  water  regions.  Whereas 
on  the  land  higher  forms,  especially  domestic  animals,  depend  on 
the  higher  fixed  plants  for  food,  in  the  water  the  higher  types  de- 
pend upon  the  smaller  floating  plant  and  animal  organisms  which 
transform  inorganic  materials  and  organic  debris  into  available 
food  substances. 

The  floating  organisms  which  taken  together  constitute  the  plank- 
ton are  grouped  into  two  purely  artificial  classes  according  to 
methods  used  in  collecting.  The  constant  use  of  fine  nets  (cf.  p.  74) 
for  collecting  plankton  organisms  led  to  a  conception  of  this  type 
of  life  that  unconsciously  assigned  a  minimum  limit  in  size.  Thus 
the  organisms  taken  in  the  plankton  net  are  all  that  the  older 
authors  included  under  the  term  plankton,  an  assemblage  which 
should  be  termed  more  correctly  the  net  plankton.  It  is  well  known 
through  the  work  of  many  investigators  during  recent  years  and 
includes  a  great  variety  of  Crustacea  and  Rotifera  with  many  Pro- 
tozoa and  Protophyta,  and  less  regularly  some  other  types. 

Within  very  recent  times  there  has  been  obtained  by  more 
precise  methods  of  collecting  what  has  been  termed  by  Lohmann 
the  nannoplankton  (dwarf  plankton)  with  a  size  limit  he  set  arbi- 
trarily at  25/x.     It  consists  of  the  most  minute  organisms  only, 


INTRODUCTION 


those  that  (Fig.  i)  pass  through  the  meshes  of  the  finest  silk  gauze, 
Swiss  bolting  cloth  No.  25,*  having  meshes  that  measure  0.04  to 
0.05  mm.  square.  The  nannoplankton  is  composed  chiefly  of 
flagellates  and  algae;  although  bacteria  are  constantly  present  they 
apparently  form  but  a  minor  con- 
stituent in  bulk  and  weight.  The 
number  and  variety  of  these  or- 
ganisms is  truly  astonishing  even 
in  the  clear  waters  of  Alpine 
lakes  where  according  to  Ruttner 
they  stand  to  the  organisms  of 
the  net  plankton  numerically  in 
the  ratio  of  160  :  3  and  at  least 
two-thirds  of  them  are  still  un- 
described  and  difficult  to  include 
in  known  genera.  The  maximum 
number  of  nannoplanktonts  thus 
far  recorded  is  from  Lake  Men- 
do  ta,  Wis.,  where  Cyclotella  has 
been  found  to  the  number  of  over 
30,000,000  per  liter  of  water. 

Ruttner  also  calculates  the  vol- 
ume of  the  nannoplankton  in  the 
Lunzer  lakes  as  three  times  that 
of  net  plankton.  According  to 
Birge  and  Juday  the  weight  of  its 
dry  organic  matter  varies  in  three 
Wisconsin  lakes  from  slightly 
less  (rarely)  to  15  or  20  times 
more  than  that  of  the  net  plankton  and  is  ordinarily  5  to  6  times 
as  great.  This  amount  is  unquestionably  of  marked  importance 
both  scientifically  and  practically,  and  the  character  of  the  or- 
ganisms indicates  even  more  clearly  their  fundamental  impor- 
tance in  the  problems  of  aquatic  biology. 

Plankton  organisms  are  characterized  by  transparency,  delicate 
colors,  and  above  all  by  their  power  of  floating  due  to  buoyancy  and 

*  New  No.  25  is  identical  with  No.  20  of  older  authors  (Lohmann). 


Fig.  I.  A  piece  of  bolting  cloth  No.  20  with 
plankton  organisms  drawn  between  the  meshes 
to  show  relative  size.  Above,  Rhizosolenia  alata. 
Upper  row,  left  mesh:  Gymnodinium.  beneath 
Amphidiniiun  rotundatum  and  Exuviaella  hallica, 
right  Pouclictia  parva;  middle  mesh:  Proroccn- 
triim  micans  and  Khynchomonas  marina;  right 
mesh:  Nitschia  sigmalella.  Acliradina  pulcltra, 
Halteria  rubra.  Nitschia  clostcrium.  Middle  row, 
left  mesh:  Tintinnopsis  nana,  Tintinnus  steen- 
strupi,  Oxyrrhis  phaeocysticola;  middle  rnesh: 
chain  of  small  Chaetoceras  species,  above  it  on 
the  left  Tlialassiosira  nana  and  saturni,  on  the 
right  Carteria;  right  mesh:  chain  of  large 
Chaetoceras  species  (Chaet.  didymum),  Tintinnop- 
sis beroidea.  Lower  row,  left  mesh:  Rhodomonas 
baltica,  Distephanus  speculum;  middle  mesh: 
Strombidium  caudatum  (?),  Meringosphaera  maii- 
terranea.  Amoeba;  right  mesh:  Coccotithophora 
wallichi.  beneath  on  the  left  Pontosphaera  huxltyi, 
on  the  right  Coccotithophora  leptopora.  above  on 
the  right  Chr>somonadine  without  shell,  at  the 
very  bottom  Rhabdosphaera  claviger.  X  no. 
(After  Lohmann.) 


8  FRESH-WATER   BIOLOGY 

form  resistance  in  contrast  with  related  organisms.  The  buoyancy 
is  achieved  by  oil  droplets  and  gas  bubbles  formed  in  the  cells 
whereas  heavy  cell  walls  and  skeletal  structures  are  wanting.  Flo- 
tation-apparatus in  the  shape  of  lateral  wings,  bristles,  spines, 
or  a  body  form  like  a  parachute,  a  spiral  thread,  or  a  gelatinous 
cover  —  pro\'ides  against  rapid  sinking.  Ostwald  has  determined 
that  the  rate  of  sinking  is  equal  to  the  excess  weight  of  the  organism 
above  that  of  an  equal  water  volume  divided  by  the  product  of  the 
form  resistance  and  the  viscosity  of  the  fluid. 

Generally  speaking  great  depth  in  a  water  body  and  large  inflow 
in  proportion  to  volume  are  unfavorable  to  the  abundant  develop- 
ment of  the  plankton  organisms  whereas  minimal  depth  and  scanty 
inflow  favor  the  production  of  plankton. 

When  water  is  first  deposited  on  the  earth  it  is  almost  absolutely 
pure,  containing  only  the  minute  amount  of  materials  which  it 
has  leached  out  of  the  atmosphere.  From  the  ground  over  which 
it  flows  or  the  soil  through  which  it  percolates  come  substances 
organic  or  inorganic,  in  solution  and  suspension,  here  of  one  type 
and  there  of  another,  that  serve  to  enrich  it  and  make  of  it  an 
environment  capable  of  supporting  life.  "The  aquatic  popula- 
tion of  a  lake  or  stream  is  thus  sustained  by  the  wastes  of  the  land, 
materials  which  would  otherwise  be  carried  down  practically  un- 
altered to  the  sea;  and  rivers  and  lakes  may  be  looked  upon  as  a 
huge  apparatus  for  the  arrest,  appropriation,  digestion,  and  assimi- 
lation of  certain  raw  materials  about  to  pass  from  our  control" 
(Forbes). 

For  the  determination  of  physical  data  on  the  character  of  bodies 
of  water,  methods  and  apparatus  of  considerable  complexity  have 
been  devised,  largely  by  students  of  oceanography,  and  adapted 
later  to  fresh-water  conditions.  By  such  means  the  investigator 
is  enabled  to  measure  in  a  comparative  way,  and  sometimes  in 
absolute  fashion,  and  to  record  environmental  conditions  such  as 
the  depth,  temperature,  turbidity,  and  other  physical  features  of 
the  water  body.  Some  of  these  determinations  are  simple  and 
require  only  limited  apparatus;  others  are  complex  and  beyond 
the  powers  of  the  ordinary  student  of  aquatic  biology.  The  appli- 
cation of  such  data  to  biologic  problems  is  discussed  in  part  in  the 


INTRODUCTION  9 

following  chapter.  An  adequate  consideration  of  methods  and 
apparatus  demands  more  space  than  is  available  here  and  for 
further  information  the  student  is  referred  to  manuals  deahng  with 
that  phase  of  aquatic  investigation.  General  methods  of  collect- 
ing and  photographing  aquatic  organisms  form  the  subject  of  a 
separate  chapter  while  such  methods  as  are  applicable  to  the  study 
of  each  special  group  are  discussed  in  the  chapter  on  that  group. 

The  environment  of  water  organisms  as  of  all  others  is  a  com- 
plex of  many  elements.  The  physical  factors  are  determined  by 
the  materials  held  in  suspension  or  in  solution  in  the  water,  by  its 
temperature,  depth,  movement,  illumination,  shore  and  bottom. 
Chemical  factors  are  found  in  the  acidity  or  alkalinity  of  the  water 
and  in  the  gases,  salts,  and  other  materials  in  it.  The  organisms 
themselves  make  the  biological  environment.  Living  or  dead,  as 
food  or  feeder,  parasite  or  host,  friend,  enemy,  or  neutral,  each 
living  thing  contributes  to  the  sum  total  of  the  biological  complex 
by  which  each  living  unit  is  surrounded.  It  is  the  problem  of 
science  to  unravel  this  tangle  and  to  determine  the  relation  of  each 
constituent,  living  or  non-living,  to  the  others.  The  conditions  of 
existence  to  which  organisms  are  subject  in  different  aquatic  en- 
vironments and  the  influence  which  these  environments  exert  on 
organisms  in  general  are  discussed  in  the  following  chapter.  In 
subsequent  chapters  an  attempt  has  been  made  to  present  these 
relations  as  illustrated  by  each  group  of  organisms.  To  become 
thoroughly  acquainted  with  a  single  group  involves  a  knowledge 
of  the  relations  its  members  bear  to  every  other  organism  in  the 
community. 

No  climate  is  too  rigorous  for  fresh-water  life.  It  exists  in 
fresh-water  lakes  at  77°  N.  L.,  hardly  if  ever  free  from  ice,  often 
only  slightly  melted  and  with  a  maximum  temperature  of  less  than 
2°  C.  at  the  bottom.  The  Shackleton  expedition  described  an 
extensive  microfauna  at  77°  30'  S.  L.  from  Antarctic  lakes  that 
are  frozen  solid  for  many  months,  often  for  several  years.  At  the 
other  extreme  of  temperature  evidence  is  less  complete  but  C}'pris 
is  recorded  from  hot  springs  at  50°  C,  ciliates  and  rotifers  from 
waters  at  65°  C,  Oscillaria  and  nostocs  from  places  that  are 
recorded  at  70°  to  93°  C 


lO  FRESH-WATER   BIOLOGY 

The  aquatic  life  of  a  permanent  fresh-water  body  is  variable 
within  certain  limits  of  time  and  space.  Each  season  witnesses 
the  coming  and  going  of  certain  types  which  are  active  only  in 
definite  periods  and  by  resting  spores,  gemmules,  or  eggs  bridge 
over  the  intervening  time.  This  known  seasonal  succession  is  so 
definite  that  it  gives  the  life  of  fresh  water  a  changing  character 
as  clear  if  not  as  conspicuous  to  the  eye  as  that  on  land.  One 
may  readily  confuse  with  seasonal  succession  (i)  the  numerical 
variation  of  a  species  or  group  due  to  favorable  or  unfavorable 
conditions,  and  (2)  the  migrations  which  alter  vertically  or  hori- 
zontally through  various  water  levels  the  distribution  of  a  given 
organism. 

One  can  demonstrate  also  a  stratification  of  aquatic  organisms 
of  at  least  two  types:  vertical,  as  when  different  species  are  found 
to  occur  within  definite  limits  of  depth,  and  horizontal,  as  when 
species  are  confined  to  particular  regions  of  streams  or  lakes.  Such 
relations  are  discussed  fully  elsewhere. 

PecuHar  types  of  aquatic  environment,  such  as  elevated  lakes, 
saline  lakes,  and  underground  waters,  have  each  special  types  of 
living  organisms.  Some  of  these  special  environments  have  been 
made  the  objects  of  extended  study  which  has  shown  the  clear  rela- 
tion of  their  Hfe  to  that  of  other  fresh-water  bodies  of  the  region 
while  demonstrating  at  the  same  time  that  they  present  a  distinct 
character  of  their  own  (cf.  Zschokke,  Banta). 

The  life  of  fresh  water  is  probably  not  original  but  derived.  It 
came  from  the  sea,  by  migration  through  brackish  waters  or  swamps 
or  up  into  stream  systems,  by  the  gradual  freshening  of  marine 
basins  cut  off  from  the  sea  and  converted  into  fresh-water  bodies, 
by  direct  transport  from  one  body  of  water  into  another  through 
the  agency  of  the  wind,  on  the  feet  of  birds  or  other  wandering 
animals,  and  finally  by  invasion  from  the  land  direct.  Perhaps 
the  bottom  forms  came  first,  as  conditions  there  were  first  estabhshed. 
Certainly  the  plankton  forms  found  no  opportunity  for  existence 
in  the  violent  instabihty  of  a  young  stream.  At  present  the  shore 
forms  are  the  most  abundant  and  the  most  varied. 

In  some  deep  lakes  has  been  found  a  peculiar  bottom  fauna, 
designated  as  the  fauna  relicta,  which  is  composed  of  types  unlike 


INTRODUCTION  II 

other  fresh-water  forms  and  closely  related  to  marine  animals. 
This  fauna  is  often  regarded  as  the  survival  from  a  period  when 
connections  with  the  ocean  were  more  immediate,  or  when  climatic 
conditions  were  different  as  during  a  glacial  epoch. 

The  poverty  of  fresh-water  life  in  variety  and  number  of  types 
in  comparison  with  that  of  the  sea  has  often  been  emphasized. 
Experimental  data  show  it  can  hardly  be  due  to  lack  of  opportu- 
nity for  marine  organisms  to  adapt  themselves  to  fresh  water  for 
in  some  geologic  periods  conditions  have  been  very  favorable 
though  in  others  distinctly  the  opposite.  The  severity  of  the 
fresh-water  climate,  the  obstacle  of  an  ever  outflowing  current 
and  the  relative  newness  of  fresh-water  bodies  are  evident  difficul- 
ties. Furthermore  marine  animals  have  generally  free-swimming 
embryos,  distributed  by  water  movements  and  sure  therefore  to  be 
eliminated  gradually  from  the  fresh-water  environment  even  if 
the  adults  were  introduced  successfully.  Fresh-water  animals 
rarely  have  free-swimming  larval  stages  and  manifest  what  is 
known  as  an  accelerated  or  abbreviated  development  in  which  the 
young  on  emerging  from  the  egg  is  at  a  well-advanced  stage. 

Man  has  been  a  powerful  agent  in  modifying  fresh-water  life. 
By  hunting  and  fishing  he  has  exterminated  many  forms  directly. 
Through  modifications  of  streams  or  shore  for  commercial  pur- 
poses he  has  indirectly  eliminated  many  more  and  finally  by  pol- 
luting the  waters  with  sewage  and  waste  he  has  rendered  extensive 
water  areas  almost  devoid  of  aquatic  life  except  bacteria  and  even 
incapable  of  supporting  any  other  forms.  Streams  below  great 
cities  and  in  mining  and  manufacturing  districts  are  aquatic 
deserts. 

Fresh-water  biology  is  relatively  a  new  field  of  study.  Its 
earliest  records  on  this  continent  are  hardly  more  than  half  a  cen- 
tury old.  Among  individual  investigators  in  this  field  mention 
should  first  be  made  of  S.  A.  Forbes,  whose  pioneer  work  on  the 
Great  Lakes  has  been  followed  by  important  work  on  the  Illinois 
river  system.  The  work  of  Birge  on  Wisconsin  lakes,  of  Reighard 
on  Lakes  Erie  and  St.  Clair,  and  of  Kofoid  on  the  Illinois  river, 
warrant  also  especial  notice.  Many  others  whose  names  and  work 
are  recorded  in  the  following  chapters  have  made  valuable  con- 


12  FRESH-WATER   BIOLOGY 

tributions    to    the   general    and    special   problems   of   fresh-water 
biology. 

Fresh-water  biological  stations  have  aided  by  organized  effort 
the  conquest  of  the  field.  The  activities  of  the  Illinois  State 
Laboratory  of  Natural  History  on  the  Illinois  river,  of  the  Wis- 
consin Geological  and  Natural  History  Survey  on  the  lakes  in  that 
state,  of  the  U.  S.  Bureau  of  Fisheries  on  the  Mississippi,  of  Ohio 
State  University  on  Lake  Erie,  of  the  University  of  Montana 
Biological  Station  on  Flathead  Lake  in  the  Rocky  Mountains, 
show  the  variety  and  scope  of  these  interests.  Unfortunately 
only  the  first  three  are  active  all  the  year  through.  Other  uni- 
versities, notably  ^Michigan,  Indiana,  Iowa,  Colorado,  North 
Dakota,  and  Cornell,  have  participated  in  the  study  of  fresh-water 
life  during  part  of  the  year  or  for  a  short  series  of  years,  and  much 
emphasis  has  been  laid  upon  the  lake  biological  station  as  a  factor 
in  teaching  biology.  Few  of  these  enterprises  have  had  contin- 
uous existence  or  permanent  support.  Such  institutions  are  slowly 
but  surely  gaining  ground;  their  future  development  will  aid  both 
the  investigations  of  pure  science  and  the  application  of  such  dis- 
coveries to  the  solution  of  practical  problems.  The  significance 
for  man  of  the  problems  outlined  in  this  chapter  and  their  bearing 
upon  the  progress  of  social  development  have  been  discussed  in 
the  final  chapter  of  the  book. 

Save  insects  which  moreover  are  primarily  terrestrial  forms,  no 
t>pe  of  fresh-water  life  has  developed  to  the  diversity  and  com- 
plexity attained  by  the  same  type  in  the  ocean.  Yet  each  type 
has  achieved  a  variety  well  illustrated  in  the  subsequent  chapters. 
Only  a  few  of  those  that  occur  in  the  ocean  are  unrepresented  in 
fresh  water  and  even  strictly  terrestrial  groups  like  the  mammals 
and  flowering  plants  or  aerial  forms  Like  birds  have  their  aquatic 
representatives.  In  subsequent  chapters  each  of  these  groups  is 
discussed  from  the  biological  standpoint  and  in  its  especial  rela- 
tions to  fresh-water  life  as  well  as  with  regard  to  its  relative  impor- 
tance as  a  factor  in  the  fresh-water  flora  and  fauna. 

The  records  of  science  contain  only  scanty  references  to  the 
t>^es  of  fresh-water  life  and  their  distribution  on  the  North  Amer- 
ican continent,  and  regarding  all  other  continents  save  one  the 
records  are  even  more  fragmentary.     Of  Europe  alone  is  the  in- 


INTRODUCTION  13 

formation  adequate  to  outline  a  picture  of  the  life  in  fresh  water. 
A  comparison  of  the  records  shows  conspicuously  the  uniformity 
of  fresh-water  life  on  the  surface  of  the  globe,  especially  among 
plankton  organisms.  Many  of  the  forms  discussed  on  later  pages 
are  identical  with  those  that  occur  in  Europe  and  many  more  are 
closely  related  species.  The  uniformity  noted  is  not  confined  to 
Europe  and  North  America,  but  extends,  within  the  limits  of  records 
already  made,  to  other  continents  also  and  even  to  the  islands  of 
the  sea.  It  is  most  striking  perhaps  among  the  lowest  groups 
as  was  emphasized  by  Schewiakoff  for  Protozoa. 

This  uniformity  is  due  in  part  at  least  to  the  ease  of  dispersal 
that  the  lower  forms  in  the  fresh-water  fauna  and  flora  enjoy. 
They  uniformly  have  hard-shelled  resting  spores,  gemmules,  or 
eggs  which  are  very  resistant  to  adverse  conditions,  and  are  pro- 
duced in  enormous  numbers.  These  structures  are  carried  from 
point  to  point  on  the  feet  of  birds  and  other  migrating  animals 
and  are  blown  about  in  the  dust  until  suitable  conditions,  e.g.j 
temperature  and  moisture,  incite  development  and  the  beginning  of 
a  new  life  cycle. 

Fresh-water  life  includes  both  plant  and  animal  organisms  of 
various  types.  The  number  of  groups  represented  among  the  plants 
is  not  so  great  as  the  animals  furnish.  For  details  on  individual 
groups  the  student  is  referred  to  the  appropriate  chapter.  The 
following  plant  groups  are  found  in  fresh  water: 
Schizomycetes  Lowest  type  of  plant  life  in  the  water;    either 

or  Bacteria  saprophytic  or  parasitic  in  habit;   found  in  great 

variety  in  different  sorts  of  aquatic  environment. 
For  a  general  discussion  of  their  relations  to 
fresh  water  consult  Chapter  IV,  page  90. 
Algae  Characteristic    and    abundant    aquatic    plants, 

nearly  all  free-living,  found  in  all  kinds  of  water 
bodies;  represented  by  a  great  variety  of  genera 
and  species. 

For   Cyanophyceae  or  Blue-Green  Algae,  see 
Chapter  V,  page  100. 

For  other  classes  of  Algae  see  Chapter  VI,  page 
11^. 


14  FRESH-WATER   BIOLOGY 

Higher  Plants  Among   these  plants  which   are   more   typically 

land  organisms,  a  few  species  of  various  sorts  have 
become  a  part  of  the  fresh-water  flora.     In  this 
change  they  have  undergone  important  modifica- 
tions adapting  them  to  an  aquatic  existence.     No 
synoptic  treatment  of  these  forms  has  been  at- 
tempted. 
For  general  biological  relations   involved   see 
Chapter  VII,  page  178. 
Animals  are  represented  in  fresh  water  by  many  more  types  and 
varieties  than  are  plants.     A  brief  outline  of  the  various  animal 
groups  indicates  in  general  the  part  played  by  each  in  aquatic  life 
and  will  serve  to  correlate  the  various  chapters  dealing  with  in- 
dividual groups.     Zoologists  are  not  agreed  as  to  the  number  and 
rank  of  the  subdivisions  of  the  animal  kingdom  which  should  be 
recognized;    and  other  texts  will  show  some  variations  from  the 
system  used  here.     The  student  should  bear  in  mind  that  the  order 
in  the  printed  text  does  not  express  the  relationship  between  higher 
and  lower  groups  and  no  arrangement  in  a  hnear  series  can  show 
that  relationship.    The  phyla  are  indicated  by  full-faced  type. 
Protozoa  Characteristic  water-hving  forms  with  numerous 

or  Single-  parasitic   t\T)es;    represented  in  fresh  water  by 

celled  Animals  .      ^  ^,     .         ,  .  4-    u      j 

many  species  frequently  found  m  great  abundance; 

in  all  regions  and  in  all  types  of  water  bodies.     The 

following  four  sub-phyla  are  usually  recognized. 
Sakcodina  The  amoeboid  Protozoa  furnish  both  free-Uving 

and  parasitic  species. 

For  the  former  see  Chapter  VIII,  page  210. 
Mastigophora       Flagellate  Protozoa  include  both  free-living  and 

parasitic   species;     forms   of    the   first   type   are 

treated  in  Chapter  IX,  page  238. 
Infusoria  Ciliate  Protozoa  include  both  free  and  parasitic 

species. 

For  the  former  see  Chapter  IX,  page  271. 
Sporozoa  Exclusively  parasitic   forms;    certain   types   are 

abundant    in    fresh-water    animals    everywhere. 

North  American  forms  almost  unknown.     Group 

not  treated  in  this  book. 


INTRODUCTION 


15 


Porifera 
or  Sponges 


Coelenterata 


Echinodermata 


Platyhelminthes 
or  Flatworms 


TURBELLAEIA 

OR  Feee-living 
Flatworms 


Trematoda 
OR  Flukes 


Cestoda 
OR  Tapeworms 


Nemertina 


Nemathelminthes 
or  Round- 
worms 


Preeminently  marine;  fresh-water  bodies  shelter 
a  considerable  number  of  characteristic  siliceous 
forms  all  embraced  in  a  single  family,  SpongilUdae. 

These  are  described  in  Chapter  X,  page  301. 
A  group  manifesting  great  variety  and  abundance 
in  the  sea,  represented  in  fresh  water  by  a  very  few 
widely  scattered  types,  both  polyps  and  medusae, 
all  belonging  to  one  class,  the  Hydrozoa;  other 
classes  confined  to  the  sea. 

For  Hydrozoa  see  Chapter  XI,  page  316. 
Includes  crinoids,  brittle-stars,  starfish,  sea-ur- 
chins, and  sea-cucumbers;  not  represented  in  fresh 
water  by  a  single  known  species. 
Four  classes  are  recognized,  all  of  which  furnish 
important  representatives  to  the  fresh-water 
fauna. 

Common  in  salt  and  fresh  waters;  species  found 
in  the  latter  generally  insignificant  in  size.  A  few 
are  terrestrial  in  moist  environments. 

See  Chapter  XII,  page  323. 
All  species  parasitic;   many  in  or  on  fresh-water 
animals;     with    developmental    stages,    embryos 
(miracidia)  and  larvae  (cercariae)  that  occur  free- 
swimming  in  fresh  water. 

See  Chapter  XIII,  page  369. 
Exclusively  parasitic  forms.     Adults  common  in 
fresh-water  vertebrates;   developmental  stages  in 
various   aquatic   animals,    mostly   invertebrates; 
rarely  with  a  free-swimming  embryonic  stage. 

See  Chapter  XIII,  page  424. 
Mostly  marine;    a  very  few  species  of  small  size 
and   simple   organization   widely   distributed   in 
fresh  water. 

See  Chapter  XIV,  page  454. 
A  confused  group  of  three  classes  showing  little 
similarity  in  structure  and  associated  in  a  single 
phylum  largely  as  a  matter  of  convenience.     All 
are  well  represented  in  the  fresh-water  fauna. 


i6 


FRESH-WATER    BIOLOGY 


Nematoda 
OR  True  Round- 
worms 


GORDIACEA 

OR  Hair  Snakes 


ACANTHOCEPHALA 

OR  Thorny- 
headed  Worms 


Trochelminthes 
or  Trochal 
Worms 

Rotatoria 
OR  Wheel 

Animalcules 


Gastrotricha 


Coelhelminthes 
(Annelida) 
or  Segmented 
Worms 

Chaetopoda  or 
Bristle  Worms 


HiRUDINEA 

OR  Leeches 


Both  free  and  parasitic  forms  common  in  all  sorts 
of  environments;  free-living  species  most  abun- 
dant in  fresh  waters  and  in  moist  soils;  parasitic 
species  common  in  fresh-water  hosts. 

For   free-living   Nematoda,   see   Chapter   XV, 

page  459- 

For   parasitic   Nematoda,    see   Chapter   XVI, 

page  510. 
Parasitic  in  young  life  in  insects;  adult  stage  free- 
living  in  fresh  water. 

See  Chapter  XVI,  page  535. 
Exclusively  parasitic,  without  trace  of  alimentary 
system.     In  many  fresh-water  hosts.     Adults  in 
vertebrates;     larval    forms    imperfectly    known, 
parasitize  invertebrates. 

See  Chapter  XVI,  page  542. 
Among   the   most   characteristic   of   aquatic   or- 
ganisms.    Favorite    objects   of    study   with    the 
early  microscopists. 

Microscopic  free-Uving  forms,  very  rarely  para- 
sitic. Abundant  in  fresh- water  bodies  of  all  sorts; 
rare  in  the  sea. 

See  Chapter  XVII,  page  553. 
Minute  free-living  forms.    Abundant  in  fresh  water 
to  which  the  group  is  limited.    Imperfectly  known. 

See  Chapter  XVIII,  page  621. 
Two  classes  in  fresh  water  both  well  represented; 
other  classes  exclusively  marine. 

One  sub-class  (Polychaeta)  confined  to  the  sea 
save  for  rare  types  in  fresh-water  bodies  near  the 
ocean;  the  other  sub-class  (OHgochaeta)  found 
mostly  in  fresh  water  and  on  land. 

See  Chapter  XIX,  page  632. 
Both  free-living  and  parasitic  species,  the  former 
mostly  in  fresh  water  with  a  few  species  also  on 
land  in  moist  regions;  rarely  marine,  as  ectopara- 
sites of  fishes. 

See  Chapter  XX,  page  646. 


INTRODUCTION 


17 


Arthropoda 


Crustacea 


ARACHNroA 


Insecta 


Tentaculata 

Bryozoa 
OR  Moss 
Animalcules 


Three  of  the  five   classes  usually  recognized  are 
found  in  fresh  water. 

Only  one  sub-class,  Cirripedia  or  Barnacles  fur- 
nishes no  fresh-water  representatives.     The  others 
are   well   represented  in   the  fresh-water  fauna. 
With  few  exceptions  free-living  forms. 
For  Phyllopoda  see  Chapter  XXI,  page  661. 
For  Cladocera  see  Chapter  XXII,  page  676. 
For  Copepoda  see  Chapter  XXIII,  page  741. 
For  Ostracoda  see  Chapter  XXIV,  page  790. 
For  Malacostraca  see  Chapter  XXV,  page  828. 
Chiefly    terrestrial    with    some    parasitic    forms. 
One  or  two  spiders  have  secondarily  invaded  fresh 
water.  ^   Among  the  mites  one  sub-order,  the  Hy- 
dracarina,    is    exclusively    aquatic.     Nearly    all 
species  inhabit  fresh  water. 

For  Hydracarina,  or  Water  Mites,  see  Chapter 
XXVI,  page  851. 
Two    aberrant    groups    often    attached    to    this 
class  are  the  following: 

Linguatulida,  exclusively  parasitic,  occur  rarely 
in  fresh-water  hosts. 

Tardigrada,  minute  free-living  forms  known  as 
water  bears;  a  few  species  not  uncommon  in 
fresh  water. 
Typically  land  animals  which  in  some  cases 
(especially  for  developmental  stages)  have  gone 
into  fresh  water  and  manifest  secondary  adapta- 
tions to  aquatic  life. 

See  Chapter  XXVII,  page  876. 
Of  two  classes,  one,  the  Brachiopoda,  is  exclusively 
marine.     The  other  follows: 
Sessile   animals,   nearly  always   colonial;    exclu- 
sively free-living;    chiefly  marine  but  with  some 
fresh-water  forms  widely  distributed. 
See  Chapter  XXVIII,  page  947. 


l8  FRESH-WATER   BIOLOGY 

MoUusca  Of  the  five  classes  commonly  recognized,  three 

which  are  relatively  small  are  not  represented  in 
fresh  water.  Two  main  classes  Lamellibranchia 
(bivalves)  and  Gastropoda  (univalves)  common  in 
fresh  waters,  widely  distributed. 

See  Chapter  XXIX,  page  957. 
Chordata  Three    of    the    four    sub-phyla    are    exclusively 

marine  in  distribution;  but  the  fourth,  the  Verte- 
brata,  which  is  also  the  largest  and  best  known, 
plays  an  important  part  in  the  fresh-water  fauna. 
No  attempt  has  been  made  to  give  a  synopsis  of 
fresh-water  vertebrates. 

For  a  discussion  of  biological  relations  of  the 

Vertebrata  to  aquatic  existence  see   Chapter 

XXX,  page  102 1. 

IMPORTANT  GENERAL  REFERENCES 

The  literature  on  the  subject  is  so  extensive  that  only  the  most  important 
and  essential  items  are  listed  below.  Many  general  papers  of  marked  value 
had  to  be  omitted  for  lack  of  space.  All  contributions  bearing  on  a  special 
phase  of  the  subject  have  been  listed  at  the  end  of  the  chapter  on  that  topic. 
Longer  bibliographies  appear  in  Steuer,  Wesenberg-Lund,  Needham,  and  others. 
In  general  only  the  latest  or  most  general  paper  of  a  given  author  is  listed  here. 

Antipa,  Gr.     191 2.     Das    Ueberschwemmungsgebiet    der    unteren    Donau. 

Bukarest.     496  pp.,  3  charts,  23  pi. 
Apstein,  C.     1896.     Das  Siisswasserplankton.     Methode  und  Resultate  der 

quantitativen  Untersuchungen.     Kiel  und  Leipzig.     200  pp.,  5  pi. 
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Washn.,  Pub.  67;  114  pp. 
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Bur.  Fish.,  23:  525-609. 
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Internationale  Revue  der  gesammten  Hydrobiologie  und  Hydrographie. 
R.  Woltereck.     Leipzig  since  1908. 

Transactions  of  the  American  Microscopical  Society.  T.  W.  Galloway,  Ripen, 
Wis.    Since  18S0. 


CHAPTER   II 
CONDITIONS    OF    EXISTENCE 

By  victor  E.  SHELFORD 

Assistant  Professor  of  Zoology,  University  of  Illinois.     Biologist  Illinois  State  Laboratory 
of  Natural  History 

Conditions  of  existence  are  of  importance  only  in  so  far  as  they 
affect  the  life  and  death  processes  of  organisms.  The  present 
knowledge  of  such  effects  is  far  from  complete  and  there  is  justifi- 
cation for  noting  in  detail  only  those  conditions  which  observation 
and  experiment  have  shown  to  be  important.  Nevertheless  if  no 
scientific  observations  or  experiments  had  ever  been  made  upon 
organisms,  water  and  its  properties  would  occupy  an  important 
place  in  a  discussion  of  conditions  of  existence  of  aquatic  life. 

Water  possesses  certain  thermal  properties  and  certain  charac- 
teristic relations  to  other  substances  which  put  it  in  a  class  quite 
apart  from  the  vast  majority  of  chemical  substances  (Henderson). 
The  thermal  properties  of  water  are  such  as  to  make  it  a  very  fit 
condition  of  existence  for  organisms.  In  raising  the  temperature 
of  water  one  degree  centigrade,  several  times  as  much  heat  is  ab- 
sorbed as  in  the  case  of  various  other  common  substances,  except 
living  matter  itself.  This  property  moderates  both  winter  and 
summer  temperatures  to  which  aquatic  organisms  are  subjected 
(Birge).  Ice  melts  at  fully  a  hundred  degrees  lower  than  the  fus- 
ing point  of  other  common  environmental  substances  and  the  latent 
heat  of  melting  ice  is  proportionately  high.  Thus  in  melting,  ice 
absorbs  large  quantities  of  heat  and  in  freezing  water  gives  off  this 
heat  again.  This  further  modifies  the  aquatic  cHmate  as  compared 
with  one  that  might  be  afforded  by  some  other  substance.  The 
latent  heat  of  evaporation  of  water  is  also  relatively  high  and  this 
tends  to  prevent  the  evaporation  of  all  the  water  from  the  surface 
of  the  land. 

The  expansion  of  water  on  freezing  is  one  of  its  most  important 


2  2  FRESH-WATER   BIOLOGY 

properties.  If  water  contracted  on  freezing  ice  formed  at  the  sur- 
face would  sink  to  the  bottom,  more  would  be  formed  and  accu- 
mulate at  the  bottom  in  winter.  Here  it  would  thaw  very  slowly 
or  not  at  all  in  summer  and  the  entire  surface  of  the  earth  would 
thus  quickly  become  refrigerated.  The  expansion  of  water  on  heat- 
ing is  also  very  important  as  it  is  responsible  for  the  setting  up  of 
currents  which  ventilate  the  aquatic  environment. 

Water  is  by  far  the  most  general  solvent  for  other  substances. 
No  other  Uquid  will  dissolve  so  many  common  substances.  Though 
it  is  one  of  the  most  stable  and  inert  compounds,  like  salts  in  solu- 
tion, it  dissociates  into  parts  or  ions  and  a  very  small  proportion 
of  pure  water  is  in  the  form  of  H"*"  (the  cation  bearing  a  positive 
electric  charge)  and  0H~  (the  anion  bearing  a  negative  electric 
charge).  These  ions  are  known  respectively  as  hydrogen  and 
hydroxyl  ions.  At  25°  C.  1000  grams  of  pure  water  contain 
0.000,000,1  gram  of  ionized  hydrogen  and  0.000,001,7  gram  of  ionized 
hydroxyl.  Salts  in  solution  in  water  are  ionized.  For  example 
common  salt,  NaCl,  exists  chiefly  as  Na"^  and  Cl~.  Henderson 
states  that  solutions  in  water  are  the  best  source  of  ions.  The 
variety  and  complexity  of  the  environment  of  aquatic  organisms 
and  the  number  and  variety  of  chemical  reactions  are  increased  by 
the  presence  of  ions. 

As  compared  with  air,  water  is  much  denser,  being  773  times  as 
heavy.  Gases  and  other  solutes  are  presented  to  organisms  in 
solution  and  gases  need  not  be  taken  into  solution  by  surfaces 
moistened  by  body  fluids  as  in  the  case  of  land  organisms.  The 
diffusion  of  gases  is  less  rapid  in  water  than  in  air.  Some  food 
substances  are  in  solution  in  water;  many  food  organisms  float  in 
it  on  account  of  its  great  density.  This  enables  some  aquatic 
animals  to  rest  in  one  position  and  secure  food  without  effort. 

Physical  and  Chemical  Conditions 

Physical  conditions  can  be  separated  from  chemical  conditions 
only  arbitrarily.  Combinations  of  the  various  physical  conditions 
in  water  may  be  included  under  the  term  physiography.  Physi- 
ography in  the  broad  sense  includes  topography  of  the  land  asso- 


CONDITIONS   OF   EXISTENCE  23 

dated  with  aquatic  environments,  size  and  texture  of  surface  ma- 
terials, direction  of  prevailing  winds,  etc. 

In  streams  the  strength  of  the  current  is  a  function  of  volume  of 
water  and  slope  of  stream  bed.  The  amount  of  sediment  carried 
and  the  size  of  the  sediment  particles  is  determined  by  the  strength 
of  the  current  and  by  the  character  of  the  materials  eroded.  The 
character  of  the  stream  floor,  the  ventilation  of  the  environment, 
and  hence  its  gaseous  content  as  well  as  turbidity,  are  determined 
by  the  same  factors.  All  these  factors  combined  comprise  impor- 
tant conditions  of  existence  which  while  they  influence  organisms  are 
often  so  difflcult  to  analyze  into  constituent  controlUng  factors  that 
for  ordinary  purposes  it  is  better  to  lump  them  together  under  the 
head  of  physiographic  conditions  in  streams.  Fishes  and  mollusks 
migrate  upstream  during  floods  and  downstream  during  drought 
periods.  Thus  different  species  of  fishes  in  a  number  of  streams 
about  equally  accessible  to  Lake  Michigan  but  differing  in  size  and 
age  as  shown  in  Fig.  2  are  very  definitely  related  to  the  longitudinal 
conditions  in  the  various  streams,  each  fish  species  penetrating  up 
stream  to  a  point  characterized  by  certain  physiographic  conditions, 
regardless  of  the  size  of  the  stream  as  a  whole  (compare  Table  I 
with  Fig.  2).  An  analysis  of  the  physical  factors  to  which  the 
fishes  respond  and  which  thus  determine  the  locahty  they  occupy 
would  be  a  very  intricate  task  but  by  a  simple  method  of  physio- 
graphic analysis  the  differences  in  their  ecological  constitution  is 
clearly  brought  out.  Thus  important  features  of  conditions  of  exist- 
ence may  be  determined  by  physiographic  analysis  and  the  classifi- 
cation of  streams  should  be  determined  by  physiographic  age  and 
physiographic  conditions. 

Conditions  of  existence  in  lakes  and  ponds  are  markedly  influ- 
enced by  physiographic  conditions.  High  surrounding  country 
broken  into  hills  and  valleys  influences  the  action  of  winds  on  the 
surface.  Wind  is  important  in  determining  circulation.  The  sur- 
rounding topography  determines  the  carrying  power  of  streams  and 
thus  the  amount  of  sediment  carried  into  lakes.  The  amount  of 
sediment  determines  the  depth  of  light  penetration. 

The  depth  of  lakes  and  ponds  is  definitely  related  to  physio- 
graphic conditions.     Coastal  lakes  are  usually  shallow  with  sandy 


24 


FRESH-WATER   BIOLOGY 


or  muddy  bottom.  Morainic  lakes  are  usually  relatively  deep 
with  clay  bottoms  and  sides.  Solution  lakes  and  ponds  of  limestone 
regions  usually  have  abrupt  rocky  sides. 


TABLE   I 

Showing  the  Distribution  of  Fish  (Nomenclature  after  Forbes  and 
Richardson)  in  Three  Illinois  Streams  at  the  Times  Indicated 

(The  observations  on  Pettibone  Creek  were  repeated  in  four  succeeding  years 
with  the  same  results.     Stars  indicate  presence;  numbers  refer  to  Fig.  2) 


Name  of  stream  and  common 
name  of  fish 

Date  and  scientific  name 

I 

* 
* 

? 
* 

2 

* 

* 
* 

* 
* 

3 

* 
* 
* 

* 
* 
* 
* 

* 
* 
* 

4 

* 

* 
* 
* 
* 
* 

* 
* 
* 
* 

* 
* 
* 
* 

5 

* 

* 
* 

6 

* 
* 
* 

7 

Glencoe  Brook 

August,  1907 

Semotiliis  atromaculatus .  . 
1007—8                           .    ... 

Horned  dace 

County  Line  Creek 

Horned  dace          .    ... 

Semotiliis  atromaculatus.. 

Rhinichthys  atronasus.  .  .  . 

Boleosoma  nigrum 

Pimephales  promelas 

Pimephales  notatus 

Catostomus  commersonii. . 
September,  1909,  and  April, 
1910 

Semotiliis  atromaculatus .  . 

Chrosomtis  erythrogaster. . 

Rhinichthys  atronasus.  .  .  . 

Boleosoma  nigrum 

Catostomus  commersonii. . 
September,  1909 

Semotiliis  atromaculatus. . 

Chrosomus  erythrogaster. . 

Rhinichthys  atronasus.  .  .  . 

Catostomxis  commersonii. . 

Pimephales  notatus 

Esox  vermiculatus 

Lepomis  pallidus 

Micropterus  salmoides  — 
Esox  lucius 

Black-nosed  dace 

Johnny  darter 

Blackhead  minnow 

Blunt-nosed  minnow.  . 

Common  sucker 

Pettibone  Creek  ^ 

Red-bellied  dace 

Black-nosed  dace 

Johnny  darter 

Common  sucker 

Bull  Creek-Dead  River. 
Horned  dace              .  .  . 

Red-bellied  dace 

Black-nosed  dace 

Common  sucker 

Blunt-nosed  minnow.  . 

Little  pickerel 

Bluegill 

Large-mouthed     black 
bass                    .... 

Pike                

Crappie      

Pomoxis  annularis 

Moxostoma  aureolum 

Erimyzon  sucetta 

Abramis  crysoleucas 

Notropis  cornutus 

Red-horse 

Chub-sucker 

Golden  shiner 

Common  shiner 

Cayuga  minnow 

Tadpole  cat 

Schilbeodes  gyrinus 

The  lower  part  of  Pettibone  Creek  has  been  destroyed  by  the  United  States   Naval  School, 
otherwise  the  table  would  include  the  records  for  a  point  5  and  perhaps  a  point  6.  but  probably  not  7. 

Physical  factors  include  bottom,  currents,  light,  temperature, 
density,  pressure,  viscosity,  etc. 

The  size  of  bottom  materials  is  an  important  condition  of  exist- 
ence.    In  streams  the  current  sorts  the  materials,  leaving  the  coars- 


ffiMir 


CONDITIONS  OF   EXISTENCE 


25 


est  in  the  swiftest  current  and  the  finest  in  the  most  sluggish  cur- 
rent. In  the  curves  of  streams  the  current  is  usually  swiftest  on 
the  outside  and  most  sluggish  on  the  inside.     Dift'erent  animals 


JjAKE      MICHIGAN 

Fig.  2. 
Diagrammatic  arrangement  of  four  streams  flowing  into  Lake  Michigan.  The  streams  are  mapped  to 
a  scale  of  one  mile  to  the  inch,  and  the  maps  are  placed  as  closely  together  as  possible  in  the  diagram. 
The  intermediate  shore  lines  are  shown  in  broken  lines  which  bear  no  relation  to  the  shore  lines  which 
exist  in  nature.  Toward  the  top  of  the  diagram  is  west.  Each  number  on  the  diagram  refers  to  the  pool 
nearest  the  source  of  the  stream  which  contains  fish,  as  follows:  i,  homed  dace  (Semotilus  alromaculatiis) ; 
2,  red-bellied  dace  {Chrosomus  erythrogaster)  \  3,  black-nosed  dace  {Rhinichthys  atronasus);  4,  the  suckers 
and  minnows;  5,  the  pickerel  and  blunt-nosed  minnow;  6,  sunfish  and  bass;  7,  pike,  chub  sucker,  etc. 
The  bluff  referred  to  is  about  60  feet  high.  The  stippled  area  is  a  plain  just  above  the  level  of  the  lake. 
(After  Shelford.) 

tend  to  occupy  the  different  kinds  of  bottom  materials  (Fig.  3). 
Thus  the  differentiation  of  bottom  constitutes  an  important  differ- 
entiation of  conditions  of  existence. 

The  bottom  of  a  swift  stream  eroding  sandy  soil  is  very  unstable 
and  the  fauna  very  sparse.  Such  streams  are  essentially  aquatic 
deserts  and  only  a  few  burrowers  are  able  to  live  in  them.  Sandy 
bottomed  streams  with  sluggish  current  have  a  luxuriant  fauna 
of  burrowers  and  flora  of  rooted  vegetation.  Rocky  and  stony 
streams  have  rich  faunas  of  clinging  and  hiding  animals. 

In  lakes  and  ponds  the  importance  of  bottom  is  determined  by 
the  strength  of  wave  action  and  the  amount  of  current.  The 
fine  bottom  materials  around  the  margin  of  a  large  lake  are  con- 
stantly moved  about;  the  particles  grind  upon  one  another  mak- 
ing the  presence  of  bottom  organisms  impossible.     Thus  the  sandy 


26 


FRESH-WATER    BIOLOGY 


shores  of  the  Great  Lakes  down  to  a  depth  of  eight  feet  or  more  are 
usually  almost  entirely  without  bottom  organisms. 

The  character  of  terrigenous  bottom  is  an  important  condition  of 
existence  chiefly  where  current  or  wave  action  is  strong  and  becomes 
of  httle  or  no  importance  where  there  is  no  movement,  as  in  the 


■'.'.'  •■.■'•.■'-■•*■"* 


Fig.  3. 
The  form  of  bottom  and  size  of  bottom  materials  in  a  cross  section  of  the  North  Branch  of  the  Chicago 
River  with  distribution  of  animals,  a  to  d  natural  size,  a,  burrowing  may-fly  nymph  (Ilexagenia  sp.); 
b,  small  bivalve  {Spharium  slamineum),  two  individuals,  two  views;  c,  viviparous  snail  {Campeloma  in- 
tegrum), seen  from  two  sides;  d,  the  long  river  snail,  young  and  full  grown  (Pleurocera  elevatum) ',  e,  cross 
section  of  the  stream  with  reference  to  a  curve  (/).     (Original.) 

bottom  of  one  of  the  Great  Lakes.  However,  bottoms  of  soft  muck 
containing  putrescible  organic  matter  occur  in  the  absence  of  current 
and  constitute  a  condition  of  existence  sharply  differentiated  from 
terrigenous  bottoms  because  they  can  support  only  certain  types  of 
organisms,  mainly  anaerobes,  and  but  few  of  these.  Many  aquatic 
animals  use  the  bottom  materials  in  the  construction  of  their  cases, 
nests,  etc.  Thus  the  caddis  worms  (certain  species  of  Mollana 
and  Geora)  build  cases  of  sand  grains  weighted  at  the  sides  by  small 
pebbles.  The  horned  dace  and  several  other  fishes  associated  with 
it  use  pebbles  to  build  their  nests.  The  pebbles  must  be  of  a  cer- 
tain average  size.     Many  animals  form  associations  (memory)  with 


CONDITIONS   OF   EXISTENCE 


27 


reference  to  certain  stones  or  pebbles  under  or  near  which  they  live 
(e.g.,  mayfly  nymphs)  and  thus  work  out  simple  homing  paths. 

As  has  been  stated,  in  streams  the  rate  of  flow  is  determined  by 
volume  of  water  and  slope  of  stream  bed.  In  a  comparatively 
straight  stream  the  current  is  swiftest  in  the  center  at  the  top  and 
least  swift  at  the  sides  near  the  bottom;  the  center  of  the  stream 
bed  has  a  current  intermediate  between  the  two.  Thus  sluggish 
portions  of  streams  like  the  Fox  River  (lUinois)  may  be  swift 
enough  at  the  bottom  of  the  center  to  support  some  swift  stream 
animals  such  as  Hydro  psyche  and  Heptageninas.  There  are  back 
eddies  about  stones  and  other  obstructions  so  that  currents  in 
streams  are  somewhat  irregular. 

In  lakes  circulation  is  determined  by  wind  and  differences  in 
temperature.  A  lake  which  is  equal  in  temperature  throughout 
has  a  complete  circulation  (Fig.  4  A).  The  wind  indicated  by  the 
arrow  (W)  tends  to  pile  the  water  up  on  one  side.     To  compensate 


..<m 


Fig.  4. 

The  circulation  of  the  water  (A)  in  a  lake  of  equal  temperature;  (B)  in  a  lake  of  unequal  tempera- 
ture. W  represents  the  direction  of  the  wind;  E,  epilimnion;  T,  thermocline;  H,  hypolimnion. 
(After  Birge.) 


for  this  currents  are  started  downward  along  the  shore  and  a  cir- 
culation across  the  bottom  and  upward  on  the  other  side  is  initiated. 
Very  shallow  lakes  and  deeper  lakes  in  the  cold  months  of  the  year 
have  a  complete  circulation.  Lakes  of  unequal  temperature  are 
very  different.  For  example  a  deep  lake  has  a  uniform  tempera- 
ture for  a  time  in  the  spring  just  after  the  ice  melts,  complete  cir- 
culation takes  place  and  the  bottom  waters  are  aerated.     As  the 


28  FRESH-WATER   BIOLOGY 

sun  warms  the  surface  waters  they  become  so  much  lighter  than 
the  deeper  colder  waters  that  the  currents  set  up  to  compensate 
for  the  piling  up  of  the  water  by  the  wind  can  no  longer  flow  to 
the  bottom  and  a  superficial  circulation  is  accordingly  set  up 
(Fig.  4  B).  A  distinct  thermocUne  (T)  is  thus  established.  The 
epilimnion  (E)  is  warm  and  constantly  aerated  by  circulation  and 
the  hypolimnion  ill)  is  stagnant.  In  the  autumn  as  the  water 
gradually  cools  the  thermocline  gradually  migrates  to  the  bottom 
and  the  earlier,  complete  circulation  (Fig.  4  A)  is  again  established. 

In  addition  to  the  general  circulation,  waves  and  their  action 
must  be  considered.  As  was  noted  in  connection  with  bottom,  the 
shifting  of  fine  bottom  materials  eliminates  most  animals  from 
sandy  shores.  On  rocky  shores  in  large  lakes  are  representatives 
of  some  of  the  same  animal  species  found  in  swift  streams.  The 
alternating  current  does  not  appear  to  exclude  many  such  species. 
In  small  lakes  and  ponds  the  small  wave  action  removes  decaying 
organic  matter  and  thus  renders  portions  of  the  shores  suitable 
for  animals  requiring  or  preferring  a  terrigenous  bottom.  The 
location  of  such  shores  which  are  usually  sandy  is  determined 
largely  by  the  form  of  the  lake  or  pond  and  the  direction  of  pre- 
vailing winds  and  inflow  of  water. 

Currents  influence  animals  directly  by  bringing  pressure  against 
parts.  Sessile  animals  respond  to  currents  by  changes  in  growth 
•form.  But  few  fresh  water  sessile  animals  have  been  studied  in  this 
respect,  and  the  exact  character  of  such  responses  cannot  be  stated, 
though  sponges  and  polyzoa  are  known  to  vary  greatly.  Motile 
animals  as  a  rule  turn  with  their  heads  upstream  and  either  move 
against  the  current,  making  progress  upstream,  or  remain  in  one 
position  by  swimming  enough  to  maintain  themselves.  Fishes 
under  experimental  conditions  will  often  swim  against  a  current 
which  is  stronger  than  their  optimum  until  they  are  exhausted. 
Many  fishes  orient  themselves  by  visual  impressions  of  the  bottom 
as  they  float  downstream.  Others  appear  to  orient  by  differences 
in  pressure  on  the  two  sides  of  the  body  or  by  rubbing  against  the 
bottom  as  they  float  down.  Sight  is  probably  ineffective  during 
floods  on  account  of  sediment.  Current  is  essential  to  the  spinning 
of  the  characteristic  cocoons  and  cases  of  some  insects  Hving  in 


CONDITIONS   OF    EXISTENCE  29 

rapids.  They  make  a  shapeless  mass  without  it.  A  few  animals 
require  very  complete  aeration  or  they  die  very  quickly.  Suckers 
appear  to  die  from  lack  of  oxygen  while  the  rainbow  darter  adds 
something  to  the  water  in  which  it  lives  which  is  not  removed  by 
artificial  aeration  and  which  kills  the  fish  unless  the  number  of  fishes 
is  small  or  the  water  changed  often. 

Light  penetrates  clear  water  to  great  depths.  During  the  cruise 
of  the  Michel  Sars  the  penetration  of  sufficient  light  to  markedly 
affect  the  most  sensitive  photographic  plates  in  80  min.  was  found 
at  a  depth  of  1000  meters  (latitude  31°  20',  June  5-6.  Sun  nearly 
over  head;  for  methods  see  Murray  and  Hjort).  No  effect  was 
obtained  at  1700  meters  with  an  exposure  of  two  hours.  Light 
sufficient  to  affect  the  plates  in  2  hours  lies  somewhere  between 
1000  and  1700  meters.  There  were  many  rays  of  all  kinds  at  100 
meters  but  least  of  the  red.  Though  penetration  is  rarely  as  great 
in  fresh  water  as  in  the  sea,  light  may  possibly  penetrate  to  the 
bottom  of  Lake  Baikal  which  is  the  deepest  fresh  water  lake  known 
(1300  to  1700  meters  are  reported). 

In  temperate  latitudes  light  does  not  penetrate  so  far  vertically 
because  it  enters  the  water  obliquely.  The  depth  of  penetration 
can  easily  be  calculated  for  any  latitude  or  season  from  the  angle 
of  declination  of  the  sun,  when  the  penetration  in  similar  water  is 
known  for  other  latitudes  and  seasons. 

The  most  important  factor  limiting  the  penetration  of  light  into 
fresh  water  is  turbidity.  Forel  found  the  light  penetration  in 
Lake  Geneva  (Switzerland)  greatest  when  the  lake  contained  least 
sediment.  Table  II  gives  the  depth  of  light  penetration  in  Lake 
Geneva  in  March  when  it  is  clearest.  Forel  used  much  less  sen- 
sitive plates  than  were  used  on  the  Michel  Sars,  the  sun  was  much 
lower  in  the  horizon  and  the  locality  15  degrees  farther  north. 
Thus  Forel's  records  show  that  light  did  not  diminish  notably  in 
the  first  25  meters,  fell  off  gradually  in  the  second  25  meters  and 
then  dropped  off  rapidly  to  zero  for  his  plates  at  no  meters.  Fol 
and  Sarasin  with  more  sensitive  silver  salts  than  were  used  by  Forel 
found  that  light  reached  200  meters  in  winter.  It  is  altogether 
probable  that  the  plates  and  apparatus  of  the  Michel  Sars  would 
show  much  light  at  three  or  four  times  the  depth  given  by  Forel. 


30 


FRESH-WATER   BIOLOGY 


TABLE    II 

Showing  Depth  of  Light  Penetration  in  Lake  Geneva  (Switzerland)  and 

Conditions  Affecting  the  Same  in  Both  Lake  Geneva  (after 

Forel)  and  Lake  Michigan 

In  the  eighth  column  the  relative  results  are  given  in  seconds,  in  terms 
of  the  effect  on  the  photographic  plate,  of  exposures  to  the  sun. 


Lake  Michigan 


Rainfall 


Inches 


2.0 
2-3 
2-5 
2.7 
35 
3-7 


Centi- 
meters 


Velocity  of  wind 
at  noon 


Miles 
per 
hour 


Meters 

per 
second 


5-1 
5-2 
6.4 
6.9 

8.9 
9-4  I 
9.2! 

7.2  I 

7-7  I 
6.6  I 
6.6  1 
5-3   ! 


17 

8 

8. 

20 

0 

9- 

20 

4 

9- 

IQ 

4 

8. 

18 

3 

8. 

14 

4 

6. 

14 

6  i 

6. 

13 

4  ; 

6. 

16 

7 

7 

17 

6 

7 

19 

0 

8 

19 

■9 

8 

Month 


Lake  Geneva,  Switzerland 


Rainfall  and 
light 


Prec. 
in  cm. 


January. . 
, February. 
.March. .  .  . 

,  April 

.  May 

.June 

•July 

.August.  .  . 
.  September 
.October.  . 
.  November 
.  December 


Light 
limit  at 
depth  in 
meters 


87 
65 

72 

no 

.68 

.91 

75 

•.S9 

.08 

45 

.04 

.42 

50 

.  10 



■  4 

'5 

.  II 

1  . 

Light  and  depth 


Intensity 
of  light 
(March) 
at  depth 
in  next 
column 


Depth 


500  sec. 
500  sec. 
500  sec. 
400  sec. 
360  sec. 
120  sec. 

60  sec. 

25  sec. 

10  sec. 
2  sec. 
o  sec. 


0.0 
19.6 
25.2 
45-5 
55-5 
65.6 
75-6 
857 
95-8 
105.4 
115.6 


Little  work  on  the  depth  of  light  penetration  has  been  under- 
taken in  the  North  American  waters.  In  Table  II  the  rainfall 
and  wind  velocity  over  Lake  Michigan  are  shown  and  the  rainfall 
for  Lake  Geneva  (Switzerland).  The  greatest  light  penetration 
in  Lake  Geneva  comes  when  the  rainfall  is  low  and  when  the 
mountains  are  still  frozen.  The  Lake  Michigan  water  commission 
found  in  a  brief  period  of  study  that  the  greatest  turbidity  fell  in 
January,  February,  March,  and  April.  The  table  indicates  that 
this  is  in  months  with  high  wind  velocity.  The  great  rainfall  of 
the  spring  and  early  summer  months  tends  to  keep  Lake  Michigan 
turbid,  so  the  greatest  light  penetration  may  be  predicted  for  Aug- 
ust which  has  least  rain  and  least  wind. 

Various  streams  are  normally  so  muddy  that  light  cannot  be  ex- 
pected to  penetrate  more  than  a  few  feet  and  the  fauna  accordingly 
lives  in  very  faint  light.     Others,  as  for  example  streams  and  lakes 


CONDITIONS   OF    EXISTENCE  31 

in  some  of  the  western  mountains,  arc  very  clear  and  one  can  see 
to  depths  of  5  to  15  meters.  Depth  at  wliich  objects  may  be  seen 
is  measured  by  lowering  a  white  disc  20  cm.  in  diameter  known  as 
the  disc  of  Secchi. 

When  light  penetrates  water  the  red  rays  are  most  rapidly  ab- 
sorbed, then  orange,  yellow,  etc.  In  the  Michel  Sars  measure- 
ments there  were  scarcely  any  red  rays  at  500  meters,  one-half  the 
depth  at  which  hght  was  measured.  Fol  found  off  Nice  that  when 
down  in  30  meters  of  water  he  could  see  a  stone  7-8  meters  away  and 
a  bright  object  at  a  distance  of  25  meters.  Red  animals  looked 
black,  while  green  and  blue  green  algae  looked  quite  bright. 

In  water  there  is  no  dawn  or  twihght.  The  surface  of  the  water 
reflects  practically  all  the  light  when  the  rays  come  to  it  very 
obliquely.  Fol  found  that  in  10  meters  of  water  solar  Hght  dis- 
appeared quite  suddenly  long  before  sunset.  In  Funchal  Harbor 
(Madeira)  the  Prince  of  Monaco  used  Regnard's  apparatus  in  which 
a  film  is  moved  before  an  opening  by  clockwork,  and  found  that  at 
20  meters  in  March  the  day  lasted  9  hours  whereas  at  40  meters 
the  film  showed  the  effects  of  light  for  only  about  15  minutes  at 

2  P.M. 

Light  profoundly  influences  the  migrations  and  distribution  of 
animals  probably  largely  because  it  has  a  marked  effect  on  Kfe 
processes.  Unfortunately,  however,  with  the  exception  of  ultra- 
violet Ught  which  penetrates  the  atmosphere  into  low  altitudes  in 
minimal  amount,  very  little  is  known  of  the  actual  physiological 
effects  of  light.  Under  experimental  conditions  animals  usually 
avoid  or  select  the  blue  end  of  the  spectrum.  Red  usually  acts  as 
darkness  or  very  faint  Hght.  Thus  animals  hving  in  very  strong 
light  usually  accumulate  in  blue  or  violet  when  exposed  to  spectrum 
colors.  Animals  hving  in  darkness  collect  in  the  red.  Animals 
living  in  moderate  hght  usually  wander  about  throughout  the  spec- 
trum but  a  majority  congregate  in  the  blue.  Probably  animals 
are  affected  through  photo-chemical  reactions  which  are  brought 
about  most  often  by  the  blue  end  of  the  spectrum.  Daphnias 
select  the  brightest  part  of  the  spectrum  which  is  the  green  or  the 
yellow  for  most  organisms,  brightness  being  determined  by  some 
specific  effect  of  particular  wave  lengths  upon  the  light  recipient 


32 


FRESH-WATER   BIOLOGY 


organs.  Yellow  is  brightest  to  the  human  retina.  In  addition  to 
color  animals  react  to  direction  and  to  intensity  of  light.  Prob- 
ably the  majority  of  fresh-water  animals  react  more  strongly  to 
direction  than  to  intensity.  Hydro  psyche  and  Argia  do  not  react 
to  intensity  at  all  but  react  to  direction  very  sharply.  Experi- 
mental conditions  in  which  direction  away  from  source  accompanies 
a  sharp  decrease  in  intensity  gives  sharpest  reactions  with  most 
aquatic  animals. 

Animals  react  to  intensity  with  reference  to  an  optimum.  The 
optimum  usually  corresponds  to  the  usual  light  in  their  natural 
environments.  The  organism  may  often  be  modified  by  changes 
in  the  chemical  character  of  the  water,  or  even  by  rough  handling 
{Daphnia,  Ranatra),  so  that  it  selects  a  different  optimum,  or  re- 
verses its  reaction  to  direction  of  rays. 

Many  animals  react  to  shadows  or  small  areas  of  illumination. 
Thus  frogs  will  hop  to  a  shadow  in  the  middle  of  a  sunny  field  and 
Amblystoma  will  follow  a  person  along  a  sunny  road.  This  type 
of  behavior  is  doubtless  an  important  thing  under  water  but  has 
been  but  little  investigated. 

One  of  the  topics  which  has  absorbed  much  of  the  attention  of 
limnologists  is  the  daily  depth  migrations  of  certain  Crustacea. 
They  usually  accumulate  near  the  surface  at  night  and  in  deeper 
water  during  the  day.  The  causes  of  these  migrations  are  very 
complex  and  Hght  is  an  important  factor.  Dice  has  recently  dis- 
cussed the  matter  in  full.  Light  is  probably  important  in  confin- 
ing certain  animals  in  deep  water,  in  turbid  streams,  under  stones 
and  logs  and  in  caves,  ground  water,  etc. 

The  early  invention  of  the  thermometer  has  led  to  quite  com- 
plete investigation  of  temperature  and  an  over-estimation  of  its 
importance  in  the  direct  control  of  the  distribution  of  life  in  water. 
The  tendency  of  modern  investigation  is  to  weaken  the  belief  in 
its  direct  importance. 

Stream  temperatures  are  probably  about  the  same  at  the  various 
points  in  any  cross-section,  except  the  shallow  sluggish  margin  on 
warm  summer  days.  The  extent  to  which  daily,  seasonal,  and 
weather  fluctuations  in  atmospheric  temperature  afifect  a  lake  is 
determined  by  the  depth  and  size.     Small  lakes  with  incomplete 


CONDITIONS   OF   EXISTENCE 


33 


circulation  in  summer  are  cold  at  the  bottom,  being  heated  at  the 
surface  only  (Fig.  4  B).  Lake  Michigan  is  a  large  deep  lake  and 
none  of  the  seasonal  temperature  changes  extend  to  the  deepest 
parts  (Table  III).  In  summer  the  water  of  the  surface  is  warmed, 
but  if  the  vertical  circulation  is  complete  all  the  heat  in  the  waters 
flowing  downward  at  the  leeward  side  (Fig.  4  B)  must  be  absorbed 
above  no  meters  (Table  III)  when  the  temperature  of  maximum 
density  is  recorded.  These  are  chiefly  bottom  records  and  do  not 
therefore  represent  the  temperatures  at  the  same  level  in  the  open 
water,  especially  in  the  shallower  situations  where  the  sun's  energy 
is  distributed  through  a  thinner  layer  of  water.^ 


TABLE  III 


Temperature 

OF  Lake 

Michigan  (After  Ward) 

Temperature 
at  depth  in 
next  column 

Depth 

Date 

Hour  P.M. 
unless  stated 

Sky 

Tem- 
perature 
of  air 

Tem- 
perature 
at  sur- 
face 

"C. 

18.3 

16.7 

7.2 

7-5 

7-2 
5-2 

5-1 

4-2 
4-2 

°p 

64 
62 

44 
45 
44 
41 
41 
39 
39 

9 
0 

9 

5 
9 
3 

I 

5 
5 

Meters 

5-66 

11.32 

22.63 

32.06 

43  38 

55-93 

108. 22 

1 1 2 . 00 

132.66 

Feet 
18.6 
37.1 
74-1 
105.2 

142.3 
183-5 
355-0 
367-5 
436.0 

A\ig.  16 
Aug.  18 
Aug.  18 
Aug.  16 
Aug.  25 
Aug.  16 
Aug.  II 
Aug.  16 
Aug.  18 

4:05 

9:00  A.M. 
12:25 
5:10 

3:25 
12:05 
10:30  A.M. 

1:50 

4:30 

Clear 
Cloudy 
Clearing 
Clear 

°C. 
16.7 
18.9 
16.7 
16.7 
20.0 
15-6 

16^7 
18.9 

18 
17 
17 
18 

19 
18 
18 
18 
18 

3 

2 

5 
3 
4 
3 
9 
3 
3 

Clear 
Hazy 
Clear 
Scattered 
clouds 

Most  fresh-water  animals  are  poikilothermic  or  cold-blooded  and 
their  temperature  varies  with  the  surrounding  temperature.  IMam- 
mals  and  birds  with  the  exception  of  the  manatee  and  rare  fresh- 
water dolphins  and  seals  are  not  truly  aquatic.  Truly  aquatic 
warm-blooded  animals  usually  have  a  thick  covering  of  fat  which 
is  a  poor  conductor  of  heat.  A  few  fishes  maintain  10°  C.  or  more 
above  the  surrounding  medium,  but  for  most  fresh-water  animals 
0.1°  to  5.0°  C.  are  reported.  Rogers  recently  reported  only  very 
minute  difference  for  goldfish.     This  heat  is  due  to  metabolism. 

^  Temperatures  below  the  surface  may  be  taken  with  a  thermometer  in  a  two-gallon 
bottle  filled  at  the  desired  lev^el  or  better  with  a  Negretti-Zambra  reversing  ther- 
mometer.    For  devices  making  continuous  records  of  temperature,  the  thermophone 
i       of  Whipple  or  Friez's  soil  and  water  thermograph  may  be  used. 


34 


FRESH-WATER   BIOLOGY 


Cold  increases  the  metabolism  of  warm-blooded  animals  and 
decreases  that  of  cold-blooded  animals.  In  the  cold-blooded 
animals  a  rise  of  io°  C.  within  limits  reasonably  compatible  with 
life  increases  the  rate  of  metaboUsm,  or  rate  of  development  of 
young,  by  two  or  three  times.  This  is  taken  as  evidence  that 
life  is  a  chemical  process  because  similar  changes  in  temperature 
have  corresponding  changes  in  rate  of  chemical  reaction. 

Thus  animals  aquatic  in  their  developmental  stages  and  which 
happen  to  be  in  very  shallow  temporary  water  are  automatically 
accelerated  in  development  as  the  sun  warms  the  water,  evaporates 
it  and  decreases  its  volume  at  the  same  time  increasing  its  tempera- 
ture. 

Animals  react  to  temperature  with  considerable  precision.  Both 
marine  and  fresh-water  animals  can  recognize  differences  of  0.2°  C. 
and  will  turn  back  when  such  slight  differences  are  encountered 
under  experimental  conditions. 

Pressure  in  water  increases  with  depth.  The  results  given  by 
Forel  are  shown  in  Table  IV. 


TABLE  IV 


Pressure  in  atmospheres 

I 

2 

3 

5 

8 

10 

20 

Depth  in  meters 

10.328 

20.6 

30 -9 

51-5 

82.4 

103.27 

206 . 49 

There  is  a  little  less  than  one  atmosphere  increase  in  pressure 
for  each  10  meters  of  depth.  According  to  this,  animals  in  the 
deepest  parts  of  a  lake  like  Lake  Michigan  are  living  under  a 
pressure  of  about  375  pounds  to  the  square  inch. 

The  effect  of  pressure  on  organisms  was  studied  by  Regnard. 
Contrary  to  the  popular  idea  he  found  that  gelatine,  agar,  and 
various  plants  and  animals  and  excised  parts  of  animals  take  up 
water,  swell  and  increase  in  weight  under  high  pressure.  This  is 
true  even  of  terrestrial  insects.  At  400  to  600  atmospheres  Para- 
mecia  become  swollen  and  immobile,  including  the  cilia.  They 
recover  from  ten  minutes'  exposure.  Carp  become  Hstless  at  200 
atmospheres,  die  at  300  and  become  swollen  and  rigid  at  400 
atmospheres.     Salmon  ova  are  destroyed  at  400  atmospheres  but 


CONDITIONS  OF   EXISTENCE 


35 


chlorophyll  bodies  of  green  algae  continue  to  work  at  600  atmos- 
pheres and  cress  seeds  have  germinated  after  an  exposure  to  1000 
atmospheres. 

Table  V  shows  the  conditions  and  distribution  of  Ufe  in  Lake 
Michigan.  The  greatest  pressure  is  27  atmospheres  which  on 
the  basis  of  the  work  of  Regnard  would  seem  trivial.  Animals 
may  react  to  pressure  differences  but  this  is  not  known  as  no  pres- 
sure gradient  can  be  estabhshed  without  involving  gravity  also. 
Pressure  would  appear  to  play  a  relatively  insignificant  role. 


TABLE  V 
Conditions  in  Lake  Michigan 


Approximate  physical  conditions 

Depth 

Vegetation  and  animals 

Meters 

Feet 

Strong  wave  action 

0-1.5 

o-S 

Bottom  organisms  wanting 
on  sandy  shores,  abundant 
on  rocky  shores 

Limit  of  sand-moving  waves 

8 

26 

Organisms  abundant 

Limit  of  daily  temperature  fluc- 
tuations; limit  of  wave  action; 
beginning  of  light  decrease; 
pressure  about  2^  atmospheres 

25 

82 

Lowest  record  of  Chara  and 
Cladophora.  Lower  limit  of 
MoUusks  except  Sphasridae 

Pressure  4  atmospheres,  light  re- 
duced to  f 

39 

128 

Scanty  filamentous  algce 

Seasonal     temperature     fluctua- 
tions less  than  i°  C;    light  re- 
duced to  1;   pressure  5^  atmos- 
pheres 

54 

177 

Lower  limit  of  most  shallow 

water  animals 
Nostoc  and  diatoms 

Light  i;  pressure  7  atmospheres 

70 

230 

No  bottom  plants  recorded 

Probably  dark  as  night;  pressure 
II    atmospheres;    little  change 
in  temperature;  nearly  uniform 
conditions 

115 

377 

No  plants  recorded 

Greatest  depth  in  lake;    pressure 
27  atmospheres 

274 

900 

No  plants  recorded 

With  a  rise  of  temperature  both  the  density  and  viscosity  of 
water  decrease.  This  tends  to  cause  such  organisms  as  behave 
like  small  inanimate  particles  to  sink.  Ostwald  suggested  that 
these  differences  are  responsible  for  the  depth  migrations  of 
plankton  organisms.     He  considered  that  a  decrease  in  viscosity 


36  FRESH-WATER    BIOLOGY 

causes  them  to  sink.  The  diffusion  currents  bring  them  up  again 
(Johnstone).  This  is  no  doubt  a  matter  deserving  investigation. 
Turbidity  is  important  largely  through  its  relation  to  Ught.  Most 
aquatic  animals  will  tolerate  much  sediment,  at  least  under 
experimental  conditions. 

Chemical  factors  are  not  directly  or  clearly  separable  from 
factors  that  may  be  regarded  as  physical  or  biological.  Under 
this  heading  are  considered  dissolved  gases,  inorganic  salts, 
acidity,  alkaUnity,  and  neutrality. 

In  order  to  support  animals  and  plants  continuously  water  must 
contain  certain  minerals  and  gases  in  solution.  Salts  (carbonates, 
sulphates,  and  chlorides)  of  magnesium,  calcium,  potassium,  and 
sodium,  and  salts  of  iron  and  siUcon  are  practically  always  in  solu- 
tion in  water  and  their  presence  in  definite  proportions  is  beheved  to 
be  essential  to  the  Hfe  of  organisms.  Pure  distilled  water  has  been 
shown  to  be  harmless  to  certain  animals  for  comparatively  short 
periods  but  it  is  doubtful  if  it  will  sustain  life  indefinitely.  Dis- 
solved gases  in  definite  proportions  are  essential. 

The  occurrence  of  gases  and  their  solubility  under  experimental 
conditions  are  shown  in  Table  VI.  A  standard  method  of  express- 
ing quantity  of  gas  in  solution  is  in  cubic  centimeters  per  liter  at 
0°  C.  and  760  mm.  of  mercury.  Values  are  commonly  given  in 
these  terms. 

Nitrogen  is  the  most  inert  and  least  important  of  the  dissolved 
gases.  It  rarely  has  any  direct  effect  on  animals  and  plants  and 
this  apparently  only  when  present  in  considerable  excess  of  satu- 
ration. Under  such  conditions  it  accumulates  in  the  blood  vessels 
and  tissues  of  fishes,  crayfishes,  insects,  etc.  In  the  organs  of 
circulation  it  may  thus  stop  the  blood  flow  and  the  animals  die  of 
asphyxia.  Birge  and  Juday  state  that  in  lakes  in  the  region  of 
the  thermocline  and  below  an  excess  of  1 2  to  38  per  cent  of  satura- 
tion occurs,  but  under  the  conditions  of  pressure  there  this  would 
have  no  effect.  It  is  probable  that  in  nature  this  condition  of 
excess  is  not  commonly  great  enough  and  does  not  often  occur  for 
a  time  long  enough  to  cause  any  fatal  results.  Several  hours  or 
days,  depending  upon  the  excess,  are  required.  Excess  nitrogen  is 
a  great  source  of  difficulty  in  aquaria. 


CONDITIONS   OF   EXISTENCE 

TABLE   VI 
Showing  the  Solubility  and  Distribution  of  Atmospheric  Gases 


37 


Composi- 
tion of  air 
in  percent- 
ages 

Gas  values  in  cubic  centi- 
meters per  liter  at  0°  C.  and 
760  mm.  mercury 

Gas 

At.  temp.  20°  C. 
760  mm. 

Maximum 
amounts 
found  in 
natural  fish 
waters, 
springs 
excepted 

Kind  of  water  having  gas 

content  given  in  preceding 

column 

Water 
absorbs 
from  air 

Water 
absorbs 
pure  gas 

Nitrogen,       argon, 

etc 

Oxygen 

Carbon  dioxide .... 
Ammonia 

Methane 

Hydrogen  sulphide. 

79.02 
20.95 

0.03 

Small 
traces 
locally 

12.32 
6.28 

0.27 

15.00 
28.38 

901 .00 
Very 
large 
quanti- 
ties 
34.00 
2900 . 00 

19.00 
24.00 

30.00 
14.00 

10.00 
0-55 

Lakes 

Streams,  lakes  in 
winter,  or  with 
green  algae 

Ponds 

Sewage  contami- 
nated 

Bottom  of  lake 
Lakes,   and   sewage 
contaminated 

The  oxygen  content  of  water  varies  from  o  cc.  per  liter  to  25  cc. 
in  the  presence  of  green  algas  on  sunny  days.  The  bottoms  of  lakes 
and  ponds  where  much  putrescible  matter  occurs  are  usually 
without  oxygen.  The  hypolimnion  of  lakes  with  a  thermocline 
is  in  part  without  oxygen  in  summer.  Probably  free  oxygen  is 
usually  necessary  to  most  organisms  except  anaerobic  bacteria. 
Most  animals  that  have  been  studied  in  behavior  experiments 
select  water  with  some  oxygen.  While  some  species  of  fishes  such 
as  suckers,  small  mouthed  black  bass,  and  some  cyprinids  appear 
to  be  affected  by  a  considerable  decrease  from  saturation  at 
ordinary  temperatures,  this  appears  to  be  the  exception  rather 
than  the  rule.  Increase  to  25  cc.  per  liter  under  experimental 
conditions  does  not  appear  to  have  any  marked  effect  upon  fishes 
so  far  as  life  and  death  are  concerned.  Allee  working  on  isopods 
found  that  an  increase  in  oxygen  increases  size,  vigor,  and  amount 
of  positive  response  to  current  as  well  as  efficiency  of  response  to 
current.  His  results  have  been  confirmed  by  several  students 
who  have  repeated  the  experiments  using  different  forms. 

Juday  has  shown  that  a  long  list  of  common  protozoa,  worms, 


^8  FRESH-WATER    BIOLOGY 

insects,  etc.,  can  live  for  a  long  time  without  free  oxygen,  and  in 
fact  occur  in  the  putrescible  organic  muds  of  the  bottoms  of  lakes 
and  ponds  and  the  hypolimnion  of  thermocline  lakes  in  summer. 
They  evidently  obtain  oxygen  from  some  chemical  compounds. 
Carbohydrates  are  present  in  the  sea  in  solution  in  minute 
quantity  and  there  is  every  reason  to  believe  them  present  in  fresh 
water.  Packard  found  that  marine  Fundulus  embryos  live  in  lack 
of  oxygen  from  73  to  141  per  cent  longer  in  the  presence  of  glucose, 
maltose,  levulose,  and  cane  sugar,  the  amount  of  increase  in  resist- 
ance differing  with  the  different  sugars.  Lactose  has  no  such  effect, 
probably  because  it  cannot  be  absorbed  or  digested. 

According  to  Mathews'  depolarization  theory  oxygen  is  obtained 
from  the  water  in  a  manner  analogous  to  the  oxidation  of  alcohol 
to  acetic  acid.     In  the  presence  of  O2  the  reaction  is  as  follows: 

C2H5OH  +  02  =  CH3COOH  +  H2O. 

In  the  absence  of  oxygen  and  the  presence  of  levulose 
C2H5OH  +  H2O  =  CH3COOH  +  2  H2 
2  H2  +  2  C6H12O6  =  2  CeHuOe. 

The  levulose  unites  with  the  hydrogen  and  thus  permits  the 
protoplasm  to  use  the  oxygen.  The  protoplasm  is  thus  a  strong 
reducing  agent. 

High  respiratory  quotients  of  various  animals  are  further  evi- 
dence   of    anaerobic    respiration.      The    respiratory    quotient    is 

Vol.  CO2  given  off  _  j^  aerobic  animals  this  value  is  less  than  i 
Vol.  O2  absorbed 

because  oxides  other  than  CO2  are  given  off  and  CO2  does  not  rep- 
resent all  the  oxygen  used.  Thus  when  the  quotient  is  more  than 
I  it  indicates  that  oxygen  is  obtained  from  some  source  other  than 
free  oxygen.  The  respiratory  quotient  of  the  medical  leech  is 
usually  near  or  a  little  more  than  i  while  that  of  a  sea  cucumber 
{Cucumaria)  and  a  sea  sponge  (Suberites)  is  over  2.5  (Putter).  A 
large  number  of  aquatic  animals  are  probably  able  to  secure  oxygen 
from  compounds  containing  it  and  they  are  therefore  facultative 
anaerobes  to  a  considerable  degree. 

Distribution  of  organisms  in  water  is  not  clearly  correlated  with 
oxygen  content.     The  minimum  for  most  animals  is  comparatively 


CONDITIONS   OF   EXISTENCE  39 

low  as,  for  example,  in  fishes  insufficient  oxygen  acts  on  the  respira- 
tory center  through  the  development  of  organic  acid  in  the  blood 
due  to  incomplete  oxidation,  and  causes  the  respiratory  movements 
to  be  increased.  There  is  some  evidence  that  respiratory  activity  is 
increased  through  direct  reflex  action  through  the  gills  and  opercles. 
This  increased  respiratory  activity  supplies  plenty  of  oxygen. 

Ammonia  occurs  in  minimal  quantities  in  natural  waters  but 
may  be  present  in  some  quantity  in  sewage  or  gas  works  wastes. 
Ammonia  like  the  other  gases  (CO,  SO2,  and  C2H4)  introduced  into 
streams  by  gas  works  is  not  only  extremely  poisonous,  but  fishes 
do  not  turn  back  from  it  when  they  encounter  it  and  are  often 
overcome  without  giving  the  avoiding  reactions  which  protect  fishes 
from  excesses  of  other  substances  normal  to  fish  environments. 

Methane  is  a  saturated  hydrocarbon  and  has  minor  effects  upon 
organisms  though  it  may  be  present  in  the  hypolimnion  of  lakes  in 
considerable  quantity.     Traces  of  carbon  monoxide  occur  also. 

Hydrogen  sulphide  is  usually  present  in  very  small  quantities  in 
the  bottoms  of  lakes  and  sewage  contaminated  streams.  It  is 
very  abundant  in  salt  lakes  and  arms  of  the  sea.  It  results  from 
putrefactions  and  from  the  reduction  of  sulphates  through  the 
action  of  the  bacteria  which  prey  upon  organic  sulphur  (Lederer). 
Though  very  poisonous  it  is  not  ordinarily  present  in  sufficient 
quantity,  to  injure  fishes  (Shelf ord  and  Powers)  though  its  absorp- 
tion of  oxygen  ^  reduces  the  amount  of  this  gas  very  materially. 

Carbon  dioxide  is  the  most  important  gas  in  fresh  water.  In 
small  quantities  it  is  essential  rather  than  detrimental  to  aquatic 

^  Samples  of  water  without  oxygen  must  be  handled  with  utmost  caution  as  an  ap- 
preciable amount  of  oxygen  will  be  absorbed  through  the  surface  exposed  by  the  nar- 
row neck  of  a  250  cc.  bottle  in  a  few  seconds.  Biologists  are  very  likely  to  attempt 
great  accuracy  in  putting  up  solutions  and  to  exercise  insufficient  care  in  taking  and  ti- 
trating samples.  For  ordinary  work,  in  making  up  solutions  it  is  sufficient  to  weigh  to 
one  decimal  place;  chemicals  must  be  carefully  selected;  especially,  KI.  The  normal 
solutions  used  will  not  be  correct  if  made  by  an  unskilled  person;  a  correcting  factor 
must  be  used  which  may  as  well  be  0.876  as  0.989.  Skill  in  titrating  and  standardiz- 
ing with  solutions  made  by  a  chemist  should  be  acquired.  For  methods  see  Birge  and 
Juday,  and  Sutton.  Routine  sanitary  analyses  include  several  items  of  unknown  or 
doubtful  value  to  Hving  organisms  and  do  not  include  some  of  the  most  important 
determinations  such  as  acidity,  alkalinity,  hydrogen  sulphide,  and  carbonaceous 
materials  that  might  be  absorbed  as  food.  Determinations  are  often  not  made  at 
once,  and  samples  are  commonly  not  collected  from  important  animal  habitats  within 
the  body  of  water. 


40  FRESH-WATER   BIOLOGY 

animals.  In  large  quantities  it  is  rapidly  fatal  acting  as  a  narcotic. 
It  is  particularly  injurious  in  the  absence  of  oxygen  which  absence 
is  usually  associated  with  it.  Abundant  oxygen  decreases  its 
toxicity  because  blood  has  greater  affinity  for  oxygen  than  for 
carbon  dioxide  and  the  latter  is  crowded  out  of  combination.  On 
account  of  the  fact  that  it  is  usually  accompanied  by  lack  of 
oxygen,  putrescible  muck  bottom,  etc.,  its  presence  in  quantities 
greater  than  6  to  7  cc.  per  liter  if  accompanied  by  a  bottom  en- 
tirely of  such  muck  would  indicate  that  the  water  was  unsuitable 
for  trout,  basses,  sunlishes,  and  crappies. 

One  of  the  most  important  characteristics  of  a  water  is  its 
acidity  or  alkalinity.  Protoplasm  must  maintain  essential  neu- 
trahty  or  it  will  die.  It  possesses  a  very  effective  physico-chemical 
mechanism  based  upon  the  presence  in  excess  of  very  weak  acids 
(carbonic  and  phosphoric)  and  alkalies  in  the  form  of  carbonates 
and  phosphates.  Since  protoplasm  must  remain  nearly  neutral 
the  acidity  or  alkalinity  of  the  surrounding  medium  cannot  be 
great.  Thus  Wells  found  that  fishes  do  not  live  well  in  alkaUne 
water  but  become  sluggish  and  inactive.  Neutrality  is  likewise 
toxic  to  some  fresh-water  fishes.  They  require  a  certain  amount  of 
acid.  The  optimum  acidity  for  the  difi'erent  species  dift'ers.  The 
optimum  for  the  bluegill  {Lepomis  pallidus  Mit.)  is  i  to  3  cc.  of 
carbon  dioxide  per  liter  and  for  crappies  {Pomoxis  annularis  Raf.) 
4  to  6  cc.  per  liter.  Wells  showed  by  using  various  other  acids 
that  the  hydrogen  ions  are  the  important  factor.  In  other  words 
fishes  require  a  certain  concentration  of  hydrogen  ion.  Neutrality 
is  avoided  by  fishes.  In  the  absence  of  acidity  they  select  alka- 
line in  preference  to  neutral  water.  Fishes  and  various  crusta- 
ceans will  live  in  distilled  water  if  it  is  slightly  acid,  while  it  is 
rapidly  fatal  if  neutral  and  more  rapidly  fatal  if  alkaline.  The 
toxicity  of  much  ordinary  distilled  water  is  due  to  colloidal  copper 
or  other  metal  from  coolers,  in  suspension  in  it. 

Wells  made  a  rearrangement  of  some  of  the  data  of  Birge  and 
Juday  which  showed  that  various  plankton  organisms  are  distrib- 
uted with  reference  to  alkalinity,  neutrality,  and  acidity,^  a  few 

1  In  the  determination  of  alkalinity  and  acidity  great  care  should  be  exercised  in 
the  making  of  collections  so  as  to  prevent  the  escape  of  CO2.     The  choice  of  indi- 


CONDITIONS   OF   EXISTENCE 


41 


species  showing  a  distinct  avoidance  of  neutrality.  In  a  number 
of  species  the  number  of  individuals  on  either  side  of  neutrality 
was  greater  than  at  the  neutral  region  (Table  VII). 

TABLE  VII 

Showing  Correlation  between  Distribution  and  Alkalinity  and  Acidity 

TO  Phenolphthalein  (after  Wells) 

(Figures  show  numbers  of  individuals  in  a  cubic  meter  of  water) 


Name  of  animal 


Alkalinity  in  cc.  per  liter 
of  CO2  to  make  neutral 


Pleosoma R 

Asplanchna R. 

Diaphanosoma C. 

Diaptomus Co 

Anuraea P. 

Cyclops Co. 

Notholca R. 

Daphnia C. 

Ceratium P. 

Polyarthra R. 

Triarthra R. 


3.925 
11,320 

2,885 
7,850 
4,000 

13,775 

625 

1,260 

52,330 

12,350 

o 


o 

400 

2,750 

6,660 

1,250 

7,620 

685 

650 

104,500 

1,620 

n.  c. 


o 

o 

n.  c. 

17,350 

200 

7,620 

65 

400 

85,160 

2,350 

o 


Neu- 
trality 


O 

O 

260 

2,220 

30 

25 

o 

130 
2,025 

160 
n.  c. 


Acidity  in  cc.  of  CO2 
per  liter 


0.25-0.5   0.75-1 


o 
o 
o 

1,440 
20 

30 

65 

1,145 

11,760 

1,190 

1,050 


o 
o 
o 

390 

20 
o 
o 

25 
750 

,240 
,110 


o 

o 

o 

100 

20 

5 
o 
o 

1,670 
40 

2,425 


R  =  Rotifer,  C  =  Cladoceran,  P  =  Protozoan,  Co  =  Copepod,  n.  c.  =  no  collection. 

The  amount  of  salt  in  parts  per  million  which  ranges  from  50- 
500  in  water  occupied  by  numerous  fresh-water  species  is  of  com- 
paratively little  significance  to  animals  but  of  much  importance  to 
plants.  The  effect  of  most  salts  upon  organisms  is  due  to  the 
character  of  the  ions,  valence,  electrical  charges,  etc.  The  effect 
of  any  combination  of  salts  is  due  to  their  combined  action.  For 
example,  marine  animals  will  not  live  in  NaCl  alone  even  when 
the  osmotic  pressure  is  the  same  as  in  sea  water;  it  is  very  toxic. 
They  will  not  live  in  NaCl  and  KCl  or  NaCl  and  CaCl2;  all  three 

cators  is  also  very  important.     Methyl  orange  is  unafifected  by  CO2  and  other  organic 

acids  because  of  their  small  ionization.     Thus  Marsh's  conclusion,  based  upon  methyl 

orange,  that  if  water  becomes  acid  it  kills  fishes  is  incorrect  for  this  reason  and  because 

H+ 10^  N  H+  10-*  N 

it  turns  red  at  ,=r^ -—-^  and  remains  yellow  at  prz^ r-rr .    Phenolphthalein  is  color- 

OH-io-i^N  -^  OH-io-»N 

less  at  ^^z^ ^:^^^  and  turns  red  at  pr^- — — -  .     Rosalie  acid  is  rose  at  ^r^j —i-^r 

OH-  10-6  N  OH-  10-6  N  OH-  10^  N 

which  is  true  neutrality.     In  the  table  above  true  neutrality  probably  falls  in  the  first 

column  to  the  right  of  the  center.     CO2  production  may  be  sufl'icient  to  neutralize 

this  slight  alkalinity  in  the  layer  of  water  next  to  the  animal.     The  terms  alkalinity 

and  acidity  are  used  in  this  chapter  in  the  sense  of  concentration  of  H+  and  OH"  ions. 


42  FRESH-WATER   BIOLOGY 

are  necessary.  This  is  believed  to  be  due  to  the  neutralization  of 
the  toxicity  of  the  NaCl  by  the  other  salts;  this  is  known  as  antag- 
onism. The  effects  are  due  to  the  cations,  one  anion  being  suffi- 
cient though  some  are  more  favorable  than  others. 

Salts  present  in  excess,  or  without  the  proper  antagonistic  salts 
or  ions,  and  salts  not  commonly  present  in  quantity  in  fresh  water 
are  toxic  to  fresh-water  animals.  The  toxicity  varies  for  different 
salts  and  according  to  the  concentration  of  hydrogen  or  hydroxyl 
ions  which  accompany  it.  Ammonia  salts  are  poisonous  to  fishes 
if  present  in  company  with  carbonates.  Carbonates  are  not  essen- 
tial to  the  hfe  of  fishes  as  sulphates  may  be  substituted  entirely, 
at  least  for  short  periods.  Carbonates  alone  are  fatal  to  fishes 
because  of  their  alkalinity.  In  the  presence  of  CO2,  however, 
carbonates  are  converted  into  bicarbonates  which  are  normally 
present  in  all  natural  fish  waters.  Bicarbonates  accompanied  by 
a  small  excess  of  CO2  are  not  harmful.  Of  the  salts  of  potassium, 
the  sulphate  is  most  poisonous ;  sodium  salts  are  less  injurious  than 
those  of  potassium.  The  presence  of  an  excess  of  calcium  causes 
the  tail  fins  of  the  rock  bass  to  degenerate  and  this  fact  was  prob- 
ably responsible  for  the  tailless  trout  found  in  certain  waters  of 
the  British  Isles  where  the  water  was  contaminated  with  waste 
from  paper  mills.  There  is  much  evidence  that  calcium  tends 
to  lower  the  metabolic  activity  of  organisms. 

As  shown  by  Wells  fishes  react  to  salts  in  solution.  They  are 
usually  negative  to  nitrates,  more  or  less  positive  to  chlorides 
(markedly  so  to  NaCl)  but  are  decidedly  negative  to  CaCL  and 
MgCl2.  They  are  positive  to  ammonium  chloride  and  are  usually 
very  negative  to  sulphates.  The  reaction  of  the  fishes  to  the  salts 
was  shown  to  have  a  distinct  relation  to  the  acidity  of  the  water,  as 
fishes  that  were  decidedly  negative  to  Na2S04  for  instance  in  slightly 
acid  water  were  made  positive  to  this  salt  by  running  the  experiment 
in  strongly  acid  water  {i.e.,  20  cc.  COo  per  liter).  A  part  of  the 
effect  of  ions  lies  in  their  effect  on  permeability.  Alkalies  increase 
permeability  of  protoplasm.   Acids  first  decrease  and  later  increase  it. 

In  animals  and  plants  there  are  various  rhythms  of  activity  con- 
stituting parts  of  their  physiological  life  histories  or  recurring 
functions  lying  within  them.     These  often  coincide  with  rhythms 


CONDITIONS   OF   EXISTENCE  43 

of  conditions.  The  principal  environmental  rhythms  are  daily, 
seasonal,  weather,  and  lunar,  and,  in  the  sea,  tidal. 

Rhythms  of  fresh-water  organisms  have  been  but  little  studied. 
From  the  seasonal  standpoint  it  has  been  observed  that  some  organ- 
isms tend  to  do  certain  things  even  though  the  external  conditions 
which  usually  accompany  them  are  delayed,  thus  showing  that  the 
environmental  rhythms  have  been  impressed  upon  the  organism. 
The  best  examples  of  this  have  to  do  with  the  tide  and  thus  do  not 
belong  to  fresh  water.  Bohn  found  that  there  are  rhythms  of 
activity  related  to  tide.  The  green  fiatworm  (Convoluta  roscojfensis) 
comes  to  the  surface  of  the  sand  at  low  tide  and  descends  as  the 
tide  comes  in.  The  worm  continues  to  ascend  and  descend  at 
tide  time  for  several  days  after  having  been  removed  from  the  sea 
and  kept  in  an  aquarium. 

One  of  the  best  known  rhythmic  movements  in  fresh  water  is 
the  daily  depth  migration  of  Crustacea.  Whether  they  show  any 
tendency  to  make  such  movements  when  placed  under  uniform 
conditions  is  not  known.  Lunar  rhythms  likewise  appear  to  have 
been  Httle  investigated  among  fresh-water  organisms  though  Kofoid 
noted  rhythmic  monthly  increases  of  Illinois  River  plankton.  The 
best  examples  of  these  are  found  among  the  marine  worms.  The 
Atlantic  palolo  swarms  within  three  days  of  the  last  day  of  the  last 
quarter  of  the  June  29  to  July  28  moon  (Mayer),  the  swarming 
taking  place  under  the  influence  of  the  light  of  the  moon. 

Various  single  factors  have  been  regarded  as  of  prime  importance 
in  the  control  of  organisms.  Thus  many  writers  emphasize  food, 
others  temperature,  etc.  Merriam  has  maintained  for  years  that 
the  total  of  temperature  above  an  arbitrary  minimum  during  the 
growing  season  controls  the  distribution  of  life  in  North  America. 
Sanderson  has  shown  that  for  some  insects  and  some  horticultural 
plants  winter  temperatures  are  more  important,  just  as  may  be 
the  case  with  organisms  like  fresh-water  sponges  and  bryozoans 
having  winter  bodies,  and  aquatic  plants  with  seeds  and  spores. 
Marine  workers  emphasize  salinity  and  density.  Birge  and  Juday 
emphasize  oxygen.  All  these  ideas  have  important  bearings  on 
questions  of  aquatic  biology  but  no  one  of  them  is  adequate. 

Dormancy  sometimes  makes  otherwise  insignificant  conditions 


44  FRESH-WATER   BIOLOGY 

important.  It  is  a  common  characteristic  of  the  eggs  of  rotiiiers, 
of  Crustacea,  insects,  and  other  arthropods,  and  also  of  the  spores 
and  seeds  of  plants.  Many  crustaceans  deposit  eggs  in  the  autumn 
which  require  freezing  before  they  will  hatch.  Some,  as  for  exam- 
ple those  of  the  fairy  shrimp  (Eubranchipus) ,  require  both  summer 
drying  and  winter  freezing.  The  statoblasts  of  the  fresh-water 
Bryozoa  germinate  better  after  freezing  or  drying.  Thus  some 
simple  condition  such  as  the  rupture  of  the  egg  shell  or  covering 
may  be  a  requirement  for  growth  as  it  is  in  some  seeds. 

Any  scheme  that  fails  to  consider  the  complete  physiological 
hfe  history  in  relation  to  complete  annual  cycles  is  inadequate. 
Still,  because  of  the  complexity  of  the  problems  involved  simple 
indices  must  be  sought  which  will  indicate  the  condition  of  waters 
with  reference  to  as  many  important  factors  as  possible.  These 
indices  must  be  selected  with  two  facts  in  mind:  First,  that  there 
is  in  each  annual  cycle  of  the  life  of  an  individual  or  a  species  a 
period  of  maximum  sensitiveness;  this  falls  at  or  near  the  breeding 
period  or  at  the  time  of  appearance  of  young.  Second,  adequate 
measure  of  hydrographic  conditions  are  to  be  found  in  the  peculiar 
character  of  the  annual  rhythm  rather  than  in  the  totals  of  this 
or  that  factor  for  the  year  or  a  particular  period. 

Many  organisms,  especially  food  fishes,  deposit  their  eggs  on  the 
bottom.  It  is  to  the  bottom  that  the  dead  bodies  of  organisms 
sink  and  at  the  bottom  that  they  decompose  and  produce  poi- 
sonous substances  in  greatest  quantity.  Decomposition  of  the 
bodies  of  plants  and  animals  results  finally  in  gases  such  as 
ammonia,  carbon  dioxide,  hydrogen  sulphide,  methane,  etc. 
The  presence  or  absence  of  fishes  and  their  animal  food  is  con- 
trolled by  (a)  their  ability  to  recognize  the  presence  of  strange 
or  detrimental  substances  and  to  turn  back  when  such  are  en- 
countered, and  (b)  by  their  survival  or  death  in  situations  where 
they  cannot  escape  the  deleterious  conditions.  Their  ability  to 
recognize  common  injurious  substances  has  been  shown  to  be 
very  marked  and  precise.  The  difference  between  different 
species  is  one  of  degree  and  special  habits.  The  effects  of  the 
various  decomposition  products  are  the  same  in  a  wide  range  of 
species  with  only  slight  differences  in  degree.     The  less  sensitive 


CONDITIONS   OF   EXISTENCE  45 

fishes  are  usually  of  less  food  value.  Food  fishes  usually  live  asso- 
ciated with  organisms  which,  like  themselves,  are  very  sensitive 
to  decomposition  products,  and  usually  disappear  with  the 
fishes. 

Indices  are  of  three  types,  (i)  results  of  the  inspection  of  the 
bottom,  (2)  results  of  chemical  tests  of  the  water  for  decomposi- 
tion products,  and  (3)  for  fishes  the  presence  or  absence  of  index 
organisms  of  a  semi-stationary  character,  such  as  snails,  etc., 
see  p.  52.     Here  the  first  two  types  only  will  be  considered. 

If  a  body  of  water  is  to  support  desirable  game  fishes  it  should 
have  an  area  of  terrigenous  bottom  covered  with  from  6  inches  to 
2  feet  of  water  for  breeding  grounds  and  an  area  of  submerged 
(Chara,  etc.)  and  of  emerging  vegetation  to  supply  food.  It  is 
probable  that  for  the  best  results  these  three  should  be  about 
equal.  The  terrigenous  bottom  should  be  comparatively  free  from 
putrescible  material.  Humus  which  does  not  contain  putrescible 
material  or  even  the  roots  of  plants  may  be  used  by  a  few  game 
fishes  for  breeding.  The  amount  of  terrigenous  (non-putrescible) 
bottom  up  to  one  third  that  occupied  by  vegetation  and  muck  is  a 
rough  index  of  the  suitabifity  of  an  ordinary  pond  or  lake  (see 
Fig.  7,  p.  58)  for  game  fishes  and  associated  organisms.  In  river 
bottom  lakes  and  bayous  floods  may  remove  putrescible  material 
and  leave  bottoms  composed  chiefly  of  silt  upon  which  luxuriant 
vegetation  springs  up.  Forbes  has  shown  that  productivity  of 
carp,  and  fishes  generally,  bears  some  direct  relation  to  the  area 
fairly  wefl  supplied  with  submerged  vegetation.  The  second  index 
must  be  appHed  to  such  waters. 

The  second  index  is  essential  but  must  accord  with  the  first. 
The  chemical  character  of  the  water  must  be  such  that  the  fishes 
will  not  suffer  from  it  or  leave  on  account  of  it.  Carbon  dioxide 
results  from  the  decomposition  of  organic  matter.  In  the  process 
oxygen  is  consumed  so  that  the  presence  of  any  large  quantity  of 
carbon  dioxide  nearly  always  indicates  lack  of  oxygen.  While 
exact  figures  cannot  be  given  it  is  probable  that  the  carbon  dioxide 
content  of  water  over  breeding  grounds  (terrigenous  bottom)  should 
not  average  more  than  three  cubic  centimeters  per  liter,  nor  ex- 
ceed  six   cubic   centimeters    during   the   summer   months.     Such 


46  FRESH-WATER    BIOLOGY 

amounts  are  not  usually  accompanied  by  lack  of  oxygen.  Thus 
the  amount  of  carbon  dioxide  may  be  taken  as  an  index  oj  the 
suitability  of  the  water.  Excessive  acidity  due  to  carbon  dioxide 
probably  favors  the  germination  of  the  Saprolegnias  fungi  which 
are  very  destructive  of  fish  eggs  and  fishes. 

Food  and  Biological  Conditions 

Nitrates  are  necessary  for  the  growth  of  aquatic  plants  and  an 
insuflicient  quantity  is  secured  from  mineral  soil.  Nitrogen  can 
be  fixed  only  by  nitrogen  fixing  bacteria,  such  as  Clostridium,  an 
anaerobe,  and  Azotobacter,  an  aerobe.  These  bacteria  occur  on 
plants  and  animals  in  the  mud  of  the  bottom  of  bodies  of  water. 
Plants  and  animals  provide  carbon  compounds  for  the  bacteria; 
bacteria  provide  nitrates  or  nitrites. 

Ammonia  results  from  the  decomposition  of  the  dead  bodies  of 
plants  and  animals.  The  bacteria  {Nitrosomonas,  Nitrobacter,  Ni- 
trococcus)  oxidize  it  to  nitrous  acid;  nitrous  acid,  to  nitric  acid. 
These  acids  unite  with  bases  to  form  nitrates  and  nitrites.  Work- 
ing against  these  two  sources  of  nitrate  and  nitrite  are  various 
denitrifying  bacteria  {e.g.,  Bacterium  actinopelte),  which  reduce 
nitrogen  compounds  to  free  nitrogen.  Their  work  is  greatly  influ- 
enced by  temperature.  Baur  placed  nitrate  inoculated  with  Bacte- 
rium actinopelte  at  several  temperatures  with  results  as  follows: 

a.  Temperature,  25°  C:  Denitrification  initiated  24  hours  after 
inoculation;   in  7  to  11  days  later  without  nitrate. 

b.  Temperature,  15°  C:  Denitrification  initiated  4  days  after 
inoculation;   in  27  days  the  solution  was  without  nitrate. 

c.  Temperature,  4  to  5°  C:  Denitrification  began  20  days  after 
inoculation;   denitrification  incomplete  112  days  after. 

d.  Temperature,  0°  C:  Denitrification  not  initiated. 

The  quantity  of  life  in  water  is  believed  to  be  in  proportion  to 
the  available  nitrogen  compounds.  The  greatest  quantity  of  plank- 
ton in  the  sea  is  in  the  polar  regions  in  the  summer.  It  has  been 
suggested  that  the  greater  retarding  effect  of  low  temperature  on 
the  denitrifying  organisms  as  compared  with  the  nitrate  producers 
is  a  cause  of  the  greater  quantity  of  life  in  the  colder  waters.  Loeb 
holds  the  theory  that  the  greater  quantity  is  due  to  the  longer  fife 


CONDITIONS   OF   EXISTENCE  47 

of  the  organism  in  cold  water.  Dissolved  nitrogen  is  important 
for  the  work  of  nitrogen  fixing  bacteria.  Oxygen  is  necessary  for 
the  production  of  CO2.  Carbon  dioxide  is  necessary  for  the  starch 
building  of  chlorophyll-containing  plants  and  animals.  These  green 
organisms  form  the  chief  food  basis  of  all  other  organisms.  Pro- 
teids  or  other  complex  foodstuffs  are  necessary  for  all  animals.  It  is 
only  animals  which  contain  chlorophyll  in  the  form  of  algae  Uving 
symbiotically  in  their  bodies,  that  can  survive  without  taking  in 
complex  foodstuffs.  Proteids  are  made  only  when  starch,  nitrates, 
and  several  other  inorganic  foods  are  present.  Because  of  their 
proteid  and  starch  demands  light  is  indirectly  necessary  to  animals 
which  can  live  in  darkness. 

According  to  Putter  and  Raben,  who  confirmed  his  determina- 
tions using  better  methods,  sea  water,  and  probably  fresh  water  as 
well,  contains  amino-acids,  oils,  and  carbohydrates.  Putter  has 
shown  that  many  aquatic  animals  absorb  nutrition  from  solution 
which  renders  them  only  in  part  dependent  upon  plankton. 

Plants  are  commonly  covered  with  a  coating  of  small  organisms, 
so  that  animals  such  as  snails  may  rasp  the  surface  and  secure  food 
without  eating  the  plant  tissues  themselves.  One  could  probably 
remove  all  the  larger  plants  and  substitute  glass  structures  of  the 
same  form  and  surface  texture  without  greatly  affecting  the  immedi- 
ate food  relations.  Aquatic  plants  are  of  particular  use  to  animals 
as  cHnging,  hiding,  and  nesting-places. 

The  quantity  of  plankton  has  been  much  studied.  Quantity 
is  usually  expressed  as  number  of  organisms  per  Hter  or  cubic 
meter  of  water,  determined  by  counting  a  part  of  a  collection;  or 
in  cubic  centimeters  per  cubic  meter  of  water.  Ward  found  an 
average  of  11.5  cc.  per  cubic  meter  in  water  from  the  surface  2  m.; 
from  2  to  25  m.,  3.9  cc;  25  m.  to  bottom,  0.4  to  1.5  cc,  in  Lake 
Michigan  (August).  Pine  Lake,  a  small  lake  adjoining,  contained 
relatively  less  plankton  than  Lake  Michigan,  the  surface  stratum 
containing  more  and  the  deeper  strata  much  less.  Lake  Michigan 
contains  twice  as  much  plankton  as  Lake  St.  Clair.  A  small 
European  lake  (Dobersdorfer  See)  contains  about  ten  times  as 
much  plankton  as  Lake  Michigan.  Kofoid  found  the  average  for 
the  year  to  be  2.71  cc.  per  cubic  meter  for  the  Illinois  River  and 


48  FRESH-WATER   BIOLOGY 

71.36  cc.  per  cubic  meter  the  maximum;    684  cc.  per  cubic  meter 
(Turkey  Lake,  Ind.)  is  the  largest  amount  recorded  by  Juday. 

Small  streams  and  lakes  with  large  inllow  and  outflow  have  little 
plankton.  Large  amount  of  plankton  is  usually  associated  with 
much  CO2,  little  oxygen,  and  a  large  amount  of  dissolved  carbonate. 

The  amount  of  plankton  fluctuates  from  season  to  season.  The 
maximum  for  the  Illinois  River  is  from  April  to  June.  It  gradually 
decreases  until  December  and  January,  when  the  minimum  is 
reached.  The  light  of  the  moon  may  increase  photosynthesis  and 
thus  the  amount  of  phyto-plankton  (Kofoid).  The  maximum  of 
Entomostraca  was  found  by  Marsh  to  fall  in  July,  August,  and 
September,  difi'ering  in  different  years.  In  smaU  bodies  of  water  an 
abundance  of  plankton  is  usually,  though  not  invariably,  associated 
with  a  large  quantity  of  larger  animals  and  rooted  plants.  Large 
lakes  like  the  Great  Lakes  are  exceptions  to  this  because  of  the 
absence  of  shallow  water  vegetation. 

Liebig's  Law  of  Minimum  has  been  appHed  to  plankton  by 
Johnstone  who  states  it  as  follows:  ''A  plant  requires  a  certain 
number  of  foodstuffs  if  it  is  to  continue  and  grow,  and  each  of 
these  food  substances  must  be  present  in  a  certain  proportion. 
If  one  of  them  is  absent  the  plant  will  die;  if  one  is  present  in  a 
minimal  proportion,  the  growth  will  also  be  minimal.  This  will  be 
the  case  no  matter  how  abundant  the  other  foodstuft's  may  be. 
Thus  the  growth  of  a  plant  is  dependent  upon  the  amount  of  that 
foodstuff  which  is  presented  to  it  in  minimal  quantity."  The 
amount  of  plankton  probably  follows  the  same  law.  All  food 
substances  must  be  present  in  correct  proportions.  The  amount 
of  plankton  may  be  determined  by  a  deficiency  in  the  amount  of 
one  substance. 

The  quantity  of  plant  and  animal  life  probably  increases  with 
the  age  of  bodies  of  water  with  small  outlet  (see  Fig.  7,  p.  58). 
This  is  because  foodstuffs  are  washed  in  with  inflowing  water,  and 
because  rooted  plants  absorb  food  from  soil  in  which  they  grow,  and 
when  they  die  and  decay  these  foodstuffs  are  added  to  the  water 
and  made  available  to  plankton  and  to  animals  in  general.  Accord- 
ingly, the  older  the  pond  and  the  longer  rooted  vegetation  has 
grown,  the  greater  the  quantity  of  Hfe  up  to  the  time  the  pond 


CONDITIONS   OF   EXISTENCE 


49 


becomes  intermittent.  This  principle  is  illustrated  by  an  age 
series  of  ponds  at  the  south  end  of  Lake  Michigan.  These  are 
similar  in  size  and  age  increases  in  order  back  from  the  lake. 

TABLE   VIII 

Showing  the  Number  of  Entomostraca  in  Approximately  go  Liters  of 

Water  (After  Shelford) 


Body  of  water 

September  3.4. 
1909 

April  30,  1910 

Average  number 
of  collections 
in  parentheses 

Relative 
age  of 
ponds 

Wolf  Lake 

213 

232 

4,115 

556 

539 

2,773 

1.039 

351 

2,870 

2,  goo 

9,333 
19,866 
Aug.  28,  1912 
104 

1,556  (3) 

4,781   (3) 

11,991   (3) 

874  (6) 

927  (6) 

2,680  (6) 

Prairie  Pond  I 

6 

Prairie  Pond  II 

28 

Pond  I 

Pond  VII...    . 

14 

28 

Pond  XIV..    . 

133 

Pond  XXIX   .... 

60* 

PondLII 

2,600 

1 1 ,400 

2,480 

104* 
178* 
I  go* 

PondLXXXIX 

Pond  CXV 

Here  the  number  of  Entomostraca  is  greater  in  the  older  ponds  though  some  irregularities  occur, 
related  to  the  amount  of  rainfall.  In  rainy  seasons  the  increase  with  age  appears  almost  throughout 
the  series. 

*  Intermittent  ponds  which  show  irregularities. 


TABLE   IX 

Showing  Ratio  of  Number  or  Quantity  of  Different  Organisms  when 

the  Maximum  is  100  (After  Shelford) 


Rooted  vegetation 
Entomostraca .... 

Midge  larvae 

vSphaeridae 

Gilled  snails 

Lunged  snails 

Amphipoda 

Crayfishes 

Insects 

Fish 


Relative  age  of  ponds 


20 
32 
80 
o 
20 
10 

50 

10 

40 

100 


60 

35 
80 

50 
50 
50 
go 
50 
go 
87 


100 

100 
100 
100 
100 
100 
100 
100 
100 
87 


The  Entomostraca  are  rated  on  the  basis  of  actual  count  of  six  collections.    The  other  figures  are 

estimates. 

In  passing  from  younger  to  older  ponds  an  increase  is  noted  in 
the  number  of  animals,  excepting  fish.  These  appear  to  decrease, 
probably  because  of  the  increasing  unsuitability  of  the  ponds  as  fish 


50 


FRESH-WATER   BIOLOGY 


breeding  places.  The  oxygen  content  decreases,  particularly  on 
the  bottom.  The  distribution  of  the  hsh  present  in  these  ponds, 
in  so  far  as  breeding  habits  were  known,  was  found  to  be  corre- 
lated with  the  distribution  of  the  bottom  upon  which  they  breed. 
This  becomes  less  and  less  in  amount  as  the  ponds  grow  older. 

TABLE  X 

Showing  Quantit.\tive  Results  of  Examination  of  Factors  Related  to 

Quantity  of  Plankton  (Original) 


No.  of 
collections 


Total  carbonates  in  parts  per  million 

CO2,  cc.  per  liter  at  bottom 

Oxygen,  cc.  per  liter  at  bottom 

Bacteria  per  cc 


Pond  numbers  —  age-series 

2 

14 

28 

138.800 
0.0 
6.28 

779 

160. 200 
3-4 
3-47 
2450 

160.300 
2.7 
2.78 
3550 

On  the  whole  the  carbonates,  CO2,  and  bacteria  are  greater  in 
quantity  according  to  age.     Oxygen  on  the  whole  is  less. 

The  increase  in  quantity  of  animals  with  increase  of  soil  fer- 
tility supports  Knauthe's  contention  that  with  fishes  productivity 
of  water  is  directly  correlated  with  the  richness  of  the  soil.  The 
weak  place  in  Knauthe's  ideas  Hes  in  the  fact  that  as  quantity  in- 
creases quahty  decreases.  The  game  basses  and  sunfishes  give  way 
to  the  more  inferior  types  and  these  are  gradually  succeeded  by 
bullheads,  mud-minnows  and  dogfish.  This  is  due  to  the  destruc- 
tion of  breeding  bottom  for  the  desirable  fishes  by  putrescible 
organic  matter  which  results  in  much  carbon  dioxide,  hydrogen 
sulphide,  ammonia,  and  lack  of  oxygen.  The  German  carp  comes 
into  such  a  series  rather  late  and  thus  productivity  in  carp  is  no 
doubt  correlated  with  a  fertile  substratum. 

The  amount  and  kind  of  rooted  vegetation  are  very  important  to 
animals.  Of  all  the  aquatic  situations  which  present  themselves 
the  largest  lakes  have  fewest  attached  plants,  and  these  are  all 
algae.  Cladophora,  Chara  and  filamentous  algae  are  the  most  com- 
mon. These  do  not  appear  to  have  been  recorded  below  about 
25  meters;  some  of  them  require  solid  bodies  for  attachment  and 
are  probably  most  abundant  on  the  rock  outcrops  of  shallow  water. 

The  vegetation  of  young  streams  consists  largely  of  holdfast 


CONDITIONS   OF   EXISTENCE 


51 


algae  similar  to  those  among  the  rocky  shores  of  a  lake.  These  are 
of  importance  to  animals.  Sluggish  streams  have  rooted  aquatic 
vegetation. 

The  vegetation  is  used  as  breeding  places.  Eggs  are  stuck  into 
plant  tissues  by  the  predaceous  diving  beetles  (Dytiscidae)  and  by 
the  water  scorpions  (Ranatra).  Eggs  are  attached  to  plants  by 
the  electric  light  bug  (Belostomidae),  back  swimmers,  may-flies, 
caddis-flies,  water  scavengers  (Hydrophihdae) ,  long  horned  leaf 
beetles  {Donacia),  snails,  and  many  fishes  (Umbra,  and  probably 
Abramis).  Young  animals  are  often  dependent  upon  plants  for 
shelter,  to  escape  from  enemies,  etc.  Many  insects  must  come 
to  the  surface  for  oxygen.  The  most  important  of  these  are  the 
Dytiscidae  (adults  and  larvae),  the  Hydrophihdae  (adults  and  larvae), 
the  back  swimmers,  Zaitha,  Belostoma,  Donacia,  snails,  Ranatra, 
and  Haliplidae.  Some,  for  example  Zaitha  and  dragon-fly  nymphs, 
lie  in  the  vegetation  and  wait  for  their  prey. 

Different  kinds  of  vegetation  have  different  values  for  animals. 
The  bulrush  is  barren  for  the  following  reasons:  (i)  hardness 
makes  it  a  bad  place  for  eggs;  (2)  there  are  no  cHnging  places; 
(3)  there  is  little  shade;  (4)  it  gives  a  high  temperature  in  summer; 
(5)  there  is  no  great  addition  of  oxygen  by  vegetation;  (6)  it 
does  not  afford  a  suitable  place  for  securing  food.  Equisetum  is 
unfavorable  for  similar  reasons.  Elodea  is  excellent;  Myriophyl- 
lum,  good;  water-Hlies  and  Chara,  only  fair. 

Animal  Communities 

Plants  and  animals  select  their  habitats  through  physiological 
characters.  Sessile  plants  and  animals  have  disseminules  which 
usually  come  to  rest  in  a  great  variety  of  conditions  and  grow  to 
maturity  only  in  those  conditions  that  are  suitable  to  stimulate 
development.  The  physiological  character  of  the  reproductive 
bodies  and  external  conditions  are  responsible  for  the  distribution. 

Animals  select  their  environments  by  one  of  three  methods: 
(i)  by  wide  dissemination  of  reproductive  bodies  and  selective 
survival,  (2)  by  turning  back  when  the  environment  in  which  they 
move  about  is  found  to  change,  and  (3)  by  selection  after  trial  in 
connection  with  migration. 


52 


FRESH-WATER   BIOLOGY 


Numbers  of  animals  select  the  same  environment  because  of 
physiological  similarity.  All  the  animals  occupying  a  relatively 
uniform  habitat  constitute  an  animal  community.  A  physiological 
agreement  exists  among  the  animals  of  a  community.  The  rapids 
community  of  a  large  creek  is  in  a  general  agreement  in  reactions 
to  certain  factors,  and  disagreement  in  respect  to  factors  differ- 
ing in  intensity  vertically.  In  Fig.  5  is  shown  a  noteworthy  agree- 
ment in  reaction  to  bottom  and  current  under  experimental  condi- 


^oSTRATA 


OPEJy  WATER 
AMONG 
STONES 

Son  stones 


V  UNDER 
^STONES 


SPECIES 

ETHEOSTOMA 

POSITIVE  REACTIONS      HYDROPSYCHE  OR  RAPIDS  COMMUNITY 

2 

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0     6 

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m 

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CAMBARUS 

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60NI0BASIS 

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Mz: 

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1      1     1     '1 

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ARGIA 

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PERLA 

'rll 

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PSEPHENUS 

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■:-!-: 

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by 

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{STRONG  current! 
HARD  BOTTOM  | 
MEDIUM  LIGHT 


UNDER  STONES R^ 
ON  STONES  ESISI 
STRONG  LIGHT  ^^ 


AMONG  STONESf?^ 
WEAK  LIGHT  ^^ 
KINAESTHESIA     tHJ 


Fig.  5- 
To  show  the  agreement  and  disagreement  of  the  reactions  of  the  animals  of  the  rapids  community. 
Note  agreement  of  reaction  to  bottom  and  current  and  disagreement  in  two  other  reactions  related  to  the 
level  at  which  the  animals  live.  These  results  were  obtained  by  placing  the  animals  under  experimental 
conditions  in  which  they  had  a  choice  between  different  kinds  of  bottom,  different  strengths  of  light,  and 
in  which  their  behavior  in  a  water  current  was  noted.  In  the  case  of  water  current  the  percentage  of  ani- 
mals headed  upstream  is  given.  When  headed  upstream  animals  are  said  to  be  positive  to  current.  In 
the  case  of  the  other  stimuli  the  percentage  of  animals  in  the  kind  of  conditions  available  was  noted  and  the 
animals  are  said  to  be  ixjsitive  to  the  conditions  in  which  tlie  greatest  number  are  found.  Thus  note 
that  the  darter  (ElheoUoma)  was  80  per  cent  among  the  stones  and  is  said  to  be  positive  to  this  kind  of 
situation.  It  will  be  noted  that  if  the  animals  had  been  100  per  cent  positive  to  the  various  stimuli  the 
entire  400  units  would  be  occupied  in  the  diagram.  This  could  be  true  only  if  there  were  no  other  factors 
entering  into  the  reactions  ol  the  animals.  The  common  names  of  the  animals  are  as  follows:  Etheo- 
iiotna,  darter,  Cambarus,  crayfish;  Goniobasis,  snail;  Ilydropsyche,  caddice  worm;  Argia,  damsel  tly; 
Perla,  stone  lly;   neptagemna,  may-lly  sub-family;    Pscphenus,  water  penny. 


tions.  The  preference  for  hard  bottom  in  these  experiments  means 
the  avoidance  of  sand  as  only  sand  and  hard  bottom  were  present 
in  the  experiments.  Animals  living  under  stones  were  under  stones 
m  darkness  in  the  experiments.  The  snail  (Goniobasis)  which  lives 
on  stones  was  found  on  stones  in  the  experiments.  The  darter 
(Etheostoma)  and  the  crayfish  (Cambarus)  which  live  among  stones 
were  found  among  stones  in  the  experiments.     Thus  the  different 


CONDITIONS   OF   EXISTENCE 


53 


animals  differ  in  their  relations  to  bottom  and  are  in  disagreement 
with  reference  to  their  vertical  distribution  in  nature.  Turning 
to  reactions  to  hght  one  finds  a  comparable  difference.  Animals 
living  beneath  stones  show  a  preference  for  weak  light;  those  living 
on  stones,  medium  Hght;  those  among  stones,  strong  Hght.  If  one 
were  to  study  the  community  in  full  one  would  find  that  reactions 
to  many  other  factors  are  of  importance.  Associative  memory  no 
doubt  plays  a  role.  Thus  there  is  agreement  in  reaction  to  factors 
of  prime  importance  in  the  community  habitat  as  a  whole  and 
disagreement  in  respect  to  factors  differing  strikingly  in  the  levels 
in  which  the  animals  live  within  the  community  habitat.     These 


Black  bass  adults 
Black  bass  young 


Fig.  6. 
Food  relations  of  aquatic  animals.     Arrows  point  to  animal  doing  the  eating.     For  explanation  see  text. 
(Original.) 

levels  are  called  strata.  The  pool  community  shows  a  striking 
difference  from  the  rapids  community  in  the  presence  of  a  strong 
preference  for  sand  bottom  and  in  the  presence  of  the  burrowing 
habit,  both  of  which  are  wanting  among  the  animals  of  the  rapids 
community.  The  non-burrowing  pool  species  are  positive  to  cur- 
rent but  the  burrowing  species  do  not  respond  within  ordinary 
lengths  of  time. 

Forbes  has  devised  a  method  by  which  the  frequency  ot  associa- 
tion may  be  determined  for  any  two  or  more  species.  Data  re- 
garding such  frequency  may  be  obtained  from  collections  made  so 


54 


FRESH-WATER   BIOLOGY 


as  to  cover  several  animal  communities.  The  association  which 
would  result  from  an  indiscriminate  distribution  is  first  eliminated. 
Then  from  the  total  number  of  collections,  the  number  of  collec- 
tions containing  each  species,  and  the  number  of  collections  con- 
taining both  species,  he  derives  a  coefficient  of  association  by  very 
simple  calculations. 

Each  animal  prefers  certain  food.  The  food  relations  of  pond 
animals  are  shown  in  Fig.  6.  For  purposes  of  illustration  one  may 
suppose  the  existence  of  a  community  composed  of  the  species 
named  only. 

Any  marked  change  of  conditions  will  disturb  the  balance  in  an 
animal  community.  Assuming  that  because  of  some  unfavorable 
conditions  in  a  pond  during  their  breeding  period  the  black  bass 
decrease  markedly,  the  pickerel,  which  devours  young  bass,  must 
feed  more  exclusively  on  insects.  The  decreased  number  of  black 
bass  would  reheve  the  drain  upon  the  crayfishes,  which  are  eaten 
by  the  bass;  crayfishes  would  accordingly  increase  and  prey  more 
heavily  upon  the  aquatic  insects.  This  combined  attack  of  pick- 
erel and  cra>'fishes  would  cause  insects  to  decrease  and  the  number 
of  pickerel  would  fall  away  on  account  of  the  decreased  food  supply. 
Meanwhile  the  bullheads,  which  are  general  feeders  and  which  eat 
aquatic  insects,  might  feed  more  extensively  upon  mollusks  because 
of  the  decrease  of  the  former,  but  would  probably  decrease  also 
because  of  the  falling  off  of  their  main  article  of  diet.  It  may 
reasonably  be  assumed  that  the  black  bass  would  recover  its  num- 
bers because  of  the  decrease  of  pickerel  and  bullheads,  the  enemies 
of  its  young.  A  further  study  of  the  diagram  shows  that  a  balance 
between  the  numbers  of  the  various  groups  of  the  community 
might  soon  result.  Under  certain  circumstances,  such  as  the  ex- 
tinction of  the  black  bass,  the  resulting  condition  would  be  entirely 
different  from  the  original  one,  but  a  balance  between  supply  and 
demand  would  nevertheless  finally  be  established.  The  commu- 
nity is  said  to  have  equilibrated  when  such  a  condition  is  reached; 
that  is,  a  new  equilibrium  is  established,  which  fnay  or  may  not  be 
like  the  old. 

The  causes  of  fluctuations  of  numbers  of  organisms  are  numer- 
ous.    Cold  winters  often  destroy  aquatic  vertebrates.     Large  rain- 


CONDITIONS   OF    EXISTENCE  55 

fall  dilutes  the  plankton  and  in  streams  carries  it  away.  Too 
little  sunshine  causes  a  poor  production  of  the  chlorophyll  bearing 
organisms  which  are  a  food  basis  of  others.  Open  winters  favor 
denitrihcation  and  may  be  unfavorable  to  certain  lower  invertebrates. 

Animals  fed  upon  certain  kinds  of  food  supply  enzymes  digest- 
ing that  kind  of  food  in  the  proper  quantity.  The  proportion  of 
the  different  kinds  of  enzymes  changes  with  changes  in  diet.  Under 
proper  experimental  conditions  anti-pepsin,  anti-trypsin,  etc.,  are 
developed  by  organisms.  Organisms  may  develop  immunity  to 
toxins  introduced  into  the  alimentary  canal  with  food,  but  the 
process  is  a  slow  one.  The  introduction  of  toxins,  or  bacteria  re- 
producing them,  directly  into  the  blood  is  doubtless  a  common 
thing  among  aquatic  animals  which  are  probably  as  subject  to 
injury  and  disease  as  are  land  animals  (see  Hill  or  Rosenau). 
Various  aquatic  organisms  must  possess  natural  immunity  for  the 
various  decomposition  products  of  fresh  water  (see  under  bacteria, 
p.  94).  Acclimatization  must  often  involve  the  development  of 
immunity.  As  knowledge  along  these  lines  is  increased  the  con- 
viction that  enzymes,  toxins,  immunity  and  related  phenomena 
play  a  very  important  role  in  the  life  of  fresh-water  animals  grows 
proportionately.  Lillie  has  recently  found  that  comparable  phe- 
nomena are  of  great  significance  in  connection  with  the  fertiliza- 
tion of  the  eggs  of  marine  animals  and  future  investigation  along 
these  lines  will  doubtless  be  of  much  importance. 

Ecological  classification  must  be  based  upon  community  or  phy- 
siological make  up,  behavior,  and  mode  of  life  and  similarity  of 
habitat.  Those  natural  groups  of  animals  which  possess  likenesses 
are  the  communities  which  must  be  recognized.  One  community 
ends  and  another  begins  where  a  general  more  or  less  striking 
difference  in  the  larger  physiological  characters  of  the  organisms 
concerned  occurs.  These  communities  generally  occupy  relatively 
uniform  environments.  For  any  given  organisms  the  other  organ- 
isms of  the  community  are  a  part  of  the  conditions  of  existence. 
There  is  general  agreement  in  the  recognition  of  strata,  of  associa- 
tions as  communities  based  upon  minor  differences  in  habitats, 
and  formations  based  upon  larger  major  differences  in  habitats 
and  considerable  agreement  in  the  use  of  consocies  and  mores. 


56  FRESH-WATER    BIOLOGY 

Communities  of  different  orders  are  given  below  with  taxonomic 
divisions  of  corresponding  magnitude  opposite  for  comparison. 
With  the  exception  of  the  tirst,  these  taxonomic  groupings  do  not 
bear  the  slightest  relation  to  the  ecological  groupings,  but  are  added 
to  indicate  magnitude. 

Ecological  Groups  Taxonomic  Groups 

(Mos)  Mores  Form  (forms)  (species) 

Consocies  Genus 

Stratum  or  story  Family 

Association  or  society  Orde; 

Formation  Class 

Extensive  formation  Phylum 

(Aquatic  and  terrestrial)  (Vertebrates  and  invertebrates) 

Mores  ^  are  groups  of  organisms  in  full  agreement  as  to  physio- 
logical life  histories  as  shown  by  the  details  of  habitat  preference, 
time  of  reproduction,  reaction  to  physical  factors  of  the  environ- 
ment, etc.  The  organisms  constituting  a  mores  usually  belong  to 
a  single  species  but  may  include  more  than  one  species  or  one 
species  may  occupy  two  or  more  habitats  and  be  made  of  several 
mores  (Shelford;  AUee). 

Consocies  are  groups  of  mores  usually  dominated  by  one  or  two 
of  the  mores  concerned  and  in  agreement  as  to  the  main  features 
of  habitat  preference,  reaction  to  physical  factors,  time  of  repro- 
duction, etc. 

Strata  are  groups  of  consocies  and  organisms  not  so  grouped, 
occupying  the  recognizable  vertical  divisions  of  a  uniform  area. 
Strata  are  in  agreement  as  to  material  for  abode  and  general  physi- 
cal conditions  but  in  less  detail  than  the  consocies  which  constitute 
them;  for  example,  the  understone  stratum  of  a  rapid  brook  (see 
Fig.  5,  p.  52). 

1  Mores  (latin  singular  mos),  "behavnor,"  "habits,"  "customs";  admissible 
here  because  behavior  is  a  good  index  of  physiological  conditions  and  constitutes  the 
dominant  phenomenon  of  a  physiological  life  history  and  of  community  relations. 
This  term  is  used  just  as  form  and  forms  are  used  in  biology,  in  one  sense  to  apply 
to  the  general  ecological  attributes  of  motile  organisms,  in  another  sense  to  animals 
or  groups  of  animals  possessing  peculiar  attributes.  When  applied  in  this  latter 
sense  to  single  animals  or  a  single  group  of  animals  the  plural  is  used  in  a  singular  con- 
struction. This  seems  preferable  to  using  the  singular  form  mos  which  has  a  different 
meaning  and  introduces  a  second  word.  The  organism  is  viewed  as  a  complex  of 
activities  and  processes  and  mores  is  therefore  a  plural  conception. 


CONDITIONS   OF   EXISTENCE  57 

A  given  animal  is  classified  primarily  with  the  stratum  in  which 
it  breeds,  as  being  most  important  to  it,  and  secondarily  with  the 
stratum  in  which  it  feeds  and  lives,  as  in  many  cases  most  im- 
portant to  other  animals.  The  migration  of  animals  from  one 
stratum  to  another  makes  the  division  Une  difficult  to  draw  in 
some  cases.  Still,  the  recognition  of  strata  is  essential  even  though 
a  rigid  classification  is  undesirable. 

Associations  are  groups  of  strata  uniform  over  a  considerable 
area.  The  majority  of  7nores,  consocies,  and  strata  are  different  in 
different  associations.  A  minority  of  strata  may  be  similar.  The 
term  is  applied  in  particular  to  stages  of  formation  development 
of  this  ranking.  The  unity  of  association  is  dependent  upon  the 
migration  of  the  same  individual  and  the  same  mores  from  one 
stratum  to  another  at  different  times  of  day  or  at  different  periods 
of  their  life  histories.  Such  migration  is  far  more  frequent  than 
from  one  association  to  another. 

Formations  are  groups  of  associations.  Formations  differ  from 
one  another  in  all  strata,  no  two  being  closely  similar.  The  num- 
ber of  species  common  to  two  formations  is  usually  small  (e.g., 
5  per  cent).  Migrations  of  individuals  from  one  formation  to 
another  are  relatively  rare. 

The  following  is  a  list  of  the  commoner  fresh-water  commu- 
nities: 

I.  Communities  of  ice,  snow,  and  glacier  pools  (Moore). 

They  live  at  0°  C.  or  below  throughout  the  year  (worms,  insects,  and 
crustaceans) . 

II.  Stream  Communities  (Shelf ord). 

1.  Communities  of  snow  and  ice  fed  streams.  They  live  at  a  little  above 
the  freezing  point  most  of  the  year.     Insects  are  the  chief  inhabitants. 

2.  Intermittent  Stream  Communities 

a.  Intermittent  rapids  —  variable  conditions  and  fauna 

b.  Intermittent  pool  —  variable  conditions  and  fauna 

c.  Permanent  pool  —  variable  aquatic  conditions  and  hardy  animals 

3.  Permanent  Stream  Communities 

a.  Spring  dominated  stages 

(i)  Spring  consocies  —  often  few  or  no  animals  on  account   of 

water  conditions 
(2)  Spring  brook  associations 


58 


FRESH-WATER   BIOLOGY 


Creek  and  River  Communities 

a.  Pelagic  sub-formations,  independent  of  bottom  and  shores 

b.  Riffle  formation  (turbulent  water  formation) 

c.  Sand  or  gravel  bottom  formations 

d.  Sandy    bottomed    stream    sub-formation,    shifting    bottom    sub- 

formation,  aquatic  desert 

e.  Silt  or  sluggish  stream  communities 

(i)  Sluggish-stream  sub-formations 

(2)  Pelagic  formations 

(3)  Bare  bottom  formations 

(4)  Vegetation  formations 


■'  QlftciALTUl 


Fig.  7- 
Three  stages  in  the  history  of  a  glacial  lake.  A,  An  early  stage  showing  bare  bottom,  and  submerged 
and  emerging  vegetation;  B  and  C,  successive  stages  in  the  deposition  of  i>eat  and  marl  and  the  migration 
of  the  submerged  vegetation  toward  the  center;  Erosion  and  bare  bottom  are  indicated  near  the  shore  at 
the  right  in  A  and  B  but  are  absent  in  C.  The  area  inside  the  emerging  vegetation  is  the  plankton 
region,     (.^fter  Trauseau.) 

III.   Large  Lake  Communities  (Shelf ord;  Whipple). 
Pelagic  formations 


Eroding  rocky  shore  sub-formations  (turbulent  water  formations) 
Depositing,  shifting-bottom  sub-formations 
Lower  shore  formations 
Deep  water  formations 


CONDITIONS  OF  EXISTENCE 


59 


IV.  Lake-Pond  Communities  (see  Figs.  7  and  8)  (Shelf ord). 

1.  Pelagic  sub-formations 

2.  Terrigenous  bottom  formations 

3.  Vegetation  formations 

a.  Submerged  vegetation  associations 

b.  Emerging  vegetation  associations 

4.  Temporary  pond  formations  (Shelford) 

Conditions  of  existence  in  fresh  water  at  any  given  point  are 
changing  in  a  definite  direction.  This  change  involves  every  item 
of  the  environment  which  has  been  enu- 
merated on  the  preceding  pages.  Streams 
wear  down  their  beds,  wear  their  valleys 
wider,  reduce  the  speed  of  their  current, 
grind  their  coarse  bottom  materials  into 
the  finest  silt.  The  waves  of  lakes  cut 
away  the  shores,  grind  up  the  rocks  they 
break  off  in  this  process,  and  deposit  the 
silt  thus  produced  in  the  bottom.  Streams 
lower  the  outlets  of  lakes  and  carry  detri- 
tus into  them. 

Ponds  and  small  lakes  support  vegeta- 
tion which  decays,  filKng  their  bottoms 
with  putrescible  material  which  is  gradu- 
ally transformed  to  humus  with  a  lowering 
of  oxygen  and  the  development  of  poison- 
ous decomposition  products.  The  ponds  sar^p^-j^^i^^ 
and  lakes  are  thus  filled  as  well  as  drained    the  ?5iqn  ofTmeJgirJ  v^egTtation^ 

J      ,,  ,  1   /-        n        1         -I  ,        Crosses  indicate  the  region  of  sub- 

and  all  become  swamp  and  finally  dry  land,    merged  vegetation.    stippUng  indi- 

11.  cates  the  region  of  deep  water  or  the 

Streams  gradually  erode  their  wav  down    hypoiimnion.  The  region  of  piank- 

•^  "^  ton  occupies  the  entire  lake  except 

to  sea  level  and  become  meandering  base  Z^Sr:li^^t:l:.7t^:Zt:l 
level  streams  with  fine  silt  bottom,  sluggish  ^^"^^^^^-^ 
current  and  an  abundance  of  vegetation.  The  base  level  streams 
and  dry  land  are  the  ultimate  fates  of  all  bodies  of  fresh  water. 
With  the  changes  enumerated,  there  is  always  almost  complete 
change  of  animal  and  plant  Kfe.  The  physiological  requirements 
of  the  Kfe  of  the  first  stages  of  the  process  are  entirely  different 
from  those  of  the  last. 


Fig.  8. 
Diagrammatic  representation  of  a 


6o  FRESH-WATER   BIOLOGY 

IMPORTANT   REFERENCES 

.\dams,  Chas.  C.     1913.     Guide  to  the  Study  of  Animal  Ecology.     New  York. 

BiRGE,  E.  A.  and  Juday,  C.     1914-     (See  list  in  Chapter  I.) 

Forbes,  S.  A.     1877.    The  Lake  as  a  Microcosm.     Peoria  Science  Assoc. 

FoREL,  F.   A.     1892-1904.     (See  list  in  Chapter  I.) 

Henderson,  L.  J.     1913.     The  Fitness  of  the  Environment.     New  York. 

Hill,  L.,  Moore,  B.,  Macleod,  J.  J.  R.,  Pembrey,  M.  S.,  and  Beddard, 

A.  P.     1908.    Recent  Advances  in  Physiology  and  Biochemistry.     London. 
Johnstone,  James.     1908.     Conditions  of  Life  in  the  Sea.     Cambridge. 
Mayer,   A.    G.     1908.     The    Swarming   of   the   Atlantic    Palolo.     Carnegie 

Inst.  Pub.  102. 
Moore,  J.  P.     1899.     A  Snow  Inhabiting  Enchytraeid.     Proc.  Acad.  Nat. 

Sci.,  Phila.,  1899  :  125-149. 
Bibliography  and  general  remarks  on  snow-inhabiting  animals. 
Murray,  Sir  John  and  Hjort,  J.     191 2.     The  Depths  of  the  Ocean.     Lon- 
don. 
NEEDHAii,  J.  G.  and  Lloyd,  J.  T.     191 5.     (See  list  in  Chapter  I.) 
Packard,  W.  H.     1907.     The  Effect  of  Carbohydrates  on  Resistance  to  Lack 

of  Oxygen.     Am.  Jour.  Physiol.,  18  :  164-180. 
Regnard,  p.     1891.     (See  Hst  in  Chapter  I.) 
RosENAU,    M.    L.     1914.     Preventative    Medicine    and    Hygiene.     Sec.    II, 

Ch.  I.     Boston. 
Shelford,  V.  E.     1913.     (See  list  in  Chapter  I.) 
Shelford,  V.  E.  and  Powers,  E.  B.     191 5.     An  Experimental  Study  of  the 

Migrations  of  Herring  and  other  Salt   Water  Fishes.     Biol.  Bull.,  28  : 

315-334- 

Ward,  H.  B.     1896.     (See  list  in  Chapter  I.) 

Wells,  M.  M.     191 5.    The  Reaction  and  Resistance  of  Fishes  in  their  Natural 
Environment   to  Acidity,   Alkalinity  and  Neutrality.     Biol.   Bull.,   29  : 
221-257. 
1915a.     The  Resistance  and  Reactions  of  Fishes  in  their  Natural  Environ- 
ments to  Salts.     Jour.  Exp.  Zool.,  19  :  243-283. 

Whipple,  G.  C.     1898.     Classification  of  Lakes  According  to  Temperature. 
Am.  Nat.,  32  :  25-53. 


CHAPTER    III 

METHODS    OF    COLLECTING    AND 
PHOTOGRAPHING 

By  JACOB  REIGHARD 

Professor  of  Zoology  in  the  University  of  Michigan;  Formerly  Director  of  the  Lake  Laboratory  of  the 
U.  S.  Bureau  of  Fisheries,  at  Pul-in-Bay,  Ohio 


Methods  of  Collecting 

I.    Vertebrates 

I.  Fish  must  be  collected  under  the  state  laws  which  usually 
forbid  the  use  in  inland  waters  of  any  apparatus  except  hook  and 
Hne  or  dip  or  lift  nets  held  in  the  hand.  In  most  states  licenses  to 
use  nets  for  scientific  purposes  may  be  obtained  either  from  the 
state  fish  commission  or  from  the  game  and  fish  warden. 

(a)  Seines  are  long  nets  with  a  weighted  lead  line  attached  to 
the  lower  edge  and  a  cork  Hne  attached  to  the  upper  edge  so  that 
the  nets  remain  upright  in  the  water.  When  the  net  is  so  stretched 
that  it  forms  rectangular  meshes  "square  mesh"  is  the  length  in 
inches  of  one  side  of  a  single  square.  For  use  in  brooks  or  for  col- 
lecting small  shore  fishes,  seines  twelve  or  twenty-four  feet  long 
and  four  or  five  feet  in  depth  are  suitable.  The  former  should 
be  of  one-quarter  inch  square  mesh,  while  the  latter  may  be  of 
one-half  inch  square  mesh. 

For  larger  fish,  seines  of  fifty  and  one  hundred  feet  in  length,  five 
to  nine  feet  deep  and  of  inch  mesh  should  be  used,  but  larger 
seines  are  not  easily  handled  by  two  persons.  The  longer  seines 
should  be  of  the  twine  ordinarily  used  for  such  purposes  and 
knotted  at  every  crossing.  For  the  shorter  lengths  the  excellent 
and  cheaper  ''common-sense"  minnow  seines  which  are  woven  to 
resemble  coarse  burlap  may  be  used.  Very  serviceable  seines 
may  be  made  of  a  good  quality  of  heavy  bobbinet  which  may 
be  had  of  dealers  in  dry  goods.  All  seines  are  much  more 
efficient  if  provided  with  a  bag  at  the  center,  as  is  the  Baird  col- 

6i 


62  FRESH-WATER    BIOLOGY 

lecting  seine,  but  seines  of  this  form  are  expensive  and  not  abso- 
lutely necessary. 

Seines  can  be  used  only  where  the  bottom  is  free  from  large 
stones  or  deadwood  and  the  water  not  much  obstructed  by  vegeta- 
tion. A  brail,  or  stout  pole,  is  fastened  by  a  double  half-hitch  to 
both  cork  and  lead  lines  at  each  end  of  the  seine  so  as  to  extend 
from  the  cork  Hne  to  the  lead  Hne  and  keep  the  seine  stretched 
between  the  two  lines.  The  seine  is  then  operated  by  two  persons 
each  of  whom  holds  a  brail  in  such  a  way  that  the  lead  line  is  kept 
close  to  the  bottom  which  it  sweeps,  while  the  seine  forms  an  arc 
of  a  circle  between  the  two  brails.  At  the  end  of  the  haul  the 
seine  is  best  landed  on  a  gently  sloping  bank  by  seizing  the  lead 
line  and  drawing  it  in  first  to  the  bank.  Where  the  bank  does 
not  afford  a  suitable  landing  place  a  short  seine  may  be  ^'tripped  " 
in  any  depth  of  water  by  quickly  pulling  up  the  lead  line  until  it 
Hes  in  the  same  horizontal  plane  as  the  cork  line.  The  seine  sag- 
ging between  the  two  lines  retains  the  fish.  A  short  seine  may  be 
throwTi  or  cast  from  a  boat  in  deep  water  and  immediately  drawn 
in  and  tripped.  Small  surface-swimming  fishes  are  caught  in  this 
way.  Where  a  long  seine  is  to  be  used  in  water  too  deep  to  wade, 
a  heavy  weight  is  attached  to  the  lower  end  of  one  brail  so  as 
to  keep  it  upright  in  the  water.  To  the  same  brail  a  short  rope 
is  so  fastened  that  it  extends  loosely  from  one  end  of  the  brail 
to  the  other.  To  the  middle  of  this  short  rope,  or  bridle,  is 
attached  a  long  hauHng  rope.  The  end  of  the  seine  is  then 
carried  out  into  deep  water  by  means  of  a  boat  and  the  free 
end  of  the  hauling  rope  brought  back  to  shore,  from  which  the 
seine  is  hauled  in  by  means  of  the  rope.  If  a  hauling  rope  and 
weight  are  attached  to  each  brail  the  seine  may  be  set  in  the  water 
at  any  convenient  distance  from  shore  and  parallel  to  it  and  may 
then  be  hauled  to  shore  by  means  of  the  ropes. 

(b)  Trammel  nets  consist  of  one  web  of  fme  twine  of  about  one 
inch  mesh  between  two  webs  of  coarse  twine  of  about  six  inches 
mesh.  A  length  of  one  hundred  feet  and  a  depth  of  six  or  eight 
feet  is  convenient.  The  finc-meshed  web  is  much  deeper  than 
the  coarser  ones  and  all  three  are  attached  between  a  single 
cork  line  and  a  single  lead  line.     The   net  is  ''laid"  in  a  boat 


METHODS    OF    COLLECTING    AND    PHOTOGRAPHING  63 

(see  below  under  gill  nets)  and  is  set  by  stretching  it  along  the 
seaward  edge  of  vegetation  or  other  shelter  in  which  fish  lurk  and 
from  which  they  cannot  be  taken  with  other  nets.  The  net  may 
be  fastened  to  stakes  or  allowed  to  float  in  water  of  about  its 
own  depth,  where  it  stands  upright  like  a  fence.  The  fish  are 
then  driven  from  their  shelter  toward  the  net,  which  they  strike 
with  such  force  as  to  carry  the  nearly  invisible,  fine  web  through 
the  meshes  of  the  coarser  webs,  so  as  to  form  pockets  in  which 
the  fish  are  held.  The  trammel  net  is  easily  transported  and 
very  effective,  especially  in  slightly  turbid  water  or  at  night. 

(c)  Fyke  Nets.  A  fyke  net  is  made  like  a  seine,  but  at  its  middle 
is  left  a  circular  opening  bordered  by  a  hoop  of  wood  or  iron.  To 
the  hoop  is  attached  the  pot,  a  series  of  truncated  cones  of  netting 
open  at  both  ends.  The  smaller  end  of  the  first  cone  leads  into 
the  larger  end  of  the  second  cone  and  this  often  into  a  third. 
The  last  cone  of  the  pot  is  closed  at  its  smaller  end  by  a  draw 
string.  Both  ends  of  the  lead  and  cork  lines  should  be  tied  into 
loops  and  the  net  should  be  ''laid"  in  a  boat  (see  below  under 
gill  nets)  and  taken  to  the  place  of  setting  together  with  two  stout 
poles  of  suitable  length,  a  rope  and  a  heavy  stone  or  other  anchor. 
The  loops  at  one  end  are  shd  over  a  pole  which  is  then  thrust  or 
driven  into  the  bottom.  The  net  is  then  paid  out  from  the  boat 
rowed  in  the  direction  in  which  it  is  desired  to  set  it.  When  the 
pot  is  reached  it  is  thrown  overboard.  When  the  other  end  of  the 
net  is  reached  it  is  fastened  to  a  pole  set  in  the  bottom  in  the 
manner  already  described,  but  the  net  is  left  quite  slack  between 
the  two  poles.  The  pot  is  then  picked  up,  the  rope  attached  to 
the  terminal  funnel  and  the  whole  pulled  usually  toward  the  shore.  ^ 
The  pull  causes  the  net  to  bend  into  a  V  the  wings  of  which 
stretch  from  the  pot  to  the  poles.  The  anchor  is  now  attached  to 
the  end  of  the  rope  and  thrown  overboard.  If  the  water  is  deep 
a  small  cord  with  a  float  at  one  end  is  attached  by  its  opposite 
end  to  the  anchor  line  and  serves  to  pull  up  the  anchor  line  when 
the  pot  is  to  be  lifted.     The  anchor  line  may  be  tied  back  to  a 

^  The  larger  fish  usually  taken  in  a  fyke  are  caught  as  they  go  from  the  vegeta- 
tion zone  or  beyond  it  into  shoal  water.  They  might  be  caught  as  they  leave  the 
shoal  water  by  setting  the  net  the  other  way  about. 


64 


FRESH- WATER    BIOLOGY 


Stake  and  the  anchor  dispensed  with.  Fykes  are  usually  set  across 
the  mouth  of  a  small  bay  or  inlet  but  may  be  placed  anywhere. 
In  running  water  the  net  may  face  either  up  or  down  stream.  It 
may  be  necessary  to  set  a  row  of  stakes  across  the  stream  above 
the  net  to  catch  drift  wood.  When  lish  attempt  to  enter  the  bay 
or  inlet  across  which  the  net  is  set,  they  follow  the  wings  of  the 
fyke  and  enter  the  pot  from  which  they  are  unable  to  escape. 
The  net  may  be  left  set  for  a  long  time  and  the  fish  taken  from  it 
at  intervals  by  lifting  the  pot  and  loosening  the  draw  string.  The 
wings  of  a  fyke  may  be  from  fifteen  to  fifty  feet  long  according  to 
its  location,  but  for  brook  use  fykes  are  made  without  wings. 


Fig  9     Showing  one  end  of  a  gill  net  as  set  when  used  in  the  cod  fishery  on  the  Massachusetts  Coast. 
I,  end  of  the  net.     2,  anchor  line.     3,  anchor.    4,  buoy  line.     5.  buoy.     (After  Ooode.) 

The  fyke  is  an  excellent  net  for  catching  turtles,  but  should  then 
be  modified  as  indicated  in  the  section  on  turtles  (p.  66). 

(d)  Gill  nets  are  made  of  very  fine  cotton  or  linen  twine  and  of 
various  meshes.  Inch  or  two-inch  square  mesh  and  a  length  of 
one  hundred  or  one  hundred  and  fifty  feet  are  useful  for  collecting. 
The  nets  are  intended  to  be  left  out  for  days,  at  least,  on  the 
bottom  in  deep  water.  They  stand  upright  in  the  water  (Fig.  9) 
and  the  fish  strike  them  usually  at  night  and  become  entangled  in 
the  meshes,  so  that  they  are  commonly  dead  when  the  nets  are 
Hfted. 

A  small  rope  of  at  least  the  length  of  the  net  is  attached  to  one 
end  of  the  cork  line  and  a  stone  or  other  heavy  weight  to  serve  as 
an  anchor  is  made  fast  to  the  other  end  of  the  rope.     The  anchor 


METHODS   OF   COLLECTING   AND   PHOTOGRAPHING  65 

is  placed  in  the  boat  and  the  rope  carefully  coiled  near  it.  The 
net  is  then  carefully  "laid"  by  folding  it  back  and  forth  after 
the  manner  of  a  folding  fan.  It  is  not  necessary  to  keep  the  net 
stretched  to  its  full  width  between  the  cork  and  lead  lines.  When 
the  opposite  end  of  the  net  is  reached  a  second  and  equal  anchor 
Hne  with  anchor  attached  is  made  fast  to  the  cork  line.  A  number 
of  gill  nets  may  be  fastened  together  end  to  end  and  used  as  a 
single  net,  with  a  single  pair  of  anchor  lines  and  anchors.  It  is 
convenient  to  lay  the  net  on  a  ''  setting  board  "  four  or  five  feet 
long  and  as  wide.  The  board  may  be  made  like  a  batten  door  of 
smooth  boards  and  placed  across  the  stern  of  the  boat,  where  the 
net  is  to  be  set.  The  net  should  be  set  where  it  is  thought  fish 
will  run,  as  across  a  narrow  neck  connecting  two  parts  of  a  lake  or 
across  the  mouth  of  a  bay.  If  the  net  is  set  down  the  wind  it  may 
be  handled  by  a  single  person.  The  upper  anchor  is  thrown  out 
and,  as  the  boat  drifts  with  the  wind,  first  the  anchor  line  and 
then  the  net  are  paid  out,  and  care  is  taken  that  the  net  is  not 
fouled  in  going  over  the  side  of  the  boat.  When  the  second  anchor 
line  has  been  paid  out  to  near  its  middle  a  small  rope,  long  enough 
to  reach  to  the  surface  of  the  water  is  made  fast  to  it  and  to  the 
free  end  of  this  is  fastened  a  piece  of  wood  to  serve  as  a  float. 
When  the  end  of  the  second  anchor  line  is  reached,  the  net  is 
pulled  taut,  and  the  second  anchor  thrown  over.  The  fish  may 
be  removed  from  the  net  by  pulling  up  the  float  line  until  the 
anchor  line  is  recovered  and  by  then  running  along  this  and  the 
cork  line  of  the  net,  hand  over  hand,  allowing  the  part  of  the  net 
that  has  been  examined  to  fall  back  into  the  water. 

{e)  Traps.  A  cylinder  is  formed  of  wire  netting  of  one-fourth 
or  one-half  inch  mesh.  Into  one  end  of  this  is  fitted  a  cone  of  the 
same  material  with  its  apex  directed  inward.  The  apex  is  trun- 
cated so  as  to  leave  an  opening  two  or  more  inches  in  diameter. 
A  similar  cone  may  be  fitted  over  the  other  end  of  the  cylinder  or 
this  may  be  closed  by  a  flat  cover  of  netting.  One  end  of  the 
.cylinder  must  be  removable  to  permit  baiting  and  removal  of  the 
fish.  The  cylinder  may  be  two  or  three  feet  long  and  a  foot  in 
diameter  and  the  cone  eight  inches  deep  —  but  larger  sizes  may  be 
used  to  advantage.     The  trap  is  baited  with  fish  or  meat  hung 


66  FRESH-WATER    BIOLOGY 

near  its  middle  by  a  wire  and  is  lowered  to  the  bottom  at  any 
depth  by  a  cord  supported  by  a  float.  It  is  used  chiefly  for  smaller 
fish,  crayfish,  or  Necturus.  It  may  be  set  anywhere  but  is  espe- 
cially useful  where  water  is  obstructed  by  vegetation,  rocks,  or 
fallen  trees  so  that  nets  cannot  be  drawn. 

(/)  Care  of  nets.  Both  fyke  nets  and  gill  nets  should  be  taken 
from  the  water  at  intervals,  washed,  dried,  and  mended  before  they 
are  agidn  used.  For  mending  it  is  necessary  to  have  a  supply  of 
twine  of  which  the  nets  are  made  and  several  wooden  shuttles  or 
needles  such  as  fishermen  use;  it  is  also  necessary  to  learn  the 
knot  used  in  maJdng  nets  by  hand.  All  nets  when  taken  from 
the  water  should  be  washed  and  carefully  dried  before  being  put 
away.  If  left  with  the  twine  clogged  with  accumulated  organic 
matter  they  rapidly  decay  and  this  decay  is  the  more  rapid  if  the 
nets  are  damp.  They  may  be  stored  by  hanging  them  loosely  in 
some  dry  loft  or  they  may  be  packed  in  bags  and  hung  from  the 
ceihng  by  cords.  If  left  accessible  to  rats  or  mice  they  may  be 
ruined  by  being  utilized  as  nest  material. 

In  laying  a  net  for  storage  or  transportation  the  lead  and  cork 
lines  should  each  be  folded  back  and  forth  on  itself.  The  lead 
Line  should  be  so  folded  that  the  leads  are  brought  together  and 
they  should  then  be  securely  tied  together.  If  this  precaution  is 
not  taken  the  loose  leads,  carrying  the  lead  line  with  them,  become 
woven  back  and  forth  through  the  net  and  the  whole  is  almost 
inextricably  tangled  together. 

2.  Turtles.  Turtles  are  best  taken  in  a  turtle  net  which  is  a  form 
of  fyke  net.  It  should  be  of  heavy  twine  and  coarse  mesh  and,  if  it 
is  desired  to  keep  the  turtles  alive,  should  be  modified  as  follows: 
The  terminal  section  of  the  pot  is  made  cyhndrical  or  the  whole 
pot  may  be  made  with  square  hoops.  A  circular  opening  is  cut  in 
the  upper  side  of  the  terminal  section  of  the  pot  and  to  this  is 
attached  the  lower  end  of  a  cylinder  of  netting  which  extends  to 
the  water's  surface.  The  upper  end  of  this  cylinder  is  attached  to 
an  opening  cut  in  one  side  of  a  wooden  box  provided  on  the  oppo- , 
site  side  with  a  hinged  lid  fastened  with  a  hasp.  The  box  is  sup- 
ported at  the  surface  of  the  water  on  poles  set  in  the  bottom. 
When  turtles  reach  the  terminal  section  of  the  pot  they  are  able 


METHODS  OF   COLLECTING  AND   PHOTOGRAPHING  67 

to  enter  the  box  through  the  cylinder  of  netting  and  are  thereby 
saved  from  drowning  which  would  ensue  if  they  could  not  reach 
the  air.  They  may  be  removed  through  the  lid  at  the  convenience 
of  the  collector. 

II.  Invertebrates 

Invertebrates  are  to  be  collected  in  three  situations:  in  the 
aquatic  vegetation  bordering  the  shore,  in  the  open  water,  beyond 
this  vegetation-zone,  and  on  the  bottom,  so  that  the  apparatus 
suitable  to  each  of  these  situations  may  be  separately  considered. 

It  is  convenient  to  consider  first  those  methods  designed  for 
quahtative  work,  for  finding  out  what  organisms  are  present,  and 
second  those  methods  by  which  the  number  or  quantity  of  organ- 
isms present  in  a  unit  volume  of  water  or  under  a  unit  area  of  sur- 
face may  be  determined. 

A.    Collecting  in  Littoral  Vegetation 

1.  By  dip  nets.  The  dip  net  (Fig.  10)  is  here  of  greatest  use.  It 
consists  of  a  conical  netted  bag  about  one  foot  in  diameter  and 
eighteen   inches  deep    attached    to    a    

stout    ring   of    brass   or   iron,    firmly 

fixed  to  a  stiff,  wooden  handle  seven 

or  eight  feet  long.     The  lower  third  of 

the  net  may  often  be  advantageously 

lined  with  thin,  cotton  cloth  to  retain 

smaller  organisms.     A  form  of  this  net 

adapted  to  scraping  flat  surfaces,  such  ^^^ 

as  logs,  flat  stones,  banks,  etc.,  is  also     ^ 

,  /_,.  .  ^     -  .      .  ,  Fig.  10.    Two  forms  of  dip  net.    For  de- 

ShOWn  (Fig.  10).        It  has  a  Semi-CirCUlar  scription  see  text.     (From  photographs 

rim  and  a  shallow  bag  of  canvas  with 

a  bottom  of  No.  6  or  8  bolting  cloth.  The  handles  used  on  dip 
nets  are  rake  handles.  The  iron  rings  may  be  made  by  any 
blacksmith.  The  bags  are  sold  as  minnow  dip  nets  by  dealers 
in  fishing  tackle  or  by  mail-order  houses. 

2.  By  collecting  larger  aquatic  plants.  With  such  nets  many 
forms  visible  to  the  naked  eye  may  be  collected  directly,  or  the 


68 


FRESH-WATER    BIOLOGY 


Fig.  II.  Pieters'  plant 
grapple.  (. After 
Pieters.) 


aquatic   vegetation   may   be   obtained   and   searched   for   smaller 

organisms.  Many  forms  that  are  detected  with  difficulty  in  the 
field  appear  in  abundance  in  the  water  of  small 
dishes  containing  aquatic  plants,  when  allowed  to 
stand  undisturbed  for  some  days  (annehds,  flat 
worms,  rotifers,  hydras,  protozoa,  etc.).  Sub- 
merged vegetation  which  grows  in  deeper  water 
and  cannot  be  reached  by  other  means  may  be 
obtained  by  dragging  behind  a  boat  the  grapple 
(Fig.  ii)  described  as  follows  by  Pieters  (1901): 
"This  is  made  by  passing  four  or  five  bent  steel 
wires  through  a  piece  of  i^-inch  pipe  and  bending 
back  the  free  ends  to  make  hooks.  The  pipe  was 
filled  with  lead  to  make  it  heavier  and  a  rope 

fastened   through  the  loops  of  the  wires." 

3.    TJie  cone  dredge.      Many  organisms  are  too  small  to  be  readily 

collected  with  dip  nets  and  many  escape  when  aquatic  vegetation 

is  gathered.     These  may  be  readily  obtained 

by  this  ingenious  device  of   Professor  E.  A. 

Birge,  which  may  be  run  among  aquatic  plants 

where  the  townet  cannot  be  used. 

The   cone    dredge    (Fig.    12)    now   used  by 

Professor  Birge  consists  of  four  parts. 

A.  The  body  is  a  cy Under  of  sheet  copper 
three  inches  in  diameter  and  one  inch  deep, 
wired  at  its  lower  edge  to  form  a  lip  on  the 
outside.  A  brass  wire  bent  into  a  V  with  an 
eye  at  its  apex  is  soldered  by  its  free  ends 
inside  the  body  while  its  apex  extends  upward 
like  the  bail  of  a  pail. 

B.  A  cone  of  brass  wire  netting  of  about 
twenty  meshes  to  the  inch  fits  over  the  bail. 
Its  base  is  soldered  to  the  body  and  its  apex 
to  the  eye  of  the  bail  which  projects  through 
it.     Two  flat   loops  of  wire   soldered   to   the 

outside    of    the    body    serve    for    the    attachment    of    cords. 

C.  The  net  is  a  conical  bag  of  cheesecloth  eighteen  to  twenty- 


FlG.  1 


Cone  dredge.  At 
bottom  hinnel-filtc-rforuse 
with  the  drcflpc.  (Original 
photograph  from  appara- 
tus loaned  by  Professor 
Birge.) 


METHODS  OF   COLLECTING   AND   PHOTOGRAPHING  69 

two  inches  long  and  may,  by  altering  the  dimensions,  be  cut  out 
according  to  the  directions  given  for  the  townet.  It  should  be 
faced  with  strong  muslin  for  two  or  three  inches  at  each  end.  It 
is  tied  by  its  upper  end  over  the  flange  on  the  body. 

D.  The  screw  lip  consists  of  the  screw  top  of  a  kerosene  oil  can, 
extended  by  soldering  to  the  male  screw  a  copper  cylinder  an  inch 
and  a  quarter  long.  The  cylinder  is  wired  at  its  top  to  form  a 
projecting  flange  over  which  the  tip  of  the  net  is  tied.  The  cap 
is  weighted  by  soldering  to  it  a  lead  ring  of  about  two  ounces. 
Two  loops  of  wire  soldered  to  the  outside  of  the  screw  tip  serve  for 
the  attachment  of  cords  from  the  loops  on  the  body  and  these 
support  the  weight  of  the  screw  tip  and  take  the  strain  off  the 
net. 

This  net  may  be  readily  dragged  behind  a  boat  among  dense 
water  plants  by  means  of  a  cord  attached  to  the  eye.  The  cone 
fends  off  the  water  plants  and  lessens  the  amount  of  debris  entering 
the  net  and  clogging  it.  The  net  may  also  be  thrown  from  shore 
to  a  distance  of  thirty  or  forty  feet  and  safely  hauled  back  through 
thick  vegetation.  It  may  also  be  run  at  some  depth  or  along  the 
bottom  by  attaching  a  suitable  weight  to  the  hne,  two  or  three  feet 
in  front  of  the  cone. 

When  a  haul  has  been  made  the  screw  cap  is  removed  so  that 
the  contents  of  the  net  fall  into  a  cup  or  jar  of  water.  Several 
successive  hauls  may  be  united.  WJien  the  foreign  matter  which 
always  enters  the  net  has  settled  to  the  bottom  of  the  jar,  the  clear 
water  containing  the  entomostraca  is  poured  into  a  metal  funnel 
with  a  long  neck  made  of  brass  wire  gauze  of  about  forty  meshes  to 
the  inch  (Fig.  12).  The  neck,  which  serves  as  a  filter,  terminates 
in  a  tin  ring  which  is  corked.  When  the  entomostraca  have  been 
filtered  from  the  water,  the  cork  is  removed  and  the  catch  washed 
into  an  eight-dram  homeopathic  vial,  short  form,  in  which  it  is 
preserved. 

When  many  catches  from  different  localities  are  to  be  kept  sep- 
arate. Professor  Birge  uses  flat  bags,  one  by  three  inches,  made  by 
stitching  together  on  the  sewing  machine  pieces  of  India  linen. 
Before  going  into  the  field  the  bags  are  numbered  and  strung  on 
a  thread  so  that  they  may  be  pulled  off  in  order.     The  catch  is 


70 


FRESH-WATER    BIOLOGY 


poured  through  an  ordinary  tin  funnel  into  the  bags,  which  are 
then  tied  and  placed  in  the  preservative. 

An  "improved"  form  of  cone  dredge  has  been  described  by  Wol- 
cott  (1901),  who  has  worked  out  a  standard  type  of  holder  for  cone 
dredge,  dip  net,  sieve,  and  scoop.  A  folding-cone  dredge  is  sold 
under  the  name  simplex  plankton  net.     Its  cone  is  made  of  cloth. 

The  plankton  pump  may  also  be  used  for  collecting  free  swim- 
ming forms  among  aquatic  vegetation. 

In  making  collections  along  the  margin  of  a  pond  or  stream,  or 
in  the  puddles  of  a  bog  or  half-dried  ditch,  it  is  advantageous  to 
use  a  dipper  with  a  cane  or  short  bamboo  handle.  One  may 
fasten  to  such  a  handle  a  wide-mouth  bottle,  a  dipper  with  fine 
metal  gauze  bottom,  a  pruning  hook  or  other  apparatus  for 
securing  samples  of  the  plant  or  animal  Hfe  in  such  places  as  are 
somewhat  inaccessible.  A  shallow  glass  dish  or  white  soup  plate 
is  very  useful  in  examining  immediately  refuse  obtained  from  the 
margin  or  bottom  of  such  pools.  By  some  such  means  the  heavier 
particles  of  sand  and  silt  may  be  separated  from  the  collection 
before  it  is  preserved. 

B.    Bottofn  Collecting 

The  dredge  that  is  commonly  used  in  deep-sea  work  is  of  little 
value  in  fresh  water  owing  to  the  relative  barrenness  of  lake  bottoms. 
The  larger  bottom  vegetation  may  be  obtained  at  any  depth  by  the 
use  of  Pieters'  grapple  already  described.  For  the  smaller  organ- 
isms that  Hve  in  the  superficial  ooze  of  the  bottom,  the  cone  dredge 
or  the  townet  may  be  used.  A  weight  heavy  enough  to  bring  the 
line  to  the  bottom  is  attached  to  the  towline  two  or  three  feet  in 
front  of  the  net.  The  cone  dredge  when  attached  to  a  weighted 
line  may  be  made  to  run  along  the  bottom  by  weighting  the  screw 
tip,  but  in  that  case  it  is  well  to  fasten  a  band  of  cloth  about  the 
base  of  the  wire  cone  so  as  to  leave  only  the  upper  part  free. 
The  net,  while  admitting  water  through  the  tip  of  the  wire  cone, 
then  gHdes  over  the  bottom  without  scraping  up  mud.  A  townet 
mounted  on  runners,  as  shown  here  (Fig.  13),  has  been  found 
very  useful  by  the  writer  for  taking  organisms  just  above  soft 
bottom.     From  the  iron  ring  which  supports  the  mouth  of  the 


METHODS   OF   COLLECTING   AND    PHOTOGRAPHING 


71 


in.  14.  Triangle  dredge 
ds  used  by  the  writer. 
For  description  see 
text.  (From  an  orig- 
inal photograph.) 


net  four  pieces  of  half-inch  band  iron  extend  radially  for  about 
three  inches  and  then  turn  and  run  parallel  to  one  another  for  some 
distance  beyond  the  tip  of  the  net. 
Here  they  are  bent  inward  and 
riveted  at  the  center. 

To  collect  organisms  that  live 
in  the  bottom  it  is  necessary  to 
use  some  form  of  dredge  that  will 
bring  up  the  bottom  material. 
To  bring  up  the  superficial  ooze 
the  weight  attached  to  the  townet 
line  or  cone  dredge  line  may  have 
the  form  of  a  rake,  or  be  other-  ' 

.  ,  1  .  .  Tig.  i^.     Townet    on 

wise  irregular,    so    that   it   stirs  up       runners,      designed 

,  ^       by  the  writer.    For 

the  ooze  and  drives  animals  from    description  see 

text.  (Fromanong- 

it  to  be  caught  in  the  net.  For  inai  photograph.) 
animals  that  cannot  be  thus  dislodged  the  writer  has  used  a 
triangle  dredge  (Fig.  14).  This  consists  of  a  bag  of  one-fourth- 
inch  square  mesh  netting,  or  burlap,  or  other  coarse  material, 
lined  at  the  bottom  with  muslin  and  hung  from  a  wrought-iron 
frame  which  may  be  made  by  any  blacksmith.  The  frame 
consists  of  an  equilateral  triangle,  twelve  to  fifteen  inches  on 
each  side,  of  heavy  band  iron,  and  of  three  stout  iron  rods, 
one  extending  from  each  angle  of  the  triangle  at  right  angles 
to  its  surface,  to  a  distance  of  about  three  feet.  The  edge  of 
the  triangle  is  formed  into  large  saw-teeth  bent  slightly  out- 
ward so  that  they  tend  to  dig  into  the  bottom.  An  eye  at  each 
corner  serves  to  attach  a  rope  which  extends  to  the  hauling  line. 
The  rods  serve  to  keep  the  triangle  upright  when  the  net  is  drawn 
along  the  bottom,  so  that  the  mouth  of  the  bag  is  open  and  the 
teeth  plow  into  the  bottom. 

Another  useful  type  of  dredge  has  the  form  of  a  triangular  or 
quadrangular  pyramid,  whose  side  and  slant  height  are  each  about 
six  inches.  A  number  of  stout  steel  wires,  about  six  on  each  side, 
are  soldered  together  so  as  to  form  the  apex  of  the  pyramid,  while 
their  opposite  ends  are  bent  slightly  outward  beyond  its  base,  so 
that  they  project  like  the  teeth  of  a  comb.     The  framework  thus 


y2  FRESH-WATER    BIOLOGY 

formed  is  covered  ^vith  wire  cloth  and  the  apex  of  the  pyramid  is 
filled  with  lead  to  the  depth  of  an  inch  and  a  half.  An  eye  at  each 
angle  serves  to  attach  a  cord.  This  dredge  is  very  effective  in 
collecting  bottom  mollusca. 

C.    Open  Water  Collecting  —  Qualitative  Methods 
I.    The  toii'uet  is  the  simplest  device  for  collecting  the  plankton 

organisms  which  abound  in  the  open  water.  The  following  direc- 
tions for  making  a  townet  are  modified  from 
Kofoid  (1898).  The  completed  net  (Fig.  15) 
consists  of  a  conical  bag  of  India  linen  or  better 
of  silk  bolting  cloth  hung  from  a  ring  which  is  sup- 
ported by  three  cords.  The  bolting  cloth  may 
be  number  12,  16  or  20  and  is  to  be  had  from 
dealers  in  mill  supplies,  but  discarded  cloth  may 
often  be  obtained  from  flour  mills.  Before  cut- 
ting the  cloth  should  be  shrunk  by  boiling  in 
soapsuds  and  then  pressed.  A  pattern  for  cutting 
two  nets  twelve  inches  in  diameter  from  a  yard 

^wkhoutbuK.  /Hvlre  of  forty-inch  wide  bolting  cloth  is  given  (Fig.  16). 
dr"aw  ?hies.    hp,  head  j^g  cloth  has  bccn  doublcd  lengthwise  (with  the 

piece  sewn  to  top  of  net.  ^11  .1  1 

linT^  '(Modified'^fmm  warp)  and  is  shown  with  the  fold  at  the  right  and 
^°fo'd)  the  two  free  edges  at  the  left.     With  a  radius  equal 

to  the  length  of  the  cloth  two  arcs  are  struck  from  the  points  a 
and  b  as  centers.  These  arcs,  which  form  the  tops  of  the  completed 
nets,  must  be  equal  in  length  to  one-half  the  circumference  of  the 
net  hoop  and  these  lengths  may  be  most  readily  determined  by 
rolling  the  net  ring  along  the  arcs.  An  additional  width  must  be 
allowed  on  the  piece  d,  since  this  is  in  two  parts  and  has  two 
seams.  This  is  accomplished  by  cutting  the  two  pieces  apart 
along  the  line  ab  a  quarter  of  an  inch  to  the  right  of  the  diagonal. 
The  pieces  are  then  formed  into  cones  and  closed  by  a  French 
seam  along  the  side  and  by  the  seam  across  the  apex.  The  top 
of  the  net  is  finished  by  sewing  on  a  band  made  of  a  doubled 
strip  of  butcher's  linen,  cut  bias  and  provided  with  a  heavy  cord 
sewed  into  its  upper  margin.  The  net  is  attached  to  the  ring 
by  over-cast  stitches  of  heavy  thread.     The  ring  r  (Fig.  15)  of 


METHODS   OF    COLLECTING    AND    PHOTOGRAPHING 


73 


No.  5  spring  brass  wire,  standard  American  gage,  has  three  pairs 
of  wire  rings  h  soldered  on  it  at  equal  distances  to  hold  the 
drawlines  dl  in  place.  To  the  drawlines  at 
their  junction  a  short  cord  wl  may  be  attached 
for  the  support  of  a  weight. 

If  the  net  is  used  in  this  form  the  catch 
must  be  removed  from  it  by  turning  it  inside 
out  and  sousing  the  tip  in  a  bottle  of  water. 
It  is  more  convenient  to  cut  off  the  tip  of 
the  net  along  the  line  ij  and  tie  into  it  a 
screw  tip  like  that  described  below  for  the 
cone  dredge,  but  without  the  weight.  A  short 
glass  tube  closed  by  a  rubber  stopper  or  a 
bucket  like  that  of  the  plankton  net  may  be 
used  in  place  of  the  screw  tip.  Provided  with 
a  bucket  the  net  is  identical  with  the  plankton 
net  except  that  it  lacks  the  canvas  cone. 

The  townet  may  be  dragged  behind  a  boat 
either  at  the  surface  or  submerged  to  any  depth 
by  means  of  a  weight  attached  to  the  weight 
line.  When  the  haul  is  completed  the  net  is 
soused  in  the  water  or  water  is  thrown  on  its  outer  surface,  until 
the  contents  are  washed  to  the  tip  of  the  net,  which  is  then  turned 
inside  out  and  the  contents  obtained  by  rinsing  the  tip  in  a  bottle 
of  water,  or  allowing  them  to  fall  into  preserving  fluid.  The  pro- 
cedure for  a  net  provided  with  a  bucket  is  described  under  the 
plankton  net  and  cone  dredge. 

2.  Plankton  Cylinders.  Various  forms  of  apparatus  have  been 
designed  for  collecting  plankton  from  a  rapidly  moving  boat.  These 
are  made  with  a  very  small  opening  for  the  entrance  of  water  and 
with  a  large  filtering  surface.  They  are  designed  to  reduce  the 
pressure  of  the  water  on  the  filtering  surface.  They  are  described 
by  Steuer  and  others.  They  are  chiefly  of  use  in  the  sea  or  in 
other  situations  accessible  only  to  large  vessels  and  are  little  em- 
ployed in  fresh  water.  The  plankton  cylinder  is  one  form  of  such 
apparatus  in  which  a  torpedo-shaped  metal  jacket  admits  water 
through  a  small  opening  on  its  conical  end  and  carries  the  filtering 
gauze  in  the  interior  or  on  its  other  end. 


Fig.  i6.  Showing  method  of 
laying  out  a  pattern  for  cut- 
ting two  townets  from  a 
yard  of  cloth  forty  inches 
wide,  a-b,  line  along  which 
cloth  is  to  be  cut.  c-d,  the 
two  net  patterns,  e-f,  seam 
by  which  the  bottom  of  the 
net  is  closed  if  no  bucket  is 
attached  (see  Fig.  15).  g-h, 
line  of  attachment  of  bucket. 
i-j,  line  along  which  net  is 
cut  ofif  when  bucket  is  used. 
(.'\fter  Kofoid.) 


FRESH- WATER    BIOLOGY 


D.    Quantilalivc  Methods  in  Open  Water 

I.  The  Quantitative  Plankton  Net.  The  plankton  net  and  pump 
are  intended  for  the  collection  of  plankton  for  quantitative  inves- 
tigations. The  plankton  net  differs  from  the  townet  described 
in  that  its  rim  extends  upward  into  a  truncated  cone  of  canvas 
(Fig.  17),  and  that  it  is  provided  with  a  removable  bucket. 

The  canvas  cone  hinders  bottom  ooze  from  entering  the  net  and 
also  hinders  the  slopping  out  of  the  contents  as  the  net  is  drawn 
above  the  surface.  It  serves  further  to  lessen  the  diameter  of  the 
net  opening,  so  that  a  larger  fraction  of  the  column  of  water  above 
the  net  opening  is  filtered  and  less  of  it  is  pushed  aside  by  the 
resistance  of  the  filtering  gauze. 

The  plankton  net  (Fig.  17)  in  use  at  the  University  of  Wisconsin 
is  here  first  described  with  the  permission  of  Professor  Birge.     The 

ring  which  supports  the  net  is  about 
seven  inches  in  diameter  and  from  this 
measurement  the  other  dimensions  of 
the  apparatus  may  be  roughly  measured 
on  the  figure.  The  canvas  cone  stretches 
from  the  net  ring  to  an  upper  ring  and 
both  rings  are  of  one-eighth-inch  spring 
brass  wire.  Three  eight-shaped  pieces 
of  lighter  wire  are  strung  on  each  ring 
through  one  opening,  while  the  other 
opening  receives  the  eyes  on  the  ends 
of  three  connecting  rods  which  hold  the 
two  rings  together.  The  upper  support- 
ing ring  has  three  brass  rings  soldered  to 
it  for  the  attachment  of  the  draw  lines. 
The  canvas  cone  and  the  band,  which 
is  ordinarily  sewn  to  the  top  of  the  net, 
are  in  this  case  cut  from  one  piece  of 
shrunken  canvas.  This  is  sewn  around 
the  upper  supporting  ring  and  is  attached 
to  the  inside  of  the  lower  ring  by  means  of  a  tape  sewn  to  its  out- 
side.    The  bolting  cloth  net  (No.  16  or  No.  20  cloth)  is  sewn  to 


Fig.  17.  Wisconsin  plankton  net. 
(Original  photograph  from  appa- 
ratus loaned   by   Professor  Birge.) 


METHODS  OF   COLLECTING  AND   PHOTOGRAPHING 


75 


8.  Bucket  of  Wisconsin  plankton  net.  From 
apparatus  loaned  by  Professor  Birge.  At  right  is  one 
of  the  writer's  tubes  for  filtering  plankton.  For  de- 
scriptions see  text.     (From  original  photographs.) 


the  inside  of  the  band,  with  its  margin  turned  back  over  its  outer 

surface  for  the  fraction  of  an  inch.     By  this  construction  the  canvas 

cone  folds  conveniently  for  transportation,  while  the  inner  surfaces 

of  cone  and  net  are  continuous  and  smooth,  so  that  plankton 

organisms  do  not  readily  lodge 

on   them.     If   convenience   in 

transportation  is  not  important 

the  cone  may  be  better  made 

of  sheet  brass. 

The  original  feature  of  this  ^^J^^^, 

net  is  the  bucket  (Figs.  i8  and 

19),  which  is  made  of  telescope 

tubing  of  two  sizes.     The  smaller  size   (two  inches  in  internal 

diameter)  is  used  to  make  the  headpiece  shown  attached  to  the  net 

in  Fig.  17.  This  (Fig.  19,  a)  is  one 
and  three  eighths  inches  long  and  is 
fastened  to  the  net  by  means  of  a 
brass  band  clamp  (Fig.  19,  h)  made  of 
two  pieces,  with  wings  at  the  ends 
through  which  pass  clamp  screws. 
A  pin  soldered  into  the  headpiece 
fits  a  hole  in  each  half  of  the  clamp 
and  prevents  its  turning  when  the 
bucket  is  twisted  to  remove  it  (seen 
near  the  upper  margin  of  Fig.  19,  a). 
Three  brass  rings  soldered  to  the  out- 
side of  the  band  clamp  serve  to  attach 
cords  which  extend  to  the  lower  sup- 

"'SJJn  pialtT  ^"."TXalpi'ift   porting  ring  of  the  canvas  cone  and 

headpiece  clamp;  c,  bucket;  d,  e,  lower  and  j.-\  •    T_  ^      r  4-1,  ^  U     ^1      *. 

upper  band  clamps;   /,   one  of   the  side  Carry  thC  WClght  Ot   the   bUCkct. 

clamps  with  screws;  g,  side  clamp  in  posi-  —,,        ,        t./t-'*  n\'  j         rj_i 

tion;    h,  semi-cylindrical  rod   soldered  to  1  hC  OUCket  (-Tig.   lo)  IS  made  01  tClC- 

strip  between  windows;  /,  stem  of  the  plug  .  i   •    i      r 

which  closes  the  spout  seen  below  at  left  of  SCODC  tubmCf  of  a  SlZC   whlCh   IltS  OVCr 

c;  J,  millimeter  scale.     For  description  see  ^ 

'^£^A!:Zhyi';ltT£^'''''''^'-   that  used  for  the  headpiece.^  Pieces 

are  cut  from  the  sides  of  this  so  as 
to  form  four  windows  separated  by  strips  about  one-half  inch  wide. 
These  strips  are  strengthened  by  soldering  to  the  inside  of  each  a 
semi-cyHndrical  rod  about  one-quarter  inch  in  diameter  (Fig.  ig,h). 


76  FRESH-WATER    BIOLOGY 

The  bottom  of  the  bucket  which  is  conical  and  ends  in  a  tapering 
spout  is  shrunk  into  place  flush  with  the  lower  edge  of  the  windows, 
after  heating  the  bucket  in  a  jet  of  steam.  A  taper  plug  of  brass, 
with  a  long  stem  (Fig.  19,  i)  which  ends  in  a  milled  head,  is 
inserted  from  within  and  closes  the  spout.  The  edge  of  the 
bucket  has  an  L-shaped  incision  which  receives  a  pin  soldered 
to  the  outside  of  the  headpiece  so  as  to  form  a  bayonet  catch 
which  holds  the  bucket  in  place  on  the  headpiece.  The  four 
windows  in  the  bucket  are  closed  by  a  single  piece  of  bolting 
cloth,  held  in  place  by  a  band  clamp  at  top  and  bottom  (Fig.  19 
d,  e)  and  by  four  side  clamps  gg  screwed  between  the  windows. 
The  holes  for  the  screws  are  conveniently  burned  through  the 
bolting  cloth  with  a  hot  wire. 

A  cheaper  bucket  described  by  Kofoid  (1898)  is  shown  in  section 

in  Fig.  20.     It  is  a  cylinder  of  sheet  copper  around  the  top  of  which 

are  soldered  two  light-wire  rings,  which  serve  to 

/       hold  in  place  the  string  5,  which  ties  the  tip  of  the 


I 
I 


h' 


W. 


net  to  the  bucket.  In  the  sides  of  the  cyHnder  are 
cut  three  equidistant  windows,  each  one  and  one- 
half  by  one  and  three-quarters  inches,  which  are 
closed  by  brass  wire  gauze  wg,  soldered  to  the 
edges.     Gauze   containing  two  hundred  meshes 

Fig.   20.    Simple  townet  ,.  .       ,  n    r         it- 

bucket  as  seen  in  sec-  per  hnear  mch  answers  very  well  for  these  wm- 

tion.  b,  conical  bottom.  r       i         t         i  •  r 

rf/>,  drip  point,  rr',  wire  doWS.  Thc  bottOm  of  thC  bUCkct  IS  a  cone  01 
rings  soldered  to  top  of  ^  •  i   •    i 

bucket.    5,  string  by  coppcr  With  a  Central  openmg  which  continues 

which  tip  of  net  is  tied  ^^  ^  ° 

Ihe^two^wi^frfngr^J!  i^^^  ^  short,  obliqucly-pointed  tube  /.  The  open- 
fot%mp?ying°^%"T  iHg  is  closcd  by  a  rubber  stopper  with  a  wire 
o/'the''th^rJ^lindoTs  handle  which  extends  above  the  top  of  the  bucket 

cut  in  sides  of  bucket.  i    •      i  .    •     ^  ^ 

The  rubber  stopper  with  and  IS  bent  into  a  loop. 

wire  handle  is  seen  at  .  i    ti  i 

center  of  bucket.  (After       The  fiet  IS  constructcd  likc  thc  townct,  except 

Kofoid.)  .  . 

that  the  tip  is  cut  off  at  the  point  ij  (Fig.  16) 
and  the  silk  slit  along  the  dotted  lines  between  gh  and  ij  to 
allow  for  the  fitting  and  fastening  of  the  bucket  in  place. 

The  plankton  net  is  drawn  from  the  bottom  to  the  surface, 
and  the  organisms  that  have  been  caught  in  it  are  washed  into 
the  bucket  by  throwing  water  onto  the  outside  of  the  net,  or  by 
sousing  it  in  the  water.     The  net  is  then  lifted  above  the  water, 


METHODS   OF    COLLECTING   AND    PHOTOGRAPHING  77 

the  bucket  removed,  and  the  water  allowed  to  drain  from  it. 
When  only  so  much  water  remains  as  tills  the  conical  bottom 
of  the  bucket,  the  stopper  is  drawn  and  the  contents  allowed  to 
fall  into  a  suitable  container.  Organisms  adhering  to  the  inside 
of  the  bucket  are  then  rinsed  into  the  container  with  a  httle  filtered 
or  distilled  water  from  a  wash  bottle.  If  the  contents  are  to  be 
preserved  they  may  be  allowed  to  fall  directly  into  a  bottle 
which  contains  the  preservative  or  fixing  fluid,  so  concentrated 
that  the  addition  of  the  plankton  brings  it  to  its  normal  consti- 
tution. Ninety-five  per  cent  alcohol  may  be  used  and  in  that 
case  the  plankton  may  be  allowed  to  fall  from  the  bucket  into 
about  three  times  its  own  volume  of  alcohol,  so  that  it  is  preserved 
in  alcohol  of  about  70  per  cent  strength. 

If  it  is  desired  to  use  a  fixing  fluid  before  preservation  in  alcohol, 
the  stronger  picrosulphuric  acid  may  be  diluted  with  two  volumes 
of  water  and  three  volumes  of  this  may  be  used  to  one  of  plankton, 
so  that  the  latter  is  fixed  in  Kleinenberg's  solution.  Other  fluids 
may  be  used  in  like  manner,  adapted  either  to  the  plankton  as  a 
whole,  or  to  special  groups  of  plankton  organisms.  The  plankton 
is  then  best  caught  in  a  strainer  made  by  removing  the  bottom  of 
a  short  eight-dram  homeopathic  vial  and  tying  bolting  cloth  over 
the  neck  (Fig.  18).  The  plankton  may  be  kept  in  this  strainer 
by  tying  bolting  cloth  over  the  bottom,  and  the  strainer  may 
then  be  passed  through  fixing  fluids  and  grades  of  alcohol.  The 
fluids  may  be  made  to  enter  the  strainer  by  withdrawing  the  air 
by  means  of  a  pipette  held  against  the  bolting  cloth  (Reighard, 
1894). 

Plankton  nets  may  be  made  closable  and  various  devices  have 
been  used  for  this  purpose  (e.g.,  by  Marsh,  1897).  Such  a  net  may 
be  lowered,  drawn  upward  any  desired  distance,  then  closed  and 
drawn  to  the  surface.  It  thus  filters  only  that  part  of  the  column 
of  water  through  which  it  is  drawn  while  open,  and  aids  the  inves- 
tigator to  determine  what  forms  occur  at  various  depths. 

Although  the  plankton  net  may  seem  to  filter  a  vertical  column 
of  water,  the  base  of  which  is  equal  in  area  to  the  net  opening, 
it  does  not  in  practice  do  this.  The  resistance  of  the  net  gauze 
causes  a  certain  part  of  this  column  to  be  pushed  aside.     The  part 


78  FRESH-WATER    BIOLOGY 

pushed  aside  not  only  is  greater  as  the  net  moves  faster  but  is 
increased  as  the  net  becomes  clogged  and  is  therefore  greater 
toward  the  end  of  the  haul  than  at  its  beginning.  The  filtering 
capacity  of  the  net  gauze  is  further  liable  to  change  with  age,  as 
its  pores  clog  and  its  threads  loosen  and  tend  to  obstruct  the 
openings.  Although  elaborate  methods  have  been  devised  for 
determining  the  errors  of  the  plankton  net,  no  one  of  them  is  satis- 
factory. 

2.  The  Plankton  Pump.  The  difficulties  encountered  in  the  use 
of  the  plankton  net  for  accurate  quantitative  work  have  led  to  the 
development  of  the  plankton  pump,  which  is  now  largely  used  in 
conjunction  with  the  ordinary  plankton  net  and  which,  used  in  that 
connection,  has  nearly  displaced  the  closable  plankton  net  (Birge, 
1895;  Marsh,  1897)  in  fresh  water.  This  may  be  any  pump  which 
delivers  at  each  stroke  a  known  and  constant  volume  of  water. 
The  water  is  drawn  through  a  hose  which  extends  from  the  pump 
to  any  desired  depth  and  may  terminate  in  a  metal  cone,  closed 
by  very  coarse  wire  netting,  which  serves  to  exclude  foreign  bodies 
from  the  hose.  From  the  pump  the  water  may  be  conveniently 
dehvered  through  a  shorter  hose  to  some  device  for  filtering  the 
plankton  from  it.  For  this  purpose  a  plankton  net  is  used.  The 
net  may  be  suspended  in  air  and  the  water  pumped  into  it,  but 
some  small  organisms  are  thus  forced  through  the  net  gauze  and 
lost,  and  others  are  doubtless  injured  by  the  impact  of  the  stream 
of  water  and  the  weight  of  the  water  in  the  net.  This  is  avoided 
if  the  net  be  held  under  water  with  only  the  canvas  cone  above 
the  surface.  The  whole  operation  may  be  readily  carried  out  by 
one  person  if  the  net  be  supported  in  the  water  by  a  wooden 
float  surrounding  the  cone  (Fig.  23)  and  the  delivery  hose  be 
attached  to  the  net  (Kofoid,  1897).  When  sufficient  water  has 
been  pumped,  the  net  is  taken  up  and  the  catch  removed  and 
treated  in  the  usual  way. 

The  end  of  the  suction  hose  may  be  allowed  to  remain  at  any 
desired  depth  during  the  pumping.  The  pump  is  calibrated  so 
that  the  volume  of  water  delivered  at  each  stroke  is  known.  The 
number  of  strokes  made  during  any  haul  is  counted,  so  that  a 
simple  calculation  gives  the  total  volume  of  water  pumped. 


METHODS   OF    COLLECTING   AND   PHOTOGRAPHING 


79 


The  end  of  the  hose  may  also  be  lowered  to  near  the  bottom  and 
may  then,  while  pumping  is  in  progress,  be  slowly  drawn  upward  at 
a  uniform  rate.  In  this  way  is  pumped  a  vertical  column  of  water 
which  extends  from  the  bottom  to  the  surface,  and  the  volume  of 
such  a  column  may  be  calculated. 

The  following  forms  of  plankton  pump  may  be  referred  to 
briefly. 

(a)  Fordyce  pump  (Fordyce,  1898).  This  invention  of  Professors 
Ward  and  Fordyce  is  shown  in  perspective  (Fig.  21)  and  in  sec- 
tion (Fig.  22).    It  "is  practically  a  force  pump.  .  .   .  The  cylinder 


qf^"^ 


Fig.  21.     Fordyce's  pump  and  strainer.    For  description  see 
text.     (After  Fordyce.) 


Fig.  22.  Fordyce's  pump  in  sec- 
tions. For  description  see  text. 
(After  Fordyce.) 


of  the  pump  is  eleven  by  three  and  one-half  inches  and  has  a  capacity 
347J  cubic  inches  per  stroke.  The  stroke  of  the  piston  is  definite 
in  length  and  is  regulated  by  a  lock  nut  as  shown  in  the  plate.  The 
valves  used  are  finely-ground  check  valves,  to  which  it  is  believed 
the  accuracy  of  the  working  of  the  apparatus  is  largely  due.  The 
pump  is  connected  with  the  water  by  a  hose  one  and  one-half 
inches  in  diameter,  whose  lower  end  is  adjusted  to  the  various  ver- 
tical zones  of  water  by  means  of  attachment  to  a  floating  block." 
For  filtering  the  water  Fordyce  uses  the  device  shown  in  Fig.  21, 
at  the  left  of  the  pump.  This  Is  similar  to  the  device  already  de- 
scribed in  connection  with  the  Wisconsin  plankton  net,  and  is  used 
in  the  same  way.  It  is  provided  with  a  rim  to  which  a  cover  of 
wire  netting  may  be  attached  to  exclude  foreign  matter.     A  net 


8o 


FRESH-WATER    BIOLOGY 


of  bolting  cloth  may  be  attached  outside  the  wire  gauze  filter,  and 
the  whole  instrument  is  then  adapted  for  the  various  work  of  the 
ordinary  net. 

On  account  of  its  cheapness  and  portabiHty  a  pump  of  this  form 
is  probably  best  adapted  for  work  not  carried  on  from  a  station 
especially  equipped  for  aquatic  biology. 

{b)  The  clock  pump  has  been  used  for  some  years  at  the  Uni- 
versity of  Wisconsin  (Juday,  1904).  At  Wisconsin  the  pump  is 
fixed  to  the  bottom  of  the  boat  and  the  water,  drawn  through 
a  half-inch  garden  hose,  is  pumped  into  a  submerged  plankton 
net  of  No.  20  bolting  cloth. 


Fig  2\  Thresher  tant-pump  m  use.  Ihe  water  reaches  the  pump  through  the  hose  at  the  left  and  is 
delivered  to  the  net  through  the  hose  at  the  right.  The  net  cone  is  seen  supported  by  a  rectangular 
wooden  float.     (After  Kofoid.) 

(c)  The  thresher  tank-pump,  a  double-acting  force  pump  with 
two  cylinders  each  six  by  nine  inches,  has  been  used  by  Kofoid 
(1897).  The  mode  of  using  the  pump  is  shown  (Fig.  23).  This 
pump  is  fastened  to  the  boat  and  is  too  heavy  to  be  carried  or 
to  be  used  apart  from  a  permanent  mounting. 

3.  The  Water  Bottle.  To  obtain  small  samples  of  water  for  the 
study  of  the  nannoplankton  a  water  bottle  may  be  used.  Many 
complicated  and  expensive  forms  of  these  bottles  have  been  devised 
(see  Helland-Hansen)  for  use  at  all  depths  in  the  sea.  The  bottle 
described  by  Theiler  appears  to  be  the  simplest  and  least  expensive 
of  them.  For  use  in  fresh  water  a  Meyer's  bottle  (Fig.  24)  serves 
fairly  well  and  is  easily  made.     A  stout  glass  bottle  of  one  or 


METHODS  OF   COLLECTING   AND   PHOTOGRAPHING  8i 

two  liters  capacity,  and  with  a  good-sized  neck  is  provided  with  a 
tight  rubber  stopper  to  which  is  attached  the  draw-cord  by  which 
the  bottle  is  to  be  lowered  and  the  stopper  drawn.  Beneath  the 
bottle  is  attached  a  weight  a  little  heavier  than  needed  to  sub- 
merge the  empty  stoppered  bottle.  The  bottle  may  be  lowered 
to  a  depth  of  a  hundred  feet  or  less  and  the  stopper  removed 
by  jerking  on  the  draw-cord. 

E.  Quantitative  Study  of  the  Net  Plankton 

If  the  plankton  net  were  a  perfect  instrument  it  should  catch 
all  the  organisms  contained  in  the  vertical  column  of  water  through 
which  it  is  drawn,  that  is,  in  a  column  of  the  diameter  of  the  net 
opening  and  equal  in  height  to  the  distance  through  which  the 
net  is  drawn.  But  the  net  filters  only  a  part  of  the  column  of 
water  through  which  it  is  drawn,  a  part  which  'depends  on  the  age 
of  the  net,  the  rate  at  which  it  is  drawn  and  upon 
the  rapidity  with  which  it  becomes  clogged  while 
being  drawn.  If  the  net  is  of  the  form  described 
above,  is  cleansed  by  throwing  a  stream  of  water  on 
it  after  each  haul  and  is  drawn  at  about  the  rate 
of  one  meter  per  second,  it  filters  about  40  per  cent 
of  the  column  of  water  which  it  traverses.  Hence, 
^o  know  the  total  amount  of  plankton  in  the  column 
of  water  traversed  by  the  net,  we  must  multiply  the 
amount  actually  taken  by  two  and  one-half.  This 
number  is  called  the  coefficient  of  the  net.  The 
coefficient  depends  on  the  construction  of  the  net, 
on  the  fineness  of  the  gauze  used,  and  on  the  rate 
at  which  the  net  is  drawn,  and  must  therefore  be 
determined  by  calculation  for  each  net  for  the 
different  rates.  Not  only  does  the  net  filter  but  a 
part  of  the  water  and  a  different  part  at  different 
times,  but  it  removes  from  the  water  filtered  only     b^otUe.  Sfter 

.        r    .-,  .  .         ,     .        .  -r-,  Wiley  and  Jones.) 

a  part  01  the  organisms  contamed  m  it.     Even  the 
finest  gauze  permits  a   leakage   through  it  of  very  many  small 
organisms.     Owing    to    the    sources    of    error    indicated    the    net 
method  is  useful  chiefly  with  the  larger  organisms,  such  as  crus- 


82 


FRESH-WATER   BIOLOGY 


tacea.  Smaller  organisms  escape  in  variable  quantity  and  the 
smallest  are  not  caught  at  all.  When  the  pump  is  used  a  known 
volume  of  water  is  drawn  from  a  known  source  and  all  of  this  is 
filtered,  so  that  the  source  of  error  arising  from  a  varying  and 
uncertain  net  coefficient  is  eliminated.  The  leakage  error  remains 
uncorrected  so  long  as  a  net  is  used  to  separate  the 
plankton  from  the  water.  The  plankton  obtained 
by  nets  whether  directly  or  by  aid  of  the  pump 
may  be  treated  quantitatively  by  the  following 
methods: 

(a)  The  volume  may  be  obtained  by  allowing  the 
alcohoHc  material  to  stand  for  24  hours  in  gradu- 
ated tubes  (carbon  tubes  of  the  chemist)  until  it  has 
settled,  when  the  volume  may  be  read  off.     There 

is  thus  obtained  in  cubic  centimeters  the  volume  of 

^'°'iesig^ed°b?'Hen'  OHC  catch  and  from  this  may  be  calculated  the  vol- 
ume per  cubic  meter  or  under  one  square  meter  of 
the  original  water. 

{h)  The  approximate  weight  may  be  obtained  by 
,    drying  the  sample  on  filter  paper  and  weighing  it. 

by  screws;   m,  spool-  ^       o  r-  ir    t.  o  c. 

tSedS^'the^'TstoJ'  ^^^  ^^^  weight  is  obtained  by  deducting  the  weight 
giass?Ecc£tdy^  o^  the  filter  paper,  and  from  this  the  number  of 
Snff  "nd^Se  glS   grams  of  plankton  per  cubic  meter  of  water  or  under 

tube  is  of  known  vol-  ^  .  f  ,  i       i     i.    j 

ume;  /.piston-rod   onc  squarc  mctcr  of  surface  may  be  calculated. 


sen.  A.  glass  vessel 
which  contains  di- 
luted plankton.  B, 
strong  glass  tube.  In- 
side the  tube  is  a  pis- 
ton made  of  alternate 
layers  of  metal  :  and 
cork  h.  held  together 


with  handle;  A',  cover 
of  vessel.  (From  Ap- 
stein,  after  Hansen.) 


(c)  Chemical  analyses  may  be  made  of  the  dried 
material  and  from  these  the  quantities  of  the 
various  constituents:  ash,  organic  material,  siHca,  etc.,  may  be 
calculated  per  cubic  meter  of  water  or  per  square  meter  of 
surface. 

(d)  The  organisms  may  be  counted  in  the  Sedgwick-Rafter  cell. 
The  ordinary  plankton  catch  is  so  concentrated  that  it  is  impos- 
sible to  count  the  organisms  in  it  until  it  has  been  diluted.  A 
measured  quantity  of  water  added  to  the  plankton  for  this  pur- 
pose replaces  the  alcohol  or  fixing  fluid.  This  water  is  then  agitated 
to  distribute  the  organisms  uniformly  through  it  and  a  carefully 
measured  sample  is  taken  from  it  with  a  specially  constructed  pipette 
provided  with  a  piston  (Fig.  25).     The  organisms  in  the  sample  are 


METHODS   OF    COLLECTING   AND    PHOTOGRAPHING  83 

then  counted  by  transferring  the  sample  to  a  glass  cell  under  the 
microscope.  If  the  bottom  of  the  cell  is  ruled  in  squares  the 
contents  of  a  certain  number  of  these  may  be  counted  without 
the  use  of  the  eyepiece  micrometer  and  the  whole  number  present 
in  the  cell  estimated.  In  the  case  of  the  larger  and  rarer  organisms 
it  is  best  to  count  all  that  the  cell  contains. 

Since  the  total  volume  of  water  from  which  the  catch  was  made 
is  known,  the  number  of  each  sort  of  organism  per  cubic  meter  of 
water  or  under  each  square  meter  of  surface  may  be  easily  calcu- 
lated, or  the  numbers  in  the  entire  lake  may  be  approximately 
determined. 

F.  Quantitative  Study  of  the  N  anno  plankton* 
The  nannoplankton  may  be  studied  in  two  ways,  namely,  by 
enumerating  the  various  organisms,  or  by  obtaining  a  sufhcient 
quantity  to  determine  its  dry  weight.  In  the  former  method  the 
organisms  may  be  counted  directly,  which  is  very  desirable  for 
the  more  abundant  forms,  or  they  may  be  concentrated  either  by 
filtering  or  by  centrifuging.  The  filters  that  are  most  generally 
used  for  concentration  are  hard  surface  filter  paper  and  sand. 
When  filter  paper  is  used  the  filtered  organisms  are  carefully 
washed  from  the  paper,  the  volume  of  the  wash  water  containing 
the  organisms  is  taken,  and  samples  of  it  are  then  used  for  enumera- 
tion. It  is  necessary  to  use  hard  surface  filter  paper  in  order  to 
prevent  undue  loss  of  organisms  in  the  meshes  of  the  paper.  Even 
with  the  best  quality  of  hard  surface  paper,  many  individuals  become 
embedded  in  the  meshes  so  firmly  that  they  cannot  be  washed  out. 
For  all  counting  the  Sedgwick-Rafter  counting  cell  is  to  be  used. 

The  Sedgwick-Rafter  sand  filter  as  described  by  Whipple  has 
been  used  extensively  in  sanitary  work.  In  this  method  also  there 
is  a  considerable  loss  of  organisms  since  some  of  them  are  so  small 
that  they  pass  between  the  grains  of  sand  and  since  it  is  practically 
impossible  to  separate  all  of  the  organisms  from  the  sand  after 
filtration.  In  all  filtering  methods  the  filters  soon  become  clogged, 
which  decreases  the  rapidity  of  the  filtering  very  markedly. 

*  This  section  has  been  prepared  by  Chancey  Juday  of  the  Wisconsin  Geological 
and  Natural  History  Survey. 


84  FRESH-WATER    BIOLOGY 

The  centrifuge  is  the  most  convenient  as  well  as  the  most  ef- 
ficient instrument  for  obtaining  the  nannoplankton.  A  rather 
high  speed  machine  is  best,  one  which  makes  2500  or  more  revo- 
lutions per  minute,  and  the  electrically  driven  type  is  most  satis- 
factory. For  most  fresh-water  organisms  the  sedimentation  is 
complete  in  five  to  eight  minutes  at  this  speed,  but  occasionally 
for  some  forms  a  second  centrifuging  is  necessary.  In  bodies  of 
fresh  water  the  nannoplankton  is  usually  so  abundant  that  only  a 
small  quanrity  of  water,  not  more  than  15  cc,  is  required  for  a 
sample.  Thus  the  standard  makes  of  centrifuges  will  serve  for 
such  investigations.  The  glass  tube  which  holds  the  sample  of  water 
should  be  well  tapered  at  the  bottom.  This  form  concentrates  the 
material  on  a  small  area  from  which  it  can  be  removed  more  con- 
veniently as  well  as  more  completely.  The  material  is  taken  up 
together  w^th  one  cubic  cendmeter  of  water  in  a  long  pipette  and 
is  then  transferred  to  a  Sedgwick-Rafter  counting  cell.  This  cell 
and  its  use  are  fully  described  by  Whipple.  Sometimes  it  is  de- 
sirable to  centrifuge  50  or  even  100  cc.  in  order  to  study  the  rarer 
forms.  For  enumeration  studies  a  combination  of  the  direct  count- 
ing and  the  centrifuge  methods  gives  the  most  satisfactory  results. 

Whenever  possible,  Hving  material  should  be  used  for  the  count- 
ing. The  samples  may  be  preserved  in  formaldehyde  neutralized 
with  sodium  carbonate  and  then  centrifuged  at  a  later  time,  but 
some  of  the  monads  are  recognized  with  difficulty  after  preserva- 
tion. Most  of  the  flagellates  do  not  move  rapidly  enough  to 
oft"er  any  serious  difficulty  in  counting  them  alive  but  the  ciHates 
do.  When  the  latter  are  present,  it  is  best  to  make  a  special  count 
for  them.  They  are  readily  killed  by  placing  a  drop  of  iodine 
solution  in  the  corner  of  the  counting  cell  before  the  sample  is  in- 
troduced. 

Material  for  a  study  of  the  dry  weight  as  well  as  the  organic 
matter  of  the  nannoplankton  may  be  obtained  either  by  filtering 
a  relatively  small  sample  of  water  through  a  coarse-grained  alundum 
cone  or  by  passing  a  large  sample  of  water  through  a  power  centri- 
fuge that  acts  continuously.  In  the  former  process  the  sample  of 
water,  from  one  to  five  liters,  is  filtered  through  the  cone  and  the 
material  and  cone  are  then  thoroughly  dried  in  an  oven.     The 


METHODS   OF   COLLECTING    AND   PHOTOGRAPHING  85 

weight  is  taken  and  the  cone  is  weighed  again  after  having  Ijeen 
ignited.     The  loss  in  weight  represents  the  organic  matter. 

Larger  samples  of  material  are  needed  for  more  accurate  quan- 
titative work,  and  especially  for  the  study  of  the  chemical  com- 
position of  the  nannoplankton.  For  the  latter  purpose  at  least 
two  or  three  grams  of  organic  matter  are  required.  In  order  to 
secure  this  amount,  even  from  a  lake  which  is  rich  in  plankton,  it 
is  necessary  to  centrifuge  one  to  two  thousand  liters  of  water. 
This  process  requires  an  apparatus  that  will  act  continuously. 
For  this  work  the  Wisconsin  Geological  and  Natural  History 
Survey  is  using  a  De  Laval  clarifier  and  filter,  belt  style,  A  size, 
in  which  the  water  is  first  centrifuged  and  then  filtered.  This 
machine  has  a  maximum  speed  of  6000  revolutions  per  minute  and 
will  both  centrifuge  and  filter  from  ten  to  twelve  liters  per  minute. 
In  general  about  ninety  per  cent  of  the  material  is  deposited  in  the 
bowl  of  the  centrifuge  and  ten  per  cent  on  the  filter  papers.  This 
method  requires  a  special  laboratory  and  equipment  {cj.  Juday, 
1916). 

Very  little  is  known  of  the  bacterial  portion  of  the  nannoplank- 
ton. The  culture  methods  used  for  the  other  bacteria  do  not  seem 
to  be  well  adapted  to  the  strictly  aquatic  forms  and  only  a  small 
part  of  them  can  be  obtained  with  a  centrifuge.  Recently,  how- 
ever, it  has  been  found  that  the  direct  count  method  of  Brew  can 
be  used  for  determining  the  number  and  distribution  of  aquatic 
bacteria,  but  no  results  have  thus  far  been  published. 

G.   Special  Methods  for  Invertebrates 

Special  methods  for  collecting  and  preserving  various  sorts  of 
fresh-water  organisms  are  described  in  the  chapters  devoted  to 
invertebrate  groups.  To  secure  the  best  results  it  is  necessary 
to  become  familiar  with  the  habits  of  the  animals.  The  collection 
of  the  larv^  of  aquatic  insects  is  facilitated  by  the  use  of  the 
ingenious  apparatus  made  by  the  Simplex  Net  Company.  The 
imagos  of  many  such  insects  are  readily  collected  at  night  by 
some  one  of  the  forms  of  traps  used  by  entomologists  in  which 
a  light  serves  as  a  lure. 


86  FRESH-WATER    BIOLOGY 

Under-water  Photography 

If  the  water  is  clear  and  the  surface  unruffled,  near  objects  may 
be  seen  almost  as  clearly  in  natural  waters  as  in  air.  If  the 
camera  be  pointed  at  them,  the  resulting  picture  rarely  shows  more 
than  the  surface  of  the  water,  as  opaque  as  that  of  milk  and  with  as 
little  visible  beneath  it.  It  is  as  though  the  camera  has  been  pointed 
at  the  blue  sky.  This  result  is  due  to  the  light  of  the  sky  and  other 
distant  objects  retlected  from  the  surface  of  the  water  into  the 
camera.  This  strong  light,  which  the  eye  neglects,  obscures  in  the 
negative  the  effects  of  the  weaker  light  from  objects  beneath  the 


Fig.  26.     The  sirr:       -,  v.    u>e    Inr  photM-r.ipliiii^   wl.jcii.    un  i.  ,         .1        ,..r  description  see  text 

(From  an  original  photograph.) 

surface  of  the  water;  if  it  be  cut  off  by  a  screen  these  objects  ma^ 
be  photographed. 

This  is  shown  (Fig.  26)  in  a  photograph  of  the  nest  of  a  black  bas: 
in  about  eight  inches  of  water.  Little  can  be  seen  beneath  th( 
water,  except  within  the  reflected  image  of  the  screen.  Withii 
this  image  the  reflected  sky  light  is  cut  off,  although  the  sun  shine: 
from  the  left  full  upon  the  nest  of  clean  stones.  What  is  clear  ii 
the  photograph  lies  not  within  the  shadow  of  the  screen  but  withii 
its  image.  A  longer  exposure  would  have  given  a  clear  picture  o 
what  Hes  within  the  narrow  shadow  at  the  bottom  of  the  screen 
In  field  practice  a  serviceable  and  portable  screen  may  be  made  b; 
tying  a  square  of  black,  opaque  cloth  to  two  poles  stuck  slantinj 


METHODS   OF   COLLECTING  AND   PHOTOGRAPHING 


«7 


■ 


in  the  bottom.  Occasionally  dense  foliage,  a  bridge  or  building  is 
so  placed  as  to  form  a  natural  screen,  within  the  image  of  which 
photography  is  possible. 

If  the  surface  of  the  water  is  rough  the  photograph  may  be 
made  through  the  bottom  of  a  water  glass  (Fig.  27).  The  glass 
(Fig.  28)  is  a  frame  of  galvanized 
iron  with  a  bottom  of  plate  glass. 
The  bail  of  band  iron  serves  to 
hold  the  screen  (Fig.  27).  The 
glass  shown  here  is  two  feet  square 
and  is  supported  on  legs  run 
through  thimbles  at  the  corners 
and  held  in  place  by  set  screws. 
That  shown  in  Figure  28  is  a 
foot  square  and  is  intended  to 
float.  At  the  left  is  shown  a 
cover  for  the  bottom  of  the  water 
glass.  This  protects  the  glass 
during  transit. 

The  difflculties  arising  from  the 
rough  or  reflecting  surface  of  the 
water  may  be  overcome  by  placing 
the  camera  beneath  that  surface. 
For  this  purpose  a  reflecting  camera 
is  to  be  preferred,  since  it  permits  focusing  with  the  sensitive  plate 
uncovered.  Any  dealer  in  photographicgoodscan  supply  catalogues 
of  such  cameras  showing  their  mechanism.  Here  it  need  only  be  said 
that  the  ground  glass  is  placed  in  the  top  of  the  camera  and  the  oper- 
ator looks  at  it  through  a  hood  extending  from  the  top  of  the  camera. 
He  focuses  the  full-sized  image  on  the  ground  glass  and  while 
looking  exposes  the  plate  by  pressing  a  button  at  the  side  of 
the  camera.  For  use  under  water  such  a  camera  is  placed  in  a 
water-tight  box  (Fig.  29),  with  a  plate  glass  front  through  which 
the  lens  looks.  The  hood  of  the  camera  extends  into  the  pyrami- 
dal Hd  of  the  box  and  the  operator  looks  into  it  through  a  second 
plate  of  glass.  A  milled  head,  shown  on  the  right  of  the  box,  is 
connected  through  a  water-tight  stuffing  box  with  the  focusing 


Fig.  27.  Water  glass  supported  on  legs  as  used 
in  rough  water  of  a  brook.  For  description  see 
text.     (From  an  original  photograph.) 


88 


FRESH-WATER    BIOLOGY 


head  of  the  camera,  while  a  similar  arrangement  on  the  opposite 
side  of  the  box  operates  the  mechanism  which  controls  the  expo- 
sure. The  operator  wades  and  holds  the  box  beneath  the  surface 
of  the  water  with  only  the  upper  part  of  the  hood  exposed.  With 
the  right  hand  he  focuses,  with  the  left  he  makes  the  exposure. 


/y 


Fig.  28.    Floating  water  glass.    For  description     Fig.  29.     Water-tight  metal  box  with  plate-glass 
see  text.     (From  an  original  photograph.)  front  for  enclosing  a  reflecting  camera  when  used 

under  water.     For  description   see  text.     (From 
an  original  photograph.) 

After  each  exposure  the  box  must  be  opened  to  change  the  plate. 
For  details  the  reader  should  consult  the  literature  cited. 


Means  of  Securing  Collecting  Apparatus 

The  various  types  of  commercial  nets  described  may  be  had  of  dealers  in 
fishing  nets.  The  Simplex  Net  Company  of  Ithaca,  N.Y.,  supplies  ingenious 
folding  townets,  plankton  nets,  and  dip  nets.  The  special  apparatus  mentioned 
can  be  constructed  by  any  skilled  mechanic  under  direction. 


IMPORTANT    REFERENCES   ON   APPARATUS   AND   METHODS 

1896. 


Apstein,  C. 
BiRGE,  E.  A.  1895 

FORDYCE,     ChAS.       ] 

State  Hist.  Soc 
IIelland-Haxsen, 


(See  list  in  Chapter  I.) 
(See  list  in  Chapter  I.) 
898.     A  New  Plankton   Pump. 
,  2:  293-296. 
B.     191 2.      The  Ocean  Waters,  an  Introduction  to  Physi- 


Proc.   and   Coll.   Neb. 


cal  Oceanography.     I.    General  Part  (Methods^ 
u.  Hydrog.,  Hydro gr.  SuppL,  i.  ser.,  Heft  2. 
Hensen,  V.     (See  list  in  Chapter  I.) 


Int.  Rev.  ges.  Hydrob. 


METHODS  OF   COLLECTING   AND   PHOTOGRAPHING  89 

JUDAY,  Chancey.     1896.     The  Plankton  of  Turkey  Lake.     Proc.  Ind.  Acad. 
Sci.,  1896.     (Description  of  plankton  net  and  its  use.) 
1904.     The  Diurnal  Movement  of  Plankton  Crustacea.     Trans.  Wis.  Acad. 

Sci.  Arts,  and  Letters,  14:  534-568,  2  figs.     (Clock  pump  and  its  use.) 
1916.     Limnological  Apparatus.     Trans.  Wis.  Acad.,  18;  566-592,  5  pi. 
Received  too  late  for  adequate  consideration  in  the  text. 

KoFom,    C.   A.     1897.     Plankton    Studies.     I.  Methods  and   Apparatus    in 

Use  in  Plankton  Investigations  at  the  Biological  Experiment  Station  of 

the  University  of  Illinois.     Bull.  111.  State  Lab.  Nat.  Hist.,  5:  1-25,  7  pi. 

1898.    Hints  on  the  Construction  of  a  Tow  Net.     Jour.  Appl.  Micros.,  i: 

111-113,  5  figs. 
1903.     (See  list  in  Chapter  I.) 
KoLKWiTZ,  R.     1907.     Entnahme  und  Beobachtungs-instrumente  fiir  biol- 
ogische  Wasseruntersuchungen.     Mitth.  Kgl.  Prufungsamt  f.  Wasserver- 
sorg.  u.  Abwasserbeseit.  zu  Berlin,  Heft  9:  111-144,  22  figs. 
Marsh,  C.  D.     1897.     On  the  Limnetic  Crustacea  of  Green  Lake.    Trans. 

Wis.  Acad.,  11:  179-224,  10  pi.     (Description  of  closable  net.) 
Needham,  James  G.     1903.     An  Outdoor  Equipment  for  College  Work  in 
Biology.     Am.  Nat.,  37:  867-874,  2  figs.      (Description  of  plankton  ap- 
paratus.) 
Reighard,  Jacob.     1894.     (See  list  in  Chapter  1.) 

1898.  Methods  of  Plankton  Investigation  in  Their  Relation  to  Practical 
Problems.     Bull.  U.  S.  Fish  Comm.,  17:  169-175. 

1908.  The  Photography  of  Aquatic  Animals  in  their  Natural  Environment. 
Bull.  U.  S.  Bureau  Fish.,  27:  41-68,  4  pi. 

1909.  An  Experimental  Field  Study  of  Warning  Coloration  in  Coral  Reef 
Fishes.  Carnegie  Inst.,  Washington,  Publication  103:  257-325,  5  pi. 
(Contains  reproductions  of  photographs  made  with  camera  under  water.) 

1910.  Methods  of  Studying  the  Habits  of  Fishes,  with  an  Account  of  the 
Breeding  Habits  of  the  Horned  Dace.  Bull.  U.  S.  Bureau  Fish.,  28: 
1111-1136,  7  pi. 

RuTTNER,  Franz.  1914.  Ueber  einige  bei  der  Untersuchung  der  Lunzer  Seen 
verwendeten  Apparate  und  Geratschaften.  Int.  Rev.  ges.  Hydrob.  u. 
Hydrog.,  6:  53-62,  i  pi. 

Steuer.     1910.     (See  list  in  Chapter  I.) 

Theiler,  a.  1914.  Ein  neuer  Wasser-  und  Planktonschopfer  nach  Fried- 
inger.     Int.  Rev.  ges.  Hydrob.  u.  Hydrog.  Biol.  Suppl.  Band  6,  Heft  4. 

Ward,  H.  B.     1896.     (See  list  in  Chapter  I.) 

Ward,  R.  H.  1895.  Improved  Methods  of  Collecting  Aquatic  Micro-organ- 
isms.   Amer.  Mo.  Micr.  Jour.,  16:  33-4 1>  i  P^- 

Whipple,  G.  C.     (See  list  in  Chapter  I.) 

WoLCOTT,  R.  H.  1901.  A  Modification  of  the  Birge  CoUecting  Net.  Jour. 
Appl.  Micros.,  4:  i407-i409»  4  figs. 


CHAPTER    IV 
BACTERIA 

By  EDWIN  O.  JORDAN 

Professor  of  Bacteriology  in  the  University  of  Chicago 

Bacteria  are  unicellular  organisms,  for  the  most  part  very 
small.  Considerable  differences  in  size,  however,  are  observed. 
A  certain  large,  rod-shaped  species  studied  by  Schaudinn  measures 
from  50M  to  60/X  in  length  and  from  4/i  to  5)u  in  width.  On  the 
other  hand  the  bacillus  of  influenza  averages  about  0.5^  in 
length  and  0.2/x  in  width.  The  average  rod-shaped  bacterium, 
such  as  is  found  in  water  and  soil,  measures  about  2^  in  length 
and  about  0.5^  in  diameter.  Some  microorganisms  are  known 
to  exist  which  are  so  small  that  they  will  pass  through  the  pores  of 
the  finest  Berkefeld  filter  and  remain  invisible  under  the  most 
powerful  lenses,  but  it  is  not  surely  established  that  all  these  so- 
called  ultramicroscopic  organisms  belong  to  the  group  of  bacteria. 

For  the  methods  of  studying  bacteria,  special  laboratory  man- 
uals or  guides  should  be  consulted.  A  number  of  such  guides  are 
in  existence,  among  which  may  be  mentioned  Heinemann  (191 1) 
and  Frost  (1905).  In  any  case  a  proper  familiarity  with  laboratory 
methods  can  be  gained  only  with  the  assistance  of  a  skilled  labora- 
tory instructor  possessed  of  individuality  and  resource. 

Bacteria  are  generally  classed  as  plants  rather  than  animals, 
but,  as  is  well  known,  the  dividing  line  between  animals  and  plants 
is  an  entirely  arbitrary  one,  and  there  is  no  general  agreement 
among  naturalists  respecting  what  shall  constitute  a  determina- 
tive plant  or  animal  characteristic.  It  is  largely  considerations  of 
convention  and  convenience  that  place  them  among  the  plants. 
From  their  lack  of  chlorophyl  and  the  fact  that  they  multiply  by 
division  or  fission  the  bacteria  are  classed  as  Schizomycetes  or  fission 
fungi. 

Within  the  group  of  bacteria  themselves  classification  is,  for 
practical  purposes,  especially  important,  but  because  they  are  so 

90 


BACTERIA  91 

minute  in  size  and  the  observable  differences  in  structure  are  so 
slight,  any  classification  grounded  on  morphological  characters, 
such  as  that  of  Migula  (1897),  meets  with  many  difficulties,  and 
would  seem  at  present  to  be  premature.  Because  of  the  great  prac- 
tical importance  of  physiological  quaUties,  bacteriologists  have 
come  to  lay  great  stress  upon  bacterial  functions,  and  considera- 
tions of  convenience  have  often  led  to  groups  being  established  on 
physiological  characteristics.  The  practice  of  dealing  with  bacteria 
in  related  groups  is  growing.  For  the  identification  of  specific  and 
group  characters  the  Report  of  the  Committee  of  the  Society  of 
American  Bacteriologists  on  Method  of  Identification  of  Bacterial 
Species  should  be  consulted. 

The  forms  of  bacteria  are  very  simple.  The  complex  and  elabo- 
rate structures  found  among  certain  other  groups  of  unicellular 
organisms  (diatoms,  desmids,  radiolaria)  do  not  occur  among  bac- 
teria. Three  principal  type  forms  are  recognized:  the  sphere 
(coccus  or  micrococcus),  the  rod  (bacillus),  and  the  spiral  (spirillum 


Fig.  30.     Forms  of  Bacteria. 


and  spirochsete)  (Fig.  30).  Closely  resembling  these  are  certain 
filamentous  organisms  known  as  Trichomycetes,  which  connect  the 
bacteria  with  the  higher  fungi  or  moulds. 

The  minute  size  of  bacteria  renders  the  study  of  their  liner 
structure  somewhat  difficult,  but  a  few  features  have  been  clearly 
determined.  Most  species,  perhaps  all,  are  provided  with  a  cap- 
sule or  outer  layer  of  gelatinous  substance  originating  from  the 
cell-membrane  and  seen  in  stained  preparations  surrounding  the 
cell  like  a  halo.  The  capsule  is  much  more  prominently  developed 
in  some  species  than  in  others.  The  cell-memhrane  is  chiefly  re- 
markable for  its  chemical  composition,  differing  as  it  does  from  the 
cell-membrane  of  the  higher  plants  in  not  being  composed  of  cel- 
lulose. The  nature  of  the  cell-substance  of  bacteria  has  been  the 
object  of  much  discussion  from  the  standpoint  of  its  relation  to  the 


92 


FRESH-WATER   BIOLOGY 


nuclear  substance  of  higher  cells.  It  has  been  held  by  different 
observers  that  a  bacterial  cell  is  to  be  compared  either  to  a  free 
nucleus  or  to  an  unnucleated  mass  of  cytoplasm,  but  these  views 
have  now  been  practically  abandoned.  It  seems  to  be  clear  from 
the  researches  of  recent  investigators  that  the  chromatin  substance 
instead  of  being  gathered  together  in  a  definite  nucleus,  as  in  the 
cells  of  most  higher  forms  of  life,  is  fragmented  and  distributed 
irregularly  through  the  body  of  the  cell.  The  bacterial  chromatin 
is  usually  present  in  great  abundance,  varies  in  amount  and  in 
position  in  different  kinds  of  bacteria  and  occurs  most  frequently 
in  a  finely-divided  condition.  Not  only  are  particles  of  chromatin 
scattered  through  the  cell,  but  other  granules  that  react  to  stains 
in  special  ways  are  present  in  the  cell  substance,  particularly  in 
certain  species.  The  physiological  significance  of  these  so-called 
metachromatic  granules,  as  they  occur  for  example  in  the  diphtheria 
bacillus,  is  unknown,  but  it  seems  probable  that  they  are  to  be 
looked  upon  as  reserve  food  substances. 

Many  forms  of  bacteria  show  independent  movement,  distinct 
from  the  oscillating  or  trembling  movement  exhibited  by  all  minute 
particles  suspended  in  water  and  known  as  the  Brownian  movement. 
The  power  of  motility  depends  upon  the  possession  of  long,  fragile, 
filamentous  appendages  termed  flagella.  In  the  case  of  certain 
large  spirilla,  flagella  can  be  seen  on  the  living,  unstained  cell,  but 
ordinarily  special  methods  of  staining  must  be  applied  to  demon- 
strate their  presence.  The  position  of  the  flagella  on  the  cell  body 
differs  in  different  species.  Some  species  possess  a  single  flagellum 
at  one  pole,  as  is  the  case  with  the  cholera  spirillum ;  others  have  a 
flagellum  at  either  pole;  others  have  polar  tufts  of  flagella;  and 
still  others  possess  flagella  attached  to  the  sides  as  well  as  the 
ends  of  the  cell  (typhoid  bacillus)  (Fig.  30).  In  certain  nonmotile 
bacteria,  such  as  the  anthrax  bacillus,  no  flagella  have  been  observed. 

Under  certain  conditions  some  bacteria  pass  from  the  ordinary 
or  vegetative  stage  into  a  highly  resistant  state,  known  as  a  spore 
or  endospore.  The  spores  of  bacteria  are  approximately  spherical  or 
oval,  are  stained  with  great  difficulty  with  the  ordinary  aniline 
dyes  and  resist  destructive  agencies,  such  as  heat  and  chemical 
disinfectants,  much  better  than  the  vegetative  forms  from  which 


BACTERIA  93 

they  spring.  A  single  cell,  as  a  rule,  gives  rise  to  but  one  spore,  so 
that  spore  formation  can  not  be  looked  upon  as  a  process  of  multi- 
plication. It  is  generally  considered  that  the  bacterial  spore  is  a 
resting  stage,  physiologically  similar  to  an  encysted  amoeba  and 
serving  to  tide  the  species  over  a  period  of  hard  times.  Not  all 
bacteria  are  spore  producing;  in  fact  the  number  known  to  form 
spores  is  rather  limited. 

Great  adaptabiUty  is  shown  by  bacteria  to  extremes  of  tempera- 
ture. Some  species  have  been  found  multiplying  in  the  water  of 
polar  seas  at  or  near  the  freezing  point,  while  others  have  been 
found  living  in  the  water  of  hot  springs  at  a  temperature  of  79°  C. 
Most  of  the  ordinary  bacteria  found  in  pond  or  river  water  multiply 
abundantly  at  a  temperature  of  about  20°  C.  When  water  is 
frozen,  most  of  the  bacteria  that  it  contains  are  killed  at  once.  A 
small  proportion  survive,  but  in  gradually  diminishing  numbers, 
so  that  at  the  end  of  a  few  weeks  clear  ice  is  practically  sterile. 
Bacteria  contained  in  masses  of  organic  matter,  however,  may 
have  their  life  in  ice  considerably  prolonged. 

Bacteria  not  only  adapt  themselves  to  great  extremes  of  tem- 
perature, but  to  varied  sources  of  food  supply.  Many  species  can 
content  themselves  with  relatively  simple  chemical  compounds, 
such  as  the  ammonium  salts  of  the  organic  acids.  Others  require 
for  their  development  complex  nitrogenous  substances.  The  nitri- 
fying bacteria,  so  abundant  in  most  soils  and  waters,  obtain  the 
energy  necessary  for  their  development  altogether  from  inorganic 
compounds.  On  the  other  hand,  certain  bacteria  are  entirely 
dependent  upon  particular  organic  compounds  present  in  the  bodies 
of  the  higher  animals,  and  can  thrive  only  in  the  presence  of  blood 
serum  or  similar  fluids. 

Fundamental  differences  exist  among  bacteria  in  respect  to  their 
relative  need  for  oxygen.  Some,  the  obligatory  aerobes,  require  free 
oxygen  for  the  maintenance  of  their  life  activities,  while  others,  the 
obligatory  anaerobes,  do  not  grow  except  in  the  almost  complete 
absence  of  free  oxygen.  There  are  also  some,  the  facultative  anaer- 
obes, that  can  multiply  either  in  the  presence  or  absence  of  free 
oxygen.  The  anaerobic  bacteria,  as  a  class,  thrive  best  in  the  pres- 
ence of  substances  capable  of  undergoing  reduction  or  fermentation. 


94  FRESH-WATER    BIOLOGY 

The  addition  of  glucose  or  nitrate,  for  example,  to  ordinary  nutrient 
broth  will  enable  certain  species  of  bacteria  to  grow  under  condi- 
tions otherwise  unfavorable.  The  relation  between  anaerobic  Hfe 
and  food  supply  is  an  intimate  one.  The  anaerobes,  in  a  word,  are 
those  organisms  able  to  obtain  their  needed  energy  from  the  simple 
splitting  of  organic  compounds  without  oxidation.  If  a  microorgan- 
ism is  so  specialized  to  an  anaerobic  mode  of  life  that  the  presence 
of  oxygen,  except  in  minute  quantities,  interferes  with  its  habitual 
method  of  attacking  food  substances,  it  is  an  obligatory  anaerobe. 
In  a  modified  form,  therefore,  Pasteur's  conception  of  fermentation 
as  "hfe  without  air"  is  not  very  far  from  the  modern  view. 

Those  decompositions  of  organic  substances  that  are  usually 
termed  putrefactions  and  are  characterized  by  the  evolution  of 
malodorous  gases  such  as  hydrogen  sulphide  and  the  production  of 
substances  like  skatol,  indol,  mercaptan,  etc.,  are  due  to  the  agency 
of  anaerobic  bacteria.  In  fact,  researches  indicate  that  the  putre- 
factive decomposition  of  native  proteins  is  wholly  the  work  of  the 
obligatory  anaerobes.  As  is  well  known,  the  ooze  at  the  bottom  oi 
ponds  and  streams  is  peculiarly  the  home  of  such  anaerobic  decom- 
positions. 

Bacteria  are  everywhere  present  in  natural  bodies  of  water. 
They  are  more  abundant  as  a  rule  in  surface  waters  than  in  ground 
waters.  Deep  well  waters  and  spring  waters  in  certain  regions 
often  contain  very  few  bacteria,  perhaps  only  five  to  ten  per  cubic 
centimeter,  while  the  water  of  lakes  and  ponds  usually  contains 
several  hundred,  and  ordinary  river  water  contains  numbers  that  at 
times  rise  into  the  thousands  and  tens  of  thousands.  As  a  general 
rule,  sewage-polluted  waters  contain  more  bacteria  than  pure  waters. 
An  excessively  polluted  stream,  such  as  the  Chicago  River  once 
was,  may  hold  as  many  as  several  milHon  bacteria  per  cubic  centi- 
meter. 

The  number  of  bacteria  in  a  river  water  varies  greatly  at  differ- 
ent seasons  of  the  year,  being  generally  larger  in  the  colder  months 
than  in  summer.  Probably  this  is  due  in  part  to  the  winter  in- 
crease in  current  caused  by  rains  and  melting  snows  which  prevents 
sedimentation;  in  part  to  the  heavy  rains  of  winter  which  wash  into 
a  stream  numberless  germs  from  cultivated  lands,  and  partly  also 


BACTERIA  95 

to  the  lower  temperature  of  the  water  in  winter  which  favors 
the  continuance  of  bacterial  vitality.  In  highly-polluted  rivers  the 
processes  of  decomposition  are  retarded  by  cold  weather;  in  con- 
sequence, bacteria  together  with  their  food  substances  travel  for  a 
greater  distance  down  stream  in  winter  than  in  summer.  This 
condition  has  been  shown  to  exist,  for  example,  in  the  Illinois 
River  which  is  heavily  polluted  with  Chicago  sewage. 

Besides  these  important  seasonal  fluctuations,  daily  and  hourly 
changes  may  be  noticed,  depending  upon  the  amount  of  rainfall, 
the  velocity  of  the  current,  the  direction  and  force  of  the  wind  and 
perhaps  the  germicidal  action  of  sunlight.  For  these  reasons,  it  is 
necessary,  in  order  to  interpret  correctly  the  sanitary  significance 
of  the  bacterial  content  of  any  body  of  surface  water,  to  make  re- 
peated examinations  under  a  variety  of  circumstances  and  with 
particular  attention  to  the  effect  of  modifying  conditions.  In  the 
case  of  ground  waters  (wells,  springs,  etc.),  the  number  of  bacteria  is 
less  affected  by  changes  in  external  conditions,  but  here  also  great 
caution  is  necessary  in  drawing  conclusions  from  a  limited  number 
of  observations. 

The  following  table  gives  some  conception  of  the  number  of 
bacteria  that  may  be  found  by  the  gelatin  plate  method  in  various 
bodies  of  water.  Great  variations  occur  and  any  such  tabulation 
can  have  only  an  approximate  value. 

Per  cubic  centimeter 

Sewages  or  sewage-polluted  waters 100,000  to  1,500,000 

Rivers  not  highly  polluted 1,000  to  10,000 

Lakes  and  ponds  not  highly  polluted 100  to  1,000 

Pure  spring  waters 5  to  50 

The  enormous  number  of  bacteria  which  such  figures  show  to  be 
present  in  all  natural  bodies  of  water  comprises  many  different 
kinds.  There  is  no  special  and  characteristic  class  of  "  water 
bacteria,"  but  germs  from  the  air,  from  the  soil,  from  decomposing 
animal  and  plant  substances  and  from  the  healthy  and  diseased 
tissues  of  animals  and  plants  may  at  times  hnd  their  way  into 
water.     The  bacterial  flora  of  a  given  stream  or  pond  is  therefore 


g6  FRESH-WATER   BIOLOGY 

constantly  changing,  and  varies  from  time  to  time  not  only  in  the 
number,  but  in  the  nature  of  the  individuals  composing  it  (Fig.  31). 
Little  work  has  yet  been  done  upon  the  changes  in  the  kinds  of 
bacteria  in  river  or  lake  water  due  to  the  shifting  seasons  and  other 

factors,  but  there  is  no  doubt 
that  important  differences  do 
exist.  Many  varieties  of  bac- 
teria have  been  isolated  from 
water.  During  the  course  of 
a  study  of  the  bacteria  in  the 
water  of  the  IlHnois  River 
the  writer  found  that  out  of 
543  cultures,  17  well-defined 
groups  and  41  subgroups  were 
represented.  These  groups 
include  a  number  of  pigment- 
,  .     .         producing     or     chromogenic 

Fig.  31.  — Photograph  of  "plate  culture,"  showing  ^  °  r  i  •    i 

different  kinds  of  bacterial  colonies.     (Original.)  formS,      SOmC     of      whlCh      arC 

among  the  most  common  inhabitants  of  water,  and  also  a  number 
of  bacterid  closely  related  to  organisms  associated  with  the 
production  of  disease  in  the  higher  animals.  Among  the  bacteria 
commonly  found  in  natural  waters  may  be  mentioned  B.  fluo- 
rescens  vars.  liqiiejaciens  and  non-liqiiefaciens  (the  green  water 
bacillus),  B.  suUilis  (the  hay  bacillus),  B.  mesentericus  (the  potato 
bacillus),  B.  proteus  and  B.  cloacae  (commonly  associated  with  the 
decomposition  of  vegetable  and  animal  matter),  B.  liquefaciens, 
B.  hyalinus,  B.  violaceiis,  and  many  chromogenic  and  non-chromo- 
genic  micrococci;  in  polluted  waters,  B.  coli  is  usually  found  in 
large  numbers  and  organisms  of  the  B.  proteus  t^^De  and  strepto- 
cocci are  more  abundant  than  in  normal  waters. 

It  is  well  known  that  the  germs  of  several  of  the  principal  infec- 
tious diseases  of  man  are  commonly  conveyed  in  drinking  water. 
Typhoid  fever  and  Asiatic  cholera  are  familiar  examples.  Both 
the  typhoid  bacillus  and  the  cholera  spirillum  have  been  found  in 
water,  although,  partly  because  the  technical  difficulties  of  investi- 
gation are  considerable,  partly  because  the  longevity  of  these 
organisms  in  water  is  Umited,  positive  findings  have  not  been  very 


BACTERIA  97 

frequent.  Under  ordinary  conditions  there  is  no  reason  to  suppose 
that  pathogenic  bacteria  multiply  in  water  or  that  they  retain 
their  vitahty  for  more  than  a  few  weeks.  In  polluted  soil,  however, 
they  may  Uve  much  longer  than  in  water,  and  a  river  may  be  con- 
tinuously polluted  during  a  long  period  by  bacteria  that  are  washed 
into  it  from  accumulations  of  fecal  material.  Other  pathogenic 
bacteria  occasionally  water-borne  are  the  dysentery  bacillus  and 
the  anthrax  bacillus. 

Since  the  search  for  specific  pathogenic  bacteria  in  a  water  is 
hardly  ever  likely  to  be  crowned  with  success,  various  indirect 
means  for  determining  the  purity  of  a  water  have  been  proposed. 
The  most  useful  of  these  analytical  methods  is  the  test  based  on 
the  determination  of  the  relative  number  of  Bacillus  coll.  This, 
the  colon  bacillus,  is  a  normal  inhabitant  of  the  healthy  human 
intestine  and  is  found  in  large  numbers  in  fresh  sewage  where,  by 
appropriate  methods,  it  is  usually  detected  in  each  -j  o  o  o  o  ^■^-  ^^~ 
amined.  Since  it  is  also  present  in  the  droppings  of  many  of  the 
larger  domestic  animals  and  hence  occurs  in  garden  soil  and  in 
pastures,  its  occasional  presence  in  water  does  not  necessarily  in- 
dicate possible  or  even  probable  pollution  with  fecal  matter  of 
human  origin.  The  researches  of  many  investigators,  however, 
have  shown  that  the  relative  abundance  of  Bacillus  coli  in  water 
is  a  very  satisfactory  criterion  of  the  sanitary  quahty  of  such  a 
water.  If,  for  example,  it  is  found  uniformly  present  in  a  water  in 
each  I  c.c.  sample,  the  water  is  looked  upon  as  distinctly  suspicious. 
In  cases,  however,  where  it  is  rarely  found  in  i  c.c.  samples  and 
only  occasionally  when  quantities  as  large  as  lo  c.c.  or  even  50  c.c. 
are  examined,  the  water  is  usually  considered  potable. 

The  bacteria  in  water  stand  in  important  relations  to  the  life  of 
other  aquatic  plants  and  animals.  It  is  a  familiar  fact  that  but  for 
bacterial  activity  the  nitrogen  and  carbon  in  complex  organic  com- 
pounds once  bound  would  remain  forever  locked  up  and  unavail- 
able for  the  nutrition  of  other  forms  of  Hfe.  As  is  well  known  also, 
the  first  steps  in  decomposition  or  the  breaking  down  of  organic 
substances  are  due  to  bacterial  agency.  Ammonia  and  ammoni- 
acal  compounds  are  among  the  chief  nitrogenous  products  of  tliis 
decomposition.     The  processes  of  disintegration  and  oxidation  do 


q8  fresh-water  biology 

not  end  with  the  production  of  such  a  relatively  simple  compound  as 
ammonia.  Further  oxidation  of  the  ammonia  to  nitrites  takes 
place  and  the  nitrites  in  turn  are  oxidized  to  nitrates.  The  for- 
mation of  nitrites  and  nitrates,  Hke  the  formation  of  ammonia,  is 
due  to  bacterial  activity;  this  process  is  known  as  nitrification. 
Special  and  peculiar  varieties  of  bacteria  are  concerned  in  the  proc- 
ess of  nitrihcation.  One  species  is  able  to  oxidize  ammonia  to 
nitrite,  but  is  unable  to  carry  the  process  of  oxidation  any  further. 
At  this  stage  of  decomposition  a  second  species  takes  up  the  work 
and  completes  the  process  by  oxidizing  the  nitrites  to  nitrates. 

If  we  follow  the  fate  of  the  nitrogen  introduced  into  a  sewage- 
polluted  river,  we  find  that  there  occurs  first  a  breaking  down  of 
the  albuminous  compounds  and  a  consequent  increase  in  the 
amount  of  "free  ammonia"  in  the  water;  further  down,  nitrites 
begin  to  appear  and  eventually  nitrates  are  found.  A  river  water 
in  which  the  process  of  nitrification  has  occurred  and  which  is 
therefore  rich  in  nitrates  affords  a  peculiarly  favorable  medium 
for  the  growth  of  plant  Hfe  and  often  ''blooms"  with  a  myriad  of 
microscopic  algae.  The  presence  of  a  multitude  of  algae  in- 
fluences in  its  turn  the  Hfe  conditions  of  aquatic  protozoa  and  of 
higher  animal  organisms.  At  times  when  through  the  advent  of 
low  temperature  or  other  unfavorable  conditions  the  algae  die  off, 
the  albuminous  compounds  constituting  their  dead  bodies  undergo 
decomposition;  ammonia,  nitrites,  and  then  nitrates  are  again 
formed,  and  the  nitrogen  cycle  begins  anew.  The  food  supply  of 
the  whole  plankton  of  fresh-water  streams  and  ponds  is  therefore 
dependent  upon  the  activity  of  bacteria,  and  the  share  of  these 
organisms  in  producing  or  modifying  the  conditions  under  which 
all  aquatic  life  is  possible  can  never  be  ignored. 


BACTERIA  99 

IMPORTANT   REFERENCES   ON   BACTERIA 

Clemesha,  W.  W.  191 2.  The  Bacteriology  of  Surface  Waters  in  the  Tropics. 
London. 

HoRROCKS,  W.  H.  1901.  Introduction  to  the  Bacteriological  Examination 
of  Water.     London. 

Houston,  A.  C.     1913.     Studies  in  Water  Supply.     London. 

Jordan,  E.  0.  1903.  The  Kinds  of  Bacteria  Found  in  River  Water.  Jour- 
nal of  Hygiene,  3:1. 

MiGULA,  W.     1900.     System  der  Bacterien.     Jena. 

OHLMtJLLER  and  Spitta.     1910.     Wasser  u.  Abwasser.     3d  ed.,  Berlin. 

Prescott  and  Winslow.  1913.  Elements  of  Water  Bacteriology.  3d  ed., 
New  York. 

Report  of  the  Committee  on  Standard  Methods  of  Water  Analysis  to  the 
Laboratory  Section  of  the  American  Public  Health  Association. 

Savage,  W.  G.  1906.  Bacteriological  Examination  of  Water  Supplies. 
London. 


CHAPTER  V 
BLUE-GREEN    ALGAE    (CYANOPHYCEAE) 

By  EDGAR  W.  OLIVE 

Curator  of  the  Brooklyn  Botanic  Garden 

The  blue-green  algae  are  found  principally  in  fresh  waters, 
although  numerous  forms  occur  also  in  the  sea,  and  are  almost 
universally  distributed  over  the  whole  earth.  In  moist  climates 
they  are  particularly  abundant,  growing  in  almost  every  conceiv- 
able situation  as  gelatinous  masses  or  strata  on  rocks,  stones,  the 
trunks  of  trees,  damp  ground,  etc.  Many  of  them  occur  abun- 
dantly in  both  marine  and  fresh-water  plankton.  The  peculiar 
phenomenon  of  'Svater-bloom"  (or  'forking"  or  ''blooming"  of 
the  lakes,  "breaking  of  the  meres,"  "Flos  aquae,"  "  Wasserblute ") 
is  due  to  the  sudden  appearance  in  lakes  and  ponds  of  a  surface 
scum  formed  of  vast  quantities  of  certain  plankton  species  of  these 
organisms.  This  frothy  scum,  forming  the  so-called  "water- 
bloom,"  is  of  common  occurrence  in  midsummer  in  quiet  waters, 
especially  after  a  protracted  period  of  heat.  Disagreeable  "pig- 
pen" odors  and  bad  tastes  are  caused  by  such  masses  when  decay 
sets  in,  due,  according  to  Jackson  and  Ellms,  to  the  decay  of  highly 
nitrogenous  organic  matter  in  which  partially  decomposed  sulphur 
and  phosphorous  compounds  play  a  large  part.  The  occurrence  of 
blue-green  algae  in  pubHc  water  supplies  often  thus  becomes  of 
great  economic  importance;  and  Moore  has  found  in  this  connec- 
tion that  such  algal  growths  in  reservoirs  may  be  readily  eradicated 
or  their  growth  prevented  by  the  use  of  a  dilute  solution  of  copper 
sulphate. 

In  addition  to  their  importance  as  polluting  organisms  in  water 
reservoirs,  some  recent  observations  appear  to  indicate  that  cer- 
tain plankton  forms  of  blue-green  algae  are  sometimes  used  as  food 
by  fish  fry.  Their  indirect  importance  in  this  respect  may  be 
regarded  as  well  established,  since  Birge  has  shown  that  the  com- 


BLUE-GREEN   ALGAE  lOi 

mon  plankton  Crustacea,  which  themselves  form  the  basis  of  the 
food  of  many  small  fishes,  depend  to  a  great  extent  upon  Aphani- 
zomenon,  Anabaena,  and  other  blue-green  algae  for  their  own  sus- 
tenance. 

Some  species  of  Cyanophyceae  have  become  adapted  to  living  in 
hot  springs;  these  organisms,  in  fact,  together  with  certain  sulphur 
bacteria,  constituting  the  sole  organic  hfe  of  thermal  springs. 
According  to  the  careful  observations  of  Setchell,  the  blue-green 
algae  grow  in  some  abundance  in  thermal  waters  up  to  68°  C, 
and  scantily  in  springs  showing  a  temperature  as  high  as  75°- 
77°  C. 

The  varied  colors  —  shades  of  yellow,  orange  red,  pink,  blue, 
and  blue  green  —  shown  by  the  siliceous  deposits  around  certain 
hot  springs  of  the  Yellowstone  Park,  are  due  in  great  part  to  the 
presence  of  brilliantly  colored  blue-green  algae  within  the  deposit. 
Weed  has  discussed  the  part  played  by  these  algae  in  the  formation 
of  carbonaceous  and  siliceous  rocks  about  hot  springs. 

Some  of  the  Cyanophyceae,  principally  of  the  genera  Scytonema, 
Stigonema,  and  Nostoc,  are  found  associated  with  certain  fungi  to 
form  lichens;  while  still  others,  notably  Nostoc  and  Anabaena,  occur 
regularly  endophytically  in  the  roots  of  Cycads  and  in  the  leaves 
of  Azolla  and  other  water  plants. 

Like  the  bacteria,  with  which  these  algae  are  supposed  to  show 
close  relationship,  most  of  the  Cyanophyceae  possess  cell  walls 
which  become  much  swollen  and  mucilaginous  in  their  outer  layers. 
Thus  most  of  the  filamentous  forms  become  invested  in  either  a 
thin  mucous  sheath  or  a  tough,  lamellose  sheathing  tube.  Many 
of  the  colonial  forms  consist  of  masses  of  cells  embedded  in  a  thick, 
jelly-like  matrix,  the  external  surface  of  which  is  often  covered 
with  a  thin  cuticle. 

Much  dispute  has  arisen  in  recent  years  as  to  the  nature  of  the 
contents  of  the  cells  of  these  algae.  On  examination  with  the 
compound  microscope,  one  usually  notes  a  number  of  granular 
bodies,  apparently  of  two  kinds  —  numerous  small  granules  and  a 
few  larger,  clear  ones.  In  the  shorter-celled  species,  the  smaller 
and  more  numerous  granules  frequently  He  in  regular  double  rows, 
on  either  side  of  the  cross  walls  which  separate  the  cells.     In  the 


I02  FRESH-WATER   BIOLOGY 

longer-celled  forms,  such  as  Nostoc  and  Tolypothrix,  the  small 
granules  generally  occur  abundantly  in  all  parts  of  the  peripheral 
protoplasm.  These  minute  granules  are  generally  regarded  as  the 
"cyanophycin  granules"  (Borzi),  and  they  are  probably  albumi- 
nous in  their  nature  and  serve  as  reserve  food.  The  few  larger 
granules  mentioned  above  are  more  hyaline  and  transparent  than 
the  cyanophycin  granules,  and  they  appear  to  lie  in  or  near  the 
center  of  the  cell.  These  larger  granules  have  been  called  by 
Palla  ''slime  globules";  by  Zacharias  "Centralkorner."  Their 
function  is  in  dispute. 

The  cells  of  favorable  forms  of  the  blue-green  algae,  e.g.,  Oscil- 
lator ia,  show  two  more  or  less  evident  portions  of  the  protoplasm  — 
a  peripheral  layer,  to  which  the  pigment  is  confined  and  in  which 
the  cyanophycin  granules  lie,  and  a  central  colorless  part,  the 
so-called  ''central  body."  The  majority  of  recent  studies  on  the 
subject  maintain  that  the  central  body  is  a  nucleus,  although  this 
conclusion  has  been  several  times  disputed.  Carefully  stained, 
thin  sections  show,  however,  that  it  is  made  up  of  both  chromatic 
and  achromatic  substances.  Moreover,  Macallum  and  others  find 
in  the  central  body  complex  proteid  substances  containing  phos- 
phorus and  "masked"  iron  to  a  marked  degree,  which  they  regard 
as  characteristic  constituents  of  chromatin.  Fischer  claims,  how- 
ever, to  have  demonstrated  by  means  of  a  tannin-safranin  stain 
that  the  central  body  is  filled  with  certain  carbohydrates,  of  the 
nature  of  glycogen. 

The  central  body  divides  according  to  some,  by  simple  amitotic 
di\dsion;  while  others  beHeve  that  the  division  is  mitotic.  At  any 
rate,  the  division  of  this  nucleus,  or  central  body,  precedes  the 
division  of  the  cell,  and,  as  in  other  lower  plants,  the  two  processes 
appear  to  take  place  independently  of  each  other.  Cell  division  is 
accomplished  in  these  forms  in  the  same  manner  as  has  been 
described  for  many  other  filamentous  Thallophytes,  by  constric- 
tion: a  ring-formed  wall  grows  in  from  the  outer  wall,  similarly  to 
the  closing  of  an  iris  diaphragm,  and  finally  cuts  the  cell  in  two. 

The  varying  shades  of  color  shown  by  these  organisms  are  caused 
by  varying  mixtures  of  the  green  chlorophyll  and  the  reddish  or 
bluish  phycocyanin,   the  pigments  being  apparently  confined  to 


BLUE-GREEN   ALGAE  103 

the  peripheral  cytoplasm.  The  phycocyanin  may  readily  be  ex- 
tracted by  killing  the  plant,  when  the  plasma  membrane  at  once 
allows  the  dissolved  pigment  to  pass  out  through  the  cell  wall. 
When  plants  are  dried  and  pulverized,  then  soaked  in  water,  a 
solution  of  the  bluish  coloring  matter  is  thus  readily  obtained.  A 
quicker  method  is  to  place  the  blue-green  algae  in  chloroform  water 
(made  by  shaking  up  a  small  quantity  of  chloroform  in  water, 
allowing  it  to  settle,  then  decanting  the  water,  which  is  then  used 
in  the  experiment),  or  in  water  containing  a  few  drops  of  carbon 
bisulphide,  for  a  short  time.  Death  of  the  plants  at  once  ensues 
and  the  dichroic  phycocyanin  passes  out  into  the  surrounding 
water,  leaving  the  filaments  bright  green  from  the  remaining  chlo- 
rophyll pigment. 

Sap  vacuoles  occur  sometimes  in  the  cells  of  the  Cyanophyceae, 
particularly  in  the  older  elongated  cells  of  such  forms  as  Tolypo- 
thrix  and  Calothrix.  Another  kind  of  vacuole,  filled  with  gas,  is 
said  by  Klebahn  and  others  to  occur  in  certain  free-floating  blue- 
green  algae,  such  as  Coelosphaerium,  Anabaena,  and  Oscillatoria, 
when  they  rise  to  the  surface  to  form  water-bloom.  These  authors 
regard  the  so-called  gas  vacuoles  as  directly  concerned  with  the 
floating  capacity  of  the  algae  which  possess  them;  their  contentions 
have  been  disputed  a  number  of  times,  however,  and  the  gas 
vacuole  theory  is  regarded  by  many  as  untenable. 

Sexual  reproduction  is  unknown  among  the  blue-green  algae. 
Asexual  multiplication  takes  place  in  the  simpler  forms  by  cell 
division  and  subsequent  separation  of  the  daughter  cells.  In  the 
higher,  filamentous  Hormogoneae,  short  one-  to  few-celled  fila- 
ments, knoJWTi  as  hormogonia,  are  regularly  set  free  and  these  frag- 
ments form  new  plants.  Spherical  or  cylindrical  resting  spores  are 
formed  in  some  species  by  the  growth  in  size  of  the  vegetative  cells 
and  by  the  thickening  of  the  walls. 

Heterocysts  are  special  cells  developed  in  some  forms  from  ordi- 
nary vegetative  cells,  whose  significance  is  not  well  understood. 
Their  protoplasmic  contents  apparently  soon  die  and  one  or  two 
polar  thickenings  appear  in  the  cell.  Undoubtedly  they  are  at 
times  connected  with  the  breaking  up  of  the  filaments,  but  in  some 
cases  they  normally  occur  at  the  basal  ends  only  of  the  filaments. 


I04 


FRESH-WATER   BIOLOGY 


A  few  of  the  Cyanophyceae  show  remarkable  oscillating,  gliding, 
or  rotating  movements,  the  cause  of  which  has  never  been  satisfac- 
torily explained.  In  Oscillatoria  and  Spirulina,  these  movements 
are  particularly  conspicuous. 

CYANOPHYCEAE 

(myxophyceae,  phycochromophyceae,  schizophyceae) 

Algae  possessing  more  or  less  of  a  blue-green  color;  free-floating  or  living  in 
gelatinous  masses  or  strata;  sexual  reproduction  unknown,  reproducing  asexu- 
ally  by  means  of  cell  division,  the  daughter  cells  either  soon  separating  into 
more  or  less  independent  cells,  or  remaining  adherent  to  form  tilaments  or 
plates  or  solid  colonies.  The  vegetative  cells  each  made  up  of  two  more  or 
less  easily  distinguishable  parts:  a  colored  peripheral  cytoplasm,  which  contains 
the  bluish  or  reddish  phycocyanin,  in  addition  to  the  chlorophyll  pigment,  and 
also  generally  a  number  of  minute  granular  bodies  —  the  "cyanophycin  gran- 
ules"; and  the  colorless  ''central  body,"  which  is  the  nucleus  of  the  cell. 
Embedded  in  the  central  body,  in  addition  to  the  chromatic  and  achromatic 
substances,  there  usually  occur  a  few  large,  globular,  transparent  bodies  — 
the  so-called  "slime  globules."  Sap  vacuoles  sometimes  occur  in  the  cyto- 
plasm. Thick-walled  resting  spores  are  formed  in  some  species;  heterocysts 
are  also  found  in  certain  forms,  which  are  peculiar  cells,  whose  protoplasmic 
contents  apparently  soon  die  and  whose  significance  is  but  Uttle  understood. 

1  (25)         One-celled  plants,  hving  either   free   or   united   into  colonies  by 

being  embedded  in  a  common  gelatinous  matrix. 

Order  Coccogoneae  Thuret  .    .      2 

2  (24)         Cells  generally  free-floating  or  forming  a  gelatinous  stratum;  not 

differentiated  into  base  and  apex. 

Family  Chroococcaceae  .    .     3 
3(8,11)     Cell  division  in  one  plane  only 4 

4  (7)  With  wide  mucous  covering 5 

5  (6)  Cells  elongate,  each  with  a  special  mucous  coat.   Gloeothece  Nageli. 

Cells  oblong  or  cylindrical,  with  thick,  sometimes  lamel- 
lose,  gelatinous  membrane;  single  or  united  into  micro- 
scopically small  colonies,  which  are  enclosed  after  the 
manner  of  Gloeocapsa  within  the  gelatinous  membrane  of 
the  mother  cell.     On  wet  rocks,  rarely  floating. 


Fig.  32.   Gloeothece  confltuns  Nageli.     X  4So.     (After  West.) 

6  (5)  Cells  httle  longer  than  broad,  many  adhering  together  to  form 
large,  irregular  colonies,  enclosed  by  a  common  mucous 
matrix Aphanothece  Nageli. 

Cells  oblong,  dividing  only  at  right  angles  to  the  long 
axis;  forming  irregular,  gelatinous  colonies  which  some- 
times grow  to  be  an  inch  or  more  in  diameter.  At 
margins  of  lakes  and  on  wet  rocks. 

Fig.  33.  Aphanothecemicroscopica'Na.gtU.  X  1000.   (Original.) 


BLUE-GREEN   ALGAE  105 

7  (4)  Cells  with  thin  cell  walls Synechococcus  Nageli. 


Cells  comparatively  large,  cylindrical  or  ellipsoidal,  living 
usually  singly  or  sometimes  forming  small  families  of  two 
to  four  united  in  a  row  or  chain.  Cell-contents  blue-green, 
sometimes  yellowish,  pinkish,  or  pale  orange.  Free-floating 
in  ponds  and  pools,  or  on  rocks. 


Fig.    34- 


Synechococcus     aeruginosus 
Kirchner.) 


Nageli.       X  575-       (After 


8(3,11)       Cell-division  in  two  planes 9 

9  (10)  Cells  spherical  or  oblong,  forming  flat,  plate-like  colonies. 

Merismopedia  Mey en . 

Cells  usually  adhering  in  groups  of  four,  and  arranged  in  reg- 
ular rows  to  form  a  flat,  rectangular,  plate-like  colony.  In 
plankton,  in  ponds,  and  lakes. 

Fig.  35.     Merismopedia  elegans  ^..'QtdiXin.      X  450.     (After  West.) 


10  (9) 


11(3,8) 

12  (23) 

13  (16) 

14  (15) 


Cells   flat,    quadrangular   in   outline,    sohtary,   or   forming   small 

colonies Tetrapcdia  Reinsch. 

Cells  with  thin  membrane;  solitary  or  united  into  flat  colonies  of  2  to  16 
cells. 

Cell-division  in  three  planes 12 

Cells  united  into  definite,  often  comparatively  large  colonies.       13 

Colonies  more  or  less  regularly  spherical 14 

Colonies  hollow;  cells  closely  and  regularly  arranged  at  the  surface. 

Coclosphaeriiim  Xageli. 

Cells  globose  or  oblong,  forming  on  the  surface  of  lakes  and 
ponds  microscopically  smaU,  hollow,  spherical  colonies  em- 
bedded in  a  mass  of  mucus;  reproduction  by  means  of  single 
cells  escaping  from  the  colony  as  well  as  through  the  con- 
striction of  old  colonies  to  form  new  ones.  Common  in  fresh- 
water plankton. 

Fig.  36.     Coelosphaeriutn  kutzingianum  Nageli.     X  465-     (Original.) 

Colonies  solid;  cells  sparsely  scattered  through  the  jelly,  pyriform 
in  shape Gomphosphacria  Kiitzing. 


Cells  enclosed  by  a  colorless  gelatinous  matrix  to  form  micro- 
scopically smaU,  solid,  globular,  or  ellipsoid  colonies;  the  peripheral 
cells  grouped  in  pairs  and  egg-shaped  or  pyriform,  or  (during 
division)  heart-shaped.   In  ponds,^  stagnant  water,  etc. 

Fig.    37.     Gomphosphaeria  aponina  Kiitzing.     X  465-     (Original.) 


16(13)  Colonies,  when  old,  generally  not  spherical i? 

17  (18,  19)    Colonies  microscopically  small,  solid,  globular,  or  clustered. 
'  ^         "^  Microcystis  Kutzing. 

(Probably  should  be  united  with  Clathrocystis .)  Cells  spherical,  or  through 
pressure  somewhat  angular;  uniting  in  great  numbers  to  form  microscopic- 
ally small  solid  colonies.     Common  in  ponds  and  ditches. 


15  (14) 


io6 


FRESH-WATER   BIOLOGY 


1 8  (17,  19)  Colonies  at  first  globular,  later  irregular  in  shape,  and  perforated 
or  netted Clathrocystis  Henfrey. 


Cells  spherical,  united  in  great  numbers  to 
form  at  first  globular,  later  irregular  colonies, 
which  often  become  clathrate,  forming  an  open 
meshwork.  Common  in  lakes  and  ponds;  C. 
aeruginosa  Henfr.  is  often  thrown  upon  rocks 
along  shores  to  form,  mixed  with  Coelosphacrium 
kiitzingianum  Niig.,   the  so-called  "green  paint." 


Fig.  38. 


Clathrocystis  aeruginosa  Henfrey.      X  465. 
(Original.) 


19  (17,  1 8)  Colonies  irregular  in  shape,  frequently  forming  films 20 

20  (21,  22)  Individual  mucous  coats  clearly  evident  for  each  daughter  cell  of 

the  colony Gloeocapsa  Ktitzing. 

Cells  spherical,  with  thick,  often 
lamellose,  gelatinous  membrane; 
solitary  or  generally  united  into 
microscopic  colonies  in  which  the 
membranes  of  the  daughter  cells 
remain  enclosed  for  a  long  time 
within  that  of  the  mother-cell. 
Forming  gelatinous  substrata  on 
moist  walls  and  wet  and  dripping 
rocks. 

Fig.  39.    Gloeocapsa  polydermatica 
Kiitzing.     X  465.     (Original.) 

21  (20,  22)   Cells  enveloped  in  a  common  gelatinous  matrix. 

Aphanocapsa  Nageli. 


Cells  globose,  forming  irregular  colonies  enclosed 
in  a  thick,  homogeneous  integument.  Differing  from 
Aphanothece  only  in  its  globose  cells.  In  stagnant 
water,  on  wet  rocks,  etc. 


Fig. 


Aphanocapsa    grevillei    Rabenhorst. 
(After  West.) 


X450. 


2  2  (20,  21)  Cells  globose,  reddish  purple,  arranged  in  a  thin  gelatinous  stra- 
tum  Porphyridium  Nageli. 

Common  on  damp  ground  and  at  the  base  of  damp  walls. 

23  (12)  Cells  solitary  or  a  few  adhering  together  in  a  group,  not  forming  a 
definite  layer Chroococcus  NageH. 


Cells  globose  or  somewhat  angular,  with  firm,  often  thick, 
lamellose  or  homogeneous  membrane.  Free-floating,  or  forming 
a  stratum  on  wet  rocks. 


Fig.  41.    Chroococcus  giganUus  West.     X  300.    (After  West.) 


BLUE-GREEN   ALGAE 


107 


24  (2)  Cells  epiphytic;  with  a  distinct  base  and  apex. 

Family  Chamaesiphonaceae. 
Only  one  genus.     .    .  Chamaesiphon  A.  Braun  and  Gninow. 


Cells  small,  ovoid,  pyriform,  or  cylindrical;  attached 
by  their  base  and  generally  widening  upwards  to  their 
free  apex.  Solitary  or  aggregated;  sheaths  present; 
cell  walls  very  thin;  cell  contents  homogeneous,  blue- 
green,  violet,  or  yellow;  reproduction  by  one-celled, 
non-motile  cells  which  are  successively  cut  off  from 
the  upper  portion  of  the  plants,  gradually  escaping 
from  the  open  apex.  Common  on  Oedogonium  and 
other  algae  in  ponds. 


Fig.    42.       Chamaesiphon    incrustans    Grunow.      X  800. 
(After  West.) 


25  (i)  Plants  filamentous;  filaments   simple   or  branched;   consisting  of 

one  or  more  rows  of  cells  generally  enclosed  within  a  more 
or  less  evident  sheath.  Asexual  reproduction  by  means 
of  hormogonia,  and  more  rarely  by  spores. 

Order  Hormogoneae  Thuret .    .      26 


26  (64) 


Filaments  cylindrical,  sometimes  narrowed  at  the  extremities. 

Suborder  Psilonemateae  .   . 


27 


27  (53)         Filaments  not  branched 28 

28  (43)         Filaments  consisting  of  a  single  row  of  cells,  seldom  {Spirulina) 

one-celled;  not  branched;  heterocysts  absent;  sheaths  vari- 
able, more  or  less  gelatinous,  and  sometimes  enclosing  more 
than  one  filament.  .    .    .  Family  Oscillatoriaceae  .   .     29 


29  (39) 

30  (31) 


Never  more  than  one  filament  within  a  sheath. 

•    Subfamily  Lyngbyeae  . 


30 


Filaments  apparently  one-celled,  coiled  into  a  regular  spiral,  often 
showing  rapid  rotatory  movements.  .    .      Spirulina  Turpin. 


Filaments  very  narrow,  consisting  of  a  single 
elongated  cell,  sometimes  of  great  length,  regularly 
spirally  coiled;  sometimes  showing  rapid  oscillat- 
ing and  rotatory  movements.  Common  in  stag- 
nant water. 


.  Fig.  43.     Spirulina  major  Kiitzing. 
inal.) 


X  1000     (Orig- 


31  (30)        Filaments  many-celled 3^ 

32  (36)        Filaments  simple,  generally  showing  oscillating  and  gliding  move- 

ments; sheaths  thin,  hyaline,  sometimes  not  evident.   .     33 


[o8 


FRESH-WATER  BIOLOGY 


33  (34-  35)  Filaments  more  or  less  confluent  by  their  mucous  sheaths. 

Phormidium  Kiitzing. 

Filaments  many-celled,  straight  or  bent;  en- 
closed in  hyaline  sheaths  which  frequently  become 
adherent  10  form  an  expanded  stratum  on  wet 
rocks  or  moist  earth,  or  entirely  submerged. 
Usually  this  stratum  is  soft  and  slimy,  but  it 
sometimes  becomes  hard  and  leathery.  A  genus 
intermediate  in  character  between  Lyngbya  and 
Oscillaioria. 


Fig. 


44.     Phormidium  subfuscum  Kiitzing.       X  575- 
(After  Kirchner.) 


34  (33 '  35)  Filaments  generally  without  conspicuous  sheaths;  free,  straight,  or 
with  curved  extremities Oscillatoria  Vaucher. 


Tr?= 


x 


Filaments  composed  of  numerous 
short  cylindrical  cells,  the  end  cell  some- 
times much  attenuated;  without  a 
sheath  or  with  an  almost  imperceptible 
one;  generally  showing  lively  creeping 
and  oscillating  movements.  Found  in 
great  profusion  in  all  kinds  of  wet  situ- 
ations; sometimes  free-floating  at  the 
surface  of  lakes  and  ponds,  or  forming 
filmy  growths  on  wet  soil  or  rocks. 
0.  limosa  is  extremely  abundant  on  the 
soil,  etc.,  in  greenhouses,  while  O.  Pro- 
lifica  occurs  in  the  plankton  of  some  lakes  in  such  quantities  as  to  impart 
a  reddish  or  purplish  color  to  the  water  and  occasionally  to  form  a  "water- 
bloom."  The  latter  species  has  been  found  in  some  instances  to  persist  even 
into  the  winter  and  to  color  the  ice  a  reddish  or  pinkish  color. 


B 

Fig.  45.     A,  Oscillatoria  prolifica  Gomont.     B.  Oscillatoria 
limosa  Agardh.      X  465-     (Original.) 


35  (33'  34)  Filaments  without  sheaths,  twisted  into  a  regular  spiral. 

Arthrospira  Stizenberger. 


Filaments  commonly  without  a  sheath,  differing  from 
Oscillatoria  in  being  regularly  spirally  coiled,  and  from 
Spiridina  in  being  many-celled.  Living  singly  or  form- 
ing dark-green  slimy  strata  in  stagnant  water. 

Fig.  46.     Arthrospira  jenneri  Stizenberger.     X  500.      (After 
Gomont.) 


36  (32)         Filaments  not  showing  oscillating  movements;  sheaths  firm.   .     37 


37  (38)         Filaments  free  and  simple,  free-floating  or  forming  an  expanded 
stratum Lyngbya  C.  Agardh. 


Filaments  many-celled,  straight  or  bent, 
each  enclosed  in  a  firm,  generally  hyaline, 
sometimes  lamellose,  membrane,  i'ree-float- 
ing,  or  forming  densely  intricate,  floccose 
masses,  or  an  expanded  stratum.  Frequently 
abundant  in  plankton. 

Fig.    47.     Lyngbya    major     Meneghini.      X  465- 
(Original.) 


BLUE-GREEN   ALGAE  109 

38  (37)         Filaments  forming  erect  tufts,  often  branched.  .   Symploca  Kiitzing. 


Filaments  densely  interwoven  to  form  a  slimy  substratum  from 
which  arise  erect  tufts  of  variable  height.  Sometimes  more  or  less 
procumbent.  False  branches  solitary;  sheaths  thin,  colorless,  firm 
or  somewhat  mucous;  apex  of  the  filament  straight,  sometimes  a  little 
tapering;  outer  membrane  of  tlie  apical  cell  slightly  thickened  in 
some  species.     In  hot  springs,  on  damp  earth,  walls,  or  trunks  of  trees. 


Fig.  48. 


Symploca   lucifuga   Harvey,    a,    X  250;   b,   natural   size.       (After 
Wolle.) 


39  (29)  Several    filaments    in    a    common    sheath   which   is   frequently 

branched Subfamily  Vaginareeae  .   .     40 

40  (41,  42)  Sheaths  often  colored;  lamellose;  filaments  few  or  many,  loosely 

aggregated  within  the  common  sheath,   Schlzothrix  Kiitzing. 

Several  filaments  enclosed  in  a  firm 
lameUose  sheath  which  is  at  first 
colorless  but  later  becomes  yellowish, 
brownish,  or  purpUsh;  filaments  simple 
or  variously  branched.  Forming  cush- 
ion-hke  masses,  erect  tufts,  or  a  flat 
stratum  on  moist  substrata,  rarely 
free-floating. 

Fig.  49.     Schizothrix  rubella  NSgeli. 
X  430.     (After  Gomont.) 

41  (40, 42)  Sheaths    hyahne,   fused    with    adjoining   sheaths.       Hydrocokiim 

Kiitzing. 

Filaments  composed  each  of 
numberless  short  cells,  the  end 
cell  with  thickened  cap-like 
membrane.  Filaments  two 
to  many  in  colorless,  slimy 
sheaths,  which  become  fused 
with  those  of  adjoining  fila- 
ments.  In  brooks  and  water- 
faUs. 

Fig.  50.  Hydrocoleum  homoeotrich- 
um  Kiitzing.  X  390.  (After 
Gomont.) 

42  (40,  41)  Sheaths   hyaline,    not   lamellose,    containing    a    large    number  of 

filaments Microcoleus  Desmazieres. 

Filaments  simple,  consisting 
generally  of  long  cells;  closcJy 
aggregated  in  great  numbers 
in  the  center  of  a  conspicuous, 
hyaline,  cyhndrical  sheath. 

Fig.  51.  Microcoleus  dclicatulm 
W.  and  G.  S.  West.  X  35°- 
(After  West.) 


no  FRESH-WATER   BIOLOGY 

43  (28)         Filaments  simple,  unbranched;  with  heterocysts;  living  singly  or  in 

gelatinous  masses,  often  of  definite  form.  Sheaths  very 
delicate,  mostly  confluent.  Cells  generally  torulose,  in  a 
single  row Family  Nostoceae  .    .     44 

44  (47)        Filaments  enclosed  within  a  gelatinous  mass  of  definite  form.      45 

45  (46)        Forming  delicate,  hollow,  cylindrical  colonies. 

Wollea  Bornet  and  Flahault. 


Delicate  colonies;  filaments  straight  or 
slightly  bent,  arranged  in  tolerably  parallel 
rows,  with  a  common  gelatinous  envelope; 
heterocysts  intercalary;  spores  in  chains, 
bordering  on  one  or  both  sides  of  the 
heterocysts.  IF.  saccala  Bor.  and  Flah. 
occurs  in  stagnant  water. 

Fig.  52.     Wollea  saccata  Bomet  and  Flahault. 
a,  X  250;   b,  natural  size.     (After  WoUe.) 


46  (45)         Colonies  spherical,  or  of  varied  form;  with  the  enclosed  filament 
irregularly  interwoven  and  contorted.    .    .  Nostoc  Vaucher. 


I 


Forming  leathery  or  slimy  gelatinous  masses,  at  first  spher- 
ical or  oblong,  later  of  varied  form,  solid  or  hollow,  and 
attached  or  unattached;  filaments  contorted  and  curved  in 
all  directions;  the  gelatinous  sheath  sometimes  sharply 
deUmited,  more  often  fused  with  the  enveloping  jelly. 
Cells  globular,  barrel-shaped,  or  cyhndrical;  heterocysts 
intercalary,  or  (when  young)  sometimes  terminal;  sp)ores 
globular  or  oblong,  formed  in  rows  in  varying  number  be- 
tween the  heterocysts.  Forming  free-floating  or  attached 
masses,  on  damp  ground,  wet  rocks,  etc. 

Fig.  55.    Nostoc  commune  Vaucher.     a,  natural  size;   b,  X  465. 
(Original.) 


47  (44)        Filaments  more  or  less  straight,  free-floating  or  forming  a  thin 

mucous  stratum 48 

48  (52)        Heterocysts  and  spores  intercalary 49 

4Q  (50,  51)  Filaments  naked,  or  with  a  thin  sheath;  single,  or  aggregated  into 
formless,  flocculent  masses;  cells  equal  to  or  longer  than 
their  diameter Anabaena  Bory. 


Filaments  straight  or  circinate,  naked  or  enclosed 
in  a  thin  sheath,  free  floating  as  single  filaments  or 
united  to  form  a  thin,  slimy  stratum;  vegetative 
cells  as  long  or  somewhat  longer  than  thick;  heter- 
ocysts numerous  and  intercalary;  spores  variously 
disposed,  borne  singly  or  rarely  in  short  chains. 
A.  flos-aquae  Breb.  and  A.  circinalis  Rabenh.  are 
frequently  abundant  in  fresh-water  plankton. 


Fig.    54- 


Anabaena    flos-aquae    fir^bisson. 
(Original.) 


X46S. 


BLUE-GREEN  ALGAE 


III 


50  (49,  51)  FUaments  short,  straight,  densely  aggregated  in  parallel  bundles  to 

form  small,  feathery,  plate-like  masses. 

.  „ Aphanizomenon  Morren. 

Filaments  without  sheath, 
straight  or  somewhat  taper- 
ing at  the  end;  united  in 
small,  spindle  -  shaped  or 
plate-like,  free-floating  bun- 
dles; spores  much  elongated, 
cylindrical,  solitary,  not  bor- 
dering on  the  intercalary 
heterocyst.        A .   Jlos-aquac 

Ralfs  is  sometimes  found  floating  in  great  abundance  in  the  still  waters  of 

ponds  and  lakes. 

51  (49,  50)  Filaments  free;  cells  shorter  than  their  diameter. 

Nodularia  Mertens. 


lBc<^.l;^t^MAW^*..mi-j»aiTgg^ 


Fig.  55.    Aphanizomenon  Jlos-aquaeRsMs.     X  465.      (Original.) 


ssia^^^ 


52  (48) 


Fig.    57. 


Filaments  enclosed  in  a  thin,  often  evanescent  sheath; 
free-floating  as  single  filaments  or  united  into  colonies  of 
indefinite  form;  heterocysts  intercalary,  depressed;  spores 
almost  spherical,  in  rows,  not  bordering  on  the  hetero- 
cysts. 

Fig.  56.     Nodularia  sp.     X  465.     (Original.) 

Heterocysts  terminal  and  the  spores  always  contiguous  to  them. 

Cylindrospermum  Kiitzing. 

Filaments  without  sheath 
relatively  short,  aggregated  to 
form  an  expanded  film  or 
colony  of  indefinite  shape; 
vegetative  cells  cylindrical, 
longer  than  the  diameter;  het- 
erocyst terminal;  spores  gen- 
erally soHtary,  borne  next  to 
Common  on  damp  earth  and  stones. 


Cylindrospermum 
X465. 


stagnale  Bornet   and    Flahault 
(Original.) 


53  (27) 

54  (60) 


the  heterocyst 

Filaments  with  true  or  false  branches 54 

Filaments  bearing  false  branches;  sheaths  firm,  of  more  or  less  equal 
thickness;  filaments  consisting  of  a  single  row  of  cells,  with 
heterocysts  (except  Plectonema). 

Family  Scytonemaceae  .    .     55 

55  (56,  59)  Without  heterocysts  or  spores Plectonema  Thuret. 

Filaments  consisting 
only  of  vegetative  cells, 
without  heterocysts;  false- 
ly branched,  branches 
single  or  in  pairs;  borne 
singly  in  a  firm,  colorless 
or  yellowish  sheath.  P. 
U'ollci  Farl.  occurs  in 
some  abundance  in 
ponds,  attached  to  stones, 
etc. 

Fig.  58.  Plectonema  uolUi 
Farlow.  X  260.  (After 
Kirchner.) 

56  (55,  59)  With  intercalary  heterocysts.    One  filament  in  each  sheath.    .     57 


112  FRESH-WATER   BIOLOGY 

57  (58)         Branches  generally  arising  in  pairs Scytonema  Agardh. 


Filaments  consisting  of  vegetative  cells  and 
heterocysts;  borne  singly  in  a  sheath;  sheath 
tough,  lamellose,  frequently  yellowish  or  brownish 
in  color;  false  branches  borne  generally  in  pairs 
between  the  heterocysts.  Forming  felt-like  masses 
on  wet  rocks,  etc. 

Fig.  59.  Scytonema  mirabiU  Thuret.   X  465-    (Original.) 


58  (57)        Branches  arising  as  a  rule  singly Tolypothrix  Kiitzing. 


Filaments  resembling  closely 
those  of  Scytonema,  but  false 
branches  arising  singly  as  a  rule 
instead  of  in  pairs,  as  outgrowths 
in  the  region  of  the  heterocysts; 
the  latter  1-5  in  a  row;  spores  (in 
a  few  species)  elliptical,  borne 
singly  or  in  rows.  Occurring 
among  various  aquatic  plants  in 
ponds  and  lakes. 

Fig.  60.       Tolypothrix  lanata  Wart- 
mann.     X  465-     (Original.) 


59  (55'  56)  With  basal  heterocysts.     Two   to   several  filaments   enclosed  in 
each  sheath Desmonema  Berkeley  and  Thwaites. 


Filaments  sometimes  slightly  branched; 
heterocysts  always  basal.  On  stones,  in  brooks, 
and  waterfalls. 


Fig.    61. 


Desmonema    wrangelii    Borzi.       X  200. 
(After  Borzi.) 


60  (54) 


Filaments  usually  stout,  bearing  true  branches;  cells  rounded,  dis- 
posed generally  in  more  than  one  row;   heterocysts  present. 
Family  Stigonemaceae  .    .     61 


61(62,63)  Sheaths  thick;  firm S tigonema  \g^rdh. 

Filaments  free-floating  or  aggregated 
on  the  substratum  to  form  felt-like 
masses;  filaments  composed  partly  of  two 
to  several  cell-rows,  sometimes  of  a  single 
row,  enclosed  in  a  thick,  lamellose,  yellow- 
ish or  brownish  sheath,  which  is  often 
of  irregular  thickness.  Hormogonia 
formed  at  the  ends  of  the  vegetative 
branches  or  in  special  short  branches. 
Heterocysts  commonly  lateral,  or  less  often 
intercalary.  Vegetative  cells  rounded, 
frequently  showing  protoplasmic  continuity.     Growing  generally  on  damp  or 


Fig.   62 

nema 


a,  Stigonema   ocellatum  Thuret;  b,  Stigo- 
minutum  Hassall.      X  440.     (After  West.) 


wet  rocks  or  moss;  sometimes  free-floating. 


BLUE-GREEN  ALGAE 


113 


62  (61,  63)  Sheaths  thin;  branches  commonly  unilateral.  Hapalosiphon  Nageli. 

Filaments  free-floating  amongst  other  algae  or  subacrial. 
Branches  long  and  flexuose,  slightly  attenuated,  generally 
narrower  than  the  main  axis  and  borne  unilaterally. 
Primary  axis  consisting  of  a  single  row,  rarely  of  2  to  3 
rows  of  cells,  enclosed  in  a  strong  sheath  of  uniform 
thickness.  Spores  and  heterocysts  intercalary.  Among 
water  weeds,  in  hot  springs,  etc. 

Fig.  63.     Hapalosiphon  hibernicus  W.  and  G.  S.  West. 
X  440.     (After  West.) 

63  (61,  62)  Sheaths  thick;  fused  to  form  an  irregular  gelatinous  mass. 

Nostochopsis  Wood. 

Forming  rounded,  Nostoc-like 
masses,  attached  to  water  plants. 
Filaments  composed  of  but  one  cell- 
row;  profusely  branched. 

Fig.  64.     Nostochopsis  lobata  Wood. 
X  330.     (After  Bornet.) 

64  (26)         Filaments  conspicuously  attenuated  towards  one  or  both  extrem- 

ities, which  are  generally  piliferous. 

Suborder  Trichophoreae  .    .      65 

Filaments  sheathed,  simple  or  branched,  attenuated  from  the  base 
to  the  apex,  which  is  piliferous;  heterocysts  generally  basal, 
rarely  absent Family  Rwularlaceae  .    .     65 

65  (68)         Filaments  free  or  forming  penicillate  tufts  or  soft  velvety  expan- 

sions  66 


66  (67)        Branches,  when  present,  distinct  and  free. 


.    ,  Calothrix  Agardh. 

Filaments  simple  or 
slightly  branched,  single 
in  a  thick  sheath;  hetero- 
cysts basal  or  intercalary 
or,  in  a  few  species, 
absent.  Forming  tufts 
or  soft  velvety  expan- 
sions on  wet  or  sub- 
merged rocks. 

Fig.  65.  Calothrix  thermalis 
Haosgirg.  X  4t)5  (Origi- 
nal.) 

67  (66)         Branches  several  (2  to  6)  within  a  common  sheath. 

Dichothrix  Zanardini. 


Filaments  more  or  less  di- 
chotomously  branched;  hetero- 
c>'sts  basal  or  intercalary.  On 
wet  rocks,  etc. 

Fig.  (i6.  Dichothrix  interrupts  W. 
andG.  S.  West.  X  4-^0  (After 
West.) 


68  (65)        Filaments  forming  a  hemispherical  or  globular  mass,  closely  united 
by  mucus 6q 


114 


FRESH-WATER   BIOLOGY 


69  (70)         Filaments  radiately  disposed  in  a  globose  or  hemispherical,  at- 
tached mass.     Spores  unknown Rivularia  Agardh. 

Forming  hemispherical,  globular,  or  hollow 
spherical  colonies  attached  to  submerged 
plants,  such  as  Chara,  Myriophyllum,  or  to 
stones  in  streams  and  cataracts.  Colonies 
composed  of  radiating  filaments  which  are 
repeatedly  branched;  filaments  attenuated 
and  with  piliferous  extremities;  heterocysts 
basal;  the  whole  enclosed  in  a  tough,  gelat- 
inous matrix. 


Fig.  67. 


Rivularia  minutula  Bornet  and  Flahault. 
X  300-     (After  West.) 


70  (69)         Filaments  radiately  disposed;  colony  often  free-floating.     Spores 
regularly  present Gloeotrichia  J.  Agardh. 

(Probably    not    sufficiently 
distinguished  from  Rivularia  to 
justify  its  being  made  a  sep- 
arate genus.)     Colony  globose, 
free-floating    or    attached    to 
submerged  water  plants;  soUd 
when  young,  but  inflated  and 
hollow  when  old;   composed  of  radiating,  branched,  attenuated  filaments. 
Spores  elongated,  cylindrical,  borne  immediately  above  the  basal  heterocyst. 
G.   pisum   Ag.    is    a  common   plankton   form   and   constituent   of   "water- 
bloom." 


Fig.  68.     Gloeotrichia  pisum  Agardh.      X  465-    (Original.) 


IMPORTANT   REFERENCES   ON   BLUE-GREEN   .\LGAE 

Farlow,  W.  G.     1877.     Remarks  on  some  algae  found  in  the  water  supplies 

of  the  City  of  Boston.     Bull.  Bussey  Inst.,  2:  75-80. 
Forti,  A.     1907.     Sylloge  Myxophycearum;   in  De  Toni's  Sylloge  Algarum 

omnium,  Vol.  V. 
Gardner,  N.  L.     1906.     Cytological   studies   in    Cyanophyceae.     Univ.    of 

CaUf.  Pub.  Bot.,  2:  237-296. 
Hyams,  Isabel  F.,  and  Richards,  Ellen  H.     1901,  1902,  1904.     Notes  on 

Oscillatoria  prolifica.     Tech.  Quarterly,  Vols.  14,  15,  17. 
Klrchner,  O.     1900.     Schizophyceae;  in  Engler-Prantl  Nat.  Pflanzenfamilien. 
Olive,  Edgar  W.    1904.     Mitotic  division  of  the  nuclei  of  the  Cyanophyceae. 

Beihefte  z.  Botan.  Centralb.,  18:  9-44. 
1905.     Notes  on  the  Occurrence  of  Oscillatoria  prolifica  in  the  Ice  of  Pine 

Lake,  Waukesha  County,  Wisconsin.    Trans.  Wis.  Acad.  Sci.,  15:  124-134. 
Oltmanns,  Friedr.     1904-05.     Morphologic  und   Biologie  der  Algen.     2v. 

Jena. 
TiLDEN,  Josephine.     1910.     The  Myxophyceae  of  North  America  and  Adja- 
cent Regions,  etc.     Minneapolis. 
West,  G.  S.     1904.     A  Treatise  on  the  British  Frcshv/ater  Algae.     Camb. 

Univ.  Press. 
WOLLE,  F.     1887.     Fresh-water  Algae  of  the  United  States.    Bethlehem,  Pa. 


CHAPTER   VI 
THE    FRESH-WATER    ALGAE 

(Excluding  the  Blue-Green  Algae) 

By  JULIA  W.  SNOW 

Associate  Professor  of  Botany  in  Smith  College,  Northampton,  Mass. 

The  fresh-water  algae  are  among  the  most  widely  distributed  of 
plants.  They  are  found  in  all  natural  bodies  of  water,  whether 
these  be  rapidly-running  streams,  brooks,  and  rivers,  or  the  more 
quiet  bodies,  such  as  pools,  ponds,  and  lakes.  They  abound  where- 
ever  there  is  moisture.  All  low-growing  vegetation  in  moist  places, 
the  bark  of  trees,  the  earth  itself,  and  even  snow-covered  moun- 
tains, bear  species,  although  they  may  be  invisible  to  the  naked 
eye. 

The  forms  of  the  fresh-water  algae  are  most  varied,  and  there  are 
all  gradations  from  the  most  minute  cell  of  primitive,  spherical 
shape  to  the  large  filamentous,  richly-branched  structure,  or  cell 
complex.  The  difference  between  the  simple  unicellular  forms  and 
many  of  the  higher  forms  is  less  than  would  appear  at  first  sight. 
The  larger  forms  often  instead  of  being  complex  organisms  with 
many  organs,  each  with  its  own  special  function,  seem  to  be  more 
Uke  aggregates  of  unicellular  individuals,  each  capable  of  perform- 
ing all  the  life  functions,  and  each  living  independently  of  its 
neighbors.  This  is  manifested  in  forms  where  a  single  cell  is  sepa- 
rated from  all  others  and  continues  to  live  and  to  reproduce.  An 
example  of  this  is  seen  in  Stigeoclonium  and  Chadophora,  which 
under  certain  conditions  fall  apart  completely,  and  each  cell  exists 
indefinitely  as  a  unicellular  organism  undergoing  division  in  three 
directions.  Such  a  state  is  known  as  the  palmella  condition. 
Each  cell  in  this  aggregate,  however,  when  in  the  right  enviromnent, 
has  the  power  to  reproduce  again  the  original  plant,  a  fact  which 
would  indicate  that  environment  as  well  as  heredity  is  a  factor 


Il6  FRESH-WATER   BIOLOGY 

in  the  determination  of  form.  It  was  formerly  thought  that  such 
a  pol>Tnorphism  was  characteristic  for  the  majority  of  the  higher 
algae,  but  though  frequent  it  is  by  no  means  universal. 

Certain  of  the  genera  of  the  unicellular  algae  must  be  closely 
related  to  certain  genera  of  the  filamentous  forms,  such  as  Slichococcus 
and  Ilormidium.  Botrydiopsls  and  Conjeroa.  The  structure  of 
the  cell,  the  color,  size,  and  shape  of  the  chromatophores,  the  repro- 
duction, the  chemica  substances  formed  by  the  cells  of  the  differ- 
ent genera,  are  in  each  case  identical,  and  practically  the  only 
difference  is  that  in  the  one  case  the  cells  are  cylindrical  and  united 
into  a  filament,  while  in  the  other  case  they  may  be  somewhat 
spherical  and  solitary. 

The  resemblance  is  so  great  between  the  Chloromonadaceae, 
Confen'a,  Botrydiopsls,  and  other  forms  in  reference  to  the  light 
color,  the  small  chromatophores,  the  nature  of  the  zoospores,  and 
several  other  points,  that  many  modern  writers  classify  them 
together  under  the  head  of  Heterokontae,  in  spite  of  the  fact  that 
some  are  unicellular,  some  flagellate,  and  some  filamentous  forms. 
Though  this  resemblance  is  fully  recognized  by  the  writer,  in  this 
brief  outline  of  the  fresh-water  algae  the  older  classification  of 
Wille  will  be  retained. 

The  adult  algal  cell  is  a  typical  plant  cell,  bounded  by  a  mem- 
brane, usually  of  cellulose,  but  in  the  Diatomaceae  of  a  siliceous 
nature.  Just  within  the  membrane  is  a  layer  of  protoplasm  which 
encloses  one  or  more  vacuoles  and  in  which  are  imbedded  one  or 
more  chromatophores  occupying  either  a  parietal  or  a  central 
position.  The  nucleus  usually  lies  near  the  center.  In  by  far  the 
larger  number  of  species  there  is  a  single  nucleus  in  a  cell,  but  in 
the  Cladophoraceae  and  the  non-septate  Siphonales  there  are  many 
nuclei.     The  non-septate  algae  are  called  coenocytes. 

The  chromatophores  of  the  algae  are  large  in  proportion  to  the 
size  of  the  cell,  and  may  be  disc-shaped,  plate-like,  star-shaped, 
or  spiral.  They  may  be  regular  or  irregular,  perforated,  netted, 
or  entire.  Nowhere  else  in  the  plant  kingdom  do  we  find  such  a 
variety  of  shapes  and  structures  among  chromatophores  as  among 
the  algae.  Within  the  chromatophores  of  many  species  is  a  body 
denser  in  structure   and  albuminous  in  character,  the  pyrenoid. 


THE   FRESH-WATER   ALGAE  II7 

This  usually  is  surrounded  by  starch  and  is  the  center  of  reserve 
material. 

Davis  regards  the  pyrenoid  as  the  center  of  activity  of  the 
chroma toph ore.  Certain  it  is  that  the  division  of  the  pyrenoid  is 
the  first  visible  stage  in  the  division  of  the  chromatophore  and  of 
the  entire  cell,  and  takes  place  in  some  cases  at  least  before  the 
division  of  the  nucleus. 

On  the  basis  of  the  color  of  the  chromatophore  of  the  different 
forms,  together  with  the  mode  of  reproduction,  are  formed  the  chief 
divisions  of  the  algae.  The  different  classes  are  as  follows  and 
each  of  them  is  treated  separately  in  a  synoptic  key  at  the  place 
indicated : 

Chlorophyceae,  color  green,  page  134. 

Cyanophyceae,  color  blue-green,  page  100. 

Phaeophyceae,  color  brown,  page  174. 

Rhodophyceae,  color  red  or  purpKsh  green,  page  175. 

Bacillariaceae,  color  yellov/,  page  125. 

In  all  cases  where  the  color  is  other  than  green  there  is  in  the 
chromatophore  a  coloring  matter  which  screens  the  chlorophyll 
and  gives  the  characteristic  hue  to  members  of  the  group.  In 
the  Cyanophyceae  the  coloring  matter  is  phycocyan;  in  the  Phaeo- 
phyceae, phycophaein;  in  the  Rhodophyceae,  phycoerythrin;  and 
in  the  Bacillariaceae,  diatomin. 

Reproduction  in  the  algae  is  either  sexual  or  asexual. 

Asexual  reproduction  may  take  place  either  by  simple  cell 
division  or  by  the  formation  of  some  cell  specially  modified  for 
that  purpose.  Cell  division  may  occur  in  one  of  two  ways:  first, 
by  fission,  where  a  membrane  is  formed  across  a  cell,  dividing  the 
original  membrane  and  contents,  as  in  Pleurococcus ;  second,  by 
internal  division,  where  the  contents  are  simply  divided  into  two, 
then  four,  and  perhaps  eight  or  more  portions,  as  in  Dactylococcus 
and  Chlorella.  The  membrane  remains  for  a  time  unaltered,  but 
finally  becomes  ruptured  when  the  daughter  cells  increase  in  size, 
thus  setting  free  the  new  individuals.  They  germinate  immedi- 
ately and  each  produces  a  new  plant. 

Oblique  divisions  of  cells,  so  frequently  attributed  to  the  algae, 
rarely  if  ever  occur.     They  appear  to  take  place  very  frequently, 


Il8  FRESH-WATER   BIOLOGY 

2is  hi  Ankistrodes?nus,  Dactylococcus ,  and  CJilamydonionas,  but  obser- 
vation proves  that  such  divisions  are  ahvays  transverse  or  longi- 
tudinal, and  that  the  parts  in  growing  slip  by  each  other  and 
elongate,  producing  the  diagonal  Une  of  demarcation  between 
them. 

In  reproduction  by  internal  division,  the  new  individuals  are 
called  by  Artari  gonidia,  by  West  autospores,  and  by  Wille  akin- 
etes,  with  the  akinete  character  but  sHghtly  developed.  The 
contents  of  such  cells  may  become  denser,  and  possibly  be  filled 
with  oil  or  starch;  at  the  same  time  the  membrane  becomes  thick- 
ened and  the  whole  cell  more  resistant  to  unfavorable  conditions, 
such  as  heat,  cold,  or  drought.  They  may  remain  in  this  condi- 
tion for  long  periods,  and  in  this  way  maintain  the  life  of  the 
organism  over  conditions  which  would  threaten  the  existence  of 
an  ordinary  vegetative  cell.  Such  cells  or  akinetes,  according  to 
Wille,  may  be  seen  in  the  palmella  condition  of  Stigeoclonium  and 
Chaetophora. 

The  modification  of  these  cells  may  continue  farther,  and  a 
rejuvenescence  occur.  Each  cell  becomes  invested  with  a  new 
membrane  and  the  old  membrane  is  cast  off  before  germination. 
These  structures  Wille  would  designate  as  aplanospores.  He  also 
calls  attention  to  the  fact  that  there  are  many  transitional  stages 
between  the  vegetative  cells  and  akinetes,  and  also  between  the 
akinetes  and  the  aplanospores. 

In  many  of  the  Confervales  and  Protococcales,  instead  of 
autospores,  there  are  formed  motile  spores  or  zoospores.  These 
are  mostly  oval  in  shape,  without  a  membrane,  with  one,  two,  or 
four  ciHa,  a  reddish  pigment  spot,  one  or  two  chromatophores, 
and  usually  two  contracting  vacuoles  in  the  anterior  end.  The 
zoosporangium,  or  cell  in  whicli  they  are  borne,  is  in  the  greater 
number  of  cases  developed  from  an  ordinary  vegetative  cell,  but 
more  rarely  from  a  cell  specialized  for  that  purpose.  The  zoo- 
spores originate  by  the  repeated  bipartition  of  the  cell  contents,  by 
which  2,  4,  8,  1 6,  32,  64,  or  even  128  spores  are  formed,  as  in  the 
production  of  autospores.  More  rarely  a  single  spore  is  formed 
from  a  cell.  The  zoospores  are  set  free  either  by  the  entire  cell 
wall  becoming  gelatinous,  or  by  its  dissolving  at  a  single  point, 


THE  FRESH-WATER  ALGAE  1 19 

through  which  the  spores  gradually  press  their  way.  In  some 
instances  the  membrane  splits  and  the  spores  are  thus  liberated. 
If  the  conditions  be  not  favorable  to  the  liberation  of  the  spores, 
however,  they  may  move  for  a  time  within  the  mother  membrane, 
or  may  never  come  into  motion  at  all,  but  may  germinate  immedi- 
ately without  being  liberated,  and  become  invested  with  membranes 
of  their  own.  They  soon  increase  in  size  so  that  the  zoosporangium 
wall  is  broken,  but  they  often  remain  adhering  to  each  other  for  a 
long  time,  thus  forming  a  cluster  of  cells  like  the  parent  individual. 

Sexual  reproduction  is  always  preceded  by  fertilization.  This 
process  consists  in  a  union  of  two  cells  which  may  be  either  alike 
or  unlike,  and  are  known  as  gametes  If  the  cells  are  alike  they 
are  called  isogametes,  but  if  unlike,  heterogametes.  The  simplest 
form  of  fertilization  is  seen  when  two  isogametes  unite  or  conjugate 
to  form  a  zygospore.  These  gametes  may  be  two  motile  cells 
resembling  zoospores,  as  n  Protosiphon,  or  they  may  be  non- 
motile  cells,  either  distinct  individuals  as  in  the  Desmids,  or  as 
parts  of  filaments,  as  in  Spirogyra.  Frequently  a  sKght  difference 
in  size  may  be  detected  between  these  two  cells,  and  undoubtedly 
this  is  a  beginning  of  sex  differentiation.  In  all  of  the  higher 
algae  this  differentiation  has  advanced  much  farther  and  a  great 
difference  exists  between  the  gametes:  the  female  cell,  the  oosphere 
or  'egg  cell,  being  large  and  non-motile,  while  the  male  cell,  the 
antherozoid  or  spermatozoid,  is  endowed  with  independent  motion. 
Only  in  the  Florideae  does  the  male  cell,  the  spermatium,  lack 
motion,  and  remain  dependent  upon  the  action  of  the  water  to 
transfer  it  to  the  egg  cell. 

The  female  organ  which  bears  the  egg  cell  is  called  the  oogo- 
nium, the  male  organ  which  bears  the  antherozoid  is  the  antherid- 
ium.  The  result  of  fertilization  of  an  egg  by  an  antherozoid  is  an 
oospore,  which  is  resistant  to  unfavorable  conditions  and  is  usually 
dormant  for  a  period  before  germination. 

The  female  organ  of  the  Florideae  is  called  the  procarp.  It  is 
flask-shaped  and  made  up  of  two  parts,  the  enlarged  basal  por- 
tion, the  carpogonium,  which  contains  the  egg  cell,  and  a  projecting 
neck,  the  trichogyne,  for  conducting  the  spermatium  to  the  egg. 
The  influence  of  fertiUzation  is  manifested  by  a  rapid  production 


I20  FRESH- WATER  BIOLOGY 

of  spores  from  the  base  of  the  carpogonium,  surrounded  by  sterile 
filaments;  these  together  form  the  cystocarp. 

Just  as  in  the  study  of  the  higher  plants  attention  has  been 
turned  largely  from  a  purely  systematic  investigation  to  a  physio- 
logical study,  so  among  the  algae  the  most  important  work  is  done 
along  the  line  of  physiology.  The  simpUcity  of  their  structure, 
the  ease  with  which  many  may  be  cultivated,  the  readiness  with 
which  they  respond  to  and  adapt  themselves  to  external  condi- 
tions make  them  a  most  valuable  group  with  which  to  experiment. 
It  would  seem  that  many  of  the  ph\siological  phenomena  which 
in  the  higher  plants  are  rendered  obscure,  due  to  intricacy  of 
structure  and  complexity  of  environment,  might  be  made  plain  in 
these  lower  forms  which  lend  themselves  so  readily  to  manipula- 
tion. 

Most  valuable  results  in  the  physiology  of  reproduction  have 
already  been  attained  by  Klebs  w^ho  has  taken  the  chief  elements 
in  the  environment  and  studied  their  effect  on  the  organism.  As  a 
result  he  has  shown  that  reproduction,  at  least  in  the  forms  studied, 
instead  of  being  a  phenomenon  which,  without  any  determining 
cause,  occurs  simply  as  a  stage  of  growth,  is  a  phenomenon  which  is 
dependent  upon  external  conditions ;  and  that  as  these  are  altered , 
the  one  or  the  other  form  of  reproduction  may  be  originated,  per- 
fected, or  altogether  checked,  according  to  the  will  of  the  investi- 
gator. He  has  shown  most  conclusively  that  the  sexual  form  of 
reproduction  does  not  of  necessity  alternate  with  the  asexual  repro- 
duction. If  the  conditions  be  maintained,  it  is  possible  in  certain 
cases  to  suppress  either  form  of  reproduction  indefinitely,  or  if  de- 
sired, to  call  forth  the  one  to  the  entire  exclusion  of  the  other.  An 
example  of  this  is  cited  by  Klebs  in  Vaucheria,  Protosiphon,  and  a 
number  of  other  forms.  These  facts  would  go  to  prove  that  an  alter- 
nation of  the  sexual  and  asexual  form  of  reproduction  does  not  exist 
in  the  green  algae,  though  West  and  others  hold  that  it  occurs  in 
a  large  number  of  the  Chlorophyceae.  The  sporophyte  generation, 
they  believe,  is  represented  by  the  sexual  spore  which  produces 
asexual  zoospores;  each  of  these  in  turn,  on  germinating,  ushers  in 
a  gametophyte  generation. 

In  studying  the  algal  flora  of  any  region  and  the  conditions  under 


THE  FRESH-WATER  ALGAE  121 

which  it  exists,  one  notes  ecological  relations  among  the  algae 
quite  as  much  as  among  higher  plants.  The  forms  which  may  be 
found  are  determined  very  largely  by  the  nature  of  their  environ- 
ment, and  many  of  them  cannot  be  transferred  from  one  set  of 
conditions  to  another.  A  large  number  of  species  which  live  sub- 
merged in  water  soon  perish  if  subjected  to  the  atmosphere,  while 
others,  such  as  the  common  Pleurococcus  vulgaris,  which  normally 
live  exposed  to  the  air,  are  never  found  in  water.  A  few  forms, 
such  as  Chlorella,  Stichococcus  and  Hormidium,  may  adapt  them- 
selves to  either  environment,  and  are  very  widely  distributed 
under  the  different  conditions  where  algae  are  found. 

As  all  forms  are  dependent  on  moisture,  the  geological  formations 
which  determine  the  amount  of  moisture  must  determine  the 
algal  flora  of  any  region.  •  In  localities  where  there  are  large  tracts 
of  level  land  without  elevations  and  depressions,  the  algal  flora  is 
extremely  meager;  while  in  a  hilly  country  where  the  water  accu- 
mulates in  depressions  of  the  earth  this  flora  is  abundant,  certain 
forms  such  as  Stigeoclonium,  Draparnaldia,  and  Batrachospermum 
preferring  the  rapidly-running  water  of  streams,  while  the  larger 
number  of  species  choose  the  quieter  water  of  ponds  and  lakes. 

From  early  spring  to  late  fall  the  algae  are  most  numerous,  but 
they  are  also  found  in  winter,  even  in  the  vegetative  condition,  as 
many  are  not  injured  by  freezing.  In  these  cases  the  chief  eft'ect 
of  cold  upon  them  is  simply  a  retarding  of  growth  and  of  repro- 
duction. But  while  some  forms  are  found  at  all  seasons,  differ- 
ent forms  predominate  at  different  times,  some  species  being  most 
abundant  at  one  period  and  others  most  abundant  at  another. 
It  does  not  follow,  however,  that  the  same  date  in  successive 
years  will  find  the  same  form  predominating.  Within  certain 
limits  the  flora  of  a  body  of  water  is  constantly  changing,  due 
probably  to  changes  in  temperature,  light,  and  nutrition,  or  pos- 
sibly to  other  causes  too  obscure  to  detect. 

Usually  the  httoral  region  supports  a  number  of  filamentous 
algae.  Cladophora  is  one  of  the  most  frequent  and  is  especially 
abundant  in  regions  where  wave  action  is  strong  and  the  current 
great.  On  the  other  hand,  if  the  water  be  shallow  and  exposed  to 
the  direct  rays  of  the  sun,  such  forms  as  Spirogyra,  Zygmma,  Oedo- 


122  FRESH-WATER  BIOLOGY 

gonium,  and  Bulbochactc  are  found.  Char  a  and  Nitella  are  found  in 
huge  beds  at  the  bottom  of  lakes  at  a  depth  of  from  one  to  many  feet. 

Of  the  unicellular  forms  also,  different  species  occur  under  different 
conditions.  An  especially  favorable  position  for  this  group  is 
among  the  leaves  and  on  the  surface  of  the  higher  aquatic  plants. 
Indeed  unless  higher  algae  or  phanerogams  exist  in  certain  locali- 
ties but  few  of  the  minute  forms  are  ever  found.  There  seem  to  be 
certain  preferences  on  the  part  of  different  species  of  unicellular 
algae  as  to  the  forms  of  the  higher  plants  with  which  they  associate. 
This  may  be  simply  that  the  shape,  texture,  and  arrangement  of 
parts  of  certain  of  these  plants  afford  a  better  shelter  and  protec- 
tion for  the  single  cells  than  do  others,  but  it  is  more  probable  that 
the  plant  itself  exerts  some  chemical  influence  which  is  attractive 
or  repulsive  to  these  forms.  For  instance,  enormous  numbers  of 
different  species  may  be  found  growing  among  Chara,  while  in 
connection  with  Ceratophyllum,  the  leaves  of  which  are  very  finely 
cut,  but  few  species  occur. 

The  endophytic  forms,  such  as  Endosphaera  and  Scotinosphaera, 
Kve  principally  in  the  tissues  of  Potamogeton,  Lemna,  and  other 
water  plants,  though  they  may  also  be  found  outside  of  the  tissues. 
The  discoid  forms,  such  as  Coleochaete  and  Ulvella,  are  found  on  the 
surface  of  the  broader-leaved  types  of  submerged  plants,  especially 
on  Potamogeton;  and  the  unicellular  blue-green  forms  occur  abun- 
dantly among  the  Charas,  though  they  are  also  numerous  in  most 
stagnant  water. 

In  the  plankton  are  always  found  many  species  that  exist  in  the 
littoral  region,  but  there  are  also  many  forms  which  are  distinctively 
plankton  types.  These  are  characterized  by  a  great  surface  in 
proportion  to  the  mass  of  the  cells,  thus  rendering  them  more 
buoyant.  This  is  provided  for  in  several  ways:  by  the  presence 
of  long  gelatinous  or  cellulose  spines,  as  in  Chodatella  and  Rich- 
teriella;  by  the  union  of  cells  into  ribbons  or  bands,  as  in  Fragila- 
ria;  and  by  the  production  of  a  homogeneous  gelatinous  matrix  in 
which  the  cells  are  imbedded,  as  in  Kirchneriella  and  Sphaerocystis. 

In  studying  the  life  history  of  the  algae,  cultivation  is  absolutely 
essential  in  order  that  development  may  be  traced  from  step  to 
step  without  confusing  the  different  phases  of  the  form  in  ques- 


THE  FRESH-WATER  ALGAE  123 

tion  with  other  species  which  may  be  found  in  connection  with  it. 
Aside  from  this,  too,  cultures  are  useful  in  determining  what  species, 
especially  of  the  unicellular  forms,  are  present  in  any  collection. 
Many  of  these  are  so  minute  that  they  could  easily  be  overlooked 
unless  they  exist  in  great  masses,  which  is  rarely  the  case.  So  if 
all  forms  of  a  locality  are  desired,  it  is  well  to  put  a  small  portion 
of  material  gathered,  bits  of  moss,  earth,  lichen,  or  washings  from 
higher  aquatic  plants  into  a  culture  medium  and  allow  it  to  stand 
3  to  4  weeks,  when  it  may  be  examined;  the  chances  are  that 
many  forms  will  appear  which  could  not  be  detected  before- 
hand. Indeed  this  is  the  only  way  in  which  certain  species  may 
be  obtained. 

When  a  pure  culture  is  desired  bacteriological  methods  for  pure 
cultures  are  most  useful,  but  one  who  is  skillful  in  working  under 
the  low  power  of  a  microscope  can  often,  by  means  of  a  tiny  capil- 
lary pipette,  isolate  a  single  cell,  or  a  cluster  of  cells,  which  he  knows 
to  be  all  of  one  kind.  If  the  medium  in  which  the  form  was  grow- 
ing contained  many  other  species,  the  chances  are  that  the  lirst 
time  that  the  cell  or  cluster  is  transferred,  a  cell  of  some  other 
minute  form  such  as  Chlorella  or  Stichococcus,  too  small  to  notice 
under  that  power,  may  be  transferred  with  the  desired  form;  so 
to  prevent  this  impurity  from  being  carried  to  the  final  culture,  thus 
making  the  culture  worthless,  the  better  way  is  to  transfer  the  cell 
first  to  a  drop  of  distilled  water  on  a  slide,  then  sterilize  the  pipette 
in  boihng  water  and,  allowing  it  to  cool,  transfer  the  cell  again  to 
a  drop  of  distilled  water;  the  process  should  be  repeated  three  or 
four  times,  and  the  cell  finally  transferred  to  the  receptacle  in 
which  the  culture  is  required. 

For  this  purpose  small  low  glass  preparation  dishes  with  loosely 
fitting  covers  are  the  best.  A  receptacle  that  will  admit  a  little 
air  is  better  than  one  that  excludes  air  entirely.  These  small 
receptacles  may  then  be  placed  directly  on  the  stage  of  a  micro- 
scope and  the  forms  studied  from  time  to  time  without  disturbing 
the  growth  in  the  least. 

The  bacteriological  method  for  obtaining  pure  cultures  emplo}'s 
gelatine  or  agar-agar  plates.  These  plates  are  prepared  by  spread- 
ing a  thin  layer  of  gelatine  or  agar-agar  mixed  with  some  good 


124  FRESH-WATER   BIOLOGY 

nutrient  solution  over  the  bottom  of  a  petri  dish  or  a  small  glass 
culture  dish.  This  must  then  be  sterilized  before  the  culture  is 
made.  In  preparing  the  culture  a  very  minute  portion  of  the  me- 
dium containing  the  desired  form  is  mixed  with  a  large  drop  of 
distilled  water  and  then  this  is  scattered  at  intervals  over  the  surface. 
The  material  must  be  diluted  with  enough  water  so  that  each  cell 
will  be  by  itself. 

In  the  course  of  a  few  days  the  single  cells  will  have  increased, 
and  then,  while  the  culture  is  on  the  stage  of  a  microscope,  the  little 
colony  of  cells  may  be  transferred  to  a  Kquid  medium  by  means  of  a 
sterilized  needle,  the  tip  of  a  line  brush,  or  a  very  fine  pipette. 

To  a  very  large  extent  the  culture  medium  must  be  adapted  to 
the  species  to  be  cultivated.  No  one  medium  is  favorable  to  all 
species  of  algae,  and  the  form  must  be  taken  into  consideration 
before  a  medium  is  prepared.  If  the  species  be  a  new  form,  various 
different  media  must  often  be  tried  before  the  right  one  is  deter- 
mined. If  a  quantity  of  different  forms  from  any  collection  be 
placed  in  one  medium  and  a  second  quantity  in  another,  the  prob- 
abilities are  that  in  the  course  of  three  or  four  weeks  but  few  of 
the  same  species  will  be  found  in  both  cultures.  Certain  forms  will 
have  died  in  one  while  perhaps  those  very  forms  have  found  in  the 
other  medium  the  substances  and  conditions  for  their  development. 

The  media  to  which  the  greatest  number  of  forms  are  adapted 
are  Moore's  solution  and  Knop's  solution: 

Moore's  solution: 

Ammonium  nitrate 0.5  gram. 

Potassium  phosphate^ 0.2  gram. 

Magnesium  sulphate 0.2  gram. 

Calcium  chloride o .  i  gram. 

Iron  sulphate trace. 

These  amounts  should  be  dissolved  in  one  liter  of  distilled  water. 

Knop's  solution: 

Potassium  nitrate i  gram. 

Potassium  phosphate i  gram. 

Magnesium  sulphate i  gram. 

Calcium  nitrate 4  grams. 

Chloride  of  iron trace. 

The  first  three  substances  are  dissolved  in  the  required  amount  of  water  to  make  from  i  to 
5  per  cent  of  the  solution,  then  the  calcium  nitrate  is  added.  This  solution  may  then  be 
diluted  as  needed;  usually  a  0.2  per  cent  or  a  0.4  per  cent  solution  is  favorable  for  ordinary 
cultures. 


THE   FRESH-WATER   ALGAE  1 25 

It  should  be  borne  in  mind  that  among  the  plankton  forms 
there  are  many  which  will  not  develop  in  either.  For  these 
the  best  solution  has  been  found  to  be  a  solution  made  from  the 
organisms  in  the  plankton  itself.  In  this  a  perfectly  normal  de- 
velopment may  be  obtained  for  many  forms,  though  even  in  this 
some  fail  of  development.  Bouillon^_earth  decoctions,  moist ,  finely 
pulverized  earthy  bits  of  bark  and  cubes  of  sterilized  peat,/  all  form 
good  substances  for  the  ordinary  cultivation  of  the  unicellular 
algae.  The  filamentouj_ algae^ are  far  more  difficult  to  cultivate. 
Before  satisfying  oii?s  self  with  the  fife  history  of  any  form,  that 
form  should  be  maintained  in  culture  for  an  extended  period, 
when  observation  can  be  made  from  time  to  time  and  the  efi'ect  of 
different  conditions  determined. 

An  attempt  has  been  made  to  give  the  principal  genera  of  fresh- 
water algae  found  in  North  America,  but  the  fist  is  by  no  means 
complete.  A  very  few  genera  of  diatoms  and  desmids  here  cited 
have  not  been  found  by  the  writer  and  no  report  of  their  occurrence 
in  North  America  could  be  obtained ;  but  these  groups  are  distrib- 
uted so  universally  that  they  probably  will  be  discovered  in  this 
territory. 

KEY   TO  NORTH  AMERICAN   FRESH-WATER  ALGAE 
Class  I.     Bacillariaceae  (Diatoms) 

Color  yellow;  plant  a  single  cell,  sometimes  united  into  chains;  membrane 
silicified,  with  minute,  definite  markings. 

These  are  unicellular  algae  but,  by  means  of  a  gelatinous  substance,  are 
frequently  held  together  in  bands  or  masses.  The  membrane  is  silicified, 
making  it  hard  and  rigid.  It  is  always  composed  of  two  parts,  valves,  which 
may  be  separated  from  each  other  and  which  are  often  compared  to  a  box  and 
itj  overlapping  cover;  the  side  where  the  edges  overlap  is  spoken,  of  as  the 
ijcirdle^e..  while  the  outer  "surface  is  referred  to  as  the \ valve  side ;  this  and, 
more  rarely,  the  girdle  side  also  are  sculptured  with  Hiie'  striations,  dots, 
dotted  lines,  and  grooves.  Many  have  extending  lengthwise  a  conspicuous 
line,  the irS^j  which  frequently  bears  at  its  rniddle  and  both  jmds  rounded 
portions  calleanodules. 

Reproduction  is  by  auxospores,  either  sexual  or  asexual.  The  asexual 
are  formed  by  the  contents  of  a  cell  collecting,  throwing  off  the  membrane, 
and  forming  either  one  or  two  spores.  The  sexual  auxospores  are  formed  by 
the  throwing  off  of  the  membrane  and  the  copulation  of  two  cells  in  one  of  the 
following  ways:  (a)  Two  cells  divide,  making  two  pairs  of  daughter-cells;  each 
individual  of  one  pair  fuses  with  one  from  the  other  pair,  thus  making  two 
spores,  (b)  Two  cells  unite  to  form  one  auxospore.  {c)  Two  cells  come 
together  but  do  not  copulate;  two  auxospores  are  formed. 


126  FRESH-WATER    BIOLOGY 

1  (9,  10)     Valves  circular,  raphe  lacking,  markings  radial 2 

2  (5)     Cells  cylindrical  or  ellipsoidal,  united  into  filaments.     Valve  side  circu- 

lar, either  convex  or  flat.    .    .  Family  Melosiraceae  .    .     3 

3  (4)     Cells  with  no  spines  or  teeth;  valves  either  smooth  or  punctate,  usually 

convex;   girdle  side  punctate Melosira  Agardh. 


-J'.. 


Melosira  is  very  common  in  ponds,  rivers,  lakes,  and 
reservoirs,  and  occurs  in  great  quantities  in  the  plankton. 
The  filaments  are  often  very  long. 

Fig.  69.     Melosira  varians  Agardh.     X  600.     (Original.) 


4(3) 


Cells  similar  to  those  of  Melosira,  but  with  a  circle  of  tooth-like  pro- 
jections between  the  valve  and  girdle  sides. 

Orthosira  Thwaites. 


Van  Heurck  and  West  include  Orthosira  under  Melosira,  while 
many  others  make  a  separate  genus.     The  Orthosira  forms  are 
found  in  the  same  localities  as  Melosira  but  are  much  less 
C       abundant. 


Fig.  70.    Orthosira  orichalcea  W.  Smith.     X  600.     (Original.) 


5  (2)     Cells  single,  disc-shaped,  not  forming  filaments;   valves  flat,  convex,  or 

undulating,  mostly  with  radial  rows  of  punctulations. 

Family  Coscinodiscaceae  .    .     6 

6  (7,  8)     Valves  circular  or  nearly  so,  with  radiating  rows  of  dots  or  areola- 

tions,  the  disc  with  a  distinct  edge,  usually  bearing  a  circle 
of  inconspicuous  submarginal  spines. 

Coscinodisciis  Ehrenberg. 


The  number  of  species  of  Coscinodiscus  is  verj'  large,  mostly 
marine,  although  some  occur  in  fresh  water  with  other  similar 
centric  forms. 


Fig.  71.     Coscinodiscus  apiculatus  Ehrenberg.     X330.     (After  Wolle.) 


7  (6,  8)  Valves  circular,  showing  a  central  smooth  or  punctate  area,  and  an 
outer  margin  of  radiating  striations.  Girdle  view  with 
undulating  ends Cyclotella  Kiitzing. 


The  cells  are  disc-shaped  and  are  distinguished  from  other  disc- 
shaped forms  principally  by  the  smooth  or  punctate  center  and  the 
undulating  ends.     It  is  found  commonly  in  the  plankton. 


Fig.  72.     Cyclotella  compta  Kutzing  var.  affinis  Grun.    a.  Valve  side;   b, 
girdle  side.     X  408.     (After  Schiitt  and  van  Heurck-Gninow.) 


THE  FRESH-WATER  ALGAE 


127 


8  (6,  7)  Valves  circular,  with  radial  rows  of  dots,  between  which  are  clear 
spaces;  center  either  punctate  or  hyaline;  on  the  margin 
a  circle  of  acute  spines;  girdle  view  with  undulating  ends. 

Stephanodisciis  Ehrenberg. 

The  length  of  the  spines  on  the  margins  of 
the  cells  varies  greatly;  in  S(jme  species  they 
are  short  and  acute,  while  in  others  they  may 
exceed  the  diameter  of  the  cell  many  times. 
Stephanodisciis  occurs  frequently  in  the  plank- 
ton, but  usually  not  in  great  quantities. 


Fig.   73- 


Suphanodiscus  niagareoe  Ehrenberg. 
X  606.     (Original.) 


9  (i,  10)     Valves  more  or  less  cylindrical,  often  in  chains,  ends  greatly  ex- 
tended, usually  forming  long  spines. 

Family  Rhizosolexiaceae. 
Only  one  genus Rhizosolenia  Ehrenberg. 


Fig.  74.     Rhizosolenia  eriensis  H.  Smith. 
Schrdter.) 


X  190.     (After 


10  (i,  9)     Valves  not  circular  or  cyhndrical,  of  different  shapes,  symmetrical  in 

reference  to  a  longitudinal  or  transverse  axis;  surface  marked 
by  costae  or  punctate  lines  making  definite  angles  with  a 
middle  raphe  or  a  median  line 11 

11  (34,  38)     A  middle  nodule  present  on  the  raphe  of  both  valves.    ...      12 

See  also  40  and  65. 

12  (32,  36)     Girdle  view  symmetrical  with  reference  to  both  a  transverse  and 

a  longitudinal  axis 13 

13  (26)     Valves  not  arched  or  keeled;  usually  symmetrical  with  reference  to  a 

straight  or  a  sigmoid  raphe.     Family  Naviculaceae  .   .      14 

Valves  symmetrical  with  reference  to  a  straight  or  curved  middle  line;   girdle  symmetrical 

with  reference  to  both  axes;  a  straight  or  curved  raphe;  a  central  and  two  end  nodules  present. 

14(15)     Cells  without  inner  partitions;  raphe  and  valves  straight.  .    .    .     16 
15(14)     Raphe  and  valves  sigmoid Pleurosigma  W.  Smith. 

Fig.  75.     Pleurosigma  attenuatum  W. 
Smith.     X  300.     (After  Smith.) 

16  (19)     Cells  linear,  oblong,  with  rounded  nodules,  the  two  end  ones  turned 

toward  one  side,  the  prominent  costae  not  punctate.  .   .     17 

17  (18)     The  costae  interrupted  by  a  plain  band  at  the  center. 

Stauroptcra  Ehrenberg. 

18  (17)     The  costae  not  interrupted  at  the  center.      .    Pinniilaria  Ehrenberg. 


^■M 


E^ilBi« 


Fig.  76.     Pinnularia  viridis 
Smith.    X600.   (Original.) 


19  (16)     Cells  more  lance-shaped,  the  end  nodules  not  turned  toward  one 
side.     Striations  composed  of  lines  of  individual  dots.  .     ^"o 


128 


FRESH-WATER   BIOLOGY 


20(23,24,25)   Central  nodule  small,  rounded,  or  slightly  elongated.      ...    21 

21  (22)     No  lateral  longitudinal  areas  of  transverse  septa.  .    .     Nmicula  Bory. 

A  form  which  grows  in  gelatinous  tubes  is  regarded  by  some 
authors  as  a  different  genus  Schizonema  but  others  regard  it  as 
a  true  Navicuki. 

Fig.  77.     Navicula  rhync/tocepftala  Kiitzing.     X  557-     (Original.) 

22  (21)     Two  lateral  longitudinal  areas  of  transverse  septa.     Mostly  imbedded 

in  a  gelatinous  pseudothallus.     .    .    .    Mastogloia  Thwaites. 


In  shape,  Mastogloia  resembles  Xavicula,  but  is  distinguished  from  it  by 
the  gelatinous  envelope  and  the  presence  of  lateral,  transverse,  siliceous  septa 
or  plates  which  divide  the  lateral  regions  of  the  cells  into-  small  compart- 
ments. There  are  transverse  striations  on  the  valves.  It  is  not  a  very 
common  genus  in  .\merica. 

Fig.  78.     Maslogloia  smiihii  Thwaites.     X  about  300.     (After  Smith.) 


23  (20,  24,  25)    Central  nodule  broad,  extending  to  near  the  margin  of  the  valves. 

Stauroneis  Ehrenberg. 

Stauroneis  occurs  frequently  in  all 
bodies  of  water  and  is  a  constituent  of 
the  diatomaceous  flora  which  forms  large 
siliceous  deposits  at  the  bottom  of  lakes. 

Fig.  79.     Stauroneis  anceps  Ehrenberg. 
X  600.     COriginal.) 

24  (20,  23,  25)     Central  nodule  elongated  to  a  short  rod.     Borne  on  gelatinous 

stalks Brehissonia  Grun. 


Fig.   80.       Brebissonia 
sp.     X  580.     (Original.) 


25  (20,  23,  24)  Central  and  end  nodules  elongated,  enclosed  with  the  raphe 
between  two  longitudinal,  parallel,  siKccous  ribs.  Frus- 
tules  sometimes  borne  in  gelatinous  tubes. 

Vanheurckia  Brebisson. 


Fig.  81.      Vanheurckia  rhomboides   Ehrenberg.      X  370. 
(After  West.) 


26  (13)     Valves  asymmetrical  with  reference  to  the  raphe  or  to  a  longitudinal 

axis;  raphe  arched,  or  nearer  one  margin  than  the  other. 

Family  Cymbellaceae  .    .     27 

27  (28)     Valves  greatly  convex;  girdle  side  elliptical  or  oval. 

Amphora  Ehrenberg. 


A  Van  Heurck  regards  A  mphora  as  one  of  the  most  difficult 
genera  of  diatoms  and  notes  that  over  200  species  have 
been  placed  in  this  genus.  It  is  believed  that  it  origi- 
nated from  CymbeUa. 

^       Fig.  82.    Amphora  ovalis  Kiitzing.     a.  Valve  side;  b.  girdle 
side.     X  600.     (Original.) 


28  (27)    Valves  flat  or  only  slightly  convex 29 


THE  FRESH-WATER  ALGAE 


129 


29  (30,  31)     Raphe  straight  or  bent,  ending  in  tlic  middle  of  the  valve  ends. 

Cells  free Cymbella  Agardh. 

Cymhella  varies  in  shape  from  that  of  a  typical  Naiicula 
to  one  strongly  arched,  and  they  have  sometimes  l)een  styled 
as  asymmetrical  Navicidas.  Some  authors  include  the  genus 
Cocconema  under  Cymbella,  but  the  name  Cocconema  is  the 
older  name  and  should  be  retained.  WoUe  reports  25  species 
of  Cymbella. 

Fig.  83.    Cymbella  cuspidala  Kutzing.     X  600.     (Original.) 

30  (29,  31)     Cells  much  as  in  Cymbella,  but  usually  larger  and  borne  on 

gelatinous  stalks Cocconema  Ehrenberg. 


Fig.  84.     Cocconema  lanceolatum  Ehren- 
berg.    X37S.     (After  West.) 


31  (29,  30)     Raphe  straight,  not  ending  in  the  middle  of  valve  ends.     Cells 
living  in  gelatinous  tubes Encyonema  Kutzing. 


Fig.   85.       Encvonema  auenvaldii  Rabenhorst.       X  250. 
(After  Wolle.) 


32' (12,  36)     Girdle  view  asymmetrical  with  reference  to  a  transverse  axis, 
the  outline  being  wedge-shaped. 

Family  Gomphonemaceae  .    .     33 

33  (35)     Girdle  side  straight Gomphonema  Agardh. 

Fig.  86.     Gomphonema  acuminatum  Ehrenberg.    a.  Valve  side; 
b.  girdle  side.     X  600.     (Original.) 


34  (11,  38)     A  middle  nodule  and  a  raphe  present  on  but  one  valve.    .    .     35 

35  (33)     Girdle  side  curved;  otherwise  similar  to  Gomphonema, 

Rhoicosphenia  Granow. 


The  two  valves  are  unlike  in  shape  and  in  the  fact  that  the  lower  valve 
possesses  a  raphe,  a  central  and  end  nodules,  while  the  upper  valve  possesses 
only  a  pseudo-raphe  and  is  without  nodules. 

Fig.  87.     Rhoicosphenia  curvata  Grunow.    a.   Valve  side;    b.   girdle  side.     X  380. 
(After  Schonfeldt.) 


36  (32,  37)     Girdle  view  symmetrical  with  reference  to  a  transverse,  but  not 
to  a  longitudinal  axis,  the  cells  being  arcuate  and  attached 

to  higher  algae Family  CoccoNEroACEAE. 

Only  one  genus  known CVrowf/j  Ehrenberg. 

Valves  oval  or  elliptical,  symmetrical  with  reference  to  both  axes;  raphe 
straight,  with  middle  nodules  but  without  end  nodules.  Markmgs  of  faint 
longitudinal  punctate  lines;   girdle  and  end  views  both  curved. 

Fig.  88.    Cocconeis  pediculus  Ehrenberg.     X  600.     (Original.) 


I30  FRESH-WATER   BIOLOGY 

37  (36)     Girdle  side  geniculate.     Valves  straight,  linear,  or  fusiform;   frus- 

tules  either  free  or  stalked.    .    .       Family  Achnanthaceae. 

Only  one  genus Achnanthes  Bory. 

Cells  so  cun-ed  that  the  two  valves  arc  not  alike,  the  one  concave  with  raphe,  middle  and 
end  nodules;   the  other  con\ex,  without  a  middle  no(lule,  but  with  a  pseudo-raphe.     Girdle  view 
s>Tnmetrical  with   reference   to   a    transverse  axis.     Cells  single  or  in  bands, 
mostly  on  gelatinous  stalks. 

The  cells  may  be  solitary,  though  they  usually  form  long,  sessile  chains  or 
bands  attached  tu  the  surface  of  green  algae.  The  genus  includes  both  marine 
and  fresh-water  forms. 

Fig.  .Sy.     AchnanUies  exUis  Kutzing.     X  600.     (Original.) 

38  (11,  34)     No  middle  nodule  present  on  either  valve,  except  in  Ceratoneis, 

or  at  most  consisting  of  a  slight,  ring-hke  elevation.  .    .     39 

39(40,41,62)  \'alves  as>Tnmetrical  with  reference  to  a  longitudinal  axis,  in 
that  on  one  margin  there  is  a  longitudinal  row  of  bead-like 
thickenings  (keel  points)  while  on  the  other  margin  they  are 

lacking Family  Nitzschiaceae. 

Only  one  genus Nitzschia  Hassall. 

Valves  linear,  sometimes  curved,  keeled,  with  canal  raphe.     Cells  rhomboidal  in  cross  sec- 
tion. 


"■■'■M»iiiimninmiiii..n.Tm.,..,.,,.,,^,,^  FiG.  90.   Nitzschia  linearis  "Svaxih.    X  575- 
_- ■ — -^  (Original.) 


40  (39,  62)     Valves  with  median,  sigmoid  keel,  compressed,  strongly  arched, 

bearing  raphe Family  Amphiproraceae. 

Only  one  genus Amphiprora  Ehrenberg. 


I^^-A^^^ 


Valves   fusiform,    with    central    and    two    end    nodules  on   raphe. 
Girdle  side  sharply  constricted  at  center. 


Fig.  91.    Amphiprora  sp.     X  400-     (Original.) 


41  (39,  62)     Valves  symmetrical  with  reference  to  a  longitudinal  axis   .   .     42 

42  (47)     Valves  each  with  two  wing-like  keels,  strongly  costate,  with  pseudo- 

raphe  but  no  nodules.  .    .     Family  Surirellaceae  .    .     43 
Cells  mostly  large,  ovate,  or  elUptical. 

43  (44)     Cells  bent  in  saddle  shape Campylodisciis  Ehrenberg. 

Though  the  shape  of  the  cells  seems  more  or  less  tri- 
angular, they  are  in  reality  circular,  and  their  seeming 
angularity  is  due  to  the  cur\'ature  of  the  frustules.  It 
is  a  very  large  genus,  some  92  species  having  been 
recorded;  the  species  are  mostly  marine,  though  a  number 
are  found  in  fresh  water.  Their  large  size  makes  them 
among  the  most  conspicuous  of  the  diatoms. 

Fig.  92.    Campylodiscus  cribrosus  W.  Smith.     X  about  300. 
(After  Smith.) 

44  (43)     Cells  not  bent  or  spirally  twisted 45 


THE   FRESH-WATER   ALGAE 


131 


45  (46)     Valves  showing  a  wave-like  margin  in  girdle  view. 

Cymatopleura  W.  Smith. 


This  is  a  large  diatom  which  is 
easily  recognized  by  the  undulat- 
ing outline  of  the  girdle  side. 

The  genus  is  rather  small,  and 
WoUe  reports  but  seven  species. 

Fig.  93.  Cymatopleura  apiculata 
W.  Smith,  a.  Valve  side.  b.  girdle 
side.     X  600.     (Original.) 


46  (45)     Girdle  view  without  wave-like  margins Surirella  Turpin. 


UUOUUL'uuuUua 


QQoaaninmaa 


This   genus   is   widely    distributed 
■4     and  of  frequent  occurrence  in  all  re- 
gions where  diatoms  are  found.     Some 
species  are  very  large  and  conspicu- 
ous, especially  in  the  plankton. 


Fig.    94.      Surirella   sp.    Smith.       a. 
Valve    side.     b.    girdle  side.      X   585- 


(Original.) 


47  (42)     Valves  without  keels.   . 4^ 


48  (59)     Cells  without  deep  inner  partitions  sometimes  with  imperfect  septa.  49 


49 


(55)     Valves  with  transverse  costae So 


qo  (';4)     Valves  symmetrical  with  reference  to  a  transverse  axis. 

Family  Diatomaceae  .    .     51 

Cells  symmetrical  with  reference  to  both  axes,  borne  in  long  chains;  transverse  striations 
distinct  and  uninterrupted  except  in  some  cases  by  a  longitudmal  plain  band. 

51  (52,  53)  Valve  side  oval  or  linear,  transverse  markings  uninterrupted, 
girdle  side  rectangular,  cells  mostly  in  zig-zag  chams.  some- 
times in  short  filament Z)/(2/c7wa  de  Candolle. 


^^^^^<^^^P^aj 


Fig.  9  V    DiaUma  elongaium  Agardh.    a.  Valve 
^    side.     b.  girdle  side.     X  about  300.     (After  W. 
Smith.) 


132 

52   (51: 


FRESH-WATER   BIOLOGY 

;3)     Characteristics  similar  to  those  of  Diatoma  except  that  the  cells 
are  borne  in  ribbons Denticida  Kutzing. 

The  valves  are  marked  by  heavy  ribs  which  are  in  reality  shallow 
septa,  between  which  are  delicate  striae. 

Denticuld  occurs  on  wet  rocks  and  in  fresh  water;  sometimes  also  m 
brackish  water. 

Fig  96.      Denlkula   inflata   Smith,     a.  Valve  side.     b.   girdle  side. 
X  600.     (Original.) 

52)     Characteristics  as  in  Dcnticula  except  that  the  striations  are  in- 
terrupted in  the  middle Odontidium  Kutzing. 

Many  place  the  members  of  this  genus  with  Diatoma,  while 
others  regard  the  interrupted  striae  and  the  formation  of  short  fila- 
ments instead  of  zig-zag  chains,  sufficient  differences  to  place  them 
in  a  separate  genus. 

Fig.  97.   a,    b.    Odontidium  mutabile  Smith,     c.    Odontidium  tabellaria 
Smith.     X  570.     (Original.) 


54  (50) 


Valves  asymmetrical  with  reference  to  a  transverse  axis. 

Family  Meridionaceae. 
Only  one  genus Meridion  Agardh. 

Both  valve  and  girdle  sides  wedge-shaped,  forming  ring- 
like or  fan-shaped  bands;  striations  uninterrupted. 

There  are  imperfect  transverse  septa  which  are  con- 
spicuous on  the  valve  side  but  show  only  laterally  on 
the  girdle  side.  Between  these  on  the  valve  side  are  fine 
punctate  striae. 

Van  Heurck  thinks  this  genus  ought  to  be  suppressed. 
It  differs  from  Diatoma  only  in  the  cuneate  shape  of  the 
valves. 


Fig.  98. 


Meridion  constrictum  Ralfs. 
Smith.) 


X  300.     (After 


55  (49)     Valves  without  transverse  costae.  .   Family  Fragilariaceae 


56 


Cells  of  much  the  same  structure  as  Diatoms. 
dots;  with  or  without  raphe  and  end  nodules. 


Transverse  striations  composed  of  separate 


56  (57,  58)     Cells  very  slender,  not  united  in  bands,  either  free  or  attached  at 
one  end,  forming  clusters  on  higher  algae. 

Synedra  Ehrenberg. 


Fig.  99.     Synedra  salina  W.  Smith. 
X  588.     (Original.) 


57  (56,  58)     Cells  forming  bands  or  zig-zag  chains. 


Fragilaria  Lyngbye. 


Fragilaria  is  a  common  genus  oc- 
curring in  ponds,  reservoirs,  and  lakes. 
F.  crotoncnsis  has  been  known  to  occur 
in  such  quantities  as  to  form  water 
bloom,  producing  a  thick  brown  scum 
on  the  surface  of  a  lake. 

Fig.  100.  Fragilaria  crotonensis  Kitton. 
a.  Valve  side.  b.  girdle  side.  X  225. 
(Original.) 


THE  FRESH-WATER  ALGAE  1 33 

58  (56,  57)     Cells  arranged  in  the  form  of  a  star.  .    .    .      Aster ionella  Hassall. 


The  radial  arrangement  of  the  cells  is  due  to  the 
presence  at  the  inner  ends  of  small  mucous  cushions 
which  unite  the  cells  in  this  manner.  The  cells  are 
linear,  unequally  enlarged  at  the  ends,  capitate  in  the 
valve  view  and  truncate  in  the  girdle  view.  The 
valves  are  marked  with  delicate  striations. 

Asterionella  is  common  in  ponds,  lakes,  and  water 
reservoirs.  It  is  especially  freciuent  in  the  plankton, 
probably  on  account  of  the  radial  arrangement  of  the 
cells,  which  would  make  it  easily  buoyed  up  by  the 
water. 


Fig.  ioi. 


Asterionella gracillima  Heihcxg.    X  li 
(After  Schroter.) 


59  (48)     Cells  with  interrupted  inner  partitions. 

Family  Tabellariaceae 


60 


Valves  linear,  oblong,  or  elliptical,  inflated  at  the  center, 
or  more  longitudinal  partitions  perforated  at  the  center. 


Girdle  side  rectangular,  with  two 


60  (61)     Cells  slender,  valves  with  only  punctate  striations. 

Tahellaria  Ehrenberg. 


I 


The  inner  partitions  appear  in  the  girdle  view 
as  distinct  lines  which  are  not  always  equally 
developed  or  opposite  each  other  at  the  two  ends 
of  the  cell.  At  the  interruption  of  the  partitions 
at  the  center  the  valve  sides  show  an  inflation. 

The  zig-zag  chains  of  Tabellaria  are  conspicu- 
ous in  almost  all  collections  of  algae. 

Fig.  102.  Tahellaria  feneslrata  Kiitzing.  a.  Valve 
side.  b.  girdle  side.  X  600.  c.  showing  characteristic 
arrangement  of  cell.     X  about  150.    (Original.) 


Cells  broader,  with  distinct  transverse  costae.  .    .     Tetracyclics  Ralfs. 

Aside  from  the  interrupted  inner  par- 
titions there  are  also  transverse  septa 
which  appear  on  the  valve  sides  as  costae, 
between  which  are  very  faint  striae.    The 


3 


septa  are  more  numerous,  and  the  cells 
more  cruciform  than  in  Tabellaria;  they 
occur  also  in  bands  instead  of  in  zig-zag 
chains. 


Fig.  103. 
Valve  side. 
Smith.) 


Tetracxclus   lacustris   Ralfs.     a. 
b.  girdle  side.     X  300.     (After 


62  (39,  41)     Valves  asymmetrical  with  reference  to  a  longitudinal  axis,  the 
cells  being  more  or  less  arcuate. 

Family  Epithemiaceae  .    .     63 

Valves  curved,  usually  with  dotted  transverse  striations,  sometimes  also  with  transverse 
costae. 


134  FRESH-WATER   BIOLOGY 

63  (64,  65)     Transverse  costae  coarse,  converging,   projecting  inward,  often 
with  lines  of  dots  between.    .    .    Epithemia  Brebisson. 


Fig.    104.      Epithemia  lurgida    Kiitzing. 
X  380.     (Original.) 


"W 


64  (63,  65)     Transverse  striations  punctate;    end  nodules  present,  but  raphe 

wanting .     Eunotia  Ehrcnberg. 

Fig.  105.     Eunotia  pectinalis  Dillw-jn.     X  625.     (Original.) 

65  (63,  64)     Valves  crescent-shaped,  the  raphe  very  near  the  concave  margin, 

with  end  and  middle  nodules.      .    .    .   Ceratoneis  Ehrenberg. 

There  is  but  a  single  species. 

Fig.  106.     Ceratoneis  arcus  Kiitzing.     X  600.     (Original.) 


Class  II.     Chlorophyceae 

Color,  a  chlorophyll-green. 

This  group  includes  by  far  the  greater  number  of  forms  of  algae  in  fresh 
water.  It  is  so  large  and  the  characteristics  of  the  different  members  so 
varied  that  no  characterization  of  the  group  as  a  whole  will  be  attempted. 

1  (253)     Plants  fine,  relatively  small 2 

In  regard  to  the  Characeae  the  uncertainty  of  their  nature  and  systematic  position  is  fully 
understood,  but  for  convenience  they  will  be  considered  at  the  end  of  the  Chlorophyceae. 

2  (67)     Plants  of  unbranched,  septate  filaments,  shppery  to  the  touch;    or 

plants  of  single  cells  of  two  exactly  symmetrical  parts,  some- 
times united  into  filaments.  Chlorophyll  in  spiral  bands, 
central  plates,  or  star-shaped  bodies. 

Order  Conjugales  .    .     3 

Filamentous  or  unicellular  algae  whose  reproduction  consists  only  in  conjugation,  that  is 
where  the  contents  of  two  cells  which  are  exactly  alike,  or  at  most  differing  only  slightly  in 
reference  to  size,  unite  to  form  a  single  cell,  the  zygospore. 

Some  authors  would  place  the  BaaUariaceae  under  this  group  on  account  of  the  union  which 
takes  place  before  the  formation  of  the  spore,  but  as  they  differ  in  many  respects  from  the  dis- 
tinctive members  of  this  group  they  have  been  placed  in  a  group  by  themselves. 

3  (59)     Plants  unicellular,  occasionally  united  into  filaments;  cells  constricted 

at  the  middle  or  not;  one-half  of  each  cell  exactly  symmet- 
rical with  the  other  half;  2,  4,  or  8  individuals  from  a  germi- 
nating zygospore Family  Desmidiaceae  .   .     4 

The  membrane  mostly  furnished  with  tiny  protuberances  and  pores,  both  with  a  definite 
arrangement;  chromatophore  radiating  from  or  including  one  or  more  pyrenoids.  Asexual 
reproduction  by  the  separation  of  the  halves  of  the  cell,  between  which  two  new  halves  are 
formed,  each  attached  to  and  identical  with  one  of  the  older  halves.  In  sexual  reproduction 
two  cells  come  together,  throw  off  their  membranes,  and  their  contents  unite  to  form  a 
zygospore.     This  is  usually  furnished  with  conspicuous  colorless  spines. 

4  (22)     Cells  after  division  united  into  filaments 5 


THE  FRESH-WATER   ALGAE  I35 

5  (11)     Cells  cylindrical,  with  no  constriction,  or  at  most  a  very  shallow  and 

broad  constriction,  giving  a  slightly  undulating  outline.      6 

6  (7,  8)     Cells  not  longer  than  broad,  sometimes  with  a  very  shallow,  broad 

constriction;  chromatophore  central,  with  6  to  10  rays  about 
a  pyrenoid Hyalotlieca  Ehrenbcrg. 

Filaments  long,  often  twisted,  and  slippery  to  the  touch. 
=-£=::5^==;«==5=^^^^-  Thc  diffctent  diameters  of   the   cells  nearly  equal,  varying 

hi^''''W^I^3^^«^IS-  ^''^"^  ^°  ^°  ^5  ^'     ^^^  median  constriction  often  ver>'  slight. 

A     Chromatophore  in  each  cell-half  of  radiating  plates  placed 
|)it5<»««ti»dks,5j^^]t^-  about  a  pyrenoid. 

!t^t4U«^(^i^»;iiig)[><'j^^^^  A  broad  gelatinous  envelop  is  always  present  but  it  is  in- 

visible without  reagents. 

Hyalotheca  is  frequent  among  filamentous  forms  of  the 
B  Conjugalcs. 

Fig.  107.    Hyalotheca  dissiliens  Brebisson.     a.  side  view.    6.  end 
view.     X  575-     (Original.) 

7  (6,  8)     Cells  but  little  longer  than  broad,  attenuated  at  the  end. 

Leptozosma  Turner. 

Filaments  long,  cateniform;  not  twisted,  or 
but  slightly  so.      Joints  united  by  a  strongly 
marked  suture;    near  to  Bambuscina  Kiitzing, 
\rA  \3A.^ri^    "^ — ^^^^^ ''^^:=:r:^_i^        ^^^  differing  therefrom  in  the  suture. 

'V\s#ss:^  Fig.  108.    Leptozosma  catenulata  Turner.     X  300. 

(After  Turner.) 

8  (6,  7)     Cells  much  longer  than  broad 9 

9  (10)     Chromatophore  a  central  plate  containing  a  row  of  pyrenoids. 

Gonatozygon  de  Bary. 

r;^S^^^n^^^S^^^^^^  Length  of  cells  100  to  200  m;  breadth  10  to  20M, 

4,;^^^,^,=,,,,,^,,;^,:^.=-.==*. — -•-:■  ''*~^     ~~"'"°^^^^        much  like  a  cell  of  Mougeotia  except  that  the 

membrane  is  covered  with  minute  projections; 
Fig.  109.    Gonatozygon  ralfsii  de  Bary.  cells  sometimes  slightly  swollen  at  the  ends. 

X  about  230.     (After  de  Bary.) 

10  (9)     Chromatophores  consisting  of  several  parietal  spiral  bands. 

Genicularia  de  Bary. 

[|^V'<pii:g.^?^-^^'^-^^^  Diameter   of   cells    17  to  22.5  n',    length 

i^'^C-;'-^'^?^;;^^^  10  to  20  times  as  great.     Alembranc   cov- 

^?> Ivis-uy  *.■.'.■. , :fvs . /i^i ^W ^tiJ^i*! Mi,^ )'S,:^^i^f^  ered  with  fine  projections  as  in  Gotiiitozygon. 

Fig.  no.    Genicularia  spirotaenia 'Rx€b\sson.     X  265.  Spiral  chromatophores  with  many  pyrenoids. 

(After  de  Bary.) 

11  (5)     Cells  not  cyHndrical 12 

12  (19)     End  view  of  cells  circular,  oval,  or  elliptical,  rarely  triangular.    .      13 

13  (16)     Cells  not  deeply  constricted  at  the  middle 14 

14  (15)     Cells  cask-shaped,  placed  end  to  end,  with  a  shallow  narrow  con- 

striction at  the  middle;    end  view  circular,  with  two  oppo- 
sitely placed  projections Gymuozyga. 

The  membrane  frequently  shows  longitudinal  stripes. 
iii^   l^Q^if^::::-^     Chromatophores  in  each  cell-half  composed  of  a  number 
^"^^^^  -"""Vj^!^*)  ^^^^r'*^     of  radially-placeil   plates  arranged  about  a  pyrenoid  at 
^51^:  ^}j^^^^^^l^     the  center. 

Fig.  III.   GymnozygabTtbissoniiNoT(\sieAi.    X  s6"^-    (Original.) 


136 

15  (i4) 


^Mt?0^W:f 


FRESH-WATER   BIOLOGY 

Cells  not  cask-shaped,  with  a  narrow,  shallow,  central  constriction: 
end  view  elliptical  or  triangular,  ends  tapering  or  round. 

Spondylosium  Archer. 

Cell?  10  to  I  2 /J  broad:  8  to  g/i  long,  cells  tapering  toward? 
the  ends.  Membrane  smooth  or  with  slight  prominences. 
A  pyrenoid  in  each  cell-half,  about  which  radiate  from  4  to  6 
chlorophyll  plates. 

The  cells  of  the  filaments  are  united  by  the  close  adher- 
ence of  the  apices  of  the  cells.  The  filaments  are  frequently 
twisted  and  enveloped  in  mucus. 


OAOQ 


Fig.  112 


Spondylosium  papillatum  \V.  and  G.  West. 
(Original.) 


X600 


16  (13)     Cells  deeply  constricted  in  the  middle 17 


17  (18)  Cell-halves  acutely  pointed  or  oval;  upper  and  lower  surface  of  each 
end  furnished  with  a  spine  which  meets  a  similar  one  on  the 
adjoining  cell;  end  view  fusiform.  .    .     Onychonema  Wallich. 

Narrow  spines  frequently  present.  In  each  cell-half  a  single  axial 
chromatophore,  composed  of  radiating  plates  about  a  central  pyrenoid. 

Onychonema  occurs  in  swamps  and  ponds  but  is  not  of  very  fre- 
quent occurrence  in  America. 

Fig.  113.    Onychonema  loeue 'iioxAsXe.dt.     X  600.     (Original.) 


18  (17)     Cell-halves  oval  in  outHne,  with  a  deep  central  constriction;    cells 
united  into  filaments  by  small  tubercles. 

Sphaerozosma  Archer. 

Cells  22  to  T^in  broad  and  about  half  as  long,  end  view  elliptical; 
membrane  smooth  or  with  tiny  warts  near  the  ends  of  the  cells. 

Sphaerozosma  is  distinguished  from  Spondylosium  by  the  cells 
being  united  by  tubercles  instead  of  by  their  apices  directly. 

S.  piilchrum  var.  inflatum  VVolle  is  reported  by  WoUe  as  occur- 
ring in  such  quantities  as  to  color  the  water  green. 

Fig.  114.    Sphaerozosma  veriebratum  Ralfs.    X  about  300.     (After  de  Bary.) 


mm 


[9  (12)     End  view  of  cells  triangular  or  quadrangular,  seldom  oval. 


20 


20  (21)     No  space  at  the  center  between  the  transverse  septa;    cells  slightly 
and  narrowly  constricted Desmidium  AgSLvdh. 


Filaments  long,  twisted.  Cells  flat  at  the 
ends,  i  to  i  as  long  as  broad,  so  constricted 
at  the  center  as  to  give  a  scalloped  lateral 
outline  to  each  cell.  End  view  with  as  many 
pyrenoids  as  there  are  angles,  from  each  of 
which  radiate  two  chlorophyll  plates. 

Fig.  1 15.  Desmidium  schwartzii  Agardh.   a.  side 
view.    b.  end  view.     X  5S0.     (Original.) 


THE  FRESH-WATER   ALGAE 


137 


21  (20)     An  oval  opening  at  the  center  between  the  transverse  septa. 

Aplogonum  Ralfs. 

A  ^  Filament?   often   twisted,  cells   sliKhfly 

longer  than  broad,  with  three  or  four 
projections  on  each  end  which  exactly 
meet  others  on  the  adjoining  cells,  some- 
times slightly  constricted.  Several  py- 
renoids  in  each  cell,  from  which  radiate 
the  plate-like  chromatophores. 

The  genus  Aplogonum  is  included  by 
many  under  Desmidiiim,  but  the  space 
at  the  center  between  two  adjoining  cells, 
the  lack  of  the  narrow  central  construc- 
tion, and  the  greater  length  of  the  cells 
would  seem  to  distinguish  it  from  Ds- 
midiunt. 

Fig.  116.  Aptogonum  baileyi  "RdXls.  a.  side 
view.    b.  end  view.    c.  optical  section.     X  425. 


(Original.) 


22  (4)     Cells  not  united  into  filaments. 


23 

23  {33)     Cells  not  constricted  at  the  center,  or  at  the  most  only  very  slightly 

so 24 

24  (25)     Cells  crescent-shaped;  tapering  toward  both  ends. 

Closterium  Nitzsch. 
Cells  varying  from  short,  thick  cells  swollen  in  the 
middle  to  very  slender  cells  sometimes  bent  in  the 
shape  of  an  S.  Membrane  smooth,  or  longitudinally 
striated,  rarely  with  a  yellow  hue.  Chromatophores 
in  each  cell-half  of  several  radially-placed  plates, 
including  one  or  more  rows  of  pyrenoids;  at  each 
end  a  large  vacuole  containing  moving  granules. 

Fig.  117.    Closterium  moniliferum  var.  concavum 
Ehrenberg.     X  about  200.     (Original.) 

25  (24)     Cells  cylindrical  or  fusiform 26 

26  (27,  28)     Chromatophore  one  or  more  parietal,  spiral  bands. 

Spirotaenia  Brebisson. 


Cells  straight,  oblong,  cylindrical,  or  fusiform,  with  rounded  ends.      Chroma- 
tophores one  or  several  parietal  bands  with  pyrenoids. 


Fig.  118.    Spirotaenia  minuta  Thnrti.     X  365.     (After  West.) 


27  (26,  28)     Chromatophore  star-shaped,  one  in  each  cell-half. 

Cylindrocystis  de  Bary. 


^0^:  /M^'^^^J^  %     yS^^  ^^'^^  ^^^^  rounded  ends,  often  oval  in  outline.  Chroma- 

C^^^^^^  W^m^^^f^0^^'\       tophores  two,  star-shaped,  many  rayed,  each  enclosing  a 
■^     'M;'-'.*:^--^  :c;>^S-.;:v.-;^?&)?'        II      pyrenoid  at  the  center. 

Fig.  119.  Cylittdrocystis  diplosporaLundcti.  X  375-   (Original.) 


28  (26,  27)     Chromatophore  straight,  simple,  or  multiple .29 


138 


FRESH-WATER  BIOLOGY 


29  (30)     Chromatophore  a  single  axial  plate  with  one  or  more  pyrenoids. 

Mesotaenium  Nageli. 

Cells  cylindrical,  with  rounded  ends,  resembling  in  structure 
A     cells  of  Mougeolia  but  smaller,  sometimes  adhering  to  each  other 
after  division  but  not  forming  distinct  filaments. 

'^ —        va'--^«*j        ^~%v  Fig.  I2C.     Mesotaenium  endlkherianum  KdigtW.     X  625.     a.  showing 

;.^*^^t¥A~«! '^^fi^^'T^^^^J  B     the  surface  of  the  chlorophyll  plate,     b.  showing  the  edge  of  the  chloro- 
phyll plate.     (Original.) 


30  (29)     In  each  cell-half  several  chlorophyll  plates 31 

31  (32)     Margins  of  radial  plates  entire;    pyrenoids  central  in  each  cell-half. 

Penium  de  Bary. 

Cells  sometimes  slightly  constricted  at  the  middle,  rounded  or  trun- 
i^^^^'^^^X  cated  at  the  ends;  length  3  to  g  times  the  breadth;  membrane  smooth, 

jl^  DgCrl  punctate,  or  longitudinally  striated;    chromatophores  radially  placed 

-  about  a  large  pyrenoid  in  each  cell-half. 

Fig.  121.     Penium  cucurbitinum  Biss.     X  295.     (After  West.) 

32  (31)     Margins  of  the  radial  plates  of  the  chromatophore  scalloped ;  pyrenoids 

several  and  scattered Netrium  Nageli. 

Cells  shaped  much  as  in  Penium.  The  scallops  of  the  outer  margin  of  the  chromatophores 
conspicuous;  pyrenoids  not  large  and  forming  a  center  about  which  the  chlorophyll  plates 
radiate,  as  in  Penium,  but  small  and  scattered. 


Fig.  122.    Melrium  lamelhsum  Brebisson.     X  200.     (After  Kirchner.) 

2,2,  (23)     Cells  constricted  at  the  center 34 

34  (42)     Constriction  at  the  sides  slight  and  usually  gradual 35 

35  (38)     Length  of  cells  usually  not  more  than  six  times  the  breadth.   .    .     36 

36  (37)     Central  constriction  very  gradual  and  shallow;    a  slight  incision  at 

the  ends Tetmemonis  Ralfs. 

Cells  straight,  fusiform,  or  cylindrical,  slightly  and  broadly 
constricted  at  the  middle;  ends  rounded,  each  with  a  slight 
linear  incision;  length  4  to  6  times  the  diameter.  Chroma- 
tophore axial  with  a  single  row  of  pyrenoids. 

Fig.  123.     Tetmemorus  sranulatus  Ra.Us.     X  465-     (Original.) 

37  (36)     Cells  short,  ends  truncate,  constriction  rather  abrupt,  but  not  deep; 

chromatophore    of   longitudinal    bands;     pyrenoids    many, 
scattered Pleurotaeniopsis  Lundell. 

_  This  is  regarded  by  Brebisson  as  a  Calocylindrus,  by  de  Bary 

•^W^«!^l^^  «»^^^  ^^  ^  Pleurotaenium  and  by  West  as  a  Cosmarium.      Formerly 

'^^j»^j£r^^3?^»%«^-^^S^  VVille  recognized  the  genus,  Pleuretaeniopsis,  but  now  includes  it 

•  */ j4&_GL#>j?'- 33:, -^  under  Cosmarium. 

Fig.  124.     Pleurotaeniopsis  lurgidus  Lund.    X  130-    (After  de  Baxy.) 


THE  IRESH-WATER  ALGAE 
38  (37)    Length  of  cells  many  times  the  breadth.      .   . 


139 
39 


39  (40,  41)  Cells  before  the  middle  constriction  swollen,  but  without  longitu- 
din?:  flutings;  chromatophore  of  radially-placed  plates,  with 
pyrenoids Pleurotaenium  Lundell 

Cells  straight,  cylindrical,  somewhat  taper- 
ing toward  the  truncate  ends.      Membrane 
smooth  or  with  small  warts;  at  each  end  a 
Fig.  125.    Pleurotaenium  nodttlosum  Rabenhorst.       colorless  vacuole  with  dancing  particles  as  in 
X  175-     (Original.)  Closterium. 


40  (39,  41)     Cells  before  middle  constriction  swollen  and  with  longitudinal 
flutings;  chroma tophores  of  longitudinal  radial  plates. 

Docidium  Lundell. 

Cells  tapering  somewhat  towards  the  ends;   no  vacuoles  with  moving  granules;   membrane 
either  smooth  or  with  minute  protuberances  and  even  with  spines  in  certain  regions. 


Fig.  126.    Docidium  baculum  Brebisson.     X  545.     (Original.) 

41  (39,  40)     Shape  of  cells  much  as  in  Pleurotaenium,  but  apices  broadly  cleft 
or  with  bidentate  processes Triploceras  Bailey. 

Cells  large,  walls  covered  with  rings  of  furcate  processes  or  small,  perpendicular  longitudi- 
nally-placed plates.     Sometimes  confused  with  Docidium. 


Fig.  127.    Triploceras  gracileBa.Hey.    One-half  of  a  cell.     (After  Cushman.) 

42  (34)     Constrictions  at  the  sides  deep  and  abrupt 43 

43  (44)     End  views  of  cells  3  to  several  angled  or  rayed. 

Staurastrum  Lundell. 


Side  view  hour-glass  shaped ;  membrane  smooth  or  with 
warts  or  spines;  chromatophores  in  each  cell-half  consisting 
of  radially-placed  plates  about  a  central  pyrenoid,  two 
plates  extending  into  each  arm  or  angle 


Fig.  128.    Staurastrum  crenulatumKa.gfi\.     X  600.     {Original.) 


44  (43)     End  views  of  cells  compressed  or  elliptical,  often  enlarged  at  the 
center 45 


45  (48)     Cells  at  end  with  notches  or  Unear  incisions 46 


I40 


FRESH-WATER  BIOLOGY 


46  (47)     Cells  disc-shaped,  each  cell-half  with  three  or  five  lobes,  the  lateral 

ones  of  which  are  more  or  less  deeply  cut .  Micrasterias  AgSLidh. 

Cells  brc  ■'dly  oval  or  rounded  in  out- 
line. Midai*;  constriction  deep,  some- 
times furnished  with  spines;  lateral  lobes 
often  one  or  more  times  dichotomously 
divided,  the  last  divisions  usually  fur- 
nished with  spines.  Chromatophore  the 
form  of  the  cell,  in  which  are  scattered 
several  pyrenoids. 

Fig.  129.  MicrasUrias  papillifera  Brebisson. 
One  half  of  a  cell.     X  365.     (Original.) 

47  (46)     Cells  at  ends  with  an  incision  or  undulation,  end  view  elliptical  with 

one  or  two  prominences  on  the  sides.    .    .     Euastrum  Ralfs. 

Cells  oblong  or  elliptical,  with  deep,  middle  constriction,  and 
variously  incised,  concave,  or  undulating  margins.  End  view 
oval,  with  one  or  more  rounded  projections.  Membrane  some- 
times with  warts  or  spines.     Chromatophore  axial. 

Fig.  130.     Euastrum  elegans  Kiitzing.     X  588.     (Original.) 

48  (45)     Cells  at  ends  without  notches  or  linear  incisions 49 

49  (54)     Cells  without  spines 50 

50  (51)     Cells  free Cosmarium  Corda. 


Cells  elliptical  or  circular,  sometimes  with  more  or  less 
undulating  or  tapering  margins;  middle  constriction  deep  and 
linear;  end  view  oval  or  circular,  often  with  rounded  projec- 
tions. Chromatophore  in  each  cell-half,  usually  of  radiating 
plates  about  one  or  more  pyrenoids;  membrane  often  punc- 
tate or  with  minute  warts. 


Fig.  131.    Cosmarium  bolrytis  Meneghini.     X  575-     (Original.) 


51  (50)     Cells  united  by  branched  gelatinous  stalks,  forming  colonies  .    .     52 

52  (53)     Colonies  loose,  not  encrusted  with  lime    .    .    .  Cosmocladium  Nageli. 


Cells  as  in  Cosmarium,  but  borne 
by  dichotomously  or  trichotomously 
branched  gelatinous  stalks,  which  are 
united  to  form  free-swimming  or 
sessile  colonies. 

The  colonies  are  invested  in  an 
indistinct  gelatinous  mass,  less  dense 
than  the  filaments  which  connect 
the  cells.  It  is  sometimes  found  in 
large  numbers  in  rivers  and  lakes. 


Fig.  132.    Cosmocladium  saxonicum  de 
Bary.     X  250.     (After  Schroder.) 


THE  FRESH-WATER  ALGAE 


141 


53  (52)     Colony  a  compact  cushion; 


stalks  encrusted  with  lime. 

Oocardium  Nageli. 

Cells  broad,  middle  constriction  slight,  chromatophores  two, 
pyrenoid  in  each.  Stalks  closely  placed  so  that  the  enveloping 
cylindrical  lime  sheaths  make  a  honeycomb-like  structure. 

They  are  sometimes  branched  and  imbedded  in  the  free  end 
of  each  is  a  single  cell,  placed  transversely.  It  occurs  where 
water  trickles  over  limestone  rocks,  and  is  also  reported  as 
being  found  in  mountain  streams. 


Fig. 


133.     Oocardium  stratum  Nageli.     X  485.     Portion  of  figure. 
(After  Senn.) 


54  (49)     Cells  with  spines 55 

55  (56)     Two  or  four  spines  on  each  cell-half  .    .    .     Arthrodesmus  Ehrenberg. 

General  characteristics  as  in  Cosmarium,  except  that  each  cell-half  is  fur- 
nished with  two  or  four  long  spines,  and  the  end  view  shows  no  lateral 
rounded  prominences. 

The  spines  in  Arthrodesmus  are  all  arranged  in  one  plane,  while  in  Xanlhid- 
iutn  they  may  be  arranged  in  two  planes. 

Fig.  134.     Arthrodesmus  convergens  Ehrenberg.     X  about  250.     (Original.) 

56  (55)     Two  rows  of  strong  spines  on  each  cell-half 57 

57  (58)     Spines  simple Xanthidium  Ehrenberg. 


Cells  oval  or  nearly  round,  with  deep,  narrow,  central  constriction;  end  view 
elliptical,  often  with  protruding  sides;  membrane  with  two  rows  of  strong, 
horn-like  spines;  chromatophore  parietal,  more  or  less  divided,  with  several 
pyrenoids. 

As  in  Arthrodesmus  the  presence  and  the  nature  of  the  spines  distin- 
guish the  genus  from  certain  species  of  Cosmarium. 

Fig.  135.     Xanthidium  fasciculaium  Ehrenberg.     X  about  300.     (Original.) 


58  (57)     Spines  branched Schizocanthum  Lundell. 


Characteristics  similar  to  those  of  Xanthidium,  except  that  the 
spines  are  thick,  short,  and  branched  at  the  ends. 

West  believes  that  Schizocanthum  should  be  included  under 
Xanthidium  as  the  only  difference  is  in  the  spines,  and  there  is  too 
much  variation  in  these,  he  thinks,  to  make  separate  genera. 


Fig.  136.    Schizocanthum  armatum  Lundell.     X  106.     (After  Wood.) 


59  (3)     Plant  filamentous,  cylindrical,  only  one  individual  originating  from 
a  germinating  zygospore   .   .  Family  Zygnemaceae  .    .     60 

Cells  cylindrical,  united  into  filaments,  usually  found  near  the  surface  of  the  water.  Chro- 
matophores different  in  different  genera,  but  all  with  several  pyrenoids.  Reproduction  .sexual, 
occurring  by  the  conjugation  of  cells  in  two  parallel  filaments,  ladder-like,  or  lateral,  between  two 
neighboring  cells  of  the  same  filament.     Parthenogenesis  may  occur. 


142 


FRESH-WATER  BIOLOGY 


60  (64)     In  conjugating  the  whole  of  the  contents  of  the  conjugating  cells 

passes  into  the  zygospore.       Subfamily  Zygnemeae  .    .     61 

61  (62,  63)     Chromatophores  two,  axial,  star-shaped;  a  pyrcnoid  in  the  center 

of  each Zygnema  de  Bary. 

Conjugation  either  ladder-like  or  lateral:  Zygospore  within  one  of  the  conjugating  cells, 
or  in  the  conjugating  lube.  According  to  Collins  aplanospores  may  take  the  place  of  zygo- 
spores, also  resting  akinetes  with  granular  contents  and  thickened  membrane  may  be  found. 


Fig.  137.    Zygnema  sp.     X  600.     (Original.) 

62  (61,  63)     Chromatophore  one  to  several  parietal,  spiral  bands,  with  many 
pyrenoids Spirogyra  Link. 

Conjugation  ladder-like  or  lateral.     Zygospore  in  one  of  the  conjugating  cells.     Parthenospores 
may  be  formed. 


Fig.  138.    Spirogyra  crassa  Kiitzing.    a.  conjugation  of  filaments,    b.  zygospores  X  100.     (Original.) 


63  (61,  62)     Chromatophore  an  axial  plate,  with  several  pyrenoids. 

Debarya  Wittrock. 

Cells  long;  conjugation  ladder-like;  zygospore  between  the  con- 
jugating cells;  the  middle  layer  of  the  spore  membrane  yellow,  with 
three  parallel  longitudinal  grooves,  connected  by  radial  striations. 

Fig.  139.    Debarya  glyptosperma  Wittrock,  showing  two  zygospores.     X  95. 
(After  de  Bary.) 


64  (60)     In  conjugation  only  a  portion  of  the  contents  of  the  conjugating  cells 
passes  into  the  zygospore. 

Subfamily  Mesocarpeae  .    .     65 


THE   FRESH-WATER  ALGAE 


H3 


65  (66)     Chromatophore  an  axial  plate,  with  several  pyrenoids.     Zygospore 
lens-shaped  or  flattened  and  angled,  in  the  conjugating  tube. 

Mougeolia  Wittrock. 
Conjugation  ladder-like  or  between  two  adjoining  cells  of  the  same  filament.     Zygospore  in 
the  inflated  conjugating  tube,  separated  from  the  conjugating  cells  by  two  or  more  transverse 
walls. 


Fig.  140.     Mougeotia  sp.    a.  showing  the  surface  of  the  chlorophyll  plate,    b.  showing  the  edge  of  the 
chlorophyll  plate.     X  about  500.     (Original.) 

66  (65)     Vegetative  portion  as  in  Mougeotia  but  zygospore  not  known. 

Gonatone^na  Wittrock. 

Aplanospores  produced  between  two  transverse  mem- 
branes near  the  center  of  an  elongated  cell.  .Spore 
membrane  double. 

Fig.  141.    Gonatonema  veniricosum '^'\ttTocV.    X  250. 
(After  West.) 

67  (2)     Plants   unicellular   or   of   few   cells.     Chromatophore   one   or   more 

parietal  bodies,  rarely  central 68 

68  (190,  249)     Plants  unicellular,  or  of  few  cells  united  into  minute  famiUes; 

frequently  imbedded  in  gelatinous  substance. 

Order  Protococcales  .    .     69 
Each  cell  carries  on  all  functions  independently,  and  complexes  may  be  regarded  as  an  aggre- 
gate of  individuals. 

Three  forms  of  reproduction  may  occur:  i,  purely  vegetative;  2,  by  asexual  zoospores; 
3,  by  isogametes.  More  than  one  method  frequently  occurs  in  one  species;  the  vegetative 
reproduction  may  be  by  simple  fission  or  internal  division. 

69  (89)     Vegetative  cells  or  colonies  for  a  portion  or  the  whole  of  their  exist- 

ence motile Family  Volvocaceae  .    .     70 

70  (77)     Cells  single  or  in  clusters,  not  forming  a  definite  colony 71 

71  (72)     Cells  spindle-shaped;  chromatophores  several,  indefinite,  with  two  or 

more  pyrenoids  and  a  pigment  spot. 

Chlorogoniiim  Ehrenberg. 


Cells  with  two  cilia;  membrane  vcr>'  thin,  pigment  spot  in 
anterior  part.  Numerous  vacuoles  and  sovcral  pyrenoids  present. 
Division  transverse.  Reproduction  by  isogametes.  Wille  makes 
this  genus  a  section  under  Chlamydomonas. 


Fig.  142.     Chlorogonium  euchlorum  Ehrenberg.      o.  a  cluster  of  cells. 
X  about  300.     (After  Ehrenberg.)    b.  single  cell.     (After  Stein.) 


144 


FRESH-WATER   BIOLOGY 


72  (71)     Cells  ellipsoidal  or  nearly  spherical 73 

73  (74)     Membrane  widely  separated  from  the  chromatophore  but  connected 

with  it  by  protoplasmic  strands.     Two  cilia  present. 

Sphaerella  Sommerfeldt. 

Chromatophore  netted,  with  two  or  more  pyrenoids  and  a  pigment  spot. 
Asexual  reproduction  by  longitudinal  division,  sexual  by  isogaraetes.  A 
palmella  condition  may  occur. 

Sphaerella  often  assumes  a  red  color,  due  to  the  presence  of  hemato- 
chromc,  and  is  reported  in  a  few  cases  as  being  the  organism  causing  "red 
rain."  It  was  also  supposed  that  S.  nivalis  caused  the  phenomenon  of  "red 
snow,"  but  the  form  described  by  Chodat  shows  the  chloroplast  as  lying 
close  to  the  membrane,  so  this  is  probably  a  Chlamydomonas. 

Fig.  143.    Sphaerella  pluvialis  Flotow.     X  about  600.     (After  Schmidle.) 

Membrane  not  separated  from  the  chromatophore 75 


74  (73) 

75  (76) 


Two  cilia  and  a  pyrenoid  present. 


Color  rarely  red. 

Chlamydomonas  Ehrenberg. 

Cells  ellipsoidal  or  spherical;  chromatophore  single,  hollow,  parietal;  a  pigment 
spot  and  two  ciha  at  the  anterior  end.  Reproduction  by  vegetative  division,  also 
by  copulation  of  gametes  which  are  either  alike  or  slightly  unlike  as  to  size.  Zygo- 
spore green  or  red.  The  products  of  the  vegetative  division  may  pass  at  once  into 
a  motile  state  with  cilia,  or  may  be  non-motile,  according  to  conditions  in  the  sur- 
rounding medium. 

Fig.  144.     Chlamydomonas  ohioensis  Snow.     X  1000.     (Original.) 


76  (75)     Structure  as  in  Chlamydomonas  but  with  4  cilia.     Some  include  this 
genus  under  Chlamydomonas Carteria  Diesing. 


The  shape  of  the  cells  in  the  different  species  differ  rather  more 
than  in  Chlamydomonas;  the  structure  of  the  cells,  however,  is 
identical,  except  for  the  cilia.  Species  also  occur  in  much  the  same 
localities  as  Chlamydomonas  but  are  less  frequent. 


Fig.  145.     Carteria  oblusa  Dill.     X  about  475.     (After  Dill.) 


77  (70)     Cells  united  to  form  a  colony  of  definite  shape  which  is  constantly 

in  motion 7^ 

78  (79)     Colony  not  surrounded  by  a  gelatinous  envelop. 

Spondylomorum  Ehrenberg. 

Colony  of  16  cells  loosely  united,  their  anterior  ends  all  pointing 
toward  one  point.  The  cells  are  obovate,  with  4  cilia  at  their 
anterior  ends,  a  pyrenoid,  and  a  pigment  spot.  A  new  colony  of  16 
originates  by  successive  division  from  a  vegetative  cell. 

Fig.  146.     Spondylomorum  quaternarium  Ehrenberg.     (After  Stein.) 

79  (78)     Colony  surrounded  by  a  gelatinous  envelop 80 

80  (83,  88)     Colony  not  spherical  or  spheroidal 81 


THE  FRESH-WATER  ALGAE 


145 


81  (82) 


Colony  a  plate  of  4  or  16  spherical  cells  in  a  single  layer,  each  with 
2  cilia.     Boundary  of  gelatinous  envelop  not  distinct. 

Gonium  Miiller. 


Cells  oval,  with  two  cilia  and  a  pigment  spot.  Chroma- 
tophore  single,  parietal,  hollow,  with  one  pyrenoid.  Re- 
production by  successive  divisions  of  each  cell,  forming  a 
new  colony;   also,  according  to  West,  by  isogametes. 

Gonium  is  one  of  the  commonest  of  the  Volvocaceae, 
occurring  in  almost  all  ponds  and  lakes.  It  is  also  one 
of  the  most  beautiful  of  the  group,  as  the  colonies  are  ex- 
ceedingly regular  and  as  they  move  they  revolve,  showing 
first  the  surface  and  then  the  edge. 


Fig.  147.    Gonium  pectorale  Miiller.     X  370.     (After  West.) 


82  (81)     Colony  flattened,  anterior  portion  rounded,  posterior  portion  with 

three  wart-Uke  projections Plalydorina  Kofoid. 

"The  two  faces  compressed  so  that  the  cells  of  the  two 
sides  intercalate;  flagella  upon  both  faces  on  alternate  cells. 
Anterior  and  posterior  poles  of  major  axis  are  differentiated 
by  the  arrangement  of  the  cells  and  by  the  structure  of  the 
envelope;  long  and  short  transverse  axes  differentiated  by 
the  flattening  of  the  colony.  Cells  similar,  bi-flagellate, 
each  with  stigma,  chroma tophore,  and  pyrenoid.  Asexual 
reproduction  by  repeated  division  of  all  the  cells,  each 
forming  a  daughter  colony." 

Fig.  148.     Plalydorina  caudata  Kofoid.     X  628.     (After  Kofoid.) 

83  (80,  88)     Colony  spherical  or  spheroidal,  but  small.    Cells  not  numerous.    84 

84  (85,  86,  87)     Colony  of  4  or  8  elongated  cells  with  irregular,  pseudopodia-like 

processes,  arranged  in  a  zone  around  the  center  of  a  firm 
gelatinous  sphere Stephanos phaera  Cohn. 

Cells  elongated,  each  with  cilia  at  the  anterior  pole  which 
penetrate  the  gelatinous  substance.  Chromatophores  irregular, 
with  one  or  several  pyrenoids.  Each  cell  gives  rise  to  a  new 
colony  by  division;   isogametes  are  also  found. 

Fig.  149.    Slephanosphaera  pluvialis  Cohn.    X  425-    (After  Hieronymus.) 

85  (84,  86,  87)     Colony  spheroidal,  or  slightly  elongated,  of  8  or  16  cells  closely 

packed  at  the  center  of  the  indistinct  gelatinous  envelop. 

Pandorina  Bory. 

Cells  heart-shaped,  with  two  cilia  at  larger  end,  a  pigment  sjx^t, 
and  a  pyrenoid,  the  latter  in  the  posterior  end  of  the  hollow 
parietal  chloroplast.  Reproduction  by  successive  division  m 
each  cell  whereby  as  many  new  colonies  are  formed  as  there  are 
cells;  reproduction  also  by  the  copulation  of  gametes  cither  alike 
or  slightly  unlike  as  to  size;  zygospore  red. 

Fig.  150.     Pam/oftna  morwm  Muller.     X  about  385.     (Original.) 


146 


FRESH-WATER   BIOLOGY 


86  (84,  85, 87)  Colony  spherical  or  ellipsoidal;  cells  of  two  types,  vegetative  and 
gonidial,  which  lie  in  the  anterior  and  posterior  parts  of 
the  colony  respectively Pleodorina  Shaw. 

Colony  consists  of  a  spherical  or  elliptical  coenobium  of 
greenish,  bi-flagellate  cells  of  two  types,  vegetative  and 
gonidial,  in  the  anterior  and  posterior  parts  of  the  colony 
respectively  which  lie  in  the  periphery  of  a  hyaline  gelatinous 
matrix  and  are  surrounded  by  a  common  hyaline  envelop. 
Cells  each  with  one  reddish  stigma  which  is  more  prominent 
in  the  anterior  part  of  the  colony.  No  connecting  filaments 
between  the  cells;  nonsexual  reproduction  by  gonidia  which 
are  formed  by  increase  in  size  of  a  part  of  the  cells  of  a  colony. 
Daughters  escape  from  parent  as  small  colonies  of  bi-flagellate 
cells  which  at  this  stage  arc  all  similar.  Se.xual  reproduction 
not  known. 

Fig.  151.     Pleodorina  illinoisensis  Kofoid.     X  335.    (After  Kofoid.) 


87  (84,  85,  86) 


Colony  spherical,  of  8  or  1 6,  32  or  64  cells  evenly  scattered  near 
the  surface  of  a  gelatinous  sphere.  .    .    Eudorina  Ehrenberg. 


Cells  spheriail  or  oval,  with  two  cilia  and  a  pigment 
spot.  Chromatophore  single,  parietal.  Vegetative  re- 
production .by  repeated  division,  forming  at  first  a 
plate-like  daughter  colony,  which  later  becomes  spher- 
ical. Sexual  reproduction  by  a  pear-shaped  anthero- 
zoid  and  a  spherical  oosphere. 

The  cells  lie  at  the  surface  of  the  gelatinous  sphere 
and  the  cilia  project  at  right  angles  to  the  surface.  All 
of  the  vegetative  cells  may  become  transformed  into 
oogonia  and  antheridia;  in  each  of  the  latter  64  anther- 
ozoids  are  formed.  The  ripe  oospores  are  brownish 
with  a  smooth  external  membrane.  The  habitats  of 
Eudorina  are  ponds,  ditches,  and  lakes. 

Fig.  152.     £«<forino  e/f|an5  Ehrenberg.     (.\fter  Stein.) 


88  (80,  83)     Colony  a  larger  gelatinous  sphere  with  a  very  large  number  of 
minute  cells  at  the  surface Volvox  Linnaeus. 

Cells  very  small,  round  or  pear-shaped,  connected  by  protoplasmic  filaments,  each  with  a 
pair  of  cilia,  a  single  chromatophore  and  two  or  more  contractile  vacuoles;  reproduction  sexual 
and  asexual;  in  the  latter  certain  cells  (parthenogonidia)  within  the  sphere  enlarge  and  through 
divisions  give  rise  to  a  new  colony.  Sexual  reproduction  occurs  by  the  union  of  a  fusiform 
antherozoid  and  oosphere;   oospore  spherical,  with  red  contents  and  a  spiny  membrane. 


89  (69)     Colonies  not  motile  in  the  vegetative  condition 90 


90  (95,  131,  175)  Cells  in  colonies,  generally  sessile  and  enclosed  in  a  definite 
gelatinous  envelop,  or  borne  on  gelatinous  stalks. 
Reproduction  asexual  by  zoospores,  or  sexual  by 
isogametes.    .    .    .   Family  Tetrasporaceae  .    .     91 


91  (94)     Cells  biciliate,  at  the  surface  of  an  inflated,  attached  colony.     Cilia 
external  and  free 92 


THE  FRESH-WATER  ALGAE 


147 


92  (93)     Colonies  macroscopic  or  microscopic,  expanded  or  intestiform,  cells 
arranged  in  fours Tetraspora  Link. 


Reproduction  by  division  in  two  directions;  zoospores 
may  originate  directly  from  the  vegetative  cells,  and  by  divi- 
sion give  rise  to  a  new  colony;  isogametes  with  two  cilia  may 
be  formed,  also  resting  spores  with  heavy  brown  walls. 

Fig.  153.     Tetraspora  explanataK\i\.z\Qg.     X  250.     (After  Nageli.) 


93  (92)     Colonies   pear-shaped,   attached,   cells   irregularly   placed   near   the 
surface Apiocystis  Nageli. 


Chromatophore  single,  parietal  with  a  pyrenoid.  Division  in 
three  directions.  A  spherical  zoospore  with  two  cilia  may  originate 
from  each  cell  and  escape  from  the  gelatinous  vesicle. 


Fig.  154.     Apiocystis  brauniana  Nageli.     X  78.     (After  Nageli.) 


94  (91) .   Cells  spindle-shaped,  clustered  on  the  ends  of  gelatinous  stalks. 

Chlorangium  Stein. 


Chromatophore  one  or  two  longitudinal  bands;  the  cells  may 
detach  themselves  and  become  zoospores  with  two  cilia  and  a 
pigment  spot.  Large  numbers  of  motile  individuals  may  be 
formed  in  each  cell,  though  copulation  is  not  known. 


Fig.    155.       Chlorangium  stentorum   Stein,      a.    X  about  200.     (After 
Cieokowski.)     b.  (After  Stein.) 


95  (90,  131,  175)     Cells   with  a  thick,  often  indistinct  gelatinous  covering, 

uniting  several  together  into  greater  or  smaller  free  swim- 
ming, rarely  attached  colonies.     Reproduction  by  fission  or 
I                                internal   division ;    in   a   few   instances   by   zoospores  and 
isogametes Family  Palmellaceae   .    .     96 

96  (102,  107)     Cells  embedded  in  more  or  less  cylindrical  and  definite  gelat- 

inous tubes,  strands,  or  stalks  which  are  broader  than  the 
cells 97 


97  (100,  10 1)     Cells  scattered  throughout  a  gelatinous  tulje  or  strand.  .   .     98 


148  FRESH-WATER  BIOLOGY 

98  (99)     Cells  at  the  ends  of,  or  distributed  along  rather  firm,  often  lamellate 

gelatinous  strands Hormotila  Borzi. 

Chromatophore  single,  granular,  without  a  pyrenoid.  Re- 
production by  cell  division,  also  by  bi-ciliate  zoospores,  eight 
of  which  are  formed  in  a  single  zoosporangium.  The  zoospo- 
rangia  are  much  larger  than  the  vegetative  cells. 

Fig.  156.     Hormotila  mucigena  Borzi.     X  268.     (After  West.) 

99  (98)     Cells  distributed  throughout  a  structureless,   cyHndrical,  branched 

gelatinous  colony Palmodaciylon  Nageli. 

Cells  spherical;  gelatinous  tubes  branched  or 
unbranched.  single  or  in  clusters.  Division  of 
cells  first  in  one,  later  in  three  directions. 
Chrom.atophore  parietal  and  often  lobed. 

The  elongated  shape  of  these  colonies  is 
thought  by  West  to  be  due  to  divisions  occur- 
ring more  frequently  in  one  direction  than  in 
others.  The  plant  occurs  in  swamps  and  quiet 
waters. 


Fig.  IS".       Palmodactylon  sp. 
colony.     X  about  600. 


Portion   of   young 
(Original.) 


100  (97) 


%S 


Cells  two  or  four  in  series,  at  the  ends  of  attached,  dichotomously 
branched  stalks;  chromatophores  several. 

Mischococcus  Nageli. 

Chromatophores  one  to  four,  without  pyrenoids.  Reproduction  by 
zoospores  and  isogametes  which  may  or  may  not  unite  before  germina- 
tion. 

Fig.  158.     Mischococcus confervicola'^sigtli.     X  about  180.    (After  Rabenhorst.) 


loi  (97, 


Cells   in   radiating   series,  often   branched,  held  together  by 
gelatinous  strands Dictyocystis  Lagerheim. 

Chromatophore  single,  central,  and  radial.     Reproduction  probably  by  division. 

Though  Dictyocystis  is  reported  by  several  botanists,  it  seems  a  somewhat  doubtful  genus. 

102  (96,   107)     Cells   at  the   surface   of   an   invisible   gelatinous   mass   and 

borne  on  fine,  radiating  gelatinous  strands 104 

103  (104,  105,  106)     Cells  reniform,  four  on  a  stalk,  two  borne  near  the  adjoin- 

ing ends  of  the  other  two.    .    .     Dimorophococcus  A.  Braun. 


Chromatophore  single  and  parietal,  each  group  of 
cells  formed  by  the  internal  division  of  a  single  mother 
cell. 

The  filaments  which  bear  the  cells  are  thought  by  some 
to  be  formed  from  the  remnants  of  the  mother  membrane, 
but  this  needs  further  investigation.  Large  colonies  may 
become  fragmented  into  smaller  colonies.  This  alga  is 
not  very  frequent,  and  occurs  in  larger  lakes  rather  than 
in  stagnant  water. 


Fig.  159- 


Dimorphococcus  lunatus  A.  Braua. 
(Original.) 


X  600. 


THE   FRESH-WATER   ALGAE  1 49 

104  (103,  105,  106)     Cells  single,  spherical,  or  oval.     Dictyosphaerium  Nageli. 


Chromatophore  single,  parietal.     Reproduction  by  internal  division. 
Fig.  160.     Dictyosphaerium  pulchellum  Wood.     X  570.     (Original.) 


105  (103,  104,  106)     Colonies  much  as  in  Dictyosphaerium  except  that  the  cells 

are  in  clusters  of  four  which  are  held  together  by  the  rem- 
nants of  the  mother-membrane Tetracoccus  West. 

Some  regard  this  as  a  young  stage  in  Dictyosphaerium. 

106  (103,  104,  105)     Cells  clustered,  grape-like,  imbedded  in  the  rather  firm, 

often  yellow  gelatinous  strands.    .    .     Botryococcus  Kiitzing. 

'^r^^mftS^yVi  West's  genus  Ineffigiata  is  probably  a  Botryococcus  where  the  gelati- 

Xr>  ^  A>vr\  K^Yp  nous  envelop  is  somewhat  contracted. 

CyQ  In  old  cultures  of  Botryococcus,  and  often  in  nature,  an  orange 

^5^2^  or  reddish  oil  is  produced  which  gives  the  cells  that  color. 

The  alga  is  found  very  frequently  in  pools,  ponds,  and  lakes;  it 
has  been  known  to  form  the  water  bloom  on  lakes  of  small 
dimensions. 

\^Y^  Fig.  161.     Botryococcus  braunii  KJitzing.     X  about  300.     (Original.) 

107  (96,  102)     Cells  not  at  the  surface  of  a  gelatinous  mass  but  distributed 

through  it 108 

108  (109)     Colonies    cyHndrical,    branching;     gelatinous    envelop    somewhat 

rigid  and  often  lamellate Palmodictyon  Nageli. 

,    -  Cells  in  groups  of  two  and  four,  the  groups  sur- 

S    Q  ®  ®  ^  ^    o  -'  rounded  by  gelatinous  vesicles  which  are   united  to 

®     ®    o®   ^             '^  -  ^        "      "*  form  the  cylindrical  colony,  and  give  a  more  or  less 

^      ^--o^                                       o'*'  netted  appearance  to  the  gelatinous  portion.    Repro- 

.  duction  by  means  of  resting  spores  with  brown  walls; 

^  -  ^  these  spores  germinate  and  produce  a  new  colony. 

/  West  states  that  the  outer  coat  often  becomes  very 

^    '  ©    ^ .    ~  tough  and  of   a  brown  color.     Palmodictyon  is  a 

\     0^_^'  very  rare  alga  in  America,   but   Collins  reports  it 

-^    ^3  '*'     **o      '''  from  Massachusetts. 

••^     ,    ">    ^^     '  '  Fig.  162.     Palmodictyon  viridis  YMUing.    X  210. 

,,^  (After  West.) 

109  (108)     Colonies  of  no  definite  shape,  of  the  shape  of  the  individual  cells,  or 

more  or  less  angled  and  showing  a  dark  gelatinous  layer  be- 
tween the  cells.     Cells  often  isolated no 

110(127,128)     Colonies  irregular m 

111  (120)     Cells  not  in  clusters "2 

112  (lis)     Gelatinous   envelop   containing    concentric    lamellae    about    the 

ceUs "3 


150  FRESH-WATER  BIOLOGY 

113(114)     Cells  spherical Gloeocystis  Kaigeli. 

The  enveloping  gelatinous  substance  showing  a  concentric  lamellate  structure. 

Reproduction  by  repeated  cell  division,  several  generations  of  cells  often  re- 
maining enclosed  in  the  original  mother-membrane.  According  to  some 
authors  reproduction  also  occurs  Vjy  bicilliate  zoospores. 

The  authenticity  of  this  genus  is  doubtful  as  the  non-motile  stage  of  certain 
species  of  Chlamydomonas  answers  this  description. 

Fig.  163.    Gloeocystis  vesiculosus  K&gtW.     X  150.     (After  Nageli.) 

114  (113)     Cells  elongated Dactylothcce  Lagerheim. 

Chromatophore  a  parietal  plate  lying  only  on  one  side  of  the  cell;  no  pyrenoids. 
Gelatinous  substance  often  lamellate. 


m 


115  (112) 


Fig.  164.     Dactylothcce  braunii  Lagerheim.     X  about  370.     (After  Lagerheim.) 

Gelatinous  envelop  not  containing  concentric  lamellae  about  the 
cells 116 


116  (117)     Gelatinous  mass  containing  segments  of  the  antecedent  mother 
cell Schizochlamys  A.  Braun. 


Cells  spherical,  scattered  in  a  gelatinous  mass  together 
with  the  visible  remnants  of  the  old  membranes  which 
are  split  into  distinct  segments. 

West  believes  that  it  is  the  formation  of  the  large  amount 
of  gelatinous  material  that  causes  the  firmer  portion  of 
the  membrane  to  become  ruptured,  and  that  this  takes 
place  previous  to  the  formation  of  the  two  or  four  daughter 
cells.  5.  gelatinosa  is  the  only  species  reported  in 
America,  and  this  occurs  as  a  pale  green  irregular  mass 
either  free  or  adhering  to  water  plants. 


Fig.  165 


Schizochlamys  gelatinosa  A.  Braun. 
(Original.) 


X  600. 


117  (116)     Gelatinous  mass  not  containing  segments  of  the  antecedent  mother- 

membrane 118 

118  (119)     Cells  throughout  the  gelatinous  mass  formed  by  the  outer  layers 

of  the  cell  walls Palmella  Lyngbye. 

Chromatophore  parietal,  with  a  pyrenoid.     Reproduction  by  division  in  three  directions, 
and  according  to  Wille,  by  macrozoospores,  microzoospores,  and  isogametes. 

119  (118)     Cells  at  the  surface  of  the  gelatinous  mass. 

Dictyosphaeropsis  Schmidle. 


Cells  free  or  attached,  round  or  elongated.     One  or  two  disc-.shaped, 
parietal  chromatophores  present.     Reproduction  not  well  known. 

Fig.  166.     Dictyosphaeropsis  palalina  Schmidle.     X  375-     (After  Schmidle.) 


120  dii)     Cells  in  clusters,  usually  of  eight,  sometimes  four  or  sixteen;  colonies, 
mostly  floating 121 


THE  FRESH-WATER  ALGAE 


151 


121  (124)     Cells  spherical 122 

122  (123)     Chromatophore  single Sphaerocystis  Chodat. 


Colonies  large;  clusters  widely  separated  from 
each  other.  Gelatinous  envelop  invisible  without 
reagents.  Chromatophore  thin,  parietal,  with  a 
pyrenoid  on  one  side  and  an  opening  on  the  other. 
Reproduction  by  internal  division. 

Sphaerocystis  is  almost  universally  found  in  the 
plankton  and  is  one  of  the  most  conspicuous  and 
beautiful  of  all  the  plankton  forms.  Sometimes  the 
colonies  are  very  large,  consisting  of  many  clusters. 


Fig.  167.     Sphaerocystis  schraeleri  Chodat.     X  520. 
(Original.) 


123(122)     Chromatophores  many,  parietal C hlorobotrys  BohVm. 


Cells  spherical,  in  a  gelatinous  matrix,  as  in  Sphaerocystis,  but  the 
chlorophyll  in  many  parietal  discs. 

Fig.  168.     Chlorobotrys  regularis  Bohlin.     X  300.     (After  West.) 


124  (121)     Cells  not  spherical 125 

125  (126)     Cells  crescent-shaped Kirchneriella  Schmidle. 


Cells  in  clusters,  as  in  Sphaerocystis,  but  strongly 
crescent-shaped . 

In  reproduction  internal  division  takes  place  trans- 
versely and  the  four  or  eight  daughter  cells  are  set 
free  by  the  breaking  of  the  cell  wall. 

Several  species  occur  in  the  plankton.  They  also 
occur  in  ponds  among  water  plants. 


Fig.  169. 


Kirchneriella  obesa  Schmidle.      X  600. 
(Original.) 


126(125)     Cells  oval  or  bluntly  pointed Oocysiis  N-^ge\l 

Cells  oblong,  single,  or  two,  four,  or  eight  in  a  gelatinous 
envelop;  in  some  cases  many  clusters  in  a  colorless  gclatmous 
matrix.  Chromatophore  single,  parietal,  with  an  openmg  on 
one  side  or  of  many  small  discs.  Pyrenoids  present  m  some 
species.  Cells  single  or  in  clusters,  as  in  Sphaerocystis,  but 
ellipsoidal  in  shape.  ,  .       ,        ,     ,  , 

Oocystis  is  frequently  found  m  the  plankton  where  it  is 
usually  in  large  gelatinous  colonies  similar  to  Sphacrocyslts 
and  Kirchneriella.  In  other  localities  the  cells  are  generally 
solitary. 

Fig.  170.     Oocystis  solitaria  Wittrock.     X  6cx).     (Original.) 


152  FRESH- WATER  BIOLOGY 

127  (no,  128)     Colonies  somewhat  cubical,  showing  a  dark,  gelatinous  layer 
between  the  cells Gloeotaeniiim  Hansgirg. 

^|?r<  "^  Cells   plobose   or   flattened,   colonies   of  two,   four,   or  eight  cells,    with 

wide  lamellate  walls.     Reproduction  by  aplanospores. 

Fig.  171.     Gloeotaenium  loitelsbergerianum'Ra.xisghg.     X  220.     (After  Transeau.) 

128(110,127)     Colonies  the  shape  of  the  individual  cells 129 

129  (130)     Cells  reniform,  colony  of  the  same  shape  or  oval. 

Nephrocytium  Nageli. 

Cells  single  or  in  clusters,  as  in  Sphaerocyslis,  but  reniform  in 
shape. 

Nephrocytium  resembles  Oocystis  except  that  the  cells  are  curved. 
It  is  widely  distributed  but  not  very  abundant. 

Fig.  172.     Nephrocytium  agardhianum  Nageli.     X  580.     (Original.) 

130(129)     Cells  fusiform ElakatothrixWdle. 


Cells  elongated,   fusiform,  gelatinous  sub- 
stance dense,  often  lamellate. 


Fig.  17.?.     Elakatothrix  viridis  Wille.       X  575- 
(Original.) 


131  (90,  95,  175)     Cells   without   a   thick  gelatinous   envelop   holding    them 

together;     sometimes    adhering    to   each   other    after   di- 
vision       132 

132  (137,  155,  174)     Reproduction  by  fission  only,  or  rarely  by  fission  and 

internal  division.      .    .   Family  Pleurococcaceae  .    .      133 

^33  (134,  135,  136)  Reproduction  by  fission  in  one  direction  only,  forming 
equal  cyHndrical  cells,  the  length  being  one  and  one-half  to 
three  times  the  breadth Stichococcus  Nageli. 

Chromatophore  a  parietal  plate  lying  only  on  one  side  of  the  cell, 
with  no  pyrenoid.  Reproduction  by  simple  fission,  the  cells  sometimes 
adhering  to  each  other  after  the  division,  but  not  forming  perfect 
filaments. 

Fig.  174.     Stichococcus  bacillaris  Nageli.     X  about  400.     (Original.) 

134  (i33>  i35>  136)  Reproduction  by  division  in  three  directions.  Cells 
spherical  or,  if  in  small  complexes,  somewhat  angled. 

Pleurococciis  Meneghini. 

Cells  either  single  or  in  small  clusters  of  two,  four,  or  more  cells  which  later 
fall  apart.  Chromatophore  a  thin  lining  to  the  membrane  with  an  opening  on 
one  side,  and  with  or  without  a  pyrenoid. 

Pleurococciis  is  the  chief  constituent  of  the  green  coating  on  the  bark  of  trees, 
old  wood,  and  stones. 

Fig.  175.    Fleurococcus  vulgaris  Mcaeghiai.     X  560.     (Original.) 


eecis 

0 

8 

00 

% 

^% 

^. 

<^ 

^V 

11 

0 

0 

THE   FRESH-WATER  ALGAE 


153 


135  {^33i  i34>  13^)     Characteristics  as  in  Pleurococcus,  but  sometimes  forming 
short  filaments Pseudo- pleurococcus  Snow. 

This  form  may  remain  indefinitely  in  either 
a  filamentous  or  unicellular  state  according 
to  the  conditions  in  the  environment.  In 
the  filamentous  state  it  resembles  a  small 
form  of  Sligeoclonium,  but  is  distinguished 
from  it  by  the  absence  of  zoospores. 

Chodat  regards  a  form  similar  to  this  as 
a  true  Pleurococcus  and  believes  that  short 
filaments  are  characteristic  of  that  genus. 


Fig.  176. 


Pseudo-pleurococcus  vulgaris   Snow. 
X  600.     (Original.) 


136  (133,  134,  135)     Reproduction  by  fission  in  three  directions  and  by  inter- 
nal division Palmellococcus  Chodat. 

Chromatophore  a  parietal  plate,  without  a  pyrenoid.  In  addition  to  reproduction  by  fission 
and  internal  division,  a  rejuvenescence  of  the  cell  contents  may  occur,  accompanied  by  a  cast- 
ing off  of  the  mother-membrane.     An  orange-red  oil  is  sometimes  present. 

174)     Reproduction  by  internal  division  only. 

Family  Chlorellaceae  . 


137  (132,  155, 

138  (142,  151) 

139  (140,  141) 


138 

Cells      spherical,      ellipsoidal,      or      irregular.      Membrane 
smooth 139 

Cells  spherical;    chromatophore  a  single,  hollow  sphere  with 
one  pyrenoid Chlorella  Beyerinck. 

Cells  spherical  or  somewhat  elongated;  chromatophore  lining  the  mem- 
brane, open  on  one  side,  with  a  single  pyrenoid. 

The  name  Zoochlorella  Brandt  has  been  given  to  this  same  genus  and  ante- 
dates the  name  of  Chlorella  by  some  years,  but  the  name  Chlorella  seems 
more  appropriate. 

Fig.  177.    Chlorella  sp.     X  600.     (Original.) 

Cells  spherical,  chromatophore  of  many  parietal  discs,  each 
with  a  pyrenoid Eremosphaera  de  Bary. 

Size  relatively  large;  chromatophores  many,  parietal;  nucleus 
prominent.     Reproduction  by  internal  division. 

The  cells  are  large,  spherical,  and  conspicuous.  The  nucleus  is 
distinct,  suspended  in  the  middle  of  the  cell  by  strands  of  proto- 
plasm. Two  or  four  daughter  individuals  may  originate  by  succes- 
sive division  of  the  contents  and  are  Hberated  by  the  rupturing  of 
the  mother  membrane.  Eremosphaera  is  almost  constantly  found 
among  Desmids  in  Sphagnum  swamps. 

Fig.  178.     Eremosphaera  viridis  de  Bar>'.     X  125.     (Original.) 

141  (139,  140)     Cells  spherical  or  irregular;    chromatophores  many,  angular, 

radially  arranged;  many  pyrenoids  in  each. 

Exccntrosphaera  Moore. 

Plant  consisting  of  a  single  cell,  in  mature  condition  var>-inR 
in  outline  from  spherical  and  elliptical  to  irregular  and  eccentric 
forms.  Chromatophores  large,  angular,  usually  radiately  ar- 
ranged, closely  lining  the  wall.  Pyrenoids  minute,  numerous  ui 
each  chromatophore.  Multiplication  by  non-motile  sjwres 
(aplanospores)  which  escape  by  the  dissolution  of  a  part  of 
the  cell  wall.     Reaction  to  all  external  stimuli  negative. 

Fig.  179.     Excentrosphacra  viridis  Moore.     X  160.     (.After  Moore.) 

142  (138,  151)     Cells  spherical  or  elongated,  membrane  with  hairs,  spines,  or 

reticulate  markings i43 


154 


FRESH-WATER  BIOLOGY 


143  (147)     Cells  spherical 144 

144  (145,  146)     Cells  solitary,  membrane  with  short  spines  or  network. 

Trochiscia  Kiitz. 

Cells  perfectly  spherical,  the  spines  or  reticulate  markings  project- 
ing but  little. 

Chromatophores  usually  several.  Reproduction  by  internal  division. 
West  also  reports  reproduction  rarely  by  fission  and  by  zoospores.  The 
genus  needs  further  investigation. 

Fig.  180.     Trochiscia  vestitus  Reinsch.     X  about  260.     (After  Reinsch.) 


145  (144,  146)     Cells  solitary,  bristles  long,  rigid,  scattered  over  the  entire 
surface Golenkinia  Chodat. 

Reproduction  occurs  by  division  in  one  or  two  directions  and 
by  autospores.  Chodat  also  reports  the  formation  of  zoogonidia 
with  four  cilia. 

Golenkinia  has  been  known  to  occur  in  great  quantities  almost 
pure  in  large  tanks  of  water;  it  also  occurs  in  the  plankton, 
though  not  very  abundantly.  Chromatophore  parietal,  with  one 
pyrenoid. 

Sir  Ray  Lancaster  believes  that  his  Archerinia  bolloni  de- 
scribed in  1885  and  referred  to  the  Protozoa  is  identical  with 
Golenkinia  radiata  described  by  Chodat  in  1894,  and  with 
Richteriella  botryoides  described  by  Lemmermann  in  1898.  If 
this  be  true  the  name  Archerinia  claims  precedence  over  the 
other  two  generic  names. 

Fig.  181.     Golenkinia  radiata  Chodat.     X  625.     (Original.) 


146  (144,  145^ 


Cells  in  colonies  of  eight,  sixteen,  thirty-two,  sixty-four,  or 
more  cells;  bristles  long,  only  on  the  outer  surface  of  a  col- 
ony  Richteriella  Lemmermann. 


Bristles  comparatively  coarse  and  in  length  many 
times  the  diameter  of  the  cells.  Chromatophore  single, 
parietal,  with  a  single  pyrenoid. 

The  cells  are  usually  clustered  in  groups  of  four  which 
are  aggregated  into  larger  colonies.  But  little  is  known 
of  its  reproduction  except  that  vegetative  division  has 
been  known  to  occur. 

It  is  found  in  the  plankton  of  large  lakes. 


Fig.  182. 


Richteriella  glohosa  Lemmermann.    X  556.     (After 
Lemmermann.) 


147  (143)     Cells  somewhat  elongated 148 


148  (14Q,  150) 


Bristles  four,  two  at  each  end  or  one  at  each  end  and  two  at 
the  center,  each  with  a  basal  swelling.   .   Lagerheimia  Choddit. 

Cells  ellipsoidal,  with  four  spines  on  short  pedicels.  Chromatophore 
single,  parietal,  with  a  single  pyrenoid.  Reproduction  by  internal 
division. 

Chodat  and  West  recognize  the  genus  Lagerheimia  but  it  is  very  doubtful 
whether  the  presence  of  only  four  spines  with  basal  swellings  is  sufficient  to 
remove  it  from  the  genus  Chodatella  where  the  spines  are  more  numerous 
and  have  not  the  basal  swellings. 

Fig.  183.     Lagerheimia  genevensis  Chodat.     X  275-     (After  Chodat.) 


THE   FRESH-WATER  ALGAE 


155 


149  (148,  150)     Bristles  varying  in  number,  without  a  basal  swelling.     Cells 
single Chodatella  Lemmermann. 

/  Cells  solitary,   ellipsoidal;    spines  evenly  distributed  over  the 

surface  or  in  circles  about  the  ends.     Chromatophore  parietal, 
^  /  with  or  without  pyrenoids. 

Chodatella  is  occasionally  found  in  the  plankton  of  larger  lakes. 

Fig.  184.     Chodatella  cilriformis  Snow.     X  500.     (Original.) 


150  (148,  149)     Bristles  numerous,  on  the  outside  of  the  colony  only.     Cells 
usually  united  into  a  small  cluster  by  a  gelatinous  substance. 

Franceia  Lemmermann. 


Chromatophores  two,  each  with  a  pyrenoid. 

This  genus  in  its  general  characteristics  resembles  Richteriella 
but  it  is  distinguished  from  it  by  the  larger  size  and  oval  shape 
of  the  cells,  the  shorter  spines  and  the  two  chromatophores. 

Reproduction  takes  place  by  division  in  a  single  longitudinal 
direction. 


Fig.  185.    Franceia  sp.     X  about  600.     (Original.) 


(138,  142)     Cells  of  some  other  shape  than  spherical  or  elliptical;  with 
points  or  angles 152 

(153,  154)     Cells  needle-like  or  fusiform,  often  variously  curved,  the  length 
often  many  times  the  diameter.    .    .  Ankistrodesmus  Corda. 

Ankistrodesmns  is  found  in  all  ponds, 
lakes,  and  rivers.  It  is  one  of  the  most 
common  and  one  of  the  hardiest  of  the 
unicellular  algae. 

Fig.  186.     Ankistrodesmus.    Various  species. 
X  600.       Orl  inal.) 


151 
152 


G 


153 


154 


(152,  154)     Cells  short,  fusiform,  length  two  to  four  times  the  diameter. 

Ddctylococciis  Niigeli. 

Cells   free,  short,  nine  to  eighteen  n  long.     Chromatophore  with  a  pyrenoid, 
opposite  to  which  there  is  an  opening.     In  reproduction  two  to  eight  cells  are 
'^J     formed  by  transverse  internal  division. 

Fig.  187.     Dactylococcus  infusionum  Nageli.     X  600.     (Original.) 

(152,  153)     Cells  distinctly  three,  to  many-angled,  angles  all  in  one  plane  or 
not;  at  the  ends  often  one  or  more  simple  or  divided  spines. 

Tetracdron  Kiitzing. 


Chromatophore  single,  parietal,  usually  with  a  pyrenoid. 

In  this  genus  there  is  the  greatest  variety  in  regard  to  the  shape, 
of  the  cells,  number  of  points,  and  size;  the  most  common  one  is, 
however,  a  minute  form  with  but  few  points. 

Fks.  188.     Tetracdron  enorme»de  Bary.      X  600.     (Original.) 


156  FRESH-WATER  BIOLOGY 

155  (132,  137,  174)     Reproduction  by  the  formation  of  zoospores  only,  or  by 
isogametes Family  Protococcaceae    .    .     156 

156(161,  168)     Cells  spherical 157 

157  (158)     Chromatophores  many,  parietal Botrydiopsis  Borzi. 

/^^^1?xC/"^  Chromatophores  without  pyrenoids;  zoospores  amoeboid,  with 

itfJ^:5rSs*Sr4,    V               B  ^  single  ciHum,  a  pigment  spot,  and  one  (sometimes  two)  chroma- 

l^i^Kl^;       V^say  tophores;  frequently  they  germinate  within  the  mother-membrane 

%'^^^^          ^^^  without  a  motile  period. 

^1       mo^  Fig.  189.     Botrydiopsis  eriensis  Snow.     a.  vegetative  cell;   b.  zoospores. 

^     ^       ^^^X^^  Xs8o.     (Original.) 

158(157)     Chromatophore  single i59 

159  (160)     Chromatophore  parietal Chlorococcum  Fries. 

^y-  Chromatophore  with  a  circular  opening  and  a  pyrenoid;  zoospores 

^      I    g^  oval,  with  two  cilia,  a  pyrenoid,  and  a  pigment  spot.     Aplanospores 

may'  form  from   non- liberated   zoospores.      An    undescribed   form 

^  which  greatly  resembles  Chlorococcum  has  isogametes.     It  should  be 

Y  placed  in  a  different  genus. 

§  Fig.  190.     Chlorococcum  infusionum  Rabenhorst.    a.  vegetative  cell. 

AS  *•  zoospores.     X  625.     (Original.) 

160  (159)     Chromatophore  central  with  radiating  strands. 

Radiosphaera  Snow. 

"^  /^7\         '^-\  Except  for  the  nature  of  the  chromatophore  this  genus 

\  resembles  Chlorococcum,  but  at  the  center  is  a  pyrenoid 

i^'^'      Q\  from  which  the  chromatophore  radiates.      Zoospores 

If      vt  cs^.            with  two  cilia  and  a  pigment  spot  are  formed. 

A       "^      "^^ 
^        \  l\  y —        Fig.  191.     Radiosphaera  sp.  Snow.    a.  vegetative  cell; 

A  V         I    \        ^  *•  zoospores.     X  580.     (Original.) 

B 

161  (156,  168)     Cells  more  or  less  irregular,  elongated,  or  tubular.  ...     162 

162  (163)     Cells  free,  more  or  less  inflated  or  tubular,  usually  with  a  long, 

colorless  cylindrical  portion Protosiphon  Klebs. 

Chromatophore  a  parietal,  net-like  layer,  with  pyrenoids.  Under  conditions  threatening 
drought,  red  resting  spores  are  formed.  In  absence  of  light  or  mcrease  of  water  bi-ciliated 
zoospores  are  formed  which  on  coming  to  rest  produce  spherical  cells,  or  they  may  copulate  and 
produce  star-shaped  zygospores. 


Fig.  19a.     Protosiphon  botryoides  Klebs.     X  75-     (After  Klebs.) 

163  (162)     Cells  endophytic,  rarely  free,  irregular,  often  with  cellulose  pro- 
jections  164 


THE   FRESH-WATER  ALGAE 


157 


164  (165)     Reproduction   by   zoospores:     chromatophore   of  many  radially- 

placed  rods  or  segments  united  beneath  the  surface. 

Scolinospliacra  Klebs. 
Zoospores  fusiform;    their  production   preceded   by  a 
contraction  of  the  chromatophore  to  the   center,  about 
which  there  is  a  granular  substance;   zoospores  penetrate 
some  water  plant  or  germinate  in  the  water. 

Resting  cells  occur  which  have  one  or  more  thicken- 
ings of  the  membrane. 

It  was  first  found  in  the  dead  leaves  and  branches  of 
Ilypniim,  and  its  normal  habitat  is  probably  in  the 
tissues  of  some  higher  water  plant,  but  it  occurs  fre- 
quently in  the  water  and  may  be  cultivated  with  ease. 
Fig.  193.  Scotinosphaera  paradoxa  Klebs.  X  about  265. 
(After  Klebs.) 

165  (164)     Reproduction  by  copulation  of  isogametes  and  in  some  cases  by 

zoospores 166 

166  (167)     Chromatophore  a  parietal  layer  with  many  pyrenoids,  later  show- 

ing a  network.     Membrane  with  cellulose  projections. 

Chlorochytrium  Cohn. 

Cells  spherical  or  slightly  irregular;  chromatophore 
with  many  inwardly  projecting  portions  containing 
many  pyrenoids.  The  zoospores  are  liberated  singly; 
the  gametes  escape  together  while  still  enveloped  by  the 
inner  lining  to  the  membrane  in  which  they  copulate. 

Chlorochytrium  occurs  in  the  intercellular  spaces  of 
Lemna.  In  some  species  a  cellulose  projection  extends 
to  the  surface  of  the  epidermis  at  the  point  of  penetra- 
tion of  the  zoospores,  but  is  not  found  in  all. 

Fig.  194.    Chlorochytrium  lemnae  Klebs.    Cells  in  the  tissues 
oi  Lemna.     X  500.     (After  Klebs.) 

167  (166)     Chromatophore  dense,  with  many  starch  grains:  membrane  lamel- 

late  Endosphaera  Klebs. 

Cells  spherical  or  irregular,  found  in  the  tissue  of  water  plants. 
In  reproduction  internal  divisions  occur,  giving  rise  to  eight  or  sixteen 
oval  isogametes  with  two  cilia  and  a  pyrenoid.  The  zygospore  {pene- 
trates into  the  intercellular  spaces  of  Patamogetoti  if  it  is  present,  but 
C  dies  if  it  cannot  be  found. 

In  the  spring  time  it  is  found  as  large  resting  cells  in  the  tissues 
of  the  dead  leaves. 


Fig, 


195.     Endosphaera  biennis  Klebs. 
of  gametes,     a.  X  about  190;   b, 


a.  young  cell;   b.  gametes;   c.  union 
.  X  about  400.     (After  Klebs.) 


168  (156,  161)     Cells  with  a  thin  stalk-like  projection  on  one  or  both  ends, 

either  free  or  attached i6q 

169  (170)     Cells  free,  Hnear,  curved,  or  spiral,  ends  with  a  spine  or  stalk-like 

projection Ophiocytium  Niigeli. 

Chromatophore  single,  parietal,  with  no  pyrenoid.  Reproduction  by 
means  of  zoospores,  eight  of  which  are  formed  in  a  single  cell  and  are 
liberated  by  the  end  of  the  cell  being  thrown  oflf  like  a  cap. 

Though  the  habitat  of  Ophiocytium  is  the  same  as  for  a  number  of 
other  Protococcaceae,  it  is  not  so  frequently  found.  When  it  does 
occur,  however,  in  a  body  of  water  it  may  be  abundant. 

Fig.  196.     Ophiocytium  cochleare  A.  Braun.     X  600.     (Original.) 

170  (169)     Cells  similar,  but  shorter  and  attached 171 


158 


FRESH-WATER   BIOLOGY 


171  (172,  173) 


172  (171,  173) 


Cells  single,  attached;    oval,  cylindrical,  fusiform,  or  curved 
in  shape.     Chromatophore  single  and  parietal. 

Ckaracium  A.  Braun. 

Cells  oval,  pointed,  or  rounded  at  the  ends,  straight  or  curved, 
sessile  or  stalked;  attached  to  a  substratum  with  or  without  a  disc. 
A  pyrcnoid  usually  present.  Reproduction  by  zoospores  which  have 
two  cilia,  a  pyrenoid,  and  a  pigment  spot. 

Characium  is  very  common  on  filamentous  algae  in  all  localities.  The 
shape  is  greatly  influenced  by  the  direction  of  the  rays  of  light. 

Fig.  197.     Characium  longipes  Rabenhorst.     X  600.     (Original.) 

Cells  as  in  Characium,  but  the  chlorophyll  in  many  small, 
parietal  discs Characiopsis  Borzi. 

The  color  is  pale  green.  The  zoospores  are  liberated  by  the  wall  of  the 
upper  portion  of  the  cell  becoming  dissolved.  According  to  West,  aplano- 
spores  may  be  formed,  each  of  which  becomes  a  gametangium  and  pro- 
duces two  or  four  gametes.  Characiopsis  is  less  frequent  than  Characium 
but  is  found  under  the  same  conditions. 


Fig. 


Characiopsis  sp.     X  600.     (Original.) 


173  (171,  172) 


174  (132 


Cells  attached,  the  new  generation  clustered  at  the  free  tip  of 
the  empty  mother  cell Sciadium  A.  Braun. 

Thallus  of  six  to  eight  cylindrical  cells,  radiating  from  the  tip  of 
a  sessile,  empty,  cylindrical  membrane;  reproduction  by  six  to  eight 
zoospxjres  with  two  cilia  each,  which  attach  themselves  at  the  tip  of 
the  mother-membrane  after  the  removal  of  a  cap  which  liberates  the 
spores. 

Lemmermann  unites  Sciadium  with  Ophiocytium  because  rarely  in 
Ophiocytium  the  new  generation  develops  from  one  end  of  the  parent 
cell,  but  the  sessile  characteristic  and  the  basal  disc  of  Sciadium 
would  seem  to  separate  it  from  Ophiocytium  where  these  characteris- 
tics are  not  found. 


Fig.  199.     Sciadium  arbuscida  K.'BraMn.     X  600.     (After  Rabenhorst.) 

Reproduction  by  fission  and  by  zoospores. 

Family  Chlorosphaeraceae. 
Only  one  genus  known Chlorosphaera  Klebs. 

Cells  usually  in  small  cell  complexes,  originating  by  fission  in 
three  directions.  Chromatophore  parietal,  with  a  pyrenoid.  Zoo- 
spores usually  eight  in  number,  originating  by  successivelnternal 
divisions.  These  have  two  cilia  and  a  pigment  spot.  Each  vegeta- 
tive cell  may  become  a  resting  spore. 

In  its  vegetative  state  Chlorosphaera  resembles  greatly  Pleura- 
coccus  vulgaris,  but  it  is  aquatic,  rather  than  aerial.  It  is  a  common 
form  in  ponds  and  lakes,  though  rarely  found  in  such  quantities  as 
to  be  noticed,  unless  developed  in  culture. 


Fig. 


Chlorosphaera  lacustris  Snow.     X  585.     (Original.) 


175  (90,  95,  131)     Cells  without  a  gelatinous  envelop  or  stalks;  closely  united 

to  form  structures  of  definite  shape  (coenobia) .    ...      176 

176  (187)     Coenobium  usually  a  cluster  of  definite  shape  and  structure,  formed 

by  the  union  of  four,   eight,  sixteen,  or  thirty-two  non- 
motile  cells  arising  from  internal  division. 

Family  Coelastraceae.   .    ,      177 

177  (182,  186)     Cells  radially  placed  or  forming  close  clusters 178 


THE    FRESH-WATER   ALGAE 


159 


178  (179,  180,  181)     Cells  spherical Coelastrum  Nageli. 

Cells  spherical  or  slightly  angled;  chromatophore  a  hollow  sphere,  open 
at  one  side,  with  a  pyrenoid  opposite  the  opening. 

Coelastrum  occurs  in  all  bodies  of  water,  and  is  found  in  the  plankton. 
It  is  very  resistant  to  unfavorable  conditions,  persisting  long  after  most 
other  algae  have  perished. 

Fig.  201.    Coelastrum  sphaericumK?iigi:]i.     X  020.     (Original.) 

(178,  180,  181)     Cells  cordate  or  reniform Sorastrum  Kutzing. 

Chloroplast  parietal,  with  a  single  pyrenoid.  Cells  on  short  stalks 
radiating  from  a  gelatinous  center,  but  both  center  and  stalks  usually 
hidden  by  the  cells.     A  new  coenobium  from  each  cell. 

Sorastrum  is  of  less  frequent  occurrence  than  most  of  the  other 
members  of  the  Coclastraceac,  but  is  found  in  most  localities  where 
they  are  found,  especially  in  the  sediment  at  the  bottom  of  ponds, 
and  occasionally  in  the  plankton. 

Fig.  202.    Sorastrum  spinulosum  Nageli.     X  600.     (Original.) 

180  (178,  179,  181)     Cells  crescent-shaped,  points  turned  outward. 

Selenastnim  Reinsch, 

Cells  acutely  pointed.     Chromatophore  parietal,  with  no  pyrenoid.     By  many 
this  is  placed  near  to  Ankistrodesmus  rather  than  with  the  Coclastraceac. 

Fig.  203.     Selenastrum  gracile  Reinsch.     X  565-     (Original.) 

181  (178,  179,  180)     Cells  club-shaped  or  elongated,  forming  a  star. 

Actinastrum  Lagerheim. 

Rays  pointed,  each  ray  composed  of  a  single  cell,  all  of  which  unite  at  the  center. 
Chromatophore  single,  parietal,  often  not  extending  to  the  ends. 

Fig.  204.     Actinastrum  hantzschii  Lagerheim.     X  SSO.     (Original.) 


182  (177,  186)     Cells  in  one  plane. 


^83 


183  (184,  185)     Cells  four,  eight,  or  sixteen  in  one  or  two  parallel  or  zigzag 
rows Scenedesmus  IMeyen. 


The  cells  oval  or  pointed,  the  membrane  either  smooth  or 
furnished  with  distinct  spines  at  the  ends.  Chromatophore 
single,  parietal,  with  an  opening  at  one  side  and  a  pyrenoid. 

This  is  one  of  the  most  common  and  the  best  known  of 
all  of  the  lower  algae,  it  being  found  in  almost  all  localities 
where  algae  are  ever  found.  Its  adaptation  to  various 
environments,  and  to  conditions  unfavorable  to  most  other 
algae,  accounts  for  its  wide  distribution. 

Fig.  205.   Scenedesmus  quadricauda  Br6b.  X  585-   (Original.) 


184  (183,  185)     Cells  grouped  in  fours,  forming  a  rectangular  plate  of  sixteen 
or  more  cells Criicigcnia  IMorrcn. 

Cells  spherical  or  elongated.     Chromatophore  thin,  parietal,  with  a  circular 
opening  and   one   pyrenoid.     This   is   regarded    by    Schmidle   as  Staurogema. 

Fig.  206.    Crucigenia  apiculata  Chodat.     X  1000.     (Origin*!.) 


i6o 


FRESH-WATER   BIOLOGY 


185  (183,  184)     Cells  four  together,  never  forming  larger  plates.     From  two  to 

five  spines  on  the  external  margin  of  each  cell. 

Tetrastriim  Chodat. 
Schmidle  regards  those  forms  with  spines  simply  as  different  species  of  Staurogenia. 

186  (182,  177)     Cells  four,  lying  in  two  planes Tdradesmus  Smith. 

^^HZi^JSH^Sr^^^         This  coenobium  resembles  a  Sccnedesmus  rolled  up,  and  in  the  size,  shape, 
:,^:-:^j^     and  structure  of  the  cells  they  are  the  same. 
*  ®     -^  Pjc   207.     Tetradesmus  wisconsiensis  Smith.     X  1500.     (After  Smith.) 


187  (176) 


188  (189) 


189  (ll 


Coenobium  a  coarse  net  or  a  concentrically-arranged  circular  disc  of 
cells,  formed  by  the  joining  together  of  zoospores  while  within 
the  mother-membrane,  or  still  within  the  liberated  inner 
lining  of  the  same.  .    .    Family  Hydrodictyaceae  .    .      i88 

Coenobium  a  free-swimming  circular  plate  of  cells,  one  layer  in 
thickness Pediastrum  Meyen. 

The  cells  arranged  either  with  intercellular  spaces  or  not;  marginal 
cells  with  one  or  two  pointed  projections;  inner  cells  angled  or  concave; 
chromatophore  parietal,  with  one  pyrenoid,  and  perforated  at  one  side. 
Reproduction  b}'  means  of  zoospores  which  are  Cast  out  together  with 
the  inner  lining  of  the  mother-membrane,  and  within  which  they  form 
a  new  coenobium. 

An  alga  which  greatly  resembles  a  two-celled  Pediastrum  was  formerly 
described  as  Euaslrum  by  Schmidle,  but  Lagerheim  places  it  in  a  new 
genus  Euaslropsis.  The  mode  of  reproduction  is  the  same  as  for  Pedi- 
aslriim;  the  zoospores,  however,  arrange  themselves  in  pairs  instead  of 
in  a  single  plate,  and  form  a  number  of  new  individuals  which  are  set 
free  while  within  the  inner  layer  of  the  mother-membrane. 

Fig.  208.     Pediastrum  boryanum  Meneghini.     X  600.     (Original.) 

Coenobium  a  coarse  net Hydrodictyon  Roth. 

Nets  large,  each  mesh  bounded  by  five  or  six 
cyhndrical  cells;  the  chromatophore  reticulate, 
parietal,  with  numerous  pyrenoids;  asexual  re- 
production by  zoospores,  those  from  each  cell 
forming  a  new  net;  sexual  reproduction  by 
many  isogametes.  The  zygospore  produces 
two  to  five  large  zoospores  which  in  turn  give 
rise  to  a  new  net  when  they  germinate. 

In  the  early  stages  the  nucleus  is  single,  but 
later  divides  rapidly  so  that  the  cell  is  multi- 
nucleate. As  the  nets  are  formed  within  the 
cyhndrical  mother-membrane  they  are  cylin- 
drical in  shape  for  some  time,  but  later  become 
torn  and  irregular.  The  nets  occur  as  a  very 
thick  light  green  scum  on  the  surface  of  ponds 
exposed  to  the  direct  rays  of  the  sun.  The  dif- 
ferent modes  of  reproduction  have  been  proved 
by  Klebs  to  depend  largely  on  the  condition  in 
environment,  and  that  by  varying  these  condi- 
ditions  the  different  phases  to  development  can 
be  produced. 


Fig.  209. 


Hydrodictyon  reticulatum  Lagerheim. 
X  100.     (Original.) 


190  (68,  249)     Plant  of  septate  filaments,  or  of  closely-arranged  cells,  forming 

plates  or  cylinders,  one  or  more  layers  thick;  attached  or 

free-swimming Order  Confervales  .    .      191 

Reproduction  asexual,  sexual,  or  both  in  the  same  species. 

191  (196,  246)     Plant  in  adult  form  a  macroscopic,  free-swimming  plate  or 

hollow  cyhnder  of  cells;  in  early  stages  often  filamentous 
and  attached Family  Ulvaceae  .    .     192 


THE   FRESH-WATER  ALGAE 


l6l 


:92  (193)     Plant  cylindrical,  flattened,  or  branched,  of  a  simple  layer  of  cells, 
reproduction  by  zoospores  and  isogametes. 

Enteromorpha  Link. 


^ 


Frequently  branched  and  variable  in  shape;  chromatophore 
parietal,  with  one  pyrenoid.  Zoospores  with  four  cilia  and  a 
pigment  spot.     Gametes  with  two  cilia. 

Both  zoospores  and  gametes  are  formed  in  the  vegetative 
cells  except  those  at  the  base. 

The  greater  number  of  species  of  Enteromorpha  are  marine, 
though  E.  intestinalis  is  found  in  the  fresh  water.  Many  of 
the  salt-water  forms  are  very  variable  so  that  the  species  are 
difl&cult  to  determine. 


Fig.  210.      Enteromorpha  intestinalis  L.  (Link),     a.  one-half  natural 
size.     (After  West.)    ft.  X  360.     (Original.) 


A  B 

193  (192)     Plant  in  the  adult  stage  a  thin,  membranaceous  plate.    ...     194 

194  (195)     Chromatophore  a  thin,  parietal  lining  to  the  membrane,  with  one 

pyrenoid Monostroma  Wittrock. 

The  plant  in  early  stages  a  hollow  sack  or  cylinder,  becoming 
torn  later,  forming  a  membranaceous  plate,  near  the  base  of 
which  certain  cells  elongate,  grow  downward  and  form  strength- 
ening supports.  Reproduction  by  means  of  zoospores  with  four 
cilia  and  smaller  gametes  with  two  cilia.  These  may  germinate 
without  copulation. 

The  membrane  is  at  first  very  thin,  but  later  becomes  gelati- 
nous so  that  the  cells  are  more  or  less  separated  from  each  other. 
Growth  is  not  localized  but  is  intercalary  and  the  cells  are  often 
clustered  in  groups  of  four. 

Monostroma  hullosum  occurs  in  shallow  ditches,  partially  sub- 
merged and  partially  swimming  on  the  surface. 

Fig.  211.     Monostroma  bullosumThMrtt.     X  3SO.     (After  Reinke.) 

[95  (194)     Chloroplast  star-shaped,  radiating  from  the  center,  with  one  pyre- 
noid  Prasiola  Meneghini. 

Plant  at  first  filamentous,  but  later  a  plate  of  cells  grouped  in 
small  areas.  Rhizoids  frequent  at  the  base.  Reproduction,  ac- 
cording to  Lagerheim,  in  three  ways:  by  isolated  iwrtions  of  the 
plant,  akinetes,  and  aplanospores.     No  zoospores  known. 

Kiitzing  has  estabHshed  a  genus  Schizogonium  which  greatly  re- 
sembles Prasiola.  The  chromatophore  is  stellate  and  the  filarnents 
divide  longitudinally  to  form  two  or  more  rows.  The  chief  differ- 
ence between  this  and  Prasiola  is  that  in  the  latter  genus  the 
longitudinal  divisions  continue,  while  in  the  former  they  cease 
after  the  first  few  times. 

Wille  makes  Schizogonium  a  subsection  under  Prasiola  and  is 
followed  in  this  by  West. 

Fig.  212.    Prasiola  crispa  Mtntghxm.     X  about  50.     (After  Oltmann 
and  Meneghini.) 

196  (191,  246)     Plant  filamentous i07 

197  (219)     Filaments  fine,  mostly  unbranched 198 

198  (217,  218)     Filaments   generally  unbranched.      Chromatophore  a  single. 

parietal  curved  plate  or  cyhnder,  rarely  a.xial,  or  of  several 

small,  distinct  discs,  rarely  more  or  less  united  into  a  network. 

Family  Ulothrichaceae  .    .     199 


I 


1 62  FRESH-WATER   BIOLOGY 

199  (211,  212,  213)     Thcchromatophoresingle,  a  parietal  plate  or  cylinder.  200 

200  (205)     Filaments  without  gelatinous  envelop 201 

201  (204)     Filament  always  simple,  composed  of  a  single  row  of  cells.   .  202 

202  (203)     Cells  cylindrical.     Reproduction  by  zoospores  and  in  some  cases 

by  resting  spores Hormidium  Kutzing. 


Zoospores   formed   singly  in   each  cell;  they  have  two  cilia  but  no  pig- 
ment spot.     Resting  spores  occur  with  reduction  of  moisture. 


Fig.  213,     Bormidium  nitenz  Meneghini.     X  400.     (Original.) 


203  (202)     Cells  but  little  longer  than  broad.     Reproduction  by  zoospores 
and  isogametes.   ' Ulothrix  Kutzing. 


Cells  relatively  short;  chromatophore  lining  the  entire 
rnembrane,  or  only  a  part,  with  a  pyrenoid.  Reproduc- 
tion by  zoospores  and  isogametes.  Zoospores  with  four 
cilia  and  a  pigment  spot;  gametes  smaller,  with  two  cilia, 
capable  of  germinating  without  copulation. 

Ulothrix  occurs  frequently  among  other  algae  in  ponds, 
lakes,  and  watering  troughs,  though  not  often  in  great 
quantities. 

The  resemblance  to  Hormidium  is  great,  though  the 
species  of  the  latter  genus  are  apt  to  be  somewhat  smaller, 
and  the  length  of  the  cells  relatively  longer  in  proportion  to 
the  breadth. 

Ulothrix  yields  readily  to  cultivation,  and  different  phases 
of  its  development  may  be  controlled  by  changes  in  the 
environment. 


Fig.  214.     Ulothrix  zonata  Kutzing;  a.  vegetative  filament.   X 
225.  6.  macrozoospore.    X388.    c.  microzoospore.    (After  Klebs.) 


204  (201)    Filament  at  first  simple,  later  becoming  a  solid  mass  of  many  cells. 

Schizomeris  Kutzing. 


THE   FRESH-WATER  ALGAE 


163 


Plant  in  early  stages  like  Ulothrix.  later  forming 
a  slender,  solid  parenchymatous  filament;  reproduc- 
tion by  zoospores,  one  from  each  cell 

Quantities  of  the  zoospores  are  liberated  from  a 
filament  at  a  time,  the  walls  becoming  partially  gelat- 
inous, but  showing  a  parenchymatous  structure  after 
the  liberation. 

By  some  European  writers  the  genus  is  regarded  as 
the  same  as  Ulothrix,  but  forms  such  as  are  found  in 
America  must  establish  it  as  a  separate  genus.  The 
zoospores  have  four  cilia  and  a  pigment  spot,  as  in 
Ulothrix;  the  vegetative  cells  may  change  into  resting 
spores. 

Schizomeris  has  been  found  growing  on  river  banks 
and  in  quiet  fresh  water. 


Fig.  215.  Schizomeris  leibleinii  Kiitzing.  a.  portion  of 
filament.  X  about  625.  b.  portion  of  filament  showing 
division  in  all  directions.  X  3°°-  c.  zoospores.  X  625. 
(Original.) 


205  (200)     Filament  with  gelatinous  envelop 206 

206  (209)     Cells  not  in  distinct  pairs 207 

207  (208)     Cells  oval,  gelatinous  envelop  homogenous. 

Hormospora  Brebisson. 

^  This  is  regarded  by  many  as  being  but  a 

phase  in  the  development  of  Ulothrix,  but  the 
very  gelatinous  membrane,  the  rounded  ends 
of  the  cells,  and  the  fact  that  this  form  is  not 
known  to  reproduce  by  zoospores  would  indi- 
FiG.  216.  Hormospora  mutabilisBT€hisson.  X  about  cate  that  it  is  an  independent  genus. 
600.      (Original.) 

208  (207)     Cells  rounded.     Gelatinous  sheath  showing  radial  fibrillar  struc- 

ture  Radiofiluyn  Schmidle. 

Chromatophore  single,  parietal,  with  one  pyrenoid. 
Cells  spherical,  ellipsoidal,  or  lenticular,  in  some 
species  united  by  short  necks.  Filaments  unbranched. 
Reproduction  by  simple  division.  Wille  includes 
Hormospora  and  Radiofilum  with  Geminella,  a  genus 
not  known  to  occur  in  America. 

209  (206)     Cells  mostly  in  pairs -^° 

210  (211)     Cells  rounded,   gelatinous  substance  lamellate,  invested  by  the 

antecedent  mother-membrane.    .    .    .  Binuclearia  Wittrock. 
Filaments  attached  when  young;  each  cell  pair 
originates  from  the  contents  of  a  single  cell,  and  is 
surrounded  by  a  more  or  less  lamellate  substance, 
about  which  the  original  membrane  is  still  visible. 
Chromatophore  parietal,  reproduction  by  division 
and  akinetes. 
Fig.  218.     Binuclearia  telrana  Wittrock.    X  about  450. 
(Original.) 

211  (199,  212,  213)     Chromatophore  axial,  with  rounded  clear  spaces  at  each 

end Phinktoncma  Schmidk'. 

Filaments  short,  free-swimming.  Cells  cylindrical,  rounded  at  the  ends,  mostly  in  pairs, 
each  pair  separated  from  the  next  by  an  apparently  empty  space.  Reproduction  by  division 
within  the  membrane  after  which  the  parts  become  separated,  probably  by  a  gelatinous  sub- 
stance. 


Fig. 


217.      Radiofilum  flavescens  West. 
X  300.     (After  West.) 


164 


FRESH-WATER  BIOLOGY 


Planktonema  resembles  in  many  respects  the  form  described  by  Wittrock  as  Binuclearia  but 
Schmidle  makes  it  a  new  genus.  The  two  genera  should  be  made  the  subject  for  further  in- 
vestigation. 

^___   _  ^  .        ,,    _,  .-    I     .. — 7rr-,r--_  Fig.  219.     Planktonema  lauter- 

(r^^nZsB^±L-i h^'^Q^^  "■  Q    O^^Tr^r:?-- — ,^_ _^_       homii  Schmidle.     X  about  1000. 

^^"^--^g^  g.^^.-W'-^lIII       (After  Schmidle.) 

212  (199,  211,  213)   Chromatophore  a  parietal  network.    Microspora  Lagerheim. 

Chromatophores  band-like  or  netted  and  thickened  at  intervals; 
membrane  often  becoming  fraii;mcntcd  into  ll-shaped  pieces.  Repro- 
duction by  macrozoospores  and  microzoospores. 

Filaments  free,  unbranched;  sometimes  resembling  Conferva.  Mem- 
brane thick,  somewhat  gelatinous,  and  distinctly  made  up  of  H-shaped 
pieces,  the  ends  of  the  H  either  just  meeting  or  overlapping.  Reproduc- 
tion by  macrozoospores  with  four  cilia,  and  microzoospores  with  two  cilia. 

Chromatophores  many,  parietal,  disc-shaped.  Filaments 
fine,  unbranched,  rarely  {Aeronemmn)  branched.  Repro- 
duction by  mono-ciliate  zoospores 214 

Filaments  unbranched,  at  first  attached:  no  pyrenoids. 

Trihonema  Derbes  and  Solier. 

Filaments  light  green,  soft  to  the  touch.  Length  of  cells  one  to  several  times  the 
breadth,' sometimes  shghtly  swollen  at  the  middle.     Chromatophores  from  two  to  many,  small, 

parietal.  Reproduction  by  zoospores,  one  or  two  of 
which  are  formed  in  a  cell  and  liberated  by  the 
membrane  falling  into  H-shaped  pieces.  Zoospores 
obovate,  asymmetrical,  with  two  chromatophores  in 
the  anterior  part,  one  ciUum,  and  no  pigment  spot. 
Resting  cells  may  occur. 

Structure  of  cells  and  zoospores  as  in  Trihonema;  filaments 
composed  of  segments  of  4  to  8  cells;  each  formed  from  the 
contents  of  a  single  vegetative  cell,  the  ruptured  wall  of 
which  is  visible  at  the  end  of  the  segment.     Division  rarely 

longitudinal Bumilleria  Borzi. 

Filaments  usually  short.  Zoospores  the  same  as  in  Trihonema,  but  liberated  through  a  dis- 
solved p>ortion  of  the  membrane,  instead  of  through  a  circular  split  dividing  the  membrane  into 
two  portions.     Resting  cells  may  be  formed. 


Fig.  220.  Microspora 
amaena  Lagerheim. 
X  345-     (After  West.) 

213  (199,  211,   212) 


214  (215,  216) 


Fig. 


221.     Tribonema    minor   Klebs. 
(Original.) 


X800. 
215  (214,  216) 


Fig.  232.  Bumilleria 
sicula  Borzi.  X  about 
330.     (After  Borzi.) 


216  (214,  215) 


Structure  of  cells  and  zoospores  as  in  Trihonema.  Filaments 
minute,  richly  branched,  easily  passing  into  a  unicellular 
condition Aeronemmn  Snow. 


Chromatophores  pale,  sev- 
eral in  a  cell,  without  pyrenoids 
and  olosely  applied  to  the  mem- 
brane. Reproduction  by  zoo- 
spores which  have  a  single  cili- 
um,  a  small  chromatophore,  and 
a  pigment  spot.  They  move 
with  an  amoeboid  motion.  This 
may  be  the  same  as  Monocilia 
Gemeck,  though  the  branching 
is  much  more  abundant  than 
is  described  in  that  form. 


Fig.  223.     Aeronemum  polymor- 
phum  Snow.     X  225.     (Original.) 


THE   FRESH-WATER   ALGAE 


l6 


217  (198,  218)  Plants  of  unbranched,  free-swimming,  more  or  less  gelatinous 
filaments,  the  cells  very  long;  chlorophyll  parietal  and  sur- 
rounding a  number  of  large  conspicuous  vacuoles  which 
show  as  a  row  of  lighter  areas;  pyrenoids  numerous.  Re- 
production by  heterogametes. 

Family  Sphaeropleaceae. 
Only  one  genus  known Sphaeroplea  Agardh. 


Fig.  224 


Sphaeroplea  annulina   Agardh. 
(After  Rauvvenhofl.) 


II33- 


Cells  cylindrical,  tapering;  length 
eight  to  twenty  times  the  breadth, 
several  nuclei  present.  Oogonia  and 
antheridia  formed  from  vegetative  cells, 
the  oogonia  containing  many  oospheres, 
and  the  antheridia  a  very  large  number 
of  antherozoids  with  two  cilia;  these  are 
liberated  through  holes  in  the  mem- 
brane and  enter  the  oogonia  through 
similar  holes;  the  oospores  are  red  and 
have  a  thick,  rough  membrane.  On 
germination  each  produces  one  to  eight 
zoospores  with  a  pigment  spot  and 
two  cilia.  Spores  may  be  produced 
parthenogenetically. 


218  (198,  217)  Plants  of  unbranched,  more  or  less  gelatinous,  filaments, 
attached  in  early  stages;  cells  short,  cylindrical,  or  swollen; 
chromatophore  single,  parietal,  with  one  pyrenoid.  Repro- 
duction by  means  of  zoospores  with  two  cilia  and  by  hetero- 
gametes  Family  Cylindrocapsaceae. 

Only  one  genus  known Cylindrocapsa  Reinsch. 


Reproduction  asexual  and  sexual;  asex- 
ual, by  zoospores  and  akinetes;  sexual,  by 
means  of  oogonia,  each  with  one  oospore, 
and  antheridia,  each  with  two  anthero- 
zoids; oospore  red  in  color. 

This  is  a  very  rare  alga  though  it  is 
reported  by  Collins  as  occurring  in  Massa- 
chusetts and  by  WoUe  as  occurring  from 
New  York  to  Florida. 

Fig.  225.  Cylindrocapsa  involuta  Reinsch. 
a.  vegetative  filament;  h.  formation  of  anthero- 
zoids; c.  oogonium  with  antherozoids.  X  575- 
(After  Cienkowski.) 


219(197)     Filaments  coarser,  mostly  branched 220 

220  (233)     Chromatophore  with  irregular,  linear,  or  net-like  perforations.     221 
221(230)     Zoospores  biciliate Family  Cladophoraceae  .    .     222 

Filaments  mostly  branched,  harsh  to  the  touch,  generally  attached;   chromatophore  parietal, 
with  irregular,  net-like  perforations;   contents  granular;   numerous  pyrenoids.   Nuclei  many. 

22  2  (223)     Filaments  never  branched  except  at  the  attachment. 

Chactomorpha  Kiitzing. 

Filaments  attached  by  a  branched,  rhizoid-like  organ.    Reproduction  by  means  of  zoospores. 
The  species  of  this  genus  are  mostly  marine. 

224 


223  (222)     Filaments  usually  branched. 


i66 


FRESH-WATER   BIOLOGY 


224  (227)     Branches  abundant 225 

225  (226)     Plants  large,  tufted;  reproduction  by  zoospores.  Cladophora  Kiitziag. 


Plant  frequently  ver\'  large;  diameter  of  the  filaments 
much  greater  at  the  base  than  at  the  ends;  the  length  of  the 
cells  one  to  twenty  times  the  diameter;  reproduction  by 
zoospores,  many  being  formed  from  a  vegetative  cell;  these 
with  two  or  four  cilia. 

The  number  of  species  of  Cladophora  is  very  large,  and 
they  are  found  in  fresh,  brackish,  and  salt  water,  but  prob- 
ably in  the  greatest  abundance  along  the  shores  of  lakes 
where  they  are  constantly  washed  by  the  waves.  Some 
species  are  believed  to  be  annual  and  some  perennial. 


Fig.  226.     Cladophora  glomerata  Kutzing.      X  85.     (Original.) 


226  (225)     Plant  forming  pulvinate  coatings,  cells  of  two  kinds,  one  light  and 

one  dark Chlorotyliiim  Kutzing. 

Plant  of  erect,  branching,  parallel  filaments,  forming  firm,  dense  tufts  imbedded  in  a  gelatinous 
mass.     In  each  filament  several  cells  with  dense  chlorophyll  alternate  with  longer  ones  contain- 
ing less  chlorophyll,  thus  giving  a  concentric  arrange- 
ment of  light  and  dark. 

Chromatophore  band-shaped,  asexual  reproduction  by 
Fig.  227.   Chlorotylium  cataractarum       biciliate  zoospores  which  are  formed  in  great  numbers 
Rabenhorst.     X  150.      (After  Raben-       in  each  zoosporagium.     Akinetes  are  also  formed, 
horst.) 

227  (224)     Branches  not  frequent,  rarely  wanting 228 

228  (229)     Branches  long,  scattered;   reproduction  by  resting  spores. 

Pithophora  Wittrock. 
Cells  long,  cylindrical;   akinetes  formed 
^-v--*^^,^^    ^/i\^^M  by  the  end  of  a  cell  being  separated  by  a 


membrane,  the  contents  becoming  much 
thicker  and  darker,  while  the  membrane 
increases  in  thickness  and  the  whole  be- 
comes swollen  in  the  middle. 


Fig.  228.  Pithophora  kewen%is'^\\.\.TO(^.  a. 
vegetative  filament;  h.  formation  of  resting 
npore      X  140.     (After  Wittrock.) 

229  (228)     Branches    short,    attenuated,    infrequent     sometimes   rhizoid-like, 
sometimes  lacking  altogether.     .    .     Rhizoclonium  Kutzing. 

Filaments  attached,  often  curved 
and  matted,  usually  with  short  infre- 
quent branches  which  consist  of  one 
or  more  cells,  sometimes  resembling 
rhizoids.     Cell  walls  lamellose. 

Chromatophore    netted,    with    sev- 
eral pyrenoids.      Nuclei  several      Re- 
production    by      biciliate    zoospores 
and  by  akinetes.     Sometimes  occur- 
Rhizoclonium  hieroglyphicum  Kutzing.      X  300.        ring  on  damp  ground. 
(Original.) 


THE  FRESH-WATER  ALGAE 


167 


230  (221)     Zoospores  with  a  circle  of  cilia  near  the  smaller  end. 

Family  Oedogoniaceae   .    .     231 

Plants  of  branched  or  unbranched  filaments,  attached  in  early  stages;   chromatophore  with 

irregular,  linear,  or  net-like  perforations  and  several  pyrenoids;   memlirane  often  with  transverse 

striations  at  one  end  of  a  cell.     Reproduction  by  means  of  zoospores  with  a  circle  of  ciha  near 

the  smaller  end  and  by  heterogametes. 

231  (232)     Plant  not  branched Oedogonium  Link. 

■*i  .... 

Plants  either  monoecious  or  dioecious;  in  the 
latter  case  the  filaments  bearing  antheridia  may 
be  normal  filaments,  or  tiny  filaments  of  single 
cells  called  dwarf  males,  attached  near  the  oogonia. 
These  originate  from  special  small  zoospores  called 
androsporcs.  But  one  oosphere  in  an  oogonium; 
the  spermatozoid  enters  through  a  perforation 
in  the  wall  or  through  an  opening  caused  by  the 
throwing  off  of  a  cap;  antheridia  single  or  many 
together,  each  containing  one  or  two  antherozoids; 
oospore  brown  or  red.  Asexual  reproduction  by 
zoospores  borne  singly  in  vegetative  cells;  they 
have  a  crown  of  cilia  about  a  colorless  spot  at  the 
anterior  end. 

Oedogonium  occurs  in  almost  all  bodies  of 
water  and  several  species  are  usually  found 
together. 


Fig.   230.    Oedogonium  crenulalo-cosiatum  Wittrock. 

a.  oospore.     X  about   600.    b.  Oedogonium  sp.,  vege- 
tative filament,   c.  division,  .d.  formation  of  antheridia. 

b,  c,  d.  X  about  520.     (Original.) 


232  (231)     Plant  branched 


Bulhochaete  Agardh. 


Most  of  the  cells  bear- 
ing a  long  colorless  hair, 
swollen  at  the  base. 
Reproduction  as  \nOedo- 
gonium;  the  dwarf  males 
ver>'  frequent. 

Though  not  so  com- 
mon as  Oedogonium  it 
is  found  all  over  the 
world  and  sometimes 
occurs  in  great  quanti- 
ties, completely  cover- 
ing submerged  higher 
plants  with  a  feathery 
coating. 

Small  branches  which 
have  been  detached  are 
also  often  found  among 
other  algae. 


Fig.  231.  Bulbochiute 
mirabilis  '  Wittrock.  a. 
Plant  with  oospore,  b. 
dwarf  male  on  oospore. 
c.  zoospores.  X  200. 
(Original.) 


i68 


FRESH-WATER   BIOLOGY 


Chromatophore  a  single  equatorial  band,  with  one  pyrenoid.  Fila- 
ments branched,  attached,  frequently  with  a  gelatinous  cov- 
ering.    Reproduction  by  zoospores  and  isogametes. 

Family  Chaetophoraceae  .    .     234 

The  zoosporangia  of  the  same  form  as  the  vegetative  cells;  the 
larger  species  usually  bearing  long  hairs. 

Subfamily  Chaetophoreae   .    .     235 

Plant  attached,  differentiated  into  base  and  apex 236 

Filaments  imbedded  in  a  firm,  gelatinous  matrix,  forming  a 
spherical  or  an  irregularly  branched,  ribbon-liKe  thallus 
attached  at  the  base Chaetophora  Shrank. 

■  Filaments  radiating  from  a  common  center,  usually  terminating  in  a  colorless  hair;   micro- 
zoospores  with  two  cilia  and  a  pigment  spot  near  the  anterior  end;  macrozoospores  also  formed. 


233  (220) 


234  (242; 


235  (239) 

236  (237,  238) 


^-<         4 


Fig.  232.     Chaetophora  pisiformis  Agardh.     X  loo.     (Original.) 

237  (236,  238)  Filaments  not  imbedded  in  a  firm  gelatinous  matrix,  the 
branches  irregularly  placed,  of  the  same  size  as  the  principal 
axis Mymn^ma  Fries. 


Plant  either  several  centimeters  long,  at- 
tached, or  verj'  minute  and  free,  often  passing 
into  a  palmella  condition.  Sexual  reproduc- 
tion by  means  of  isogametes  with  two  cilia 
and  a  pigment  spot;  asexual,  by  zoospores 
with  four  cilia,  and  by  akinetes. 

Myxonema  is  widely  distributed,  the  mi- 
croscopical forms  occurring  almost  univer- 
sally on  mosses  and  liverworts  in  damp  local- 
ities, while  the  larger  forms  are  frequent  in 
running  water.  They  have  been  known  to 
completely  cover  the  beds  of  streams.  The 
smaller  forms  are  microscopical,  and  can  be 
detected  only  after  portions  of  the  mosses 
and  liverworts  are  placed  in  culture  and  the 
Myxonema  allowed  to  develop. 

It  will  then  sometimes  cover  the  top  of  a 
culture  with  a  thin  film  of  minute  plants. 


Fig.  23V  ,  . 
portion  of  branch. 
X285.     (Original.) 


m    lubricum     Kiitzing.    a. 
b.  isogometes.    c.  zoospores. 


5VTQ^oolov^lo.i^v\ 


THE   FRESH-WATER   ALGAE 


169 


238  (236,  237)     Lateral  branches  in  whorls  or  tufts,  smaller  than  the  main 
axis Draparnaldia  Bory. 

Plant  attached  by  a  disc  of  cells.  Terminal  cells  usually  ending  in  a  long,  colorless  hair. 
Reproduction  by  means  of  zoospores  with  four  cilia  and  a  pigment  spot.  No  fertilization 
known. 

In  Draparnaldia  the  photosynthesis  takes  place  principally  in  the  tufted  branches,  as  the 
chloroplast  of  the  principal  axis  is  reduced  to  a  small,  equatorial  band  in  each  cell. 

All  forms  of  Draparnaldia  are  large  and  are  found  in  much  the  same  localities  as  the  larger 
forms  of  Myxonema. 


Fig.  234.     Draparnaldia  plumosa  Agardh.    X  about  50.     (Original.) 


239  (235)     Plant  epiphytic  adhering  throughout  to  other  plants. 


240 


240  (241)     Plant  01  irregularly  branched  filaments,  setae  or  hairs  not  abundant. 

Herposteiron  Nageh. 


Plant  small,  cells  with  a  parietal  chromatophore,  a 
pyrenoid,  and  frequently  a  long  colorless  hair;  re- 
production by  means  of  egg-shaped  zoospores,  with 
four  cilia  and  a  pigment  spot,  two  spores  being  formed 
in  a  single  cell. 


This  is  of  frequent  occurrence  on  other  filamentous 
algae  but  usually  occurs  only  as  small  isolated  in- 
dividuals. 

It  has  long  been  included  under  the  name  of 
Aphanochacte,  but  the  name  Herposteiron  seems  to 
have  priority. 


Fig.  235.    Herposteiron  confervicola  Nageli.     X  450.     (After  Hazcn.) 


170 


FRESH-WATER   BIOLOGY 


241  (240)     Individual  cells  flask-shaped,  each  with  a  long  slender  hair  from 

the  smaller  portion Chaetospliaeridiiwi  Klebahn. 

Chromatophore 
parietal,  with  one 
pyrenoid.  Repro- 
duction by  zoo- 
spores, four  of 
which  are  produced 
in  a  cell.  Horizon- 
tal divisions  of  the 
cells  also  occurs, 
the  lower  of  the 
daughter  cells  pass- 
ing gradually  to  the 
side  of  the  upper 
one. 

Chaelosphacridium 
is  widely  distrib- 
uted in  the  United 
States  though 
rarely  occurring  in 
quantities  exceed- 
ing a  few  cells  at  a 
time. 
These  are  usu- 
._  ally  attached  to  fil- 
amentous algae  and 
are  inconspicuous, 
though  the  long 
setae  are  usually 
somewhat  promi- 
nent 

Fig.  236.     Chaetosphaeridium  pringsheitnii  Klebahn.     X  about  425.     (After  Hazen.) 

242  (234)     The  zoosporangia  different  from  the  vegetative  cells. 

Subfamily  Chroolepideae   .    .     24^ 

243  (244,  245)     Plant  minute,    tree-like   in   its   branching;     reproduction  bj 

zoospores Microthamnion  Nageli 

Branches  from  the  upper  end  of  a  cell  and  not  sepa 
rated  by  a  membrane;  obtuse  at  the  tip;  color  pale 
chromatophore  a  parietal  band  with  no  pyrenoid.  Zoo- 
spores formed  in  zoosporangia  at  the  ends  of  filaments 


Fig.  237- 


Microthamnion  kulzingianum  Nageli. 
(Original.) 


X600. 


244  (243,  245) 


Plant  coarse,  irregularly  branched,  partly  erect  and  partl> 
creeping  on  stones  and  trees;  when  aerial,  often  colored  rec 
by  haematochrome.  Membrane  thick;  reproduction  b} 
zoospores  and  gametes Trentepohlia  Martius 

Chromatophores  many,  irregular  discs,  without  pyre 
noids;  gameLangia  and  zoosporangia  mostly  terminal 
gametes  and  zoospores  similar,  being  egg-shaped,  wit! 
two  cilia  and  haematochrome,  but  no  definite  pigmen 
spot.     A  palmella  condition  may  occur. 

These  are  sometimes  referred  to  as  the  aerial  algat 
because  they  e.xist  principally  in  the  air  and  form  oftei 
bright-colored  incrustations  on  the  bark  of  trees  am 
stones.  They  are  not  infrequently  found  in  connectioi 
with  lichen  fungi. 

As  the  Trentepohlias  are  principally  aerial,  the  lib 
eration  of  the  zoospores  and  gametes  can  occur  only  a 
the  time  of  a  rain  or  in  the  presence  of  a  heavy  dew. 

Fig.  238.      Trentepohlia  wainoi  Hariot.     X  125.      (After 
Collins  and  Hariot.) 


THE  FRESH-WATER  ALGAE 


171 


245  (243,  244)  Structure  as  in  Trentepohlia  but  many  of  the  cells  having 
setae Nylandera  Hariot. 

,.     =    ..     ..===ss;='  There  is  but  one  species  of  this  genus  described,  and  the  only 

point  of  distinction  between  this  and  Trentepohlia  is  the  rather 
coarse  and  unsegmented  setae. 

Fig.  239.    Nylandera  tentaculata  Hariot.     X  140.     (After  Hariot.) 

246(191,196)     Plant  an  attached  disc 247 

247  (248)  Plant  a  small,  attached  disc  or  cushion  of  cells,  made  up  of  radiating 
rows  of  cells  either  separate  or  grown  together,  bearing  on 
the  surface  long  sheathed  hairs.  Reproduction  by  means 
of  zoospores  and  by  heterogametes. 

Family  Coleochaetaceae. 

Only  one  genus Coleochaete  Brebisson. 

Cells  with  a  single,  large,  parietal  chromatophore  and  a  pyrenoid.  Any  vegetative  cell  may 
give  rise  to  an  egg-shaped  zoospore.  Plants  either  monoecious  or  dioecious;  oogonia  flask-shaped, 
at  the  end  of  a  branch  or  row  of  cells;  antheridia  near  the  oogonia,  each  bearing  a  single  anthero- 
zoid;  a  layer  of  cells  develop  about  the  oospore.  On  germination  the  oospore  divides,  producing  a 
number  of  cells,  in  each  one  of  which  a  zoospore  is  formed;  these  reproduce  the  parent  plant. 


248  (247) 


Fig.  240.    Coleochaete  scutta  Brebisson.    Portion  of  a  disc.     X  about  215. 

Plant  a  disc,  of  one  or  more  layers  in  thickness,  adhering  through- 
out to  a  substratum,  often  bearing  gelatinous  hairs.  Repro- 
duction by  means  of  zoospores,  and  in  some  instances  by 
isogametes Family  Mycoideaceae. 

Only  one  genus  recorded  here Ulvclla  Crouan. 


/e 


\cSf 


^cj^^iw^iy' 


Fig.  241.  Ulvella  americana  Snow  (  = 
Pseudulvella  americana  WiUe).  X  150. 
(Original.) 


Plant  a  disc  of  radiating  rows  of  cells,  a  single 
layer  in  thickness  on  the  margin  and  several  in  the 
middle;  chromatophore  single,  but  thickened  so  as 
to  give  the  appearance  of  many;  pyrenoid  single. 

Appearance  much  as  in  Coleochaete  except  that  mem- 
brane and  hairs  are  more  gelatinous  and  the  hairs 
have  no  sheaths.  Reproduction  by  zoosjwres  only. 
These  have  cilia,  and  arise  first  at  the  center  of  the 
disc  and  later  toward  the  margin.  On  the  surface  of 
water  plants.  Mr.  F.  S.  Collins  believes  this  to  be 
Chactopeltis  but  sexual  reproduction  characteristic  for 
Chaetopeltis  has  not  been  observed  in  this  form. 


172 


FRESH-WATER  BIOLOGY 


249  (68,  190)     Plants   of    non-septate,   branched  filaments,   forming  felt-like 

masses  on  water  or  earth;  or  plants  minute,  growing  on  the 
surface  of  moist  earth  or  in  the  tissues  of  higher  plants; 
nuclei,  many.     Reproduction  by  zoospores,  isogametes,  or 

heterogametcs Order  Siphonales     .    .     250 

Many  marine  forms;  fresh  water  forms  few,  diflering  greatly  in  appearance  and  reproduction. 

250  (251,  252)     Plant  a  felt-like  mass  of  branched  filaments  which  contain  no 

septa  except  when  reproductive  bodies  are  formed. 

Vaucheria  de  Candolle. 

Plant  branched;  chromatophorcs  nu- 
merous, parietal,  disc-shaped;  asexual 
reproduction  either  by  zoospores  or  by 
akinetes,  the  former  borne  singly  in  ter- 
minal sporangia,  the  latter  occurring  as 
spherical  cells  on  short,  lateral  branches; 
oogonia,  each  containing  one  oosphere,  and 
antheridia,  each  with  many  antherozoids 
are  borne  side  by  side  either  laterally  or 
on  the  ends  of  short  branches. 
Fig.  242.  Vaucheria  repens  Hassall.  X  300. 
(Original.) 

251  (250,  252)     Plant  growing  on  moist  earth,  about  i  mm.  broad,  erect,  green, 

balloon-shaped,  with  branched,  colorless  rhizoids  at  smaller 
end Botrydlum  Wallroth. 


Chromatophorcs  numerous,  minute,  parietal,  each  with  a  pyre- 
noid;  reproduction  by  zoospores;  under  dry  conditions  resting  spores 
may  be  formed  in  the  branched  rhizoid-like  organ  of  attachment. 


z;^\..^-^j: 


Fig.  243. 


Botrydium  granulatum  Greville. 
Woronin.) 


X  15-     (After  Goebel  and 


253  (i) 


Plants  growing  on  the  tissues  of  higher  plants. 

Phyllosiphon  Kuhn. 

Plants  parasitic  in  the  leaves  and  stems  of  aquatic 
plants.  The  lower  end  is  inflated,  green,  the  upper  part 
colorless.  In  the  vegetative  part  the  chromatophores  are 
indistinct.  Reproduction  by  internal  division  or  aplano- 
spores  which  are  liberated  by  the  rupturing  of  the  cell  wall. 
In  these  the  chromatophore  is  distinct. 

Fig.  244.    Phyllosiphon  irisari  Kiihn.    Cells  of  host  not  shown. 
X  40.     (After  Just.) 

Plant  coarse,  at  least  several  centimeters  long,  with  a  linear,  cylin- 
drical, occasionally  branched  axis,  showing  nodes  and  inter- 
nodes;  at  the  nodes,  whorls  of  cylindrical  leaves  which  in 
turn  bear  leaflets;  sometimes  encrusted  with  lime.  Growth 
apical Order  Charales. 

Only  one  family Characeae    .    .     254 


THE   FRESH-WATER   ALGAE 


173 


Leaflets  and  internodes  of  both  axis  and  leaf  are  each  of  but  a  single  cell,  the 
walls  of  which  are  lined  with  chloroplasts  and  in  the  center  of  which  is  a  large 
sap  cavity.  In  Chara  the  internodal  cell  is  more  or  less  completely  covered  by 
a  layer  of  cortical  cells  of  the  same  structure.  A  swamp-Uke  odor  is  usually 
present.  Reproduction  sexual  only;  plants  either  dioecious  or  monoecious,  but 
in  the  latter  case  the  antheridia  mature  before  the  oogonia.  The  antheridium 
is  spherical,  its  wall  composed  of  eight  ''shields"  which  contain  red  chromo- 
plasts  on  their  inner  surfaces.  Attached  to  the  middle  of  each  shield  and  pro- 
jecting inward  is  a  club-shaped  cell,  the  manubrium,  which  in  turn  bears  a 
short  cell,  the  capitulum.  To  the  capitula  are  attached  secondary  capitula 
bearing  four  long,  slender  filaments  made  up  of  many  cells,  each  containing 
an  antherozoid;  the  antherozoids  are  spiral  in  form  and  have  two  ciha  at  their 
anterior  ends;  the  oogonia  are  egg-shaped  and  are  covered  by  five  spiral 
cells,  the  tips  of  which  are  divided,  once  in  Chara  and  twice  in  Nitella,  to  form 
the  "crown."  The  term  sporophydium  has  been  suggested  for  the  structure 
including  the  oospore,  its  basal  cell,  and  enveloping  cells.  Below  the  crown 
cells  the  antherozoids  penetrate  to  effect  fertilization.  Oospores  are  brown  or 
yellowish;  on  germination  they  produce  first  a  simple  row  of  cells,  the  pro- 
embryo,  on  which  the  new  individual  arises. 

254  (257)     Points  of  the  crown  of  the  oogonium  two-celled. 

Subfamily  Nitelleae    .    .255 


255  (256)     Leaflets  projecting  beyond  the  tips  of  the  leaves,  giving  the  appear- 
ance of  forked  leaves Nitella  Agardh. 


Axis  and  leaves  never  with  a  cortical  covering  and  seldom  encrusted 
with  lime.  Leaves  with  but  one  whorl  of  leaflets,  but  these  in  turn 
may  bear  whorls  of  leaflets,  those  of  the  last  order  always  projecting 
beyond  the  leaves,  giving  them  a  divided  appearance.  The  antheridium 
always  terminal  on  the  middle  leaf  or  leaflet.  Oogonia  either  single  or 
several  together,  in  the  place  of  lateral  leaflets. 


Fig.  245.    Nitella  sp.    Natural  size.    (Original. 


256  (255)    Leaflets  not  projecting  beyond  the  tips  of  the  leaves,  or  not  present. 

Tolypclla  A.  Braun. 


Stem  and  leaves  never  with  a  cortical  covering.  Leaves  with  one  to 
three  whorls  of  leaflets,  which  in  turn  may  bear  other  whorls  of  leaflets, 
much  smaller  than  the  first.  Antheridia  single  or  several  together,  which 
arise  from  the  basal  or  the  first  node  of  a  leaf.  Oogonia  several,  sur- 
rounding the  antheridia.     Plants  usually  monoecious. 


Fig.  246.     Tolypella  nidifica  v.  Leonh.     Three-fourths  natural  size, 
of  figure  after  Wille.) 


(Portion 


174 


FRESH-WATER  BIOLOGY 


2^1  C2i;A)     Points  of  the  crown  of  the  oogonium  one-celled. 
^'  ^  ^-^^                                                                             Subfamily  Chareae. 
Only  one  genus  known  in  America Chara  A.  Braun. 

Plants  mostly  encrusted  with  lime.  Principal  axis  and  leaves  more  or  less  completely  cov- 
ered with  a  layer  of  cells  forming  the  cortex.  Leaves  six  to  twelve  in  a  whorl,  each  usually 
with  several  whorls  of  leaflets,  mostly  with  stipular  outgrowths.  Antheridia  and  oogonia  on 
the  upper  side  of  leaves.     Plants  either  monoecious  or  dioecious. 


Fig.  247. 


Chara  fragilis  Derv.     A.  two-thirds  natural  size  portion  of  figure.     (After  Wille.)     B.  portion 
of  leaf  showing  cortication.   C.  Chara  coronala  Ziz.     a.  oogonium,    b.  anthendmm. 


In  Europe  two  other  genera  have  been  recognized  under  the  Chareae  as  fol- 
lows: 

A.  Sporophydia  borne  on  the  inferior  side  of  the  cell  which  carries  the 
antheridium Lamprothamnus  A.  Braun. 

B.  Sporophydia  occupying  the  place  of  a  leaflet  on  the  anterior  side  of  the 
leaf,  situated  between  antheridia Lychnothamnus  Leonh. 


Class  III.    Phaeophyceae 

Color  brown;  plant  coarse  and  large;  or  fine,  filamentous. 

All  species  are  attached  and  have  a  dark  or  olive  green  color.  Many  are 
small  and  resemble  the  Confervales  while  others  reach  an  enormous  size. 
Sexual  reproduction  takes  place  by  antheridia  and  oogonia  in  the  larger  species, 
and  by  isogametes  and  zoospores  in  the  smaller. 

The  members  of  this  class,  with  a  very  few  exceptions,  occur  in  salt-watef, 
and  the  classification  of  some  fresh-water  forms  which  are  often  placed  in  this 
group  is  doubtful. 


THE   FRESH-WATER   ALGAE 


175 


Only  one  genus  listed  here.  Plant  upright,  many  centimeters  long,  differ- 
entiated into  a  pseudo-parenchymatous  principal  axis  and  branches,  covered 
with  short,  unbranched  hairs.     Color  an  olive  brown Thorea  Bory. 


Reproduction  asexual  only,  con- 
sisting in  the  formation  of  sp)orangia 
on  the  outer  surface  of  the  axis, 
each  containing  but  a  single  spore, 
without  cilia  and  without  membrane. 
The  position  of  this  alga  in  the  sys- 
tem of  classitiaition  is  very  doubtful, 
but  for  convenience  it  is  placed  with 
the  Phaeophyceae. 

Fig.  248.  Thorea  ramosissima  Bor>-. 
Portion  of  a  longitudinal  radial  section. 
X  about  150.  (After  Hedgccock.  & 
Hunter.) 


Class  IV.     Rhodophyceae 

Color  red,  or  a  dull,  purpHsh  green;  plant  sometimes  complex  in  structure; 
reproduction  sexual  and  in  most  cases  asexual  also. 

Only  one  order Florideae. 

Plants  mostly  inhabitants  of  salt  water,  but  represented  in  fresh  water  by  several  genera. 
The  structure  of  the  different  fresh-water  genera  varies,  but  the  sexual  form  of  reproduction  is 
essentially  the  same  in  all.  The  male  reproductive  organs  are  borne  on  the  ends  of  filamentous 
branches,  the  contents  of  each  of  which  produce  a  single  spermatium.  The  female  organ  is 
flask -shaped,  in  the  larger  portion  of  which,  the  carpogonium,  lies  the  oosphere;  through  the 
long  neck,  the  trichogyne,  the  spermatium  is  conducted  to  the  oosphere  at  the  base,  it  having 
been  previously  carried  by  the  water  to  the  projecting  tip  of  the  trichogyne.  As  a  result  of 
fertilization,  densely  branched  filaments  arise  from  the  base  of  the  carpogonium,  on  the  ends 
of  which  are  borne  carpospores;  these  spore-bearing  branches,  and  the  sterile  branches  which 
usually  surround  them,  together  form  the  cystocarp.  In  Chantransia  and  in  many  salt- 
water species  tetraspores  are  also  formed. 


1  (8)     Plant  branched 2 

2  (5)     Branches  simple  and  not  in  whorls 3 

3  (4)     Plants   coarse,   of  simple  or  occasionally  branched,   hollow,   tapering 

bristles  with  node-like  swellings;    brownish  or  dark  bluish- 
green  in  color Lcmanca  Bory. 


Bristles  attached  to  a  fine,  filamentous  structure  which  is  furnished 
with  rhizoids.  Bristles  hollow,  with  a  single  row  of  cells  through  the 
center,  supported  at  intervals  by  transversely  placed  cells.  Anther- 
idia  borne  in  great  numbers  on  the  surface  of  the  node-like  swellings, 
a  single  spermatium  in  each.  Carpogonia  imbedded  in  the  outer 
wall  of  the  bristles,  the  tip  of  the  trichog>'ne  only  projecting.  Chains 
of  carpospores  project  toward  the  center. 


Fig.  249.     Lcmanca  torulosa  Agardh.     One-half  natural  size.     (After 
Kirchner.) 


176 


FRESH-WATER   BIOLOGY 


4  (3)  Plant  a  steel  blue,  brownish  or  red,  consisting  of  a  single,  branched 
row  of  cells,  the  branches  of  the  same  structure  as  the 
principal  axis,  irregularly  placed  and  not  in  whorls. 

Cliantransia  Fries. 

Sexual  reproduction  resembling  that  of  Batracho- 
spermum;  carpogonia  on  lateral  branches;  tetra- 
spores  resembling  carpospores  on  the  tips  of  cells. 
Plants  dioecious. 


Fig.  250. 


Chantransia  chalybea  Fries.     X  igo. 
(After  Kirchner.) 


5  (2)     Branches  in  whorls. 


6  (7)  Plant  purplish  or  bluish,  beaded  in  appearance,  due  to  whorls  of  dichot- 
omous,  accessory  branches,  composed  of  a  single  chain  of 
cells  on  a  pseudo-parenchymatous  axis. 

Batrachospermum  Roth. 

Plant  several  centimeters  long;  occasionally  dioecious,  the  antheridia  at  the  ends  of  acces- 
sory- branches,  the  carpogonia  frequently  near  the  axis;  the  carpospores  give  rise  to  a  proto- 
nema  on  which  the  adult  form  may  originate  as  a  branch.  The  protonema  may  also  give  rise 
to  asexual  spores  which  again  may  produce  protonema. 


Fig.  251. 


Batrachospermum  grabussoniense  Sirodot.     A .  portion  of  plant. 
X  225.    C.  procarp.     X  580.     (Original.) 


X  about  25.     B.  branches. 


7  (6)  Thallus  erect,  richly  branched,  several  centimeters  high;  beaded 
throughout,  due  to  whorls  of  branches  which  are  so  closely 
packed  and  grown  together  as  to  form  a  continuous  outer 
sheath,  the  diameter  of  which  is  greater  opposite  these 
branches Tuomeya  Harvey. 


Antheridia  at  the  ends  of  branches,  mostly  at  the  nodes;  carpo- 
gonia in  the  axils  of  branches.  This  genus  is  synonymous  with 
Baileya  of  Kiitzing. 

Fig.  252.     Tuomeya  fluviatalis  Harvey.     X  375-     (After  Sctchell.) 


THE   FRESH-WATER   ALGAE 


177 


8  (i)     Plant  an  unbranched  filament  of  one  or  more  rows  or  cells. 

Bangia  Lyngbye. 


Structure  simple,  hair-like;  color  of  different  shades  of  red;  attached 
at  one  end.  Found  usually  in  rapidly-flowing  water  on  wood  and 
stones. 

Fig.  253.     Bangia  atro-purpurea  Agardh.     X  225.     (After  Kiitzing.) 


IMPORTANT   REFERENCES   ON  NORTH  AMERICAN   FRESH- 
WATER ALGAE 

Collins,  F.  S.     1909.     The  Green  Algae  of  North  America.     Tufts  College 

Stud.,  Vol.  II,  No.  3.     191 2.     Supplement.     Tufts  College  Stud.,  Vol. 

Ill,  No.  2. 
Conn,  H.  W.  and  Webster,  L.  W.     1908.    A  Preliminary  Report  on  the  Algae 

of  Fresh  Water  of  Connecticut.      State  Geol.  Nat.  Hist.  Surv.,  Bull. 

No.  10. 
De  Toni,  J.  B.     1 887-1907.     Sylloge  algarimi  omniimi  hucusque  cognitarum. 

Vol.  I,  Chlorophyceae.     Vol.  II,  Bacillariaceae.     Padua. 
Engler,  Ad.  and  Prantl,  K.  A.  E.     1887-1909.     Die  naturlichen  Pflanzenfa- 

milien.     4V.  in  17.     Leipzig. 
Hazen,  T.  E.     1902.     The  Ulothricaceae  and  Chaetophorae  of  the  United 

States.     Mem.  Torrey  Bot.  Club,  Vol.  XL 
Pascher,  A.     1912.      (See  list  in  Chapter  I.) 
Saunders,  D.     1894.      Protophyta-Phycophyta.     Flora  of  Nebraska,  i :  1 5- 

68.     Lincoln. 
TiLDEN,  J.  E.    1909.    Minnesota  Algae  (Schizophyceae) .    Mmn.  Bot.  Survey. 
Transeau,  E.  M.     1913.     Annotated  List  of  the  Algae  of  Eastern  lUinois. 

111.  Acad.  Sci.,  6:69-89. 
Van  Heurck,  H.     1896.     A  Treatise  on  the  Diatomaceae.     London. 
West,  G.  S.     1904.     (See  list  in  Chapter  V.) 
West,  W.  and  G.  S.     1904-1912.     A  Monograph  of  the  British  Dcsmidiaccae. 

4V.     Ray  Soc.  Publ,  Vol.  42.     London. 
WOLLE,  Francis.     1884.     Desmids  of  the  United  States.     1887.     Fresh-water 

Algae  of  the   United  States.      2V.   Text   and  Atlas.      Bethlehem,   Pa. 
1890.     Diatomaceae  of  North  America.     Bethlehem,  Pa. 


CHAPTER   VII 
THE    LARGER    AQUATIC    VEGETATION 

By  RAYMOND  H.  POND 

Late  Professor  of  Botany,  Texas  Agricultural  College 

Nearly  all  of  the  larger  plants  which  have  distinct  roots,  stems, 
and  leaves  grow  attached  to  the  muddy  substratum.  This  habit 
of  the  larger  plants  to  grow  as  attached  organisms  is  so  universal 
that  it  can  hardly  be  regarded  as  an  accident  and  it  is  reasonable 
to  suppose  that  such  attachment  offers  some  advantage  to  the 
organism.     Even  the  simple  filamentous  algae  are  often  attached. 

When  a  plant  is  floating  free  any  portion  of  it  may  be  exposed 
to  the  surface  hght,  or  to  the  air,  because  the  water  movements 
may  turn  its  body  in  any  direction  and  such  a  plant  is  better  off 
without  specialized  organs  which  would  be  destroyed  by  exposure. 
It  is  common  to  see  drifting  plants  which  are  dying  rapidly  be- 
cause, among  other  reasons,  the  roots  are  exposed  to  the  intense 
light  at  the  surface  of  the  water,  The  small,  free-floating  forms 
are  simple  in  structure  because  no  portion  of  the  organism  has  a 
distinct  en\dronment  of  its  own  and  changes  in  position  are  so 
frequent  that  all  parts  of  the  body  are  equally  exposed.  The 
common  duckweed,  Lemna,  moves  with  the  changing  currents  and 
shows  a  marked  differentiation  into  an  upper  and  a  lower  side. 
Notable,  however,  is  the  fact  that  its  movement  is  always  in  a 
horizontal  direction  so  that  the  upper  side  is  uniformly  up  while 
the  lower  side  is  down,  with  its  roots  in  the  water,  and  shaded  by 
the  cap-like  upper  side.  Thus  it  is  that  Ceratophylliim,  which  is 
usually  regarded  as  a  dicotyledon  and  which  certainly  occupies  a 
much  higher  station  in  the  natural  system  than  Lemna,  shows  less 
differentiation  in  outer  structure  than  the  latter.  In  the  case  of 
Ceratophyllum  attachment  is  purely  accidental  so  far  as  special 
organs  for  the  purpose  are  concerned.  Well-developed  roots  have 
never  been  found  on  this  plant  although  the  rudiment  of  a  root  is 

178 


THE  LARGER  AQUATIC  VEGETATION  1 79 

present  in  the  embryo.  The  rigid  segments  of  the  forked  leaves 
frequently  catch  on  the  bottom  so  that  a  portion  of  the  stem  may 
become  buried  and  secure  the  plant  to  the  soil.  Just  as  often, 
however,  the  plants  float  free  in  the  water  at  the  mercy  of  any 
influence  that  may  arise  to  change  their  relative  position.  Exam- 
ination shows  the  entire  surface  of  this  plant  to  be  so  uniform  in 
structure  that  it  makes  no  difference  what  part  of  the  plant  body 
is  vertical  or  horizontal  in  the  water. 

Attachment,  therefore,  favors  and  necessitates  differentiation 
into  speciaUzed  organs. 

In  land  plants  the  roots  are  organs  of  absorption  as  well  as  of 
attachment,  but  until  recently  the  general  understanding  has  been 
that  the  roots  of  aquatic  plants  serve  for  anchoring  only.  In- 
vestigations of  the  writer  have  proved  that  the  roots  act  as  organs 
for  the  absorption  of  mineral  matter  from  the  substratum  and  in 
this  respect  are  perfectly  analogous  to  the  roots  of  land  plants. 

Root-hairs  are  present  on  the  roots  of  terrestrial  plants  with  but 
comparatively  few  exceptions.  These  dehcate  structures  are  uni- 
cellular with  thin  walls  and  are  formed  by  the  enlarging  and  pro- 
truding of  the  ordinary  peripheral  cells  of  the  root.  Their  presence 
greatly  increases  the  absorbing  surface  exposed  to  the  soil  and  thus 
the  passage  of  mineral  matter  into  the  plants  is  provided  for  with 
a  minimum  expenditure  of  tissue.  Several  authors  have  stated 
that  root-hairs  are  absent  in  the  case  of  submerged  aquatics.  This 
does  not  seem  to  be  the  case,  however,  as  the  writer  has  found  them 
present  on  17  out  of  the  20  species  common  in  Lake  Erie.  Even 
without  experimental  evidence  it  would  be  reasonable  to  suppose 
that  the  presence  of  root-hairs  indicates  that  the  roots  act  as  organs 
for  the  passage  of  mineral  matter  into  the  plant.  Such  delicate 
structures  can  hardly  be  regarded  as  lingering  rudiments  of  more 
active  organs  present  when  perhaps  the  species  was  terrestrial. 

Land  plants  have  developed  a  highly  specialized  tissue  system 
adapted  to  the  transfer  of  water  from  the  roots  to  stem,  branches, 
and  leaves.  This  conductive  tissue  is  usually  called  the  vascular 
system  and  the  necessity  for  it  in  land  plants  is  very  apparent  when 
the  rapidity  with  which  water  passes  from  the  plant  is  taken  into 
account.     That  water  plants  Ukewise  have  conductive  tissue  has 


i8o  FRESH- WATER   BIOLOGY 

been  known  for  a  long  time  and  a  great  deal  of  attention  has  been 
given  to  a  study  of  its  structure.  The  vascular  system  of  aquatics 
is  much  simpler  than  that  of  land  plants  and  seems  to  represent  a 
degenerate  type  of  the  latter.  This  general  fact  has  thus  far  been 
interpreted  uniformly  as  indicating  that  a  conductive  tissue  is 
useless  in  water  plants.  By  logical  inference  such  plants  were  once 
terrestrial  but  degeneration  of  the  vascular  system  has  accom- 
panied adaptation  to  the  aquatic  habit.  A  very  different  interpre- 
tation may,  however,  easily  be  made.  The  significant  fact  is, 
that  even  those  plants  which  live  wholly  submerged  and  are  with- 
out organs  of  attachment  show  at  least  the  rudiments  of  a  con- 
ducting system.  But  why  should  such  plants  have  any  vascular 
tissue  at  all?  The  epidermis  is  thin  and  permeable  to  solutions  of 
mineral  matter,  the  tissues  are  usually  only  a  few  cells  in  thickness, 
and  in  plants  \vithout  roots,  as  Ceratophyllum,  absorption  must  take 
place  in  such  a  large  number  of  the  cells  that  a  special  tissue  system 
for  the  conduction  of  water  is  unnecessary. 

An  aquatic  environment  does  not  favor  the  great  differentiation 
of  tissue  characteristic  of  terrestrial  plants.  When  in  water  plants 
very  simple  imitations  of  the  land  plant  structure  are  found,  this 
condition  does  not  represent  the  extreme  that  has  been  developed 
through  a  long  succession  of  aquatic  ancestors,  but  is  to  be  re- 
garded as  indicating  the  tendency  toward  simplihcation  made 
necessary  by  increasing  adaptation  to  the  water  life.  From  this 
point  of  view  the  conductive  tissue  is  becoming,  rather  than  has 
become,  unnecessary.  So  it  seems  probable  from  anatomical  study 
that  a  simplification  of  the  vascular  system  is  in  progress  which,  if 
continued,  will  eventually  lead  to  a  suppression  or  total  disappear- 
ance of  special  conductive  tissue.  At  present,  however,  it  may 
safely  be  said  that  the  majority  of  our  larger  water  plants  have 
need  of  vascular  tissue. 

The  leaves  of  water  plants  may  be  either  floating  or  submerged. 
Some  plants  have  only  the  floating  or  only  the  submerged,  while 
several  species  have  both  kinds  on  the  same  plant  at  the  same  time. 
The  floating  leaves  do  not  show  a  great  variety  of  form  and  tend  to 
be  elUptical,  oval,  or  round,  while  some  are  shield-shaped.  Since 
an  aquatic  environment  is  more  uniform  one  cannot  expect  as 


THE  LARGER  AQUATIC  VEGETATION 


l8l 


great  variety  in  leaf  form  as  is  noticeable  in  land  plants.  The 
floating  leaves  are  usually  borne  on  a  stalk  which  in  most  cases  is 
flexible,  so  that  the  leaf  blade  may  rise  or  fall  with  the  fluctuating 
level  of  the  water.  The  exposed  surface  of  the  floating  leaf  is 
usually  waterproof.  This  is  provided  for  in  a  variety  of  ways. 
In  some  cases  a  waxy  coating  renders  the  skin  nearly  impermeable. 

This  is  true  with  some  of  the  Potamo-       ^i^ 

gctons.  In  some  cases  a  coating  of 
very  dehcate  hairs  so  abundant  as  to 
enclose  an  envelope  of  air  prevents 
the  water  from  actually  touching  the 
epidermis  proper.  This  is  to  be  ob- 
served in  the  case  of  Nelumbo.  Some- 
times one  may  see  drops  of  water 
standing  on  the  surface  of  such  leaves 
and  when  the  leaf  is  submerged  and 
then  allowed  to  emerge  the  water  rolls 
off  leaving  the  leaf  apparently  dry. 

In  striking  contrast  to  the  floating 
leaves  the  submerged  ones  seldom 
have  a  distinct  blade  and  stalk.  This 
is  consistent  with  the  general  tendency 
to  uniformity  of  structure  under  a 
uniform  environment.  Vallisneria 
(Fig.  254)  may  be  regarded  as  show- 
ing a  typical  ribbon  form  which  is  well 
adapted  to  life  under  water,  because 
it  is  so  flexible  and  is  thus  able  to 
endure  swiftly  flowing  currents  or 
wave  movements.  In  some  species,  as  that  of  Potamogeton  pcr- 
foliatus,  the  submerged  leaves  are  expanded  into  blades  but  are 
sessile  on  the  stem,  that  is,  are  without  a  leaf  stalk.  The  latter 
would  be  of  no  advantage  to  leaves  which  are  not  intended 
to  reach  the  surface.  They  would  tend  to  make  the  plant  top- 
heavy  and  easily  uprooted  by  a  sudden  rush  of  water.  Moreover, 
it  is  quite  probable  that  a  greater  exposure  of  leaf  surface  is  nec- 
essary because  of  the  diminished  hght  under  water.     Linear  or 


Fig.  254.  Vallisneria  spiralis.  Staminate 
and  pistillate  plants,  showing  the  long  rib- 
bon leaves  which  are  all  blade  and  have 
no  apparent  stalk.  (After  Kerner  and 
Oliver.) 


l82 


FRESH-WATER  BIOLOGY 


Fig.  255.  Potamogeton  natans. 
One  floating  leaf  and  three 
submerged  leaves,  representing 
the  thread-like  form  of  the 
raonocotyledonous  type  of  sub- 
merged leaf.     (After  Gobel.) 


thread-like  leaves  are  very  common  and  may  be  the  only  kind  occur- 
ring on  the  plant,  as  in  Potamogeton  pedinatus,  or  they  may  occur 
on  the  same  plant  together  with  floating 
leaves,  as  in  Potamogeton  natans  (Fig.  255). 
It  is  to  be  noticed  that  most  of  the  monocoty- 
ledons conform  to  some  one  of  the  types 
mentioned,  while  the  dicotyledons  seem  to 
favor  another  habit,  such  as  is  seen  in  the 
finely  dissected  leaves  oiRanuncnlus  aqnatilis , 
Myriophyllum  spicattwi,  Bidens  beckii  (Fig. 
256) ,  and  Ceratophylliim.  Among  the  dicoty- 
ledons in  which  both  floating  and  submerged 
leaves  are  present,  as  in  Ra- 
nunculus and  Cabomba  (Fig. 
257),  the  tendency  to  fiinely 
dissected  leaves  is  conspicuous,  while  in  the  monocot- 
yledons, having  both  floating  and  submerged  leaves 
on  the  same  plant,  the  latter  tend  to  assume  the 
ribbon-Uke  or  the  long  linear  outline,  as  in  Fig.  255. 
Some  of  the  true  water  plants,  as  Bidens  beckii  and 

Myriophyllum  spi- 
catum,  support  a 
vertical  portion  of 
the  main  stem  con- 
siderably above  the  ^^g,1,i?^S" Lfves 
water  surface  and  yrriJd  Ssln: 
on  this  emersed 
portion  ordinary 
aerial  leaves  are 
borne.  It  is  some- 
times possible  in  the  case  of  such 
plants  to  find  leaves  which  seem 
to  be  midway  in  form  between  the  finely  cut  submerged  leaves  and 
the  bladed  emersed  ones,  so  it  seems  probable  that  the  submerged 
leaves  are  to  be  regarded  as  exposed  leaves  which  have  changed  in 
form  because  fife  under  water  requires  such  modification.  Such  a 
modification  has  been  produced  experimentally.     Some  plants  in 


tire  or  slightly  ser- 
rate. One  whorl 
shows  the  transition 
stage  from  the  sub- 
merged  to  the 
emersed  form.  ^ 
natural  size. 
(After  Gobel.) 


Fig.  257.  Cabomba.  Floating  leaves,  entire  and  pel- 
tate. Submerged  leaves  with  finely  dissected 
blades  typical  of  Dicotyledons.     (After  Gobel.) 


THE  LARGER  AQUATIC  VEGETATION 


183 


nature  seem  to  be  able  to  bring  forth  cither  floating  or  submerged 
leaves  or  both  as  the  conditions  imposed  seem  to  require.  If  grow- 
ing shoots  of  Ranunculus  aquatilis  are  not  allowed  to  reach  the 
surface  of  the  water  only  the  segmented  leaves  develop.  If  speci- 
mens of  Potamogeton  heterophyllus  are  suddenly  left  stranded  by 
receding  water  the  floating  leaves  may  persist  and 
be  succeeded  by  more  floating  leaves,  thus  enabUng 
the  plant  to  live  for  a  considerable  time,  often 
persisting  until  the  rising  water  returns.  In  such  a 
case  the  submerged  leaves  soon  die  from  exposure, 
but  the  floating  leaves  have,  on  the  upper  surface, 
stomata  w^hich,  in  cooperation  with  the  thick 
cuticle,  are  able  to  regulate  the  loss  of  water. 

Some  of  the  amphibious  species,  such  as  Sagit- 
taria  natans,  are  especially  variable  in  leaf  form. 
The  early  seedHng  leaves  are  bladeless  and  ribbon- 
like, while  the  later  leaves  which  rise  above  the 
surface  have  a  distinct  blade  and  stalk  (Figs.  258 
and  259).  From  the  evident  plasticity  of  these 
plants  it  may  be  supposed  that  the  form  of  leaf  to 
be  produced  is  not  predetermined  but  depends 
upon  conditions.  Wachter  has  experimented  with 
Sagittaria  natans  and 
finds  that  plants  hav- 
ing the  ribbon-like 
leaves  may  be  pre- 
vented from  later  pro- 
ducing bladed  leaves 
either  by  reducing  the 
intensity  of  Hght  or 
by  partial  starvation. 
Plants  which  have  already  formed  bladed  leaves  may  be  induced 
in  like  manner  to  bring  forth  the  ribbon  form.  In  \iew  of  such 
results  it  is  not  unreasonable  to  suppose  that  both  the  floating 
and  the  submerged  leaves  may  easily  have  developed  during  the 
past  from  aerial  leaves  and  that  both  kinds  are  useful  to  many 
species. 


Fig.  258.  Sagittaria 
natans.  Transition  from 
ribbon-like  to  bladed 
leaves.  I  natural  size. 
(After  VViichter.) 


Fig. 259. 


Sagittaria  chinensis.  Transition 
from 'bladed  to  ribbon-like  leaves.  The 
reversion  has  been  produced  by  cutting 
otT  the  roots  repeatedly,  i  natural  size. 
(After  Wachter.) 


l84  FRESH-WATER    BIOLOGY 

Many  of  the  delicate  submerged  plants  will  wither  rapidly  when 
taken  from  the  water  and  exposed  to  the  air.  This  occurs  be- 
cause the  outer  layer  of  tissue  or  epidermis,  as  it  is  called,  is  thin 
and  allows  the  water  contained  in  the  plant  rapidly  to  pass  into 
the  air  as  vapor.  If  a  plant  which  bears  both  floating  and  sub- 
merged leaves  is  exposed  it  will  be  noticed  that  the  latter  wilt  and 
dry  out  much  more  rapidly  than  the  former.  Examination  will 
show  the  cuticle  of  the  floating  leaves  to  be  thicker  and  much  less 
permeable  to  water,  if  at  all  so,  than  that  of  the  submerged  leaves, 
while  special  openings  may  be  discovered  through  which  water 
vapor  escapes  instead  of  passing  oft  all  over  the  surface  as  in  the 
submerged  leaves.  These  special  openings  are  called  stomata  and 
are  the  same  in  structure  as  those  which  occur  on  the  leaves  of 
land  plants.  The  size  of  these  openings  may  vary  from  time  to 
time  according  to  the  needs  of  the  plant.  Each  opening  is  sur- 
rounded by  two  ceUs,  called  guard  cells,  which  also  vary  in  size 
and  shape  according  to  the  amount  of  water  they  contain.  When 
turgid  they  become  somewhat  kidney-shaped,  curving  away  from 
the  opening  and  thus  making  it  larger.  When  flaccid  because 
there  is  little  water  in  the  plant  they  tend  to  straighten  out  and 
thus  make  the  opening  smaller.  Thus,  by  the  activity  of  these 
stomata  whose  action  depends  upon  the  amount  of  water  in  the 
plant,  the  amount  of  water  passing  from  the  plant  by  transpiration 
is  regulated. 

The  number  of  stomata  occurring  on  the  exposed  surface  of  a 
floating  leaf  may  be  quite  large.  One  author  counted  the  number 
of  stomata  present  in  the  area  of  i  sq.  mm.  at  five  different  loca- 
tions on  the  upper  surface  of  the  floating  leaves  of  one  of  the  Pota- 
niogetons.  He  found  a  minimum  of  216  and  a  maximum  of  276 
with  an  average  of  255  per  sq.  mm. 

It  is  evident  that  stomata  are  intended  for  leaves  which  must 
endure  exposure  to  the  air,  but  they  do  occur,  though  rarely,  on 
the  submerged  leaves  also  (Fig.  260).  Sometimes  only  one  or 
two  submerged  leaves  of  a  given  plant  will  have  them  and 
again  several  specimens  of  the  same  species  may  be  examined 
without  finding  any  at  all.  The  only  explanation  for  the  occur- 
rence of  such  structures  on  submerged  leaves  is,  that  the  ancestors 


THE   LARGER   AQUATIC    VEGETATION 


I8S 


Fig.  260.  Zannichellia 
repens.  Submerged 
leaf  showing  stom- 
ata.  X  about  100. 
(After  Sauvageau.) 


of   the    plants   bearing    them   were    adapted   to   hfe  on  land  or 
at  least  lived  under  exposure  to  loss  of  water  by  transpiration. 

Other  openings  in  the  leaf  have  also  been  found  in 
some  species.  These  occur  at  the  apex  of  the  leaf 
more  frequently  in  the  submerged  leaves  than  in 
the  floating  ones.  The  opening  does  not  show  any 
special  structure,  as  is  true  of  stomata,  and  is  formed 
by  the  decay  and  falling  away  of  the  tissue  at  the 
apex,  so  that  the  conductive  vessels  in  the  veins  of 
the  leaf  become  exposed  to,  and  in  direct  communi- 
cation with,  the  water.  In  some  cases  this  disin- 
tegration of  tissue  at  the  apex  may  go  so  far  as  to 
change  to  a  marked  degree  the  shape  of  the  apex, 
making  it  rounded  instead  of  pointed  (Figs.  261  and  262). 

The  formation  of  the  opening  seems  to  occur  before  the  leaf 
matures  but  is  seldom  found  on  the  young  leaves.    In  addition  to  the 

species  already  known  as  bearing  these 
openings  the  writer  may  mention  that 
of  Vallisneria  spiralis  on  whose  half- 
grown  leaves  he  has  observed  them. 
Some  authors  have  suggested  that  the 
passage  of  water  through  the  conduc- 
tive tissue  is  facilitated  and  that  the 
This  is  really  a 
supposition  and  has  never  been  proved. 
The  presence  of  an  earthy  coating  on  the  leaves  and  stems  of 
some  water  plants  may  be  commonly  ob- 
served. This  mineral  incrustation  appears 
like  a  coating  of  mud  on  the  leaf  in  many 
cases,  while  in  others  it  is  not  so  conspicuous 
and  is  only  noticeable  when  the  plant  is 
handled.     Only  the  submerged  organs  seem 

.        V  1  •  .  ViG.  2()2.  Potamogctondensus.  Lesim 

to  bear  the  mcrustation,  even  the  lower     longitudinal  section.  The  decayed 

,  tissue  has  fallen  away,  leaving  the 

surface  of  fioatme  leaves  beins  less  favor-     vessels  e.xposed  to  the  surrounding 

°  f^  water.       X    about    135.       ^Altef 

able  to  its  formation  and  much  less  fre-     ^''^^-^e^^" ' 

quently  bearing  it.     Potamogeton   peclinatus   is   seldom,    if   ever, 

incrusted,  while  other  species  of  this  genus  usually  are.     Chara  is 


Fig.  261.  Zosiera  nana.  Apical  portion  of 
a  mature  submerged  leaf,  showing  the 
change  of  form  at  the  apex  due  to  decay  ^.^^.^^+*  „  ,•  „:j^j 
of  apical  tissue.  X  about  40.  (After  eXCrctlOU  IS  aided 
Sauvageau.) 


1 86  FRESH-WATER   BIOLOGY 

seldom  found  without  an  incrustation,  while  Vallisneria  is  never 
found  with  it,  although  the  two  plants  frequently  grow  side  by  side 
and  essentially  under  the  same  conditions.  The  leaves  of  Vallisneria 
are  very  flexible  and  almost  always  bending  with  the  current, 
hence,  a  deposit  of  soHd  matter  is  prevented.  It  seems  probable, 
however,  that  the  physiological  processes  going  on  in  the  plant 
determine  largely  whether  or  not  an  incrustation  is  to  be  formed. 
The  coatings  are  not  firmly  fastened  to  the  leaf  and  may  be  easily 
scaled  off  or  loosened  by  bending  the  leaf.  The  presence  of  the 
coatings  seems  to  make  little  difference  to  the  plant  as  the  tissue 
beneath  appears  of  a  healthy  green  color  though  frequently  of 
more  delicate  tint  than  the  unincrusted  areas  of  the  leaf. 

In  all  cases  known  the  substance  of  the  incrustation  has  been 
found  chemically  to  be  the  neutral  carbonate  of  lime,  which,  of 
course,  is  insoluble.  Microscopic  examination  by  polarized  light 
has  revealed  the  presence  of  minute  crystals  in  the  incrustation 
formed  on  Chara  and  the  same  may  possibly  prove  to  be  the  case 
with  plants  of  other  families.  The  chemistry  of  the  formation  of 
this  incrustation  is 'not  known.  There  is  usually  present  in  the 
water  the  soluble  bicarbonate  of  lime  which  by  loss  of  carbon 
dioxid  is  changed  to  the  neutral  or  insoluble  carbonate.  Some 
have  supposed  that  as  the  plants  withdraw  carbon  dioxid  from  the 
water  to  use  in  the  process  of  starch  manufacture,  this  insoluble 
neutral  carbonate  is  formed  and  deposited  on  the  leaf.  This  proc- 
ess may  be  expressed  chemically  thus: 

Soluble  Insoluble 

CaH2  (003)2  =  CaCOa  +  CO2  +  H2O 

Another  explanation  may  be  that  the  oxygen  liberated  by  the  plant 
in  starch  making  acts  catalytically  upon  the  bicarbonate  to  change 
it  to  the  neutral  carbonate.  The  former  process  would  more 
likely  occur  in  water  containing  a  larger  amount  of  the  carbonate 
in  solution  which  would  be  precipitated  except  for  the  solvent 
action  of  the  carbon  dioxid  in  the  water.  The  latter  process 
would  be  more  probable  in  water  containing  very  small  amounts 
of  the  bicarbonate  which  would  remain  in  solution  in  the  absence 
of  the  carbon  dioxid. 


I 


THE  LARGER  AQUATIC  VEGETATION  187 

Since  the  escape  of  oxygen  and  withdrawal  of  carbon  dioxid  are 
simultaneously  in  progress  during  the  time  the  plant  is  making 
starch,  both  processes  may  operate  to  precipitate  the  neutral 
carbonate.  If  the  plants  secrete  an  alkaline  carbonate  this  would 
immediately  upon  its  escape  from  the  plant  decompose  the  soluble 
bicarbonate  in  the  water  with  the  formation  of  the  neutral  insol- 
uble carbonate.  It  is  uncertain,  however,  that  such  an  alkaline 
carbonate  is  secreted  by  the  plant  and  not  much  emphasis  can  be 
placed  upon  this  hypothesis.  The  most  recent  explanation  rests 
upon  the  discovery  that  a  soluble  calcium  salt  of  succinic  acid  is 
present  in  the  cell  sap  of  Chara.  The  occurrence  of  this  salt  in 
the  sap  of  other  plants  has  not  been  determined,  but  as  succinic 
acid  is  a  very  probable  by-product  in  the  ordinary  processes  of 
plant  physiology,  its  wide  distribution  may  reasonably  be  expected. 
As  the  calcium  salt  escapes  from  Chara  by  osmosis  it  is  most  likely 
decomposed  with  the  formation  of  the  insoluble  carbonate. 

Possibly  the  incrustation  offers  protection  to  the  plant  in  some 
way,  but  this  seems  hardly  probable,  and  at  present  one  can  only 
say  that  its  formation  is  a  consequence  of  processes  in  the  plant 
and  that  its  presence  is  of  little  benefit  or  of  harm  to  the  plant. 

Various  plant  organs  are  often  found  to  be  covered  with  a  gelati- 
nous coating.  This  may  occur  on  the  lower  surface  of  floating 
leaves  as  in  species  of  Nymphaea.  Young  leaves  and  growing  tips 
are  often  encased  with  it.  In  the  axils  of  leaves  arising  in  a 
rosette  around  a  shortened  stem  it  is  likely  to  occur.  Seed  coats 
are  often  slimy  and  in  some  fruits  the  seeds  at  maturity  are  em- 
bedded in  a  mass  of  gelatinous  substance  which  on  sweUing  rup- 
tures the  ovary  walls  and  allows  the  seeds  an  exit.  Some  plants,  as 
Brasenia  peltata,  have  special  glands  to  furnish  the  slime,  but  often, 
as  in  leaf  axils,  there  are  no  distinct  structures  for  furnishing  this 
substance.  Many  of  the  algae  are  embedded  in  a  mass  of  slime 
just  as  the  eggs  of  frogs  are.  Amphibious  plants  and  those  sub- 
ject to  temporary  exposure,  as  in  the  case  of  plants  which  grow  in 
tide-water,  are  doubtless  protected  from  too  rapid  loss  of  water  by 
such  covering.  It  may  also  serve  as  a  protection  for  young  buds 
and  leaves  against  devouring  animals.  It  is  quite  possible  tliat 
the  gelatinous  masses  in  which  seeds  are  found  embedded  arc  of 


i88 


FRESH-WATER   BIOLOGY 


very  different  composition  from  the  slime  which  occurs  on  the  lower 
surface  of  a  floating  leaf.  The  occurrence  of  the  latter  may  be 
accidental  so  far  as  the  plant  is  concerned  and  have  little  im- 
portance in  its  welfare.     In  the  algae  and  even  with  deUcate  parts 

of  higher  plants  such  a  coating 
may  serve  to  retard  the  ex- 
change of  liquids,  thus  pre- 
venting plasmolysis,  or  in  like 
manner  it  may  enable  the 
plant  to  maintain  a  cell  sap 
of  much  greater  density  than 
''irftnno^^'ATiyTse^^^^^  that  of  the  surrouudiug  watcr 

(After  Gobel.)  (Fig.   26^). 

Quite  a  number  of  terrestrial  species  are  especially  adapted  for 
retaining  and  digesting  as  food  small  animals  which  are  so  unfor- 
tunate as  to  wander  into  the  traps  borne  by  the  plant.  Few 
aquatic  species  have  acquired  this  habit  but  there  are  some  mem- 
bers of  the  genus  Utricu- 
laria  remarkable  for  the 
special  organs  developed  to 
secure  animal  food.  The 
bladders  are  generally  re- 
garded as  modified  leaves, 
and  structures  resembling 
stomata  have  been  found 
on  them  in  some  cases. 
The   bladders  have   small  ,,.,..      ^,  ^,  , ,       ,,  , 

Fig.  264.  Utrtcularta  minor.  Numerous  bladders  on  the  leaves, 
nnpninrrc  cniarHpH  hv  hairs  >1 ,  enlarged  bladders.  L,  flower-stalk  rising  above  the  water. 
OpemngS    gUaraeU    U>    lldirij       ,^^^  ^^^^  ^^^^  ^^.^  ^^  ^^^^  .^  ^^  ^^  imagined  as  horizontal 

and  closed  by  a  sort  of  trap-     »"  ^^^  ^^t«^-   ^^^^^  ^'^^""^-^ 

door  which  permits  small  animals  in  the  water  to  enter  but  which 

prevents  any  escape  for  the  victims  (Fig.  264). 

These  plants  may  float  free,  so  far  as  roots  are  concerned,  but,  as 
with  Ceratophyllum,  accidental  attachment  or  rather  anchorage  fre- 
quently occurs  through  entanglement  with  other  plants  or  by  being 
partly  buried  in  the  mud. 

All  of  the  species  raise  the  inflorescence  above  the  water  and 
Utricularia  inflata  sends  out  whorls  of  leaves  with  inflated  petioles 


THE   LARGER   AQUATIC   VEGETATION 


189 


from  the  flower-stalk  to  serve  as  floaters.  As  there  are  land  species 
of  Utricularia  which  also  have  bladders,  it  seems  quite  probable  that 
the  aquatic  forms  have  been  derived  from  the  land  species. 

Some  authors  have  suggested  that,  being  without  roots  and  re- 
quiring more  nitrogenous  food  than  can  be  obtained  from  sub- 
stances in  solution  in  the  water,  these  bladders  have  been  developed 
to  secure  animal  food.  It  is  just  as  probable  that  the  aquatic 
forms  are  merely  using  structures  that  were  characteristic  of  their 
ancestors,  which  were  land  plants.  Why  the  land  species  have 
developed  such  structures  has  never  been  demonstrated. 

Few,  if  any,  of  the  flowering  water  plants  depend  upon  seed  repro- 
duction. Vegetative  reproduction  by  runners,  tubers,  buds,  stem 
fragments,  etc.,  is  particularly  prominent  among  these  aquatics. 
Seed  reproduction  is,  however, 
common  and  many  are  the  con- 
trivances utilized  for  securing 
the  transfer  of  pollen  and  cross 
pollination.  In  some  few  cases, 
as  Ceratophyllum,  Naias,  and 
Zannichellia,  poUination  occurs 
under  water  and  the  pollen 
is  transferred  by  the  water. 
The  wind  is  an  important  agent 
in  the  transfer  of  pollen  espe- 
cially for  many  of  the  Potamo- 
getons  (Fig.  265). 

The  stamens  and  pistils  of  Potamogeton  crispus  do  not  mature 
on  the  same  plant  at  the  same  time.  As  the  pistils  mature  first 
they  must  receive  pollen  from  some  other  plant  and  by  the  time 
the  stamens  of  their  own  plant  are  ready  to  shed  pollen,  they 
have  been  polhnated  and  are  no  longer  receptive  to  pollen.  The 
poUination  of  Vallisneria  spiralis  has  become  a  classic  illustra- 
tion of  the  remarkable  capacity  for  adaptation  possessed  by  some 
plants.  The  individuals  of  this  plant  are  of  two  kinds  —  one 
bearing  stamens  and  the  other  bearing  pistils  only.  The  staminate 
flower  cluster  is  enclosed  in  a  sac  which  finally  ruptures  and  the 
staminate  flowers  immediately  rise  to  the  water  surface.     After  a 


Fig.  265.     Potamogeton  crispus.    Pollen  distribution  by 
the  wind.     (After  Kerner.) 


IQO 


FRESH-WATER    BIOLOGY 


Fig.  266.     Vallisneria  spiralis. 


short  exposure  to  the  air  the  flowers  reflex  the  sepals  to  form  a 
little  boat  which  floats  about  with  the  dehiscing  stamens  exposed 
to  the  air,  so  that  whenever  the  boat  lodges  by  a  pistillate  flower 

some  pollen  is  deposited  upon  the 
receptive  stigma.  The  pistillate 
flower  is  solitary  upon  a  long  stalk, 
which,  rising  from  the  leaf  axils, 
elongates  very  rapidly  until  the 
flower  floats  on  the  water  surface, 
when  the  stigma  is  soon  exposed 
to  receive  the  pollen  from  the 
passing  boats  of  staminate  flowers 
(Fig.  254,  page  181,  and  Fig.  266). 
Sometimes  where  Vallisneria  is  abundant  the  water  surface  is 
completely  covered  by  the  staminate  flowers,  just  as  Lemna,  the 
duckweed,  often  covers  certain  areas.  As  soon  as  the  pistillate 
flower  is  fertilized  the  stalk  contracts  to  a  spiral,  thus  drawing  the 
flower  under  water  to  mature  the  frviit. 

To  what  extent  Vallisneria  is  propagated  by  seed  is  not  known. 
It  has  been  necessary  for  the  writer  to  take  hundreds  of  these 
plants  from  the  lake  for  experimental  pur- 
poses and  a  seedhng  has  not  as  yet  been 
found.  The  plants  growing  in  water  2.5  to 
3.5  meters  deep  frequently  do  not  flower  at 
aU  but  readily  propagate  by  runners. 

As  previously  mentioned,  Zannichellia 
palustris  conducts  its  pollination  under 
water  (Fig.  267).  The  staminate  and  pis- 
tiUate  flowers  stand  in  the  same  axil 
filament  of  the  sohtary  staminate  flower 
elongates  to  raise  the  anthers  above  the 
stigmas  of  the  pistiUate  flowers.  The  pollen  is  heavy  enough  to 
slowly  sink  after  escaping  from  the  stamens  and  in  still  water 
may  pollinate  the  flower  of  its  own  plant,  but  in  running  water  is 
usually  carried  to  a  neighboring  plant. 

The  pollen  grains  of  aquatic  plants  differ  in  one  particular  from 
those  of  land  forms  in  that  they  have  only  one  coat.     Perhaps  this 


1  he  Fig.  267.  Zannichellia  palustris. 
Pollination  occurs  under  water. 
Anthers  are  raised  above  the 
stiecmas  by  the  loni;  filament. 
X  about  8.     (After  Gobel.) 


THE  LARGER  AQUATIC  VEGETATION  191 

is  because  they  are  little  exposed  and  do  not  need  protection  against 
a  rapid  loss  of  water. 

Very  few  species  develop  a  showy  corolla  under  water,  but  Ileter- 
anthera  graminea  is  one  which  has  a  fairly  conspicuous  flower  under 
water. 

Most  of  the  attached  flowering  plants  are  perennial,  and  vegeta- 
tive propagation  is  very  common.     Naias  flexilis  is  an  annual. 

There  is  a  period  of  rest  for  water  plants  just  as  for  land  plants 
and  as  in  the  latter  so  in  the  former  this  period  occurs  during  the 
cold  season.  Not  all  of  our  perennial  aquatics  make  special  prep- 
aration for  passing  the  winter,  and  some,  as  Ranunculus  aquatilis, 
Ruppia,  and  Zannichellia,  may  be  found  in  normal  condition  even 
during  the  winter.  The  drifting  fragments  of  Ceralophyllum  often 
become  attached  by  accidental  lodgment  and  pass  the  winter  in 
the  vegetative  condition. 

Some  Potamogetons,  Ranunculus  aquatilis,  and  others  will  con- 
tinue to  grow  uninterruptedly  all  winter  if  planted  in  aquaria  and 
kept  at  favorable  temperature  in  the  greenhouse. 

Vegetative  reproduction  is  the  conspicuous  method  of  propa- 
gation among  the  larger  aquatics,  and  although  many  of  the  species 
produce  seed  there  are  few  which  could  not  easily  persist  if  seed 
production  were  to  be  discontinued.  In  some  cases  fruit  formation 
has  been  abandoned.     Elodea  and  Potamogeton  rohhinsii  rarely  fruit. 

The  rhizomes  of  most  of  the  water  plants  are  well  developed  and 
represent  a  considerable  portion  of  the  vegetation.  In  some  cases, 
as  in  Potamogeton  perfoliatus,  if  a  plant  be  taken  carefully  from  the 
soil  fully  one-half  the  fresh  weight  of  the  plant  will  be  found  to 
consist  of  roots  and  rhizomes.  With 
the  approach  of  cold  weather  the 
stems  and  leaves  gradually  disin- 
tegrate but  the  rhizomes  remain 
alive  and  pass  the  winter  buried  in 
the  mud  and  in  the  spring  send  up  j,^^  ^^g  p,i,Z,eio»  pecUnaius.  Rhizomes  in 

shoots      from      the      buds      previously      November  with  winter  buds,    (.^fter  Irm.sch.) 

formed  (Fig.  268).  Heteranthera  graminea  has  long  black  rhizomes 
that  are  cord-Uke  and  often  quite  tough.  The  young  plants  seem 
in  some  cases  to  rise  from  the  nmncrs  adventitiously.      Among 


192 


FRESH-WATER   BIOLOGY 


the  Nymphaeaceae  large  tubers  are  common  and  young  plants  of 
Nymphaea  alba  may  sometimes  be  found  floating  about  attached 
to  a  tuber. 

The  swamp  plants,  such  as  Typha  and  Scirpus,  also  have  exten- 
sive rhizome  systems  which  are  important  means  of  wintering  and 
acquiring  new  territory. 

Some  plants  have  winter  buds  or  hibernacula  which  form  in 
autumn,  separate  from  the  parent  plant,  often  drift  to  a  new 
locality,  and  finally  sink  to  pass  the  winter 
in  a  dormant  condition  only  to  commence  a 
new  generation  the  following  spring  (Fig.  269). 
Such  winter  buds  are  commonly  formed  by 
Utricularia,  Potamogeton  crispus,  P.  zosterijo- 
lius,  P.  pusillus,  P.frasii,  and  possibly  others. 
The  sinking  of  those  winter  buds  may  be  ac- 
complished by  the  intercellular  spaces  becom- 
ing injected  with  water,  as  is  the  case  with 

Fig.  269.    Potamogeton  crispus.  '^        •' 

\yinter  bud  germinating  in    ^]^g  autumu  plauts  of  Lemua  mifior. 

the  spnng.      A  rhizome  with  ^^^ 

TevdoSed''''(Mre?^T??vi;f-       Asidc  from  spccial  organs  of  propagation 
""^^  quite  a  few  plants  acquire  new  stations  by 

means  of  the  fragments  of  vegetative  parts  accidentally  set  adrift. 
It  is  common  to  find  floating  stems  of  Elodea,  from  the  nodes 
of  which  adventitious  roots  have  risen.  These  roots  grow  straight 
downward  and  the  stem  makes  Httle  growth  in  length  while  the 
roots  are  seeking  the  soil.  A  fragment  of  Elodea  was  found  floating 
in  Lake  Erie  which  had  an  adventitious  unbranched  root  45  cms. 
in  length.  The  roots  do  not  branch  in  some  species  until  the  soil 
is  penetrated  and  then  a  system  of  lateral  branches  develops  to 
anchor  the  plant. 

In  Potamogeton  perfoliatus  the  adventitious  roots  usually  arise 
from  the  nodes  of  new  rhizomes  which  develop  in  the  leaf  axils  of 
the  cutting. 

With  land  plants  the  development  of  roots  on  the  seedhng  is  as 
marked  as  the  growth  of  stem  and  leaves,  but  in  several  water 
plants  the  root  development  is  subordinated  to  that  of  the  stem 
and  leaves,  while  in  some  species  a  genuine  functional  root  is  not 
developed.     The  rudiment  of  a  root  may  be  present  as  a  part  of 


THE  LARGER  AQUATIC  VEGETATION 


193 


the  embryo  in  the  seed,  but  in  germination  this  rudiment  is  sup 
pressed  in  its  development  and  never  gets  to  be  a  real  root. 

The  seeds  of  Ranunculus  aquatilis  will  germinate 
either  on  land  or  in  water  but  the  development  of  the 
seedling  is  not  alike  in  each  case 
(Fig.  270).  The  seed  leaves  are 
similar,  except  that  those  of  the 
land  seedling  are  a  little  wider  in 
proportion.  The  true  leaves  of 
the  land  plants  have  broad,  seg- 
mented blades,  while  the  water 


Fig.  270.  Ranunculus  aqua- 
tilis. A.  Seedling  ger- 
minating in  water.  B. 
Seedling  germinating  on 

land.  (After  Askenasy.)  foHii  has  ouly  a  icw  thread-like 


Fig.  271.  Potamogeton 
lucens.  Seedling 
with  temporary 
primary  root  bearing 
cluster  of  root-hairs. 
(After  Warming.) 


branches  with  little  indication  of  a  distinct  blade. 

Potamogeton  lucens  and  Naias  major  send  out  a  primary  root 
from  the  seed  upon  which  a  cluster  of  root-hairs  soon  develops  to 
help  anchor  the  plant.  But  this  primary  root  is  not  lasting  and  is 
soon  succeeded  by  adventitious  roots  which  spring 
from  the  joints  of  the  runners  which  developed  in  the 
meantime  (Figs.  271  and  272). 

Ceratophyllum  furnishes  a  very  interesting  instance 
of  suppressed  root  development.  There  is  present 
in  the  embryo  of  the  seed  a  rudimentary  root,  but 
it  never  develops  into  an  organ  of  attachment  or 
serves  for  the  entrance  of  mineral  salts.  When  the 
seed  germinates  this  rudiment  of  a  root  pushes  out 
far  enough  to  let  the  plumule  rise 
from  between  the  emerging  cotyle- 
dons and  then  its  growth  practically 
stops  (Fig.  273).  So  far  as  known, 
adventitious  roots  never  appear  on  ^'j,^lfsum.'''''SZ 

J.T-*      „1        i.  with  cotyledon,  radi- 

tniS  plant.  cle  and  tirst  leaf  pair. 

In  Nuphar  and  Brasenia  the  seed-     ^*  ^" 
ling  escapes  from  the  seed  by  pushing  out  a  plug  which  before 
germination  occupies   the  passage  intended  for  the  exit  of  the 
young  plant. 

The  seeds  of  Utricularia  commence  to  genninate  in  the  muddy 
substratum,  but  as  the  embryo  emerges  the  newly  formed  tissues 


Fig.  272.  Naias  major. 
Seedling  with  tem- 
porary primary  root 
bearing  cluster  of 
root-hairs.  (After 
Irmisch.) 


194  FRESH- WATER  BIOLOGY 

are  so  buoyant  that  the  seedUng  rises  to  the  water  surface  often 
carrying  with  it  the  remains  of  the  old  seed. 

By  vertical  distribution  is  understood  that  which  exists  in  a 
plane  more  or  less  perpendicular  to  the  earth's  surface  and  may  be 
illustrated  by  the  distribution  one  may  observe  in  passing  from 
valley  to  mountain-top  or  by  comparison  of  species  found  at  vari- 
ous depths  in  lake  or  ocean.  Horizontal  distribution  is,  of  course, 
in  a  plane  more  or  less  conformable  to  the  earth's  surface  and  is 
such  as  one  notices  in  passing  from  east  to  west  or  north  to  south, 
etc.  Now  the  factors  which  determine  the  horizontal  distribu- 
tion of  water  plants  are:  first,  the  chemical  composition  of  the 
water,  a  factor  which  gives  the  two  large  divisions  of  fresh  and  salt 
water  plants;  second,  temperature  which  gives  zones  of  plant  life 
such  as  arctic,  temperate,  tropical,  etc. ;  third,  competition  among 
the  plants  themselves,  a  factor  which  is  hkewise  influential  in 
vertical  distribution  though  perhaps  to  a  less  degree;  and  fourth, 
the  nature  of  the  substratum,  which  is,  of  course,  most  influential  in 
the  distribution  of  species  which  grow  rooted  to  the  bottom. 

To  what  extent  chemical  composition  of  the  water  is  a  factor  in 
the  distribution  of  fresh-water  plants  cannot  at  present  be  stated. 
Sulphur  springs  and  waters  having  unusual  composition  are  not,  of 
course,  fresh  water.  By  the  latter  term  is  understood  such  as 
occurs  in  the  rivers  and  lakes  and  such  as  may  be  used  as  drink  by 
the  animals,  so  far  as  chemical  composition  is  concerned.  Such 
waters  differ,  of  course,  in  the  quantity  and  quality  of  constituents; 
but  whether  such  differences  are  in  themselves  independent  of 
other  factors,  sufficient  to  determine  distribution,  cannot  at  present 
be  stated. 

Suppose  we  should  find  that  the  water  of  some  lake  in  Wisconsin 
is  considerably  different  in  chemical  composition  from  that  of  a 
lake  in  New  York  and  a  species  of  Potamogeton,  for  example,  which 
is  abundant  in  the  Wisconsin  lake  but  unknown  to  the  waters  of 
the  New  York  lake,  be  taken  to  the  New  York  lake  and  planted 
there.  If  this  plant  grows  well  in  the  New  York  lake  we  would 
say  that,  other  conditions  being  equal,  the  difference  in  chemical 
composition  of  the  water  in  the  two  lakes  is  not  a  determining 
factor  in  the  horizontal  distribution  and  that  the  absence  of  the 


THE   LARGER  AQUATIC   VEGETATION  195 

Wisconsin  species  in  the  New  York  lake  must  be  attributed  to 
some  other  cause  or  causes.  Experimental  evidence  is  lacking  for 
stating  to  what  extent  the  chemical  composition  of  the  water 
becomes  a  determining  factor  in  fresh  water. 

The  important  influence  of  temperature  on  distribution  is  at 
once  apparent,  although  the  influence  exerted  by  it  is  much  farther 
reaching  than  is  at  first  supposed.  Of  course,  the  forms  of  the 
arctic  waters  would  be  '' cooked"  by  the  heat  of  the  tropical  waters. 
It  has  recently  been  ascertained  that  the  colder  waters  support  a 
more  abundant  plankton  than  the  tropical  waters,  and  one  writer 
has  explained  this  fact  upon  the  basis  that  the  colder  waters  are 
richer  in  nitrates  and  nitrites  because  the  decomposition  of  organic 
matter  proceeds  much  more  slowly  and  the  organisms  causing  decay 
are  not  so  numerous  and  less  active.  Such  considerations  offer  a 
gHmpse  of  how  indirectly,  yet  effectively,  the  various  factors  may 
operate  to  determine  distribution. 

The  competition  of  species  for  space  may  be  considered  a  factor 
in  horizontal  distribution,  although  it  operates  quite  locally  and 
does  not  work  to  modify  the  flora  of  large  areas.  Chara  is  infre- 
quent on  the  alluvial  bottoms  where  other  species  are  present  in 
abundance,  but  this  is  not  because  it  prefers  poorer  soils  but  because 
it  is  prevented  from  occupying  the  soil  of  its  choice  by  the  other 
species. 

The  character  of  the  substratum  is  an  important  factor;  in  fact, 
it  is  possible  to  predict  the  nature  of  the  bottom  from  the  species 
that  are  found  growing  in  it.  Among  the  islands  of  western  Lake 
Erie  Potamogeton  heteropkyllus  is  common  on  the  reefs  and  pebbly 
shores  but  is  not  noticeable  in  the  coves  with  a  good  soil  substra- 
tum and  so  prominent  is  it  in  the  former  places  that  its  presence 
may  be  considered  characteristic  of  the  flora. 

Light  cannot  be  counted  a  factor  in  horizontal  distribution  be- 
cause there  is  always  sufficient  illumination  within  the  limits  estab- 
lished by  other  factors.  In  vertical  distribution  light  is  probably 
the  most  important  factor.  The  amount  of  illuminating  power 
lost  in  passing  to  a  given  depth  is  quite  variable  in  different  waters. 
Fol  and  Sarasin  found  in  Lake  Geneva,  in  September,  hght  at 
170  meters,  and  at  120  meters  a  photographic  plate  was  darkened. 


196  FRESH-WATER    BIOLOGY 

In  April  they  were  able  to  detect  light  at  250  meters.  Of  course 
the  clearness  of  the  water  has  much  to  do  with  the  penetration  of 
light  rays.  One  can  see  deeper  into  the  water  of  Lake  Superior  or 
of  Lake  Huron  than  into  that  of  Lake  Erie.  The  latter  is  shal- 
lower with  much  of  the  bottom  clay,  so  that  the  water  always  holds 
minute  particles  in  suspension  which  greatly  interfere  with  the 
penetration  of  light.  The  red  and  yellow  rays  contained  in  the 
beams  of  sunlight  are  more  readily  absorbed  than  those  of  higher 
refrangibility,  as  the  blue  and  violet,  but  whether  this  is  of  any 
importance  in  determining  the  vertical  distribution  cannot  be 
stated. 

Schimper  gives  6  meters  as  the  maximum  depth  for  phanerogams, 
although  the  lower  forms,  such  as  Char  a  and  Nitella,  are  said  to 
have  been  found  as  deep  as  30  meters.  Temperature  is  of  little 
importance  because  the  variations  are  so  slight  within  the  limits 
established  by  light.  This  is  not  so  much  the  case  with  the  free- 
swimming,  lower  forms,  but  only  the  larger  plants  are  considered 
here. 

It  is  impracticable  to  attempt  an  elaborate  classification  of  water 
plants  according  to  their  habitat  or  adaptation  to  environment. 
In  some  localities  distinct  zones  of  vegetation  may  be  observed 
which  are  apparently  determined  by  the  depth  of  water.  Magnin 
was  able  to  distinguish  four  zones  in  the  lakes  of  the  Jura.  First 
is  the  littoral,  with  a  maximum  depth  of  3  meters,  which  may  be 
divided  into  Phragmitetum  with  Phragmites  communis  as  typical 
and  Scirpetum  with  Scirpiis  lacustris,  sedges,  Eqiiisetmn,  etc.,  as 
representative.  A  second  zone,  the  Nupharetum,  extending  to  3  or 
4  meters,  is  composed  of  plants  with  large  floating  leaves  such  as  are 
common  among  the  Nymphaeaceae.  The  third  zone,  the  Pota- 
mogetonetum,  in  water  4  to  6  meters  deep,  is  characterized  by 
presence  of  several  species  of  Potamogeton,  especially  perjoliatus, 
crispus,  lucens,  and  others.  The  fourth  zone,  Characetum,  occupies 
deep  water,  8  to  12  meters,  where  Chara,  Naias,  and  some  mosses 
cover  the  bottom. 

The  flora  of  almost  any  lake  may  be  regarded  as  composed  of 
zones  and  even  rivers  and  small  streams  show  plant  societies,  but 
a  grouping  for  one  locality  is  frequently  inapplicable  to  some  other, 


THE  LARGER  AQUATIC  VEGETATION  197 

and  the  depth  oi  water  for  a  species  varies  much  according  to 
clearness  and  other  factors  which  may  be  incidental  to  a  particular 
region. 

It  is  possible  to  make  a  general  grouping  which  will  indicate  the 
important  conditions  and  varieties  of  environment.  To  some  one 
of  the  groups  thus  established  any  aquatic  plant  may  be  assigned. 

I.   Plants  without  attachment. 

((z)  Plankton,  free  swimming,  microscopic. 
{b)  Macroscopic,  possibiUty  of  attachment  by  accidental 
lodgment,  as  Lemna,  Ceraiopliyllum,  filamentous  algae 
common  on  plants  in  coves. 
II.   Plants  attached  to  substratum. 

(a)  Submerged,  algae  as  Chara  and  Cladophora,  and  phan- 

erogams as  Vallisneria,  Elodea. 

(b)  Partially  submerged,  usually  with  floating  or  emersed 

leaves,  as  Nymphaea,  Bidens  beckii. 
III.    Swamp  plants  or  marsh  forms  with  roots  and  rhizomes  under 
water  but  leaves  usually  emersed   though  able   to 
endure  inundation  and  temporary  submersion. 

Sometimes  representatives  of  each  of  these  three  classes  may  be 
found  in  one  small  lake,  especially  if  the  water  gradually  deepens 
from  a  marsh  or  low  shore  as  in  Lake  St.  Clair  w^here  the  wholly 
submerged  species  become  so  abundant  as  to  form  an  aquatic 
meadow.  Potamogeton  perfoliatus,  P.foliosus,  P.  zosteraejoliiis,  Val- 
lisneria, Naias,  Chara,  Nitella,  Elodea,  and  Myriophyllum  may  be 
found  in  dense  patches  covering  the  bottom.  In  such  formations 
the  struggle  for  space  must  be  severe  and  from  observations  during 
three  summers  on  Lake  Erie  I  should  say  that  Vallisneria  is  a  con- 
queror. Naias  flexilis  may  be  found  in  distinct  formations  in 
which  other  species  are  very  infrequent  but  being  an  annual  the 
creeping  rootstocks  of  Vallisneria  may  easily  invade  its  territory. 

In  many  of  the  small  inland  lakes  the  water  plants  are  important 
agents  as  soil  collectors.  The  aquatic  meadows  tend  to  filter  the 
water  so  that  suspended  matter  sinks  to  the  bottom.  As  the  lake 
gradually  becomes  filled  and  the  water  grows  more  shallow  a  suc- 
cession of  plant  societies  occurs.     The  aquatic  meadows  >'icld  to  the 


ig8  FRESH- WATER    BIOLOGY 

Potamogetons  with  floating  leaves  and  especially  the  Nymphaea- 
ceae  which  are  followed  by  amphibious  species  until  finally  the 
bog  vegetation  appears  which  may  later  support  the  ordinary 
terrestrial  plants. 

It  may  be  supposed  that  aquatic  phanerogams  have  descended 
from  aquatic  or  from  land  species.  The  former  supposition  im- 
plies that  the  plants,  as  they  are  now,  represent  the  maximum  of 
complexity  in  structure  that  has  thus  far  developed.  The  latter 
supposition  impHes  that  the  simpler  vascular  system  is  not  to  be 
considered  as  foreshadowing  a  more  elaborate  structure  to  be 
evolved  in  the  future  but  is  a  reduced  form  of  more  highly  developed 
structure  present  in  the  terrestrial  ancestors.  Perhaps  some  spe- 
cies have  had  land  ancestors,  while  others  have  descended  from 
aquatic  forms. 

Considering  the  whole  list  of  fresh-water  plants,  it  is  noteworthy 
that  the  abundant  groups  are  algae  and  phanerogams.  Bryophytes 
and  pteridophytes  do  occur,  but  infrequently  in  comparison  with 
the  former  groups,  the  thallophytes  and  spermatophytes,  which 
include  a  large  percentage  of  aquatic  vegetation. 

Would  the  great  plant  groups  be  represented  in  this  proportion 
if  the  evolution  of  aquatic  forms  had  proceeded  as  in  the  case  of 
land  plants?  Does  not  a  water  environment  insure  greater  uni- 
formity of  conditions  and  would  not  the  evolution  proceed  more 
slowly  and  the  intermediate  forms  more  likely  persist  in  such  en- 
vironment? How  could  the  great  groups  of  monocotyledons  and 
dicotyledons  ever  become  differentiated  from  ancestors  living 
wholly  submerged?  How  could  the  seed  habit  so  essentially  like 
that  of  land  plants  ever  be  acquired  by  the  descendants  of  sub- 
merged forms?  On  the  other  hand  if  water  forms  have  been 
derived  from  land  forms,  why  are  not  the  bryophytes  and  pterido- 
phytes which  are  frequent  in  moist  locahties  better  represented 
in  the  aquatic  flora?  The  change  from  aquatic  structure  to  ter- 
restrial must  be  much  more  difficult  than  from  terrestrial  to  aquatic. 
When  a  water  plant  is  suddenly  exposed,  the  loss  of  water  by  drying 
is  so  rapid  that  the  plant  must  die,  while  a  land  plant  may  endure 
submersion  tor  a  considerable  period.  In  one  case  the  change  of 
environment  causes  a  sudden  demand  for  a  complex  vascular  system 


THE  LARGER  AQUATIC  VEGETATION  1 99 

that  the  plant  Is  unable  to  supply.  In  the  other  case  the  land 
plant  may  persist  and  gradually  reduce  in  complexity  structures 
already  present.  Thus  it  is  that  the  reduction  of  the  vascular 
system  has  proceeded  in  the  same  manner  in  both  the  dicotyle- 
dons and  monocotyledons,  so  that  the  simplest  stem  structure  is 
alike  for  members  of  either  group.  In  Ceratophyllum  the  vascular 
system  has  become  so  simplified  that  its  dicotyledonous  relation- 
ship cannot  be  established  by  the  stem  structure. 

How  is  the  presence  of  stomata  on  submerged  leaves  to  be  ac- 
counted for?  It  can  hardly  be  supposed  that  they  are  developing 
in  anticipation  of  the  time  when  the  species  is  to  have  a  transpiring 
surface.  More  likely  is  it  that  these  stomata  are  reminders  of 
the  time  when  the  species  had  an  exposed  surface. 

In  the  genus  Utricularia  there  are  land  as  well  as  water  species 
and  the  presence  of  bladders  characterizes  both  varieties.  It  is 
hardly  probable  that  submerged  plants  accustomed  to  the  food 
supplied  in  solution  by  the  surrounding  water  should  acquire  an 
appetite  for  animal  food  and  develop  such  elaborate  and  unique 
organs  for  securing  nitrogenous  nourishment. 

In  some  cases,  as  in  Lemna,  the  ancestry  is  not  so  obvious  and 
convincing  evidence  is  difficult  to  obtain. 

The  pollination  o£  Zannichellia  under  water  has  been  previously 
mentioned  (Fig.  267).  In  such  cases  the  evolution  of  stamens  and 
pistils  cannot  be  regarded  as  having  occurred  in  wholly  submerged 
plants.  Much  less  difficult  it  is  to  understand  how  land  plants 
with  stamens  and  pistils  already  developed  could  gradualh'  be- 
come adapted  to  an  aquatic  habit  before  these  organs  would  dis- 
appear by  reduction. 

It  is  now  known  that  the  roots  of  several  of  our  genuine  aquatic 
species  bear  root-hairs  whose  presence  certainly  testifies  to  the 
absorbing  activity  of  the  roots  and  the  Ungering  terrestrial  habits 
necessitating  such  organs. 

It  must  be  noted  that  the  foregoing  discussion  is  purely  theo- 
retical and  the  intention  has  been  to  awaken  interest  in  the  study 
of  the  aquatic  flora  rather  than  to  offer  a  theory  of  origin  for  which 
any  originahty  could  be  claimed. 

Experimental  evidence  may  be  obtained  that  roots  are  organs 


200  FRESH-WATER   BIOLOGY 

for  absorption.^  It  is  possible  by  means  of  very  simple  apparatus 
to  actually  measure  the  water  which  a  root  absorbs  in  a  given  time. 
In  one  experiment  of  the  writer's  a  small  cutting  20  centimeters 
long  bearing  a  root  14  centimeters  long  was  used  and  this  un- 
branchcd  single  root  absorbed  5  cubic  centimeters  of  water  in 
24  hours. 

Another  method  can  be  used  to  demonstrate  that  roots  are 
organs  of  absorption.  A  certain  substance,  namely,  Uthium  nitrate, 
which  is  soluble  in  water,  is  offered  in  solution  to  the  roots.  The 
lithium  in  this  compound  burns  with  a  rose  red  flame  and  very 
small  traces  of  this  substance  in  plant  tissue  may  be  detected  by 
burning  portions  of  the  tissue  and  observing  the  color  given  to  the 
flame,  and  by  using  the  spectroscope  the  test  becomes  very  deUcate. 
In  this  method  it  is  only  necessary  to  enclose  the  root  in  a  bottle 
containing  the  lithium  nitrate  solution  by  means  of  a  flexible 
stopper  made  by  saturating  cotton  in  melted  vasehn.  After  a 
time  portions  of  the  stem  which  could  not  possibly  contain  lithium, 
unless  it  had  passed  to  it  from  the  roots,  are  burned  and  the  flame 
observed  with  the  spectroscope.  Such  tests  have  been  made  re- 
peatedly and  the  presence  of  the  Uthium  may  always  be  traced 
through  the  plant  to  whatever  distance  the  tissue  used  in  the 
test  allowed  it  to  travel  in  the  plant.  There  can  be  no  doubt 
then  but  that  the  roots  are  organs  for  absorption  and  that  sub- 
stances absorbed  by  them  are  conducted  upward  into  the  stem  and 
leaves.  The  distance  that  the  lithium  travels  in  a  given  tissue 
probably  does  not  represent  exactly  the  rate  of  ascent  of  the  up- 
ward current  but  indicates  a  rate  of  ascent  which  is  less  than  that 
of  the  water  passage  through  the  plant;  that  is,  water  travels 
upward  a  little  faster  than  the  lithium  which  it  holds  in  solution. 

Mention  has  been  made  of  the  fact  that  when  cuttings  of  Ranun- 
culus aquatilis  are  left  to  drift  in  the  water,  new  roots  arise  from 
the  stem  at  the  nodes.  These  roots  grow  directly  downward  and  do 
not  branch  until  after  penetrating  the  soil,  when  they  then  commence 
to  branch  repeatedly,  and  as  the  main  root  pushes  through  the  soil 

1  It  is  not  strictly  correct  to  speak  of  roots  as  organs  for  absorption.  The  struc- 
ture of  roots  is  such  that  solutions  can  pass  into  them.  However,  the  term  is  so 
commonly  employed  as  to  make  it  impracticable  to  use  other  phraseology  here. 


THE   LARGER   AQUATIC   VEGETATION  20I 

more  branches  are  formed  in  succession.  The  following  experi- 
ment seems  to  strongly  indicate  that  light  inhibits  the  formation 
of  lateral  branches  of  the  roots  and  that  the  roots  of  drifting  plants 
do  not  branch  because  of  the  exposure  to  the  Hght.  Five  cuttings 
of  equal  length  were  mounted  in  bottles  so  that  about  3  nodes  of 
the  stem  were  inside  the  bottle.  Five  similar  cuttings  were  Uke- 
wise  mounted  in  bottles  which  were  wrapped  with  black  cloth  so 
that  the  roots  which  developed  from  the  nodes  of  the  cutting 
inside  the  bottle  were  protected  from  the  light.  The  darkened 
plants  developed  in  all  22  roots  having  a  total  length  of  1048  centi- 
meters and  bearing  in  all  73  branches.  The  plants  exposed  to 
light  developed  28  roots,  having  a  total  length  of  459  centimeters 
and  bearing  not  one  single  branch.  The  influence  of  light  is  very 
evident. 

There  are  two  possible  reasons  why  soil  may  be  necessary  for 
good  growth.  First,  as  a  source  of  food  and,  second,  as  a  substratum 
into  which  the  roots  can  penetrate  to  anchor  the  plant.  If  the 
soil  is  not  necessary  as  a  source  of  food  the  ordinary  water  in  which 
the  plant  grows  should  furnish  sufficient  food.  If  the  soil  is  neces- 
sary only  as  a  substratum  to  anchor  the  plant  a  clean  washed 
sand  substratum  ought  to  do  equally  as  well.  Experiments  along 
this  line  have  been  completed  by  the  author  and  it  has  been  found 
that  soil  is  necessary  for  the  good  growth  of  every  one  of  the  plants 
tested.  Clean  washed  sand  cannot  be  substituted  for  soil  without 
sacrifice  of  growth  to  the  plant.  It  is  reasonably  certain  that  not 
one  of  our  common  water  plants  which  naturally  grows  well  rooted 
in  a  good  soil  bottom  could  live  through  an  entire  growing  season 
if  clean  washed  sand  should  be  substituted  for  its  ordinary  soil 
substratum. 

The  behavior  of  Ranunculus  aquatilis  is  interesting  as  indicating 
(figuratively  speaking)  an  effort  on  the  part  of  the  plant  to  secure 
a  soil  attachment.  This  species  lives  wholly  submerged  in  shallow, 
slowly  flowing  water.  The  leaves  are  finely  divided  and  collapse 
when  the  plant  is  taken  from  the  water.  The  stem  branches 
freely,  any  branch  being  able  to  continue  the  growth  of  the  plant 
if  the  main  stem  be  removed.  Roots  may  arise  at  any  exposed 
node,  except,  perhaps,  the  terminal  one.     If  a  fragment  a  few  inter- 


202  FRESH-WATER  BIOLOGY 

nodes  in  length  be  detached  and  left  floating,  roots  will  spring 
forth  from  the  nodes  or  joints  of  the  stem  in  from  6  to  lo  days. 
While  the  roots  are  lengthening  toward  the  bottom  the  stem  does 
not  increase  in  length  but  quickly  resumes  its  growth  after  the 
root  has  penetrated  the  soil.  More  roots  then  arise  from  the  newer 
nodes  of  the  stem  and  as  they  also  enter  the  soil  the  plant  is  drawn 
farther  down  and  fmally  becomes  firmly  anchored.  The  roots  of 
such  fragments  do  not  branch  before  reaching  the  soil  but  do 
so  very  shortly  after  the  substratum  is  penetrated.  Numerous 
lateral  roots  then  arise  and  form  in  succession  as  the  main  root 
advances. 

The  roots  are  well  supplied  with  hairs;  those  arising  from  the 
floating  fragments  are  often  covered  almost  their  entire  length 
with  root-hairs.  In  one  instance  a  root  was  found  to  be  clothed 
with  root-hairs  for  a  distance  of  45  centimeters,  which  was  practi- 
cally its  entire  length.  Since  this  plant  ordinarily  grows  rooted 
in  the  soil  whatever  growth  it  makes  under  natural  conditions 
must  be  regarded  as  the  normal  growth  and  there  is  no  escape 
from  the  conclusion  that  the  growth  becomes  abnormal  when 
sand  is  substituted  for  soil. 

How  is  the  superior  growth  of  plants  rooted  in  the  soil  to  be 
accounted  for?  Is  it  possible  that  the  soil  furnishes  plants  rooted 
in  it  with  food  materials  that  are  not  available  to  plants  suspended 
in  the  water  standing  over  it?  In  1850  it  was  discovered  that 
liquid  manure  loses  its  color  if  drained  through  a  layer  of  soil 
sufficiently  thick.  Not  only  does  the  solution  lose  color  but  the 
organic  and  inorganic  matter  originally  in  it  is  considerably  re- 
duced after  filtering  through  the  soil.  This  property  or  capacity 
of  soil  to  withdraw  salts  from  solution  is  now  well  established 
although  not  well  understood.  For  a  time  authors  were  not 
agreed  as  to  whether  the  retention  or  fixation  of  salts  by  the  soil 
is  a  chemical  or  a  physical  process.  Now  it  is  generally  under- 
stood that  both  chemical  and  physical  processes  operate  to  this 
end.  Some  substances  seem  to  be  held  much  more  firmly  by  the 
soil  than  others.  Various  investigations  go  to  show  that  most 
soils  absorb  the  oxids,  salts  of  the  alkalis  and  alkaline  earths  of 
potassium,  ammonium,  magnesium,  sodium,  and  calcium  in  the 


THE  LARGER  AQUATIC  VEGETATION  203 

order  given.  It  must  be  remembered,  however,  that  this  reten- 
tion of  dissolved  substance  by  the  soil  is  neither  absolute  nor  per- 
manent. We  may  suppose  that  in  the  case  of  a  lake  there  are  two 
opposing  processes  operating  in  which  the  soil  on  the  one  hand 
tends  to  withdraw  salts  from  the  water  and  retain  them,  while  the 
water  on  the  other  hand  tends  to  bring  salts  from  the  soil  into 
solution.  As  a  consequence  of  those  two  processes  the  lake  water 
contains  certain  salts  in  much  greater  proportion  than  others 
which  seem  to  be  firmly  held  by  the  soil.  Just  how  such  condi- 
tions influence  the  plant  is  only  partially  known. 

It  seems  as  though  the  substances  needed  by  the  plant  are  the 
ones  most  firmly  retained  by  the  soil,  —  especially  the  nitrogen, 
phosphorous,  and  potassium  compounds,  —  and  yet  it  is  hardly 
possible  to  say  that  the  water  does  not  contain  enough  of  those 
substances  in  solution  for  the  larger  plants.  While  plants  cannot 
select  certain  substances  and  reject  others  they  can  to  a  certain 
extent  regulate  the  amount  of  a  substance  which  they  absorb. 
It  is  evident  that  all  of  the  substances  absolutely  necessary  for 
the  growth  of  plants  must  be  present  in  the  water  in  solution 
because  there  are  so  many  forms  which  Hve  as  freely  swimming 
objects  and  depend  wholly  upon  the  water  in  which  they  live  for 
food.  Lemna,  the  so-called  duckweed,  Hves  in  the  water  and  de- 
pends upon  the  water  only  for  food  (mineral),  but  Lemna  has 
been  analyzed  and  found  to  contain  substances  in  much  greater 
proportion  than  does  the  water  in  which  it  grows.  One  investi- 
gator found  the  ash  of  this  plant  to  contain  13.16  per  cent  of  potas- 
sium, and  8.73  per  cent  of  phosphoric  acid,  while  the  mineral  resi- 
due obtained  by  evaporating  some  of  the  water  in  which  the  Lemna 
was  growing  contained  those  substances  in  the  respective  propor- 
tions of  3.97  per  cent  and  2.619  P^^  cent.  However,  the  fact  that 
Lemna  can  obtain  all  the  food  necessary  from  the  water  alone  and 
that  some  other  plants  must  be  rooted  in  the  soil  to  thrive  is  no 
more  remarkable  than  the  fact  that  some  animals  are  herbivorous 
while  others  are  carnivorous. 

Water  plants  may  be  found  growing  in  clayey,  sandy,  gravelly, 
or  loamy  soil.  From  field  observation  one  would  say  that  the 
loamy  soil  supports  the  greatest  variety  of  species.     Wherever  the 


204 


FRESH-WATKR   BIOLOGY 


soil  is  very  sandy  the  species  may  be  abundant  and  likewise  where 
the  substratum  is  distinctively  clay  or  gravel.     From  field  observa- 
tion alone  it  would  hardly  be  possible  to  say  that  the  quality  of 
the  soil  is  the  determining  factor,  because  sand  and  gravel  are  more 
common  where  other  factors  come  in  to  influence  growth  and 
species  selection.     The  loamy  soil  is  most  abundant  in  the  coves 
and  bayous  where  the  water  is  quiet  and  it  is  in  just  such  places 
that  plants  make  good  growth  and  wealth  of  species  abounds. 
Plants  which  would  perish  in  exposed  situations  make  excellent 
growth  in  the  protected  coves  and  we  cannot  be  certain  from  field 
observ'ation  whether  the  difference  is  to  be  attributed  to  the  soil 
or  to  the  more  favorable  locality.     By  direct  experiment,  however, 
it  is  not  difficult  to  ascertain  what  quality  of  substratum  favors 
growth.     In  such  experiments  it  is  very  desirable  to  have  condi- 
tions as  nearly  Uke  those  in  nature  as  possible.     Three  tyipes  of 
soil  were  selected,  clayey,  sandy,  and  loamy.     A  large  rectangular 
glass  aquarium  was  used  to  contain  a  substratum  of  each  one  of 
the  given  soil  t}^es.     Then  the  three  aquaria  were  placed  upon  a 
submerged  platform  so  that  the  aquaria  themselves  were  also  sub- 
merged.    This  arrangement  made  the  aquaria  similar  in  all  condi- 
tions except  as  to  the  quality  of  soil,  and  differences  in  the  growth 
of  plants  in  each  aquarium  could  be  very  easily  referred  to  the 
varying  quality  of  soil.      Two  types  of   plants  were    tested   in 
this  way  —  one  was  Vallisneria,  a  t^-pical  water  plant  of  the  phan- 
erogams, and  Chara,  one  of  the  higher  algae.     The  latter  does  not 
have  roots  but  simple  structure  called  rhizoids  which  help  to  secure 
attachment.     With   both   of   these   plants   the   best  growth   was 
made  in  the  loamy  soil  and  the  poorest  in  the  clay  soil,  while  the 
sandy  soil  which  of  course  contained  some  organic  debris  supported 
a  medium  growth.     In  the  case  of  Chara  an  equal  number  of  plants 
of  equal  size  were  planted  so  that  the  dry  weight  of  the  total 
growth  in  each   aquarium  might  be  compared.     If   the  poorest 
growth  in  clay  be  taken  as  one,  then  that  in  sand  would  be  about 
2.06,  while  that  in  the  loamy  soil  would  be  about  3.33.     The  total 
dry  weight  is  of  course  a  fair  indication  of  the  relative  amount  of 
growth  made  and  there  can  now  be  no  doubt  but  that  the  qaahty 
of  soil  is  much  concerned  with  the  plant  growth  upon  it  and  that 


THE  LARGER  AQUATIC   VEGETATION  205 

of  these  three  types  of  soil  the  loamy  one  is  capable  of  supporting 
the  best  growth. 

That  soil  is  necessary  for  good  growth  has  been  previously  men- 
tioned and  explained.  The  interesting  question  arises  — why  is  it 
that  plants  artificially  anchored  but  not  allowed  to  root  in  the  soil 
are  unable  to  make  a  good  growth?  It  surely  must  be  a  matter 
of  nutrition,  because  the  soil  could  hardly  be  so  potent  an  influence 
in  any  other  way.  When  the  plants  are  artificially  anchored  all 
other  conditions  are  the  same  as  with  plants  rooted  in  the  soil 
except  that  the  roots  of  the  suspended  plants  are  exposed  to  light 
and  are  unable  to  absorb  nourishment  from  the  soil.  That  light 
in  some  measure  retards  root  development  and  thus  diminishes  the 
absorbing  capacity  of  the  plant  is  certain,  but  this  factor  is  entirely 
too  small  to  account  for  the  stunted  growth  of  plants  denied  a  soil 
substratum. 

Chemical  analysis  has  been  employed  for  the  purpose  of  securing 
if  possible  some  clue  to  the  reason  why  these  plants  cannot  make 
normal  growth  unless  rooted  in  the  soil.  Vallisneria  spiralis,  the 
eel-grass,  whose  elaborate  arrangement  for  pollination  has  been 
described,  was  selected  as  a  typical  water  plant  of  wide  distribu- 
tion. The  history  of  the  material  to  be  analyzed  must,  of  course, 
be  known,  and  in  this  case  a  large  number  of  small  plants  of 
uniform  size  were  carefully  taken  from  the  lake  bottom  and  trans- 
ferred to  submerged  boxes  which  were  alike,  except  that  one  con- 
tained soil  and  the  other  did  not.  The  roots  of  the  plants  arti- 
ficially anchored  in  the  box  without  soil  were  not  permitted  to 
touch  the  box,  but  dangled  in  the  water,  and  thus  from  the  water 
only  could  nourishment  be  taken.  After  a  certain  time  the  plants 
were  gathered  and  carefully  washed,  only  the  Uving  specimens,  of 
course,  being  saved.  In  order  to  establish  a  basis  for  comparison 
the  volume  of  each  group  of  plants  was  obtained  b)'  immersion  in 
water  and  measuring  the  displacement.  The  volume  of  the  plants 
rooted  in  soil  was  taken  to  be  just  twice  the  volume  of  the  plants 
artificially  anchored.  This  material  was  then  dried  out  and  the 
dry  weight  taken,  which,  for  the  plants  rooted  in  soil,  was  52.7 
grams  and  for  those  suspended  37.2  grams.  These  figures  show  at 
once  that  the  suspended  plants  are  relatively  much  heavier  than 


2o6  FRESH-WATER  BIOLOGY 

the  others.  Further  analysis  discloses  the  reason  for  this.  The 
suspended  plants  were  found  to  contain  relatively  twice  as  much 
starch  as  the  others.  This  means  that  the  suspended  plants,  though 
dwarfed  to  one-half  the  normal  size,  still  contained  the  same  weight 
of  starch  that  they  would  have  contained  if  allowed  to  grow  as  the 
others  did  in  the  soil.  Evidently  the  retarded  growth  cannot  be 
because  of  any  scarcity  of  starch.  Since  this  process  of  starch- 
making  is  one  of  the  very  vital  processes  of  the  plant  it  is  im- 
portant to  know  that  being  artificially  anchored  does  not  disturb 
this  fundamental  function  of  the  plant.  However,  as  a  conse- 
quence of  this  fact,  it  is  evident  that  the  suspended  plants  must 
soon  become  overcrowded  wHlth  stored  starch  and  this  result  in 
itself  may  be  a  reason  for  further  disturbance  of  \ital  processes 
with  eventually  fatal  consequences. 

The  proteid  content  of  the  suspended  plants  was  found  to  be 
smaller,  suggesting  that  sufficient  supply  of  nitrogenous  food  was 
not  available  for  them.  This  shows  that  the  suspended  plants 
must  have  very  soon  fallen  into  an  abnormal  condition  in  which 
the  two  very  fundamental  functions  of  starch-making  and  of  pro- 
teid synthesis  were  not  properly  balanced. 

The  analysis  showed  further  that  the  suspended  plants  contained 
a  relatively  smaller  proportion  of  mineral  matter,  which  of  course 
indicates  that  they  were  unable  to  secure  and  use  as  much  mineral 
food  as  they  needed.  The  elements  most  deficient  in  the  suspended 
plants  were  potassium  and  phosphorus,  two  of  the  most  essen- 
tial substances  which  are  no  doubt  much  concerned  with  the  man- 
ufacture of  food  materials. 

So  far,  then,  as  present  knowledge  is  concerned  we  can  say  that 
the  plants  are  dependent  upon  the  soil  for  a  sufficient  supply  of 
certain  substances,  especially  nitrogen,  potash,  and  phosphorus. 
When  the  plants  are  compelled  to  take  all  their  nourishment  from 
the  water  an  abnormal  condition  soon  arises  by  reason  of  a  dis- 
proportion between  proteid  synthesis  and  starch  manufacture  which 
is  manifested  by  a  retarded  growth  and  final  death. 

That  such  statements  are  not  conclusively  proven  must  not  be 
overlooked  and  just  why  they  cannot  be  regarded  as  beyond  doubt 
would  be  tedious  to  explain  here. 


THE   LARGER  AQUATIC  VIXETATTON  207 

The  natural  conditions  of  our  lakes  and  rivers  are  undoubtedly 
changing  from  decade  to  decade.  The  extensive  destruction  of 
forests  that  has  occurred  in  the  lake  region  and  along  tributary 
streams  has  certainly  indirectly  affected  the  plant  and  animal  life 
in  the  lakes,  although  at  present  it  cannot  be  stated  in  any  detail 
how  such  influences  have  operated.  The  same  may  be  said  in 
regard  to  the  vast  volume  of  organic  matter  that  constantly  comes 
to  the  lakes  and  rivers  as  sewage  from  the  cities.  The  influences 
which  operate  to  regulate  or  determine  the  food  supply  of  the 
water  are  numerous.  Adequate  knowledge  is  only  possible  by  a 
thorough  study  of  the  food  relations  among  the  animals  themselves, 
between  the  animals  and  plants  and  between  the  plants  and  the 
soil. 

Cycle  of  matter.  —  Animals  cannot  organize  food  from  inorganic 
substances  but  must  use,  as  food,  matter  that  is  already  organized, 
either  as  vegetable  or  animal  substance.  Plants,  however,  can 
and  do  organize  food,  using  both  the  mineral  salts  occurring  in  the 
soil  or  water,  and  the  gaseous  carbon  dioxid  which  occurs  in  the 
air  and  in  the  water.  The  dependence  of  the  animals  upon  the 
plants  is  at  once  apparent  and  the  dependence  of  the  plants  upon 
the  earth  and  air  is  also  apparent.  The  most  important  influence 
exerted  by  plants  in  fresh-water  biology  is  undoubtedly  concerned 
with  their  nutrition  but  they  are  also  important  in  other  ways. 

As  geological  agents  in  the  formation  of  marl.  —  The  formation  of 
lime  incrustations  by  water  plants  has  already  been  considered,  so 
that  it  is  only  necessary  to  state  here  that  considerable  e\idence  has 
been  brought  forward  to  show  that  the  large  marl  deposits  in  the 
marl  lakes  have  accumulated  as  already  described  through  the  ac- 
tivity of  plants,  especially  Chara. 

As  aerating  agents.  —  Both  animals  and  plants  must  have  air  to 
breathe,  and  in  running  water  or  open  lakes  there  is  usually  suffi- 
cient oxygen  dissolved  in  the  water  to  support  the  respiration  of 
the  organisms  present.  In  the  still  waters  of  coves  and  bayous, 
however,  conditions  are  different.  It  is  in  such  places  that  organic 
debris  tends  to  accumulate,  and,  in  decay,  overcharges  the  water 
with  the  gases  of  decomposition,  especially  that  of  carbon  dioxid. 
Of  course,  whatever  animal  life  is  present  under  such  conditions 


2o8  FRESH-WATER   BIOLOGY 

still  further  reduces  the  oxygen  supply  and  increases  the  carbon 
dioxid.  The  green  plants  on  the  other  hand  during  sunlight  are 
constantly  using  the  carbon  dioxid  for  making  starch  and  giving 
off  oxygen  as  a  waste  product  of  the  process.  In  this  process  the 
volume  of  oxygen  released  equals  the  volume  of  carbon  dioxid 
used,  so  that  an  aquatic  meadow,  growing  vigorously  in  a  still- 
water  cove,  would  be  very  efficient  in  keeping  the  water  well  aerated 
and  much  to  the  advantage  of  all  the  animal  hfe  finding  food  and 
shelter  there. 

As  ajfording  shelter  and  refuge  for  small  animals.  —  In  these 
aquatic  meadows  many  kinds  of  young  fish  spend  their  early  Ufe 
during  the  period  when  they  require  protection  from  enemies. 
Here,  too,  many  of  the  smaller  animals  pursued  by  enemies  find 
temporary  refuge  or  are  able  to  evade  their  pursuers. 

As  a  base  of  attachment  for  algae.  — Wherever  the  larger  plants 
occur  may  be  found  also  many  smaller  and  more  lowly  organized 
forms  which  use  the  larger  plants  as  supports.  The  simple  forms, 
which  are  usually  algae,  would  be  unable  to  Hve  as  free  swimming 
individuals,  and  since  many  of  them  are  used  as  food  by  the  animals 
it  is  important  that  they  should  be  allowed  to  develop  abundantly. 
The  dead  as  well  as  the  Hving  larger  plants  may  be  useful  in  this 
way  and  only  direct  observation  will  reveal  to  one  how  much  of 
importance  the  larger  plants  are  in  this  one  particular. 

As  organizers  of  matter  and  distributors  of  nourishment  for  the 
plankton.  —  If,  as  formerly  supposed,  water  plants  take  their  min- 
eral food  from  the  surrounding  water  and  not  from  the  soil  at  all, 
then  it  is  evident  that  during  the  growing  season  these  rooting 
aquatics  would  be  continually  diminishing  the  food  supply  of  the 
free  swimming  plants,  or  the  plant  plankton,  and  this  would,  of 
course,  result  in  a  decreasing  food  supply  for  the  animals  dependent 
upon  the  plant  plankton  for  nourishment.  In  view  of  the  evidence 
now  at  hand  it  is  certain  that  these  larger  plants  rooting  in  the 
bottom  absorb  inorganic  matter  from  the  soil  and  organize  this 
material  into  plant  tissue  which  can  be  used  as  food  by  the  animals 
and  also  by  parasitic  and  saprophytic  plants  which  can  also  be  used 
as  food  by  the  animals.  This,  then,  is  perhaps  the  most  important 
role  of  the  larger  aquatic  plants,  in  that  their  life  work  results  in  an 


THE   LARGER   AQUATIC  \'EGETATIOX  209 

actual  contribution  of  organic  matter  to  the  food  supply  of  the 
animal  Ufe.  There  is  no  doubt  but  that  in  a  body  of  water  like 
Lake  Erie  this  contribution  of  organic  matter  made  from  soil  and 
air  constituents  that  would  otherwise  remain  unused  could  be  meas- 
ured in  tons  even  in  a  single  growing  season. 

In  the  marshes  and  shallow  places  immense  quantities  of  plant 
debris  are  constantly  occurring  and  with  changing  wind  these 
masses  of  organic  matter  are  carried  far  out  into  the  lake,  where, 
during  the  period  of  slow  decay,  they  furnish  food  to  hosts  of  small 
animals  and  in  the  decay  yield  valuable  mineral  salts,  thus  enrich- 
ing the  water  to  the  advantage  of  the  free  swimming  forms. 

IMPORTANT  REFERENCES   ON   HIGHER   AQUATIC   PLANTS 

Britton,  N.  L.,  and  Brown,  A.     1896-98.     Illustrated  Flora  of  the  Northern 
United  States,  Canada,  and  the  British  Possessions.     3  v.     New  York. 

CoNARD,  H.  S.     1905.     The  Waterlilies:  a  Monograph  of  the  Genus  Nym- 
phaea.     Carnegie  Inst,  of  Wash.,  Pub.  No.  4. 

Coulter,  J.  M.,  Barnes,  C  R.,  and  Cowles,  H.  C.     191  i.     Textbook  of 
Botany.     Vol.  2.     New  York. 

Engler,  A.     1900+.     Das  Pfianzenreich.     Leipzig. 

Engler,  A.,  and  Prantl,  K.    1887+.    (See  list  in  Chapter  VL) 

Gluck,  Hugo.  1905-06.  Biologische  und  morphologische  Untersuchungen 
iiber  Wasser  und  Sumpfgewachse.     2  v.     Jena. 

Kerner,  a.,  and  Oliver,  F.  W.  1895.  The  Natural  History  of  Plants, 
their  Forms,  Growth,  Reproduction  and  Distribution.  2  v.  in  4 
New  York. 

Morong,  Thomas.     1886.     Studies  in  the  Typhaceae.    Bull.  Torrey  Bot. 
Club,  15:   1-8,  73-81. 
1892-93.     The  Naiadaceae  of  North  America.     Mem.  Torrey  Bot.  Club, 
V.  4,  No.  2;  65  pp.,  55  pi. 

Pieters,  a.  J.     1894.     The  Plants  of  Lake  St.  Clair.     Bull.  Mich.  Fish  Com., 
No.  2;  10  pp.     Map. 
1901.     The  Plants  of  Western  Lake  Erie  with  Observations  on  their  Distri- 
bution.    Bull.  U.  S.  Fish  Comm.,  21:  57-79,  10  pi. 

Pond,  R.  H.  1905.  The  Biological  Relation  of  Aquatic  Plants  to  the  Sub- 
stratum.    Rept.  U.  S.  Com.  of  Fish  and  Fisheries  1003:  483-526. 

Warming,  J.  E.  B.  1909.  Oecology  of  Plants;  an  Introduction  to  the 
Study  of  Plant  Communities.     Oxford. 


CHAPTER   VIII 
AMOEBOID    PROTOZOA    (Sarcodina) 

By   C.   H.   EDMONDSON 

Assistant  Professor  of  Zoology,  University  of  Oregort 

The  minute  animals  consisting  of  but  a  single  cell  throughout 
their  existence  are  commonly  called  Protozoa.  They  are  world- 
wide in  their  distribution,  swarming  the  seas  from  the  surface  to 
great  depths  and  being  found  abundantly  under  almost  all  condi- 
tions of  moisture  in  fresh  water  as  well  as  in  the  fluids  and  tissues 
of  other  animals  where  many  exist  as  parasites. 

The  Protozoa  may  be  grouped  under  the  following  subphyla: 

Subphylum  I.  Sarcodina.  —  Moving  by  means  of  temporary 
extensions  of  the  protoplasm,  called  pseudopodia. 

Subphylum  II.  Mastigophora.  —  Pro\ided  with  one  or  more 
whip-hke  processes,  called  flagella,  as  organs  of  locomotion  or  for 
securing  food. 

Subphylum  III.  Infusoria.  —  Locomotor  organs  in  the  form  of 
fine  hair-like  structures,  called  cilia,  present  during  the  entire  ex- 
istence or  during  the  embryonic  stage  only. 

Subphylum  IV.  Sporozoa.  —  Without  true  organs  of  locomo- 
tion; usually  reproducing  by  spores.  Parasitic.  No  free  living 
forms. 

It  will  be  observed  that  the  above  grouping  is  based  upon  the 
organs  of  locomotion.  This  basis  has  been  found  a  convenient 
one  for  classification  and  study,  little  difficulty  arising  except  in 
unusual  cases  where  species  are  found  to  possess  more  than  one 
kind  of  motile  organs  or  where  species  pass  through  distinct  phases 
during  their  life  cycle.  Of  all  the  Protozoa  those  representing  the 
highest  degree  of  simplicity  of  structure  and  the  greatest  general- 
ization of  life  processes,  if  not  the  oldest  in  point  of  time,  are  to  be 
found  in  the  group  possessing  pseudopodia.  These  form  the  sub- 
ject of  the  present  chapter,  the  flagellate  and  ciliate  forms  are 
considered  in  the  next,  and  the  parasitic  Sporozoa  do  not  properly 
call  for  attention  in  this  work. 

210 


AMOEBOID   PROTOZOA    (SARCODINA)  21  i 

Previously  unknown  on  account  of  their  diminutive  size,  these 
organisms  at  once  attracted  the  early  workers  with  the  microscope. 
Although  Leeuwenhoek  as  early  as  1675  initiated  the  study  of 
Protozoa  by  his  discovery  of  Vorticella,  an  infusorian,  without 
doubt,  Rosel's  description  of  Amoeba  proteus  under  the  name  ''  Der 
kleine  Proteus,"  in  1755,  represents  the  first  recorded  observa- 
tion of  a  fresh- water  protozoon  of  the  group  Sarcodina. 

In  1835  Dujardin  called  the  viscid,  transparent  substance  com- 
posing the  bodies  of  marine  Protozoa,  which  he  then  had  under 
observation,  sarcode,  but  it  was  not  until  1883  that  BiitschU  first 
employed  the  term  Sarcodina  and  included  under  it  all  forms  of 
Protozoa  which  move  by  means  of  protrusions  of  protoplasm  from 
the  body  proper,  called  pseudopodia. 

Most  of  the  Sarcodina  are  very  minute  in  size.  Very  few  of 
them  can  be  seen  by  the  unaided  eye  and  none  can  be  studied 
with  any  degree  of  satisfaction  without  the  aid  of  a  compound 
microscope.  These  forms  vary  greatly  in  general  appearance. 
Many  of  them  are  naked  masses  of  protoplasm  tending  to  be 
globular  when  first  placed  under  the  microscope  but  soon  assum- 
ing variable  shapes,  protruding  from  the  body,  w^ith  more  or  less 
rapidity,  blunt,  lobe-like,  or  filiform  pseudopodia,  often  branching 
and  sometimes  anastomosing.  Others  are  provided  with  envelopes 
or  shells,  very  diverse  in  form  and  composition,  sometimes  secreted 
by  the  animal  itself,  sometimes  consisting  of  picked-up  fragments 
firmly  cemented  together.  These  envelopes  may  be  compact  and 
rigid,  or  flexible,  and  are  provided  with  one  or  more  apertures 
through  which  the  pseudopodia  are  extended.  Still  other  forms, 
commonly  known  as  the  HeHozoa  or  ''sun  animalcules,"  are  t}pi- 
cally  spherical,  sometimes  with  shells  of  delicate  structure  and 
always  with  fine  ray-like  pseudopodia,  usually  rendered  somewhat 
rigid  by  the  presence  o^  stiffened  axial  filaments. 

Fresh-water  Sarcodina  may  be  found  in  very  diverse  habitats 
and  within  wide  ranges  of  temperature.  They  occur  from  I  he 
level  of  the  sea  to  the  tops  of  very  high  mountains.  Perhaps  no 
other  animals  have  such  a  vast  altitudinal  range  as  certain  com- 
mon species  of  Sarcodina.  Roadside  pools  and  also  ponds,  lakes 
and  rivers  are  habitats  of  myriads  of  these  low  organisms.     In 


212  FRESH-WATER   BIOLOGY 

most  of  the  Sarcodina  there  is  a  marked  differentiation  between 
the  endoplasm  and  ectoplasm,  the  difference  consisting  in  the 
greater  density  and  opaqueness  of  the  inner  region.  This  dis- 
tinction between  endoplasm  and  ectoplasm  reaches  a  high  degree  in 
certain  marine  forms,  the  Radiolaria,  where  a  distinct  perforated 
membrane,  the  "  central  capsule,"  separates  the  two  regions.  None 
of  the  fresh- water  forms  possess  a  "  central  capsule."  The  greater 
density  of  the  endoplasm  is  accounted  for  by  the  character  of  the 
inclusions  suspended  in  it  and  by  the  size  of  the  vesicles  which 
make  up  its  structure. 

The  inclusions  consist  of  various  elements:  food  which  is  to 
be  built  into  body  protoplasm,  products  which  may  enter  into  the 
composition  of  the  shell,  waste  material  on  the  way  to  the  exterior, 
or  foreign  elements  which  have  no  part  in  the  physiology  of  the 
animal.  In  some  Sarcodina  algae  or  bacteria  are  constant  features 
of  the  endoplasm,  this  symbiotic  relationship  being  apparently 
essential  to  the  Hfe  of  the  protozoon. 

The  nucleus  is  confined  to  the  endoplasm.  In  a  few  Sarcodina 
condensed  nuclear  elements  have  not  been  observed,  but  in  these 
cases  the  chromatin  is  without  doubt  diffused  throughout  the  cell 
and  has  the  same  functional  value  as  a  centralized  body. 

Usually  a  single  nucleus  is  present,  often  two  is  the  normal  num- 
ber, but  in  some  forms  several  hundred  or  even  several  thousand 
have  been  counted  in  certain  stages. 

Commonly  the  nucleus  is  spherical,  but  may  be  modified  in 
form,  due  to  the  shape  of  the  body  and  to  the  flexibiHty  of  the 
nuclear  membrane  which  sometimes  permits  considerable  deformity. 

In  most  Sarcodina  the  chromatin  within  the  nuclear  membrane 
is  arranged  in  one  or  more  masses,  but  in  some  of  the  Hehozoa  it 
is  arranged  in  a  network  not  unlike  that  of  the  cell  of  a  metazoon. 

Contractile  vacuoles,  the  function  of  which  is  the  extraction  of 
waste  fluids  and  gases,  are  not  found  in  all  Sarcodina.  These  are 
absent  in  many  of  the  marine  forms  and  in  some  fresh-water  genera. 
When  present,  the  number  varies  from  one  to  many.  Habitually 
the  contractile  vacuole  is  spherical  but  in  some  species  it  assumes  a 
characteristic  lobed  form.  The  position  of  the  contractile  vacuole 
is  not  always  fixed  but  may  frequently  be  shifted  about  by  the 


AMOEBOID   PROTOZOA   (SARCODINA)  213 

flowing  protoplasm.  In  some  forms  its  general  position  is  fixed 
and  it  reappears,  after  contraction,  in  the  same  place.  As  the 
vacuole  becomes  inflated  by  waste  fluids  and  gases  it  rises  toward 
the  periphery  and  collapses,  pouring  its  contents  through  the  open- 
ing formed  in  the  body  wall.  In  some  of  the  Hehozoa  are  seen 
very  large  contractile  vacuoles  which  rise  to  the  surface  and  push 
the  peripheral  film  outward  Hke  a  bubble  before  the  collapse  takes 
place. 

Many  of  the  shell-bearing  forms  are  capable  of  raising  or  lower- 
ing themselves  in  the  water.  This  is  believed  to  be  brought  about 
by  the  presence  of  distinct  gas  vacuoles.  The  animals  seem  to  be 
able  to  alter  the  supply  of  carbon  dioxide  in  these  vacuoles  and 
thereby  change  their  specific  gravity. 

The  ectoplasm,  when  distinct  from  the  endoplasm,  usually  ap- 
pears as  a  clear  hyaline  zone,  of  greater  or  less  width,  at  the  periph- 
ery of  the  body.  In  most  forms  the  vesicles  of  the  ectoplasm 
are  very  minute  but  in  some  of  the  Heliozoa  they  exceed  those  of 
the  endoplasm  in  size  and  may  be  arranged  in  a  regular  manner 
about  the  periphery,  as  in  Actinosphaerium  eichhornii. 

The  protrusion  of  the  ectoplasm  is  the  initial  movement  in  the 
formation  of  a  pseudopodium  after  which  there  may  be  a  flow  of 
the  granular  endoplasm  into  the  axis  of  the  finger-like  extension  of 
the  ectoplasm.  At  times  pseudopodia  are  but  broad  extensions 
of  the  ectoplasm  with  no  appearance  of  endoplasm  taking  an\'  part 
in  their  formation. 

Great  variation  is  seen  in  the  pseudopodia  which  are  character- 
istic features  of  the  Sarcodina.  Among  the  fresh-water  forms 
several  general  types  may  be  observed.  The  naked  and  many  of 
the  shell-bearing  Sarcodina  produce  broad,  blunt,  finger-like,  or 
more  slender,  filiform,  pseudopodia;  the  latter  may  be  delicate, 
pointed  and  finely  branched,  but  neither  of  these  fuse  or  anastomose 
when  in  contact.  Another  variety  is  represented  by  delicate  thread- 
like pseudopodia  which  tend  to  run  together  and  mingle,  forming  a 
great  network  of  flowing  protoplasm.  This  is  the  anastomosing 
type  and  is  seen  in  a  few  fresh-water  genera,  but  is  characteristic 
of  many  marine  forms. 

In  the  Heliozoa  is  seen  another  variety.     Here  the  ray-like 


214  FRESH-WATER   BIOLOGY 

pseudopodia  are  usually  supported  by  "axial  filaments"  which  con- 
sist of  stiffened  protoplasmic  supports  forming  the  axes  of  the 
pseudopodia  along  which  the  soft  protoplasm  flows.  These  axial 
supports  enter  the  body,  the  inner  ends  apparently  resting  on  or 
near  the  nuclear  membrane.  The  supports  permit  the  flexing  of 
the  rays  and  at  times  they  may  become  soft  and  be  absorbed  by 
the  protoplasm  of  the  body. 

Shells,  which  are  characteristic  of  many  Sarcodina,  may  be  com- 
posed of  materials  secreted  by  the  protoplasm  of  the  animal  itself, 
such  as  chitin,  siHca,  and  calcium  carbonate;  or  may  be  constructed 
of  picked-up  foreign  materials  such  as  sand  grains,  diatom  shells, 
dirt,  etc. 

Shells  of  chitin  are  common  among  fresh-water  forms.  This 
material  is  deposited  about  the  body  as  a  membrane  with  one  or 
more  openings  for  the  pseudopodia.  It  may  or  may  not  be  applied 
closely  to  the  body  and  is  variable  in  thickness  in  different  species 
as  well  as  with  age.  In  young  individuals  the  envelop  is  usually 
thin  and  transparent;  with  age  it  may  become  thicker  and  more 
opaque.  In  many  forms  the  envelop  is  always  thin  and  flexible, 
permitting  changes  in  shape  of  the  body  from  the  flowing  of  the 
enclosed  protoplasm.  When  the  deposit  is  in  sufficient  quantity 
a  firm,  rigid  shell  is  produced.  If  the  body  does  not  completely 
fill  the  shell  the  former  is  united  to  the  inner  surface  of  the  latter 
by  protoplasmic  threads  and  is  capable  of  considerable  amoeboid 
movements  within  the  envelop.  Some  chitinous  shells  are  very 
delicate,  transparent  and  apparently  without  separate  elements, 
while  others  are  composed  of  distinct  plates  arranged  with  more 
or  less  regularity. 

Species  of  Dijjlugia  and  other  related  forms  are  provided  with 
shells  composed  of  foreign  materials  including  grains  of  sand, 
diatom  shells,  and  particles  of  dirt.  These  materials  are  attached 
to  a  thin  chitinous  layer  and  cemented  together  into  a  compact, 
rigid  shell  with  one  aperture  through  which  the  pseudopodia 
extend. 

Shells  may  be  composed  primarily  of  siUca.  In  many  fresh- 
water forms  these  siUceous  elements  are  laid  down  in  the  form  of 
regular  plates  which  build  up  a  firm  shell.     Others,  as  some  fresh- 


AMOEBOID   PROTOZOA   (SARCODINA)  215 

water  Heliozoa  and  the  marine  Radiolaria,  secrete  spicules  which 
may  be  loosely  connected,  forming  an  envelop,  or  cemented  to- 
gether, building  up  skeletons  of  most  delicate  and  beautiful  designs. 
Sometimes  spicules  are  developed  for  temporary  purposes  as  the 
formation  of  envelopes  during  encystment.  Calcium  carbonate  is 
the  chief  constituent  of  the  shells  of  marine  Foraminifera  but  is  not 
an  element  of  importance  in  the  shells  of  fresh -water  Sarcodina. 

In  a  one-celled  animal  the  vital  processes  of  the  body,  though  not 
different,  except  in  degree,  from  those  of  a  metazoon,  must  neces- 
sarily be  simpler.  Here  all  of  the  Hfe-forces  have  their  origin  and 
all  of  the  metabolic  changes  take  place  within  the  confines  of  a 
single  cell. 

The  entrance  of  food  Into  the  body  in  the  Sarcodina  is  a  simple 
process.  No  mouth  being  present,  material  may,  in  general,  enter 
at  any  point  on  the  surface.  In  naked  forms  of  the  Amoeba  tj-pe 
the  pseudopodia  flow  around  the  particle  to  be  ingested  and  in  this 
way  it  is  enclosed.  The  pseudopodia  of  shell-bearing  forms  draw 
in  the  food  through  the  apertures  of  the  shells  where  it  is  engulfed 
by  the  protoplasm. 

Most  of  the  Sarcodina  are  herbivorous,  their  chief  food  being 
unicellular  plants,  as  bacteria,  diatoms,  algae,  etc.  The  plant  cells 
are  usually  entirely  ingested  and  the  soft  parts  absorbed,  after 
which  the  indigestible  parts  are  excreted  from  the  body.  However, 
in  case  of  Vampyrella,  the  parasite  penetrates  the  cells  of  algae  and 
absorbs  their  contents. 

Some  Sarcodina  are  known  to  be  carnivorous,  feeding  upon 
closely  related  species.  Penard  believes  that  species  of  Nebcla 
may  make  use  of  the  plates  of  QuadruleUa,  Euglypha,  Triucma,  etc., 
upon  which  they  feed,  in  building  up  their  own  shells. 

Digestion  in  all  of  the  Protozoa  is  intracellular.  After  the  ma- 
terial enters  the  body  surrounded  by  a  film  of  water  forming  a  food 
vacuole,  digestive  fluids  and  enzymes  act  upon  it  converting  it  into 
suitable  elements  for  the  life  of  the  cell.  Excretion  in  the  Sarco- 
dina consists,  as  elsewhere,  in  the  release  of  waste  products.  Waste 
solids  may  leave  the  body  at  any  point  of  the  surface.  The 
process  is  the  reverse  of  ingestion,  often  consisting  in  the  mere  flow- 
ing away  from  the  material  to  be  discarded. 


2l6  FRESH-WATER   BIOLOGY 

Waste  fluids  resulting  from  the  metabolism  of  the  cell  are  col- 
lected in  contractile  vacuoles  in  most  of  the  fresh-water  Sarcodina 
and  thereby  removed.  Surplus  water  which  has  been  ingested  is 
eliminated  at  the  same  time  and  possibly  carbon  dioxid  may  also 
be  extracted  by  the  contractile  vacuole.  In  those  forms,  however, 
which  do  not  possess  contractile  vacuoles,  the  waste  fluids  and  gases 
escape  from  the  general  surface  of  the  body. 

Respiration  in  the  Sarcodina  is  performed  by  an  interchange  of 
gases  through  the  body  wall.  Oxygen  is  received  from  the  sur- 
rounding water  and  carbon  dioxid  transmitted  to  it  by  osmosis. 
The  symbiotic  relationship  between  algae  and  some  forms  of  Sar- 
codina, without  doubt,  has  an  important  respiratory  as  well  as 
nutritive  function,  the  plants  furnishing  oxygen  and  carbohydrates 
to  the  animals,  while  the  latter  supply  carbon  dioxid  and  nitroge- 
nous waste  for  the  algae. 

Reproduction  in  the  Sarcodina  takes  place  either  by  the  division 
of  the  body  into  two  parts,  a  process  commonly  called  fission ;  by 
the  separation  from  the  parent  of  one  or  more  small  masses  of 
protoplasm  known  as  buds;  or  by  the  production  of  swarm  spores. 

In  fission,  or  simple  cell  division,  which  is  common  among  fresh- 
water forms,  the  nucleus  divides  first  and  this  is  followed  by  the 
separation  of  the  cytoplasm  into  two  parts,  each  of  which  encloses 
a  portion  of  the  original  nucleus.  Growth  proceeds  until  maturity 
is  reached,  when  the  process  of  division  is  repeated. 

When  an  envelop  is  present  the  enclosed  body  may  divide  by 
fission  after  which  one  portion  creeps  out  at  the  aperture  and  con- 
structs a  new  shell  about  itself.  If  the  envelop  be  chitin  and  with- 
out distinct  elements  it  is  gradually  developed  at  the  periphery 
of  the  newly  separated  individual,  but  if  it  be  of  regular  chitinous 
or  siliceous  plates,  these  elements,  in  some  cases  at  least,  are  de- 
veloped in  the  cytoplasm  of  the  parent  and  pushed  out  to  form  the 
new  envelop  of  the  separating  bud. 

That  the  nucleus  is  concerned  with  cell  division  has  long  been 
known.  Recent  observations,  however,  have  thrown  light  upon 
the  presence  of  extranuclear  material  scattered  throughout  the 
cytoplasm  in  many  Sarcodina  as  well  as  other  protozoa.  This 
material  has  the  form  of  minute  granules  termed  ''idiochromidia" 


AMOEBOID    PROTOZOA    (SARCODINA)  217 

and  results  from  the  transfusion  of  part  of  the  chromatin  through 
the  nuclear  membrane  or  from  the  breaking  up  of  the  nucleus  into 
small  granular  bodies  which  become  diffused  through  the  cyto- 
plasm. 

In  some  Sarcodina  a  number  of  buds  may  separate  from  the 
parent,  each  enclosing  a  quantity  of  idiochromidia  which  is  built 
into  a  nucleus.  This  extranuclear  material  apparently  has  a 
functional  value  in  reproduction  and  may  be  compared  to  the 
micronuclei  of  Infusoria.  During  the  quiescent  state  of  encyst- 
ment  the  bodies  of  many  Sarcodina  break  into  swarm  spores. 
These  are  minute  organisms  each  with  a  portion  of  the  parent 
nucleus  and  provided  with  fiagella  or  pseudopodia  as  motile  organs. 
The  swarm  spores  may  fuse  with  each  other  and  develop  into  an 
adult  form  or,  in  some  cases,  they  may  develop  without  fusion. 

Conjugation,  in  the  form  of  a  temporary  union  or  a  permanent 
fusion  of  the  bodies  of  two  individuals  of  the  same  species,  has 
been  observed  in  some  Sarcodina.  After  temporary  union  and 
separation,  in  a  few  cases,  swarm  spores  have  been  observed  to  be 
developed  from  both  conjugants. 

In  most  of  the  instances  of  permanent  conjugation  reported 
there  is  no  clear  evidence  that  the  fusion  resulted  in  a  union  of  the 
nuclei  of  the  individuals,  as  is  the  case  in  true  conjugation.  Actual 
fusion  of  the  nuclei,  however,  has  been  observed  in  the  common 
''sun  animalcule,"  Actinophrys  sol.  Here  two  indi\iduals  come 
together,  fuse,  and  become  encysted.  Nuclear  changes  take  place 
which  follow  in  a  general  way  the  processes  of  maturation  and 
fertilization  after  which  mitotic  division  results  in  the  formation  of 
daughter  cells. 

Many  kinds  of  Sarcodina  are  exceedingly  abundant  and  collect- 
ing them  is  not  a  difficult  matter.  Other  forms  are  rare  and  only 
occasionally  obtained.  Everywhere  among  wet  mosses  and  in 
sphagnous  swamps  many  fine  examples  of  shell-bearing  species 
will  be  found,  some  inhabiting  no  other  localities.  Some  prefer 
clear,  fresh  water,  while  others  thrive  in  stagnant  ponds  and  ditches. 

By  carefully  collecting  submerged  decaying  vegetation  from  shal- 
low water  and  allowing  it  to  stand  in  the  laboratory  for  a  few  days 
many  of  the  Amoeba  and  Difflugia  types  arc  usually  found. 


2l8  FRESH-WATER  BIOLOGY 

The  ooze  at  the  bottom  of  ponds  or  lakes  is  the  habitat  of  nu- 
merous shell-bearing  as  well  as  naked  forms.  Others,  like  the 
Heliozoa,  are  commonly  found  among  algae,  diatoms,  or  mosses  and 
may  be  collected  with  these  plants.  Inactive  or  encysted  forms 
gathered  during  cold  seasons  of  the  year  wil  become  active  on 
being  placed  in  a  warm  laboratory.  Shallow  aquaria  are  best 
adapted  for  preserving  quantities  of  living  Sarcodina.  For  those 
species  which  require  it,  the  water  may  be  kept  fresh  by  algae  or 
other  aquatic  plants,  but  for  many  forms  the  water  may  be  allowed 
to  become  stagnant,  replenishing  it  only  as  evaporation  takes  place. 
The  Sarcodina  may  be  studied  with  a  considerable  degree  of  satis- 
faction, as  it  is  possible  to  keep  them  under  observation  for  an  in- 
definite time,  owing  to  their  slow  movements.  For  detailed  study 
a  good  compound  microscope  including  an  oil  immersion  lens  is 
necessary.  Concave  microscopic  slides  on  which  living  forms  may 
be  isolated  and  retained  for  extended  observation  are  useful. 
Methylenblue,  used  as  an  intravitam  stain,  is  successful  in  render- 
ing the  nuclear  elements  visible,  especially  in  species  without  shells 
or  with  transparent  envelopes. 

When  permanent  mounts  are  desired  the  following  method,  rec- 
ommended by  Benedict  in  the  Journal  of  Apphed  Microscopy, 
Vol.  VI,  p.  2647,  i^2,y  be  employed:  ''Smear  a  glass  slide  with 
albumen  fixative,  as  in  preparing  for  the  mounting  of  parafifin  sec- 
tions. Then  place  on  the  surface  of  the  film  of  fixative  a  drop  or 
two  of  water  containing  the  forms  which  it  is  desired  to  stain. 
Let  nearly  all  the  water  evaporate  by  exposure  to  the  air  of  the 
room  until  only  the  film  of  fixative  remains  moist.  The  slide  can 
now  be  immersed  in  Gilson's  or  any  other  fixing  reagent  and  then 
passed  through  the  alcohols,  stains,  etc.,  in  the  same  way  that 
mounted  sections  are  handled." 

The  above  method  is  recommended  for  other  Protozoa  as  well  as 
for  Sarcodina.  As  a  rapid  fixing  agent,  the  fumes  of  osmic  acid 
have  been  found  satisfactory.  By  careful  manipulation  of  fine 
dissecting  needles  under  the  microscope,  the  shells  of  many  forms 
may  be  isolated,  arranged  as  desired  and,  when  dried  on  the  slide, 
permanently  mounted  in  balsam. 


AMOEBOID    PROTOZOA    (SARCODINA) 


219 


KEY   TO    NORTH   AMERICAN    FRESH-WATER   SARCODINA 


I  (161)     Pseudopodia  without  axial  filaments. 


Class  Rhizopoda 


2  (144)     Pseudopodia  lobose,  sometimes  pointed  but  never  anastomosing. 

Subclass  Amoebea   .    ,        3 

3  (21)     Without  shells Order  Gymnamoebida    .    .       4 

4  One  family  recognized.     Characteristics  of  the  order. 

Family  Amoebidae  .    .       5 

5  (6)     Body  and  pseudopodia  bristling  with  minute  spicules. 

Dinamoeha  Leidy. 
Representative  species Dinamoeba  mirabilis  Leidy  iSy 4. 

Very  changeable  in  shape  with  many  tapering  pseudo- 
px)dia.  Papillae-like  projections  often  appearing  at  the  pos- 
terior extremity.  Entire  body  sometimes  surrounded  by  a 
jelly-like  envelop.  A  contractile  vacuole  and  two  nuclei 
present.  Habitat  standing  water.  Size  may  reach  200  n, 
including  pseudopodia. 


Fig.   274.      Dinamoeba  mirahilis 

6  (5)     Body  smooth,  without  spicules 

7  (8)     Body  usually  enclosing  symbiotic  bacteria 


X  100.     (After  Leidy.) 


Large  size.     Nuclei  many. 

Pelomyxa  Greeff. 

Representative  species Pelomyxa  palustris  Greeff  1870. 

A  very  large  form  moving  slowly  by  broad  extensions 
of  the  ectoplasm.  Endoplasm  enclosing  sand,  brilliant 
corpuscles  and  bacteri;i;  with  numerous  vacuoles  in  the  ecto- 
plasm. Nuclei  may  number  1000  or  more.  Habitat  ooze 
of  ponds  and  sphagnous  swamps.  Maximum  length  20CX3  n. 
P.  carolinensis  Wilson,  described  in  American  Naturalist, 
Vol.  34,  p.  535,  is  apparently  without  symbiotic  bacteria. 

Fig.    275.     Pelomyxa  palustris.     x  25.     (After  Pcnard.) 

8  (7)     Body  not  enclosing  symbiotic  bacteria 9 

9  (10)     Ectoplasmic  membranes  produced  between  the  pseudopodia. 

Hyalodiscus  Hcrtwig  and  Lesser, 
Representative  species.   .    .    .  Hyalodiscus  rubicund  us  H.  and  L.  1S74. 

Body  discoidal,  moving  by  extending  thin  sheets  of  ecto- 
plasm which  are  penetrated  by  ray-like  pseudopodia.  En- 
doplasm reddish-yellow  in  color  enclosing  numerous  vacuoles 
and  one  or  more  nuclei.  Habitat  ooze  of  ponds,  not  common. 
Size  40  to  60  At. 

Fig.  276.      Hyalodiscus  rubicundus.      X  J15      (.•\fter  Penard.) 

10  (9)     Ectoplasmic  membranes  not  produced  between  the  pseudopodia. 

Amoeba  Ehrenberg      .      ii 

11(14)     Pseudopodia  sharply  distinguished  from  the  body 12 

12(13)     Pseudopodia  lobe-like i mocba  proteus  Lc'idy  iS,-jS,. 

Very  changeable  in  form,  usually  with  numerous  pseudo- 
podia. The  nucleus  is  always  single,  oval  and  of  large  size. 
Contractile  vacuoles  one  or  more.  Habitat  both  stagnant 
and  clear  water.  Size,  one  of  the  largest  species  of  the  genus; 
may  reach  300  ^  or  more  when  extended. 
Fig.  277.    Amoeba  Proteus.     X  loo      (Original  from  a  prcixiralion.) 


2  20 


FRESH-WATER   BIOLOGY 


[3  (12)     Pseudopodia  ray-like. 


Amoeba  radiosa  Ehrenberg  1830. 


r^:<^«* 


Body  spherical  with  pseudopodia  more  or  less  rigid,  not  withdrawn 
and  retormed  rapidly.  Nucleus  spherical.  Habitat,  very  common 
among  algae;  widely  distributed.  Size,  usually  less  than  icxjm  with 
pseudopodia  extended. 

IiG.  278.    Amoela  radtusa.    a,  contractile  vacuole       X  loc     (After  Leidy.) 

14(11)     Pseudopodia  not  sharply  distinguished  from  the  body 15 

15  (20)     Contractile  vacuole  spherical 16 

16(17)     Posterior  extremity  villous Afnoeha  Umax 'Du]3.rdm  1S41. 

Slug -like,  usually  moving  with  the  broad  end  forward.  Endo- 
plasm  filled  with  brilliant  granules.  Contractile  vacuole  usually 
single.  Nucleus  changeable  in  form.  Habitat  ooze  ol  ponds. 
Size,  large  individuals  usually  less  than  ioom- 

Fig.  279.     Amoeba  limax.      x  225.     (Alter  Penard.) 

17  (16)     Posterior  extremity  not  villous 19 

18  (19)     Surface  wrinkled,  large  size.      .    .  Amoeba  verrucosa  Ehrenberg  1838. 

A  sluggish  species,  moving  by  a  slow  rolling  motion.  Pseudo- 
podia short,  broad  lobes.  Body  proper  enclosed  by  a  delicate 
membrane.  Surface  marked  by  lines  crossing  each  other  re- 
sulting in  a  wrinkled  appearance.  Habitat  sphagnous  swamps. 
Large  individuals  may  reach  3cmd  ^  in  length  when  extended. 

Fig.  280.     Amoeba  verrucosa .     X  100      (Alter  Leidy.) 

19(18)     Surface  not  wrinkled,  small  size.    .    .    ylwoefta  gM/Zw/a  Dujardin  1841. 

Body  usually  oval  in  outline,  moving  with  the  broad  end  forward. 
Pseudopodia  short,  broad  lobes  produced  by  sudden  expansions  of  the 
protoplasm.  Nucleus  single  and  one  large  contractile  vacuole.  Habitat 
stagnant  water.     Size  30  m- 

Fig.  281.    Amoeba  guttula.     X  400.     (Alter  Penard.) 

20  (15)     Contractile  vacuole  not  spherical.   .    .    .  Amoeba  striata  Penard  1890. 

Moving  rapidly  by  broad  extensions  of  ectoplasm  but  not  changing 
form  rapidly.  Usually  from  two  to  four  longitudinal  lines  on  the  surface. 
Two  contractile  vacuoles  often  present,  the  anterior  one  changeable  in 
shape.     Habitat  among  algae;  not  abundant.     Size,  from  30  to  60  n. 

Fig.  282.     Amoeba  striata.     X  250.     (After  Penard.) 

With  shells Order  Testacea  .    .     22 

Pseudopodia  thick,  finger-like,  rarely  filiform. 

Family  Arcellidae  .    .  23 

Pseudopodia  thick,  sometimes  pointed 24 

Shell  membranous,  more  or  less  flexible 25 

Membrane  covered  with  organic  or  foreign  particles 26 

Shell  membrane  double Diplochlamys  Greefif.    .  27 

Hemispherical  to  cup-shaped,  loosely  coated  with  organic  and  siliceous 
particles Diplochlamys  fragilis  Venard  igog. 


Color  gray,  spotted  with  black.  Inner  membrane  very  fragile 
but  capable  of  distention.  Nuclei  usually  from  30  to  .40.  Vacuoles 
numerous.  Pseudopodia  short  and  thick.  Diameter  70  to  125  fx. 
Habitat  mosses.  Not  common.  Reported  from  Ontario  by  Dr. 
Penard. 

Fig.    283.     Diplochlamys  jragilis.     X  150.     (After  Penard.) 


21 

(3) 

22 

(103) 

23 

(96) 

24 

(35) 

25 

(32) 

26 

(29) 

27 

(28) 

AMOEBOID    PROTOZOA    (sARCODINA)  221 

(27)     Hemispherical  to  cup-shaped,  densely  coated  with  organic  particles. 

Diploclilamys  fimida  Penard  iqoo. 

Yellowish-gray  or  brown.      Inner   membrane   very  delicate,  flexible 

but    resistant.      Nucleus  single.      Vacuoles   numerous.       PseuflojxKJia 

y'\vj^^-/X  large  at  the  base,  pointed,  rarely  extended.      Diameter  45  ^t.      Habitat 

'-^^"^a"^  mosses.     Reported  from  Ontario  by  Dr.  Penard. 

'^x^  Fig.   284.     Diploclilamys  timida       X  275.     (After  Pen.ird  ) 

29  (26)     Shell  membrane  single .30 

30  (31)  Hemispherical;  slightly  or  not  at  all  flexible.     .    .    Parmulina  Penard. 

Representative  species Parmulina  cyalhus  Penard  1902. 

In  this  species  the  shell  is  rigid  but  in  P.  obtrcla  Gruber  it  is  flexible 

about  the  aperture.    Shell  is  coated  with  fine  particles  of  sand.  dirt.  etc. 

___.  Pseudopodia  are  broad,  rounded  lobes  extending  from  the  aperture. 

/o-  '*^  Nucleus  and  contractile  vacuole  each  single.      Habitat  among  mosses. 

.^ '..*"•  .^  j)janieter  45 //. 

Fig.    285.     Parmulina  cyalhus.     X  27v     (After  Penard.) 

31  (30)     Commonly  ovoid  or  hemispherical,  but  very  changeable. 

Corycia  Dujardin. 
Representative  species Corycia  flava  Gtqq^  i^dd. 

The  membranous  covering  is  dome-shaped  but  very  changeable  in 
1^^^^^^^  form.      Pseudopodia  very  short  and   thick.      Vacuoles   numerous, 

i  (^  "to^      0^  Nucleus  single,  usually  concealed  by  the  granules  of  the  endoplasm. 

V  Vl^®;'^^^,^^  Habitat  among  mosses.     Diameter  80  to  100  m- 

^^^i^si^-^"**"^  Fig.  2S6      Corycia  flava.      X  210      (After  Penard.) 

32  (25)     Membrane  without  foreign  particles;  regularly  punctate.     .    .    ■     i?, 

33  (34)     Patelliform;  slightly  flexible Microchlamys  Cockerell. 

Representative  species. 

Microchlamys  patella  Claparede  and  Lachmann  i860. 

Shell  circular  from  dorsal  or  ventral  view   convex  above  with  a 

very  large  aperture  beneath.  Pseudopodium  single.  Contractile 
vacuoles  numerous.  Nucleus  single.  Habitat  among  mosses  in 
swamps.     Diameter  40  n. 

Fig.  287.     Microchlamys  patella.      X  .^10.     (After  Penard.) 

34  (33)     Commonly  dome-shaped,  but  exceedingly  flexible  and  changeable. 

Cochlio podium  Hertwig  and  Lesser. 
Representative  species.  .     CocJil io podium  bilimbosum  AueThach  1856. 

y^^^X  The  membranous  covering  is  capable  of  great  expansion,  especially  at 

r>''''^m  ^^^  aperture.    Pseudopodia  pointed,  usually  numerous.     Nucleus  and 

KilCH  contractile  vacuole   each   single  and   large.      Common   among  algae. 

y^^^^'^^^^-r^  Diameter  of  envelop  25  to  50  fi. 

f'"';f''"'\  Fig.  288.     Cochliopodium  bilimbosum.     m,  nucleus.     X  300.      (After  Leidy.) 

35  (24)     Shell  membranous,  rigid '^^ 

36(45)     Shell  discoidal ^^ 

37  (44)     Shell  with  regular  markings  more  or  less  distinct.     No  foreign  par- 

ticles attached.     Aperture  central ,^8 

38  (43)     Shell  with  regular,  distinct  punctae.     Aperture  small. 

Arcclla  Ehrenberg  .    .     30 

39  (42)     Periphery  of  shell  without  projecting  points 4° 


222 


FRESH-WATER   BIOLOGY 


40  (41)     Shell  strongly  convex. 


41  (40) 


42  (39) 


.    .    .    Arcella  vulgaris  Ehrcnberg  1830. 

Shell  may  be  smooth  or  with  re^'ular  undu- 
lations. Protoplasm  united  to  the  inside  of  the 
shell  by  delicate  threads.  Pseudopodia  long, 
straight  and  very  transparent.  Contractile 
vacuoles  numerous.  Nuclei  two,  opposite  in 
position.  This  species  shows  great  variation  in 
size  and  form.  \'ery  common  in  pond  water. 
Diameter  80  to  140  n. 
Fig.  289.    Arcdlavul\:,aris.    Lateral  and  interior  views 

oi  the  same  individual.      X  150.     (After  Leidy.) 

Shell  very  flat Arcella  discoides  Ehrcnberg  1843. 

Shell  smooth,  regularly  punctate,  with  a  large  circular  aperture.  It 
is  a  shy  species,  the  pseudopodia  seldom  being  observed.  Contractile 
vacuoles  numerous.  Nuclei  two.  Common  in  pond  water.  Diameter 
from  72  to  264  /i. 

Fig.  290.     Arcella  d'ncoide^.     X  i75-     (After  Penard.) 

Shell  periphery  with  projecting  points. 

Arcella  dentata  Ehrcnberg  1830. 
When  viewed  laterally  the  shell  has  the  appearance  of  a  crown, 
the  teeth-like  points  being  produced  from  the  base  of  the  low 
dome.  Nuclei  two;  contractile  vacuoles  numerous.  Habitat 
bogs  and  swamps.  A  rare  species.  Diameter  132  to  184  m- 
Fig.  291.  Arcella  dentata.  Lateral  and  inferior  views  of  the  same  indi- 
vidual.     X  100.     (After  Leidy.) 

43  (38)     Shell  with  punctae  sometimes  indistinct.     Aperture  very  wide. 

Pyxidicula  Ehrcnberg. 
Representative  species Pyxidicula  cymhalum  Penard  1902. 

Shell  pateUiform,  brown  in  color,  with  distinct  punctae.  Aper- 
ture round,  nearly  as  wide  as  the  diameter  of  the  shell,  bordered 
by  a  narrow  rim.  Contractile  vacuole  single.  Nuclei  probably 
two.  Pseudopodia  not  observed  in  this  species.  Identified  by 
Penard  in  material  from  Summit  Lake,  Colorado.  The  only  spe- 
cies of  the  genus  thus  far  reported  from  North  America.  Diameter 
85  to  90  M-     Habitat  mosses. 

44  (37)     Shell  without  regular  markings,  but  with  foreign  particles  attached. 

Aperture  eccentric Centropyxis  Stein. 

Representative  species Centropyxis  aculeata  Stein  1857. 

Shell  compressed  laterally,  resulting  in  both  mouth  and  fundus 
being  eccentric.  Color  some  shade  of  brown.  Slender  spines 
usually  developed  from  the  fundus.  Nucleus  single;  contractile 
vacuoles  two  or  more.  The  species  is  very  shy,  sometimes  ex- 
tending a  single  large  pseudopodium.  A  common  species  among 
algae.     Diameter  88  to  260  /i- 

Fig.   293.     Centropyxis  aculeata.     X  150.     (After  Leidy.) 

45  (36)     Shell  not  discoidal 46 

46  (51)     Shell  spiral,  compressed,  largely  composed  of  minute,  curved,  rod- 

like plates Lecquereusia  Schlumberger   .    .     47 

47  (48)     Shell  primarily  of  sand  grains,  few  plates. 
^3^  Lecquereusia  modesta  Rhumbler  1845. 

This  species  has  a  short,  broad  neck,  slightly  turned  to  one  side. 
Nucleus  single.  Pseudopodia  few,  large  and  long.  Found  among 
mosses  in  swamps.     Length  from  125  to  150  m- 

Fig.  294.     Lecquereusia  modesta.     X  125.     (After  Penard.) 


Fig.  292.  Pyxidicula  cym- 
balum.  X  210.  (After 
Penard.) 


AMOEBOID   PROTOZOA    (SARCODINA) 


223 


48  (47)     Shell  of  rod-like  plates 49 

49  (50)     Plates  slender,  elongate.      .    .    Lecquereusia  spiralis  Ehrenberg  1840. 

The  neck  in  this  species  is  prominent  and  turned  sharply  to 
one  side.  The  siliceous  plates  are  cemented  very  closely  to- 
gether, forming  the  shell.  Sand  and  diatoms  may  sometimes 
be  incorporated  with  the  plates.  Pseudopodia  few,  long  and 
large.     Habitat  sphagnous  swamps.     Length  125  to  140  ^. 

Fig.  295.     Lecquereusia  spiralis.     X  125.     (After  Penard.) 

50  (4q)     Plates  thick,  short Lecquereusia  epistomium  Penard  1893. 

In  this  species  the  neck  is  very  sharply  distinguished  from  the 
rounded  shell  and  very  abruptly  turned  to  one  side.  The  shell  is 
clear,  without  foreign  particles  attached.  Habitat  sphagnous  swamps. 
Length  125  yt. 

Fig.  296.     Lecquereusia  epistomium.     X  150.     (After  Penard.) 

51  (46)     Shell  not  spiral 52 

52  (57)     Shell  chitinous,  transparent,  structureless,  with  no  foreign  particles  or 

formed  elements  attached.  .    .    Hyalosphenia  Stein   .    .     53 

53  (54)     Surface  of  shell  with  undulations.    .    Hyalosphenia  elegans  Leidy  1874. 

The   shell   is   flask-shaped,  compressed,  brownish  in  color, 

transparent.  Two  minute  pores,  opposite  each  other,  are  in 
the  base  of  the  neck.  Protoplasm  colorless.  Nucleus  single. 
Pseudopodia  few.  Common  in  sphagnous  swamps.  Length 
from  90  to  100  /x. 

Fig.  297.     Hyalosphenia  elegans.     X  250.     (After  Penard.) 

54  (53)     Surface  of  shell  without  undulations 55 

55  (56)     With  pores  through  the  fundus.   .    Hyalosphenia  papilio  Leidy  1875. 

Shell  ovoid  or  pyriform,  compressed,  yellowish  in  color.  Slight 
variation  in  size,  shape  and  constitution  shown  in  this  species.  Pro- 
toplasm not  filling  the  shell  but  attached  to  the  inner  surface  by  pro- 
toplasmic processes.  Endoplasm  always  containing  chlorophyl. 
Pseudopodia  often  numerous.  From  two  to  six  small  pores  a!x)ut 
the  border  of  the  fundus.  Common  in  sphagnous  swamps.  Length 
from  no  to  140^1. 

Fig.  298.     Hyalosphenia  papilio.     X  200.     (Alter  Leidy.) 

56  (55)     Without  pores  through  the  fundus.   .   Hyalosphenia  cuncata  Stein  1857. 


Shell  exceedingly  transparent  and  greatly  compressed. 
Pseudopodia  few  in  number,  often  but  one.  Habitat 
is  reported  to  be  clear  water.  A  rare  species.  Length 
from  60  to  75  n. 

Fig.  299.     Hyalosphenia  cuneata.     Broad  and  narrow  lateral 
views,     ft,  nucleus.     X  300.     (After  Leidy.) 


57  (52) 

58(75)     Shell  primarily  of  foreign  particles 59 


Shell  chitinous,  more  or  less  densely  covered  with  foreign  particles 
or  formed  elements 58 


224 

59  (72) 

60  (6i) 


Fig  300. 
X  no. 

61  (60) 

62  (69) 

63  (66) 

64  (65) 


FRESH-WATER    BIOLOGY 

Shell  without  internal  partition  or  diaphragm. 

Difflugia  Leclerc  .    .     60 

Aperture  not  central Difflugia  constricta  Ehrenberg  1841. 

Shells  of  various  forms  from  nearly  spherical  to  oval  and  elon- 
gate.    Aperture  always  eccentric.     Pseudopodium  single,  rarely 
observed.     Spines  sometimes  developed  from  the  fundus.      This 
:iccaaii>'  species  is  closely   related   to  Centropyxis  aculeala.      A  common 

species,   widely  distributed.     Large  forms  may   reach   200  m  m 
Difflugia  constrict. I.     length.     Most  individuals  are  very  much  smaller. 
(After  Leidy. ' 

Aperture  central 62 

Shell  typically  spherical 63 

Margin  of  aperture  smooth 64 

Neck  deeply  constricted;    aperture  small,  with  margin  always  re- 
curved  Difflugia  urceolata  Carter  1864. 

This  species  is  without  spines,  but  a  variety,  D.  urceolata  var. 
olla,  may  possess  a  few  short  stubby  spines  developed  from  the 
fundus.  The  protoplasm  does  not  fill  the  shell.  Pseudopodia 
numerous;  nuclei  many.  Found  in  the  ooze  of  pond  water.  Large 
forms  reach  a  length  of  350  ix. 

V^?:=;?Clb  Fig.  301.     Difflugia  urceolata.    X  75-     (After  Leidy.) 


65  (64)     Neck,  when  present,  not  deeply  constricted;-  aperture  wide,  with 
margin  seldom  recurved.  .    .    .    Difflugia  lehes  Penard  1893. 

In  many  respects  this  species  resembles  the  preceding  one. 
The  thin,  recurved  collar  is  sometimes  present  but  the  aperture 
is  much  larger.  The  shell  is  very  fragile.  Nuclei  sometimes  more 
than  100.  Found  in  ooze  at  the  bottom  of  ponds,  lakes,  etc. 
Very  large,  some  reaching  400  m  in  length. 

Fig.  302.     Difflugia  lebes.     X  60.     (After  Penard.) 


66  (63)     Margin  of  aperture  not  smooth 67 

67  (68)     Margin  with  numerous  teeth.     .    .    .     Difflugia  corona  Wallich  1864. 

Shell  composed  of  large  sand  grains  but  ver>'  smooth  and  regular 
in  outline.  Teeth  usually  more  than  twelve  in  number,  very  evenly 
arranged.  Nucleus  single.  Pseudopodia  numerous  and  large. 
From  six  to  nine  spines  usually  developed  from  the  fundus.  A  very 
common  species  in  ooze  of  ponds.     Length,  with  spines,  200  to  250  /*• 


Fig.  303. 


lugia  corona.     Oral  view.     X  90.     (After  Leidy.) 


68  (67)     Margin  with  few  blunt  lobes.    .    .    .    Difflugia  lohostoma  Leidy  1874. 

Shell  ovoid  or  nearly  spherical,  usually  with  a  quadrilobate  aper- 
ture. However,  the  lobes  are  somewhat  irregular,  a  trilobate  aperture 
sometimes  appearing.  Pseudopodia  few.  Found  among  algae  and  in 
the  ooze  of  ponds;  common.     Average  length  150  m- 

Fig.  304.     Difflugia  lobostoma.    Oral  view.     X  105.     (After  Edmondson.) 

69  (62)     Shell  never  spherical 70 


AMOEBOID    PROTOZOA    (SARCODINA)  225 

70  (71)     Pyriform,  with  posterior  border  usually  rounded. 

Difflugia  pyriformis  Perty  1852. 

This  very  common  species  is  exceedingly  variable  in  form  and 
VJAy^SS'H^     size.     Penard  recognizes  six  varieties,  var.  claviformis  sometimes 
•■:^^i^'^i^^^:sr:^^     reaching   a  length  of  450  m-     The  posterior  border  is  usually 
rounded   but   some   forms   may  approach  the  acuminate  type. 
Fig.  305.    Difflugia  pyriformis.     Found  everywhere  in  the  ooze  of  ponds  and  lakes. 
X  60.     (After   Leidy. ) 

71  (70)     Elongate,  cylindrical,  with  posterior  border  acuminate. 

Difflugia  acuminata  Ehrenberg  1830. 
Shell  cylindrical,  the  slightly  broader  posterior  extremity  taper- 
ing to  an  acute  point  ending  in  a  knob-like  process.      Very  widely 
distributed  with  other  species  of  the  genus.    Large  forms  may  reach 
a  length  of  275  m- 

Fig.   306.     Difflugia   acuminata.     X  125.     (After  Leidy.) 

72  (59)     Shell  with  internal  partition  or  diaphragm 73 

73  (74)     Shell  with  deeply  constricted  neck  and  transverse,  perforated  parti- 

tion at  the  point  of  constriction.    .     Pontigidasia  Rhumbler. 
Representative  species.      .    .    .   Pontigidasia  spectahilis  Penard  1Q02. 

Resembling  Difflugia  pyriformis  in  appearance,  except  for  the 
deeply  constricted  neck.  The  internal  partition  has  one  round 
opening  and  one  or  two  other  apertures,  the  latter  being  closed  by 
transparent  opercula.  Pseudopodia  few,  long,  and  move  rapidly. 
Found  with  species  of  Difflugia.     Average  length  150  m- 

Fig.  307.     Pontigulasia  spectabilis.     x  100.     (After  Penard.) 

74  (73)     Shell  with  a  short  neck;    aperture  partially  closed  by  a  transverse 

diaphragm Cucurhitella  Penard. 

Representative  species.     .    .    Cucurbitella  niespiliformis  Penard  1902. 

The  neck  is  quadrilobate  with  an  undulating  margin.      On  the  inside 

'^Su-H^^  of  the  neck  is  a  transverse  peristome  covered  with  sand  grains,  resulting 

w^ri^'ij  in  the  rounded  aperture  being  much  smaller  than  the  diameter  of  the 

f^T^.'^'.a,  neck  itself.     Pseudopodia  numerous,  straight.     Found  at  the  bottom  of 

)\r^  ponds  and  lakes.     Length  from  125  to  140  n. 

<l\\X.  Fig.  308.     Cucurbitella  mespiliformis.     X  125.     (.\fter  Penard.) 

75  (58)     Shell  primarily  of  formed  elements 76 

76  (81)     Shell  not  compressed,  of   small  siliceous  particles,  aperture  lunate 

with  inferior  and  superior  lips 77 

77  (78)     Shell  hemispherical  or  elliptical,  superior  lip  with  pores.     Large  size. 

Bull  inula  Penard. 
Representative  species Bullinula  indica  Penard  iqc]. 

?k-'?>^7tcr^i?3(^^  Shell  brownish,  of  small  siliceous  plates,  closely  cemcnttxl  to- 

gether.      Superior    lip    slightly    overlapping    the    inferior    lip. 
'%\  Nuclei  numerous.     Diameter  igo  to  200  m.     Habitat  mosses. 

■^n^'^Rr^^^SrW  Fig.  309.     Bullinula  inJica.      X  120.     (.■\f tor  Penard.) 


78  (77)     Shell  hemispherical,  superior  lip  without  pores.     Small  size. 

PI  agio  pyxis  Penard 


79 


2  26  FRESH-WATER    BIOLOGY 

79  (80)     Inferior  lip  rounded,  dipping  far  into  the  interior  of  the  shell. 

Plagiopyxis  calUda  Penard  1910. 

Shell  gray,  yellow,  or  brown  in  color,  usually  smooth  and  clear.      The 
lips  overlap  to  such  an  extent  that  the  aperture  is  ditlicult  to  observe. 
v\r--l         Pseudopodia  large  at  the  base  with  furcate  extremities.     Nucleus  single. 
Kj-^K!']        Diameter  g2  to  103  /i-     Habitat  mosses. 

Fig.  310.     Plagiopyxis  callida.     X  150.     (.^fter  Wailes  and  Penard.) 

80  (79)     Inferior  lip  triangular,  slightly  dipping  into  the  interior  of  the  shell. 

Plagiopyxis  lahiata  Penard  191 1. 

Brown  in  color.  Smaller  than  the  preceding  species.  Nucleus  sin- 
gle. Pseudopodia  not  observed  by  Dr.  Penard,  who  reports  the  species 
from  Australia  and  Vancouver,  B.  C.     Diameter  80  to  88  p. 

Fig.  311.     Plagiopyxis  labiata.      X  155.     (After  Penard.) 

81  (76)     Shell  more  or  less  compressed;  aperture  not  lunate 82 

82  (83)     Plates  quadrangular Qiuidndella  Cockerell. 

Representative  species.    .  Quadmlella  symmetrica  F.  E.  Schultze  1875. 

In  this  species  the   shell   is  normally  pyriform,  one  variety 

^  being  short  and  another  long.      The  plates  are  very  transparent, 

usually  regularly  arranged  in  transverse  and  longitudinal  series. 

;rt>/J;;'?^^  Pseudopodia  few.       Common  in  sphagnous  swamps.      Length 

from  80  to  140  ^l. 

Fig.  312.     Quadrulella  symmetrica,     cv,  contractile  vacuole.      X  i7S- 
(After  Leidy.) 

83  (82)     Plates  not  quadrangular 84 

84  (91)     Shell  pyriform,  sometimes  ovoid  or  rounded,  compressed  with  round, 

oval,  or  irregular  plates Nebela  Leidy   .    .     85 

85  (88)     Shell  pyriform 86 

86  (87)     Neck  long,  narrow;  plates  round.  .   Nebela  lageniformis  Penard  1890. 

Body  of  shell  oval,  prolonged  as  a  tubular  neck.      There  are  no 
'j—onc^  ^^^\  lateral  pores  through  the  shell  as  in  some  species.      The  plates  are 

fo^^^^^^^of'^^^fl  round  and  very  clear.      Pseudopodia  few.       Found    commonly 

\<r£ii22£Q2hxi^^^-Ci.(^^  among  mosses;  very  abundant  in  some  localities.     Length  125  n. 

^Ss=^  Fig.  313.     Nebela  lageniformis.     X  i7S-     (After  Penard.) 

87(86)     Neck  short;  plates  round  or  oval.     .    .    .   Nebela  collaris  Leidy  iSyg. 

In  this  species,  large,  round,  and  oval  plates  are  usually  inter- 

A  r!^^??3?^?^ySl^^^^  mingled.     Sometimes  foreign  elements  enter  into  the  composition 

^c^--.>o^  _..{^^4^  of  the  shell.      It  is  a  ver>'  common  species,  found  abundantly  in 

'••o.;,.;^-^M,a.J<9  sphagnous  swamps  and  presents  many  variations  in  size  and  form. 

Large  individuals  average  about  1 20  /x. 

Fig.  314.     Nebela  collaris.     X  150.     (After  Leidy.) 

88  (85)     Shell  not  pyriform 89 

89  (90)     Shell  rounded,  border  of  aperture  smooth. 

Nebela  flabell urn  Leidy  1874. 
The  transverse  diameter  usually  equals  or   exceeds  the  length,  but 
'pypJ'?^h.  apparently  transitional  forms  between  this  species  and  the  preceding 

jm^ooo'^W^         one  are  sometimes  observed.      Possibly  this  is  but  a  variety  of  Nebela 
W^^^OQ^^         collans.     The  plates  are  similar  in  the  two  species.     Habitat  sphagnous 
'^°-^'?^Sct^         swamps.     Length  50  to  100  m- 

Fig.  3x5.    Nebela  Jiabellum.     X  150.    (After  Leidy.) 


AMOEBOID    PROTOZOA    (SARCODINA)  227 

90  (89)     Shell  ovoid;  border  of  aperture  crenulate. 

f?;^-^  Nebela  dentistoma  Penard  1890. 

The  shell  is  very  clear  with  round  or  oval  plates,  the  arranRement  of 
the  plates  at  the  margin  of  the  aperture  forming  the  rounded  crenu- 
lations.  Pseudopodia  very  active.  Found  in  sphagnous  swamps. 
Length  66  to  130  a*. 

Fig.  316.     Nebela  dentistoma.     x  160.     (After  Penard.) 


mm 


91  (84)     Shell  ovoid,  compressed  with  round,  oval,  or  irregular  plates.   .    .     92 

92  (93)     Aperture  oval,  terminating  a  short  tube  formed  by  the  thickened 

oral  membrane.     Plates  irregular. 

Awerinzewia  Schouteden. 
Representative  species.    .  Awerinzewia  cyclo^tomata  ^choxxitdtn  1902. 

Shell  a  chitinous  envelop  covered  by  siliceous  plates,  some  large,  scatter- 
ing, others  small,  filling  in  between  the  large  ones.      Sand  grains  often  at- 
tached to  the  posterior  border.      Color  usually  violet.      Nucleus  single. 
Closely  allied  to  the  genus  Heleopera.    Length  135  to  1 78  m.    Habitat  mosses. 
Fig.  317.     Awerinzewia cyclostomata.     X  100.     (After  Penard.) 

93  (92)     Aperture  elliptical  or  Hnear,  not  terminating  a  tube. 

Heleopera  Leidy   .    .     94 

94  (95)     Chlorophyl  always  present Heleopera  picta  Leidy  1874. 

The  shell  is  very  regular  in  outline,  of  a  yellowish  tint, 
usually  with  little  foreign  material  attached.  The  presence 
of  chlorophyl  seems  to  be  necessarj^  to  the  life  of  the  animal. 
Pseudopodia  numerous.  Found  in  sphagnous  swamps. 
Length  100  to  iiom- 

Fig.  318.     Heleopera  picta.     X  150.     (After  Leidy  ) 

95  (94)     Wine-red  in  color Heleopera  rosea  Penard  1890. 

This  species  may  be  known  by  its  color,  the  tint  being  of  variable 
^__^     ,_  depths.       Sand  grains  and  other  foreign  elements  cover  the  fundus  of 

%'^€.^^^^n         the  shell.      A  thin,  yellowish  lip  borders  the  aperture.      Found  among 
fe^^^^^^"^         mosses  in  swamps.     Length  90  to  100  /i. 
~  ^  Fig.  319.     Heleopera  rosea.     X  150.     (After  Penard.) 

96  (23)     Pseudopodia  sometimes  thick,  sometimes  linear 97 

97  (100)     Shell  chitinous,  densely  covered  with  sand  grains,  diatom  shells,  and 

other  foreign  elements.     .    .    .   Phryganella  Penard   .    .     98 

98  (99)     Large  size;  foreign  elements  large,  rough. 

Phryganella  nidulus  Penard  1902. 

The  shell  is  hemispherical  and  usually  oi  rough  contour. 
Aperture  large.  Pseudopodia  slender  but  often  accompanied 
by  broad  lobes  of  protoplasm.  Found  in  the  ooze  of  ponds 
and  lakes.     Large  forms  are  200  n  in  diameter. 

Fig.  320.     Phryganella  nuiulus.     x  90.     (.\ftcr  Penard.) 


FRESH-WATER   BIOLOGY 

Small  size;  foreign  elements  small.  . 

Phryganella  hcmisphacrica  Penard  1890. 

Shell  hemispherical,  composed  of  small  diatom  shells 
and  sand  grains.  Pseudopodia  usually  slender,  some- 
times thick.  Found  in  the  ooze  of  ponds  and  lakes. 
Diameter  40  to  55  /i. 

Fig.  321.   Phryganella  hemisphaerica.    X  250.    (After  Penard.) 

100  (97)     Shell   chitinous,   without   or    sparsely   covered   with    foreign   ele- 
ments  i°i 

loi  (102)     Shell  occasionally  with  foreign  elements  attached.     Aperture  ter- 
minal  Cryptodifflugia  Penard. 

Representative  species.  .    .    Cryptodifflugia  ovijormis  Penard  1890. 

This  species  has  a  transparent,  yellowish  or  brownish  shell  without  foreign 
elements  attached.  Ovoid  in  form.  The  protoplasm  does  not  fill  the  shell  and 
pseudopodia  are  seldom  extended.     Found  in  marshes.     Length  16  to  20  m- 

Fig.  322,     Cryptodifflugia  oviformis.      X  450-     (After  Penard.) 


Fig.  323.  Platoiim  parvum 
X  725.     (After  Penard.) 


102  (loi)     Shell  without  foreign  elements.     Aperture  terminal  or  subterminal. 

Platoum  F.  E.  Schultze. 

In  1875  Schultze  described  a  form  under  the  n-Ame  Platoum  parvum. 
Ovoid  with  smooth  envelop  without  structure,  slightly  elastic,  aper- 
ture terminal  or  subterminal.  Penard,  more  recently,  observed 
numerous  empty  shells  and  inactive  organisms  which  he  provision- 
ally refers  to  this  genus.  Some  had  undulating  envelopes  with 
apertures  terminal  or  directed  obUquely.  Nucleus  and  contractile 
vacuole  each,  single.  Pseudopodia  not  observed.  Length  16  to  21/1- 
In  preserved  material  from  Alaska,  G.  H.  Wailes  found  forms 
which  he  considers  within  this  genus,  probably  P.  parvum.  Thus 
far  this  is  the  only  record  of  the  genus  in  North  America. 

103  (22)     Pseudopodia  delicate,  filiform,  usually  branched,  and  pointed. 

Family  Euglyphidae   .    .     104 

104  (107)     Shell  flexible,  transparent Pamphagus  Bailey   .    .      105 

105  (106)     Shell  spherical Pamphagus  hyalinus  Ehrenberg  1838. 

The  aperture  of  the  shell  is  very  large  and  capable  of  great 
dilation.  Protoplasm  Is  clear,  colorless.  Nucleus  spherical; 
contractile  vacuole  single.  Pseudopodia  numerous,  straight,  and 
pointed.     Found  in  clear  water.     Diameter  of  shell  30  to  48  n. 

Fig.    324.      Pamphagus    hyaltnus.      cv,    contractile  vacuole.       X  260. 
(After  Leidy.) 


106  (105)     Shell  ovoid  or  elongate. 


Pamphagus  mutahilis  Bailey  1853. 


Body  very  changeable  in  form.  Protoplasm  enclosing  brilliant 
granules.  Nucleus  large,  spherical.  Contractile  vacuoles,  one  or 
two.     Found  in  clear  water.     Length  of  shell  50  to  70  n. 

Fig.  325.     Pamphagus  mutabilis.     X  165.     (After  Penard.) 


107  (104)     Shell  rigid 108 

108(113)     Shell  retort-shaped lOQ 


AMOEBOID    PROTOZOA    (SARCODINA) 


229 


109  (no)     Plates  small,  round,  more  or  less  covered  by  foreign  particles. 

Campascus  Leidy. 
Representative  species Campascus  cor  nut  us  Leidy  i^-j-j. 

This  species  has  lateral  processes  developed  from  the  fundus. 
In  common  with  other  species  of  the  genus,  a  delicate,  transpar- 
ent collar  surrounds  the  aperture,  extending  perpendicular  to  it. 
In  common  with  the  genus  Cyphoderia,  the  bodies  of  all  species 
of  this  genus  enclose  minute  yellow  or  l^rown  granules  very  re- 
sistant to  reagents.  Apparently  a  very  rare  species.  Leidy  re- 
ports it  from  but  one  locality,  China  Lake,  Wyoming,  at  an 
altitude  of  10,000  feet.  Length  112  to  140 /i. 
Fig  326.  Campascus  cornutus.  cv,  contractile  vacuole.  x  150. 
(After  Leidy.) 

no  (109)     Plates  small,  regular,  not  covered  by  foreign  particles. 

Cyphoderia  Schlumberger  .    .      in 

III  (112)     Fundus  rounded  or  mamillate. 

Cyphoderia  ampulla  Ehrenberg  1840. 

Plates  round  or  oval,  cemented  together  in  diagonal  rows, 
presenting  a  hexagonal  appearance.  The  plates  do  not  over- 
lap. Minute  perforations  exist  between  the  plates,  appearing 
as  fine  punctae.  Pseudopodia  few  but  very  long.  Found 
among  mosses,  ooze  of  ponds  and  lakes.  Length  Oi  to  195  ti. 
Several  varieties  of  fnis  species  are  known. 
Fig  327.  Cyphoderia  ampulla.  cv,  contractile  vacuole.  X  160. 
(After  Leidy.) 

112(111)     Fundus  tapering.   .   Cyphoderia  ampidla  V3iT.  papillata  Wsiiles  iQii. 

This  variety  resembles  the  type  species  except  in  the  shape  of  the 
^-^''^"'^-^  fundus.      The   plates  are  sometimes  set  very  close  together  in  this 

"    ■  \  variety  but  do  not  overlap.     Found  in  ooze  of  lakes.    Length  113  to 

CT.  -3  135  M. 

Fig.  328.  Cyphoderia  ampulla  var.  Papillata.   X150.  (From  a  prepared  mount.) 

113(108)     Shell  Straight "4 

114  (115)     Shell  without  distinct  plates,  chitinous,  covered  with  sand,  dirt. 

etc Pseudodifflugia  Schlumberger. 

Representative  species. 

Pseudodifflugia  gracilis  Schlumberger  1S45. 

Shell  ovoid,  elongate,  usually  yellowish  or  brownish.  Pseudo- 
podia numerous,  very  long  and  delicate.  Found  in  the  ooze  of 
ponds,  lakes,  etc.     Length  20  to  65  m- 

Fig.  329.     Pseudodifflugia  gracilis,     n,  nucleus.      X  250.    (After  Leidy.) 

115  (n4)     Shell  with  distinct  plates 116 

n6  (n9)     SheU  not  compressed,  with  a  short  tlattcncd  neck.     Plates  round  or 
oval 5/>//e;/('(/('r/(2  Schlumberger  n; 

117  (n8)     Margin  of  neck  dentate.     .    .    .     Sphcnodcria  dcntata  \\\r.\Xi.\  x'^oo. 

This  species  may  be  known  by  the  elongate-oval  form  of  the  shell  and 
the  presence  of  the  teeth.  The  plates  overlap  givnig  the  appearance  of  a 
hexagonal  design.     Found  among  sphagnum.     Length  35  to  50  m- 

Fig.   330.     Sphenoderia  dcnlata.     X  jio.     (After  Pcnard.) 


230  FRESH-WATER   BIOLOGY 

1 18  (117)     Margin  of  neck  not  dentate.     Sphcnoderia  lenta  Schlumberger  1845. 

Shell  ovoid  or  rounded  with  large,  round  imbricating  plates.      The  aper- 
ture consists  of  a  narrow,  elongated  opening,  extending  between  two  lateral 
[■t>.'.-i&}yy         points  opposite  each  other.     Pscudopodia  are  numerous  and  very  long. 
%-lji  Habitat  sphagnum.     Length  from  .s5  to  50  ti.     Leidy  describes  a  species 

under  the  name  5.  macrolcpis,  dilTering  from  other  species  by  the  angular 
plates  composing  the  shell.     Habitat  sphagnum.     Length  24  to  39  n. 

^    '"'~'        FiG.^31.     Sphenoderia  lenta.     a,  contractile  vacuole.      X  300-     (.\fter  Leidy.) 

119(116)     Shell  compressed,  without  a  neck 120 

120(137)     Aperture  terminal 121 

121(136)     Margin  of  aperture  dentate 122 

122  (125)     Plates  elongate-elliptical;   margin  of  aperture  finely  dentate. 

AssiiUna  Ehrenberg   .    .     123 

123(124)     Large  size,  rounded l552///«a  5ewJww/MW  Ehrenberg  1848. 

Adult  forms  of  this  species  are  chocolate  brown  in  color.      Con- 
tractile vacuole  single.     Nucleus  very  large,  elliptical.     Pseudopodia 
•MP  -yu\  seldom  observed.      Common  in  sphagnous  swamps.      Length  60  to 

Fig.  332      Assulina  seminidum.     cv,  contractile   vacuole.      X  290. 
(After  Leidy.) 


124(123)     Small  size,  oval l552///;/(Z  ;;?/;?or  Penard  i8qo. 

This  species  is  also  brown  in  color  but  clearer  than  the  preceding  one  and 
l-«Tjf.xi|A  the  aperture  is  more  regularly  crenulate.  The  hexagonal  design  formed  by  the 
MM]1        imbricating  plates  is  very  symmetrical.     Found  among  mosses.     Length  35  m- 

w'tvi 

^^''^'''^  Fig.  333.     Assulina  minor.      X  30°-     (.^fter  Penard.) 

125  (122)     Plates  round  or  oval;  margin  of  aperture  with  prominent  denticles. 
Spines  often  developed.       .    .    .   Euglypha  Dujardin   .    .      126 

126(133)     Aperture  circular 127 

127  (130)     Spines  at  apex  only 128 

128(129)     Spines,  one  or  two Euglypha  mucronata  Leidy  iSjS. 

The   shell   not   compressed;    plates  imbricating,  arranged  in 
^________,.^_^^  longitudinal,  alternating  rows.     The_  fundus  tapers  to  a  point 

'r^^^^f^^i^_^^'^^'y^'^^:^^^  which  is  provided  with  one  or  two  spines.     Found  in  sphagnous 

"^j^^^^i^D^'l^X--.^ '  swamps.      Reported  from  North  America  only.      Length  108  to 

Fig.  334.     Euglypha  viucronala.     X  165.     (After  Leidy.) 

129(128)     Spines  in  a  tuft Euglypha  cristata  Leidy  iSy 4. 

Shell  elongated,  very  little  compressed  if  any,  with  plates  arranged 
as  in  preceding  species.       Pseudopodia  rarely  extended.      Habitat 
i^i^,^,  sphagnous  swamps.     Length  33,  to  84  m- 

'-^'"^  ^'  Fig.  335.     Euglypha  cnsiata.      X  425-     (After  Leidy.) 

130  (127)     Spines  not  at  apex  only 131 


AMOEBOID    PROTOZOA    (SARCODINA) 


231 


131  (132)     Spines  lateral Euglypha  brachiata  Lcidy  1878. 

This  species  may  be  known  by  the  straight  shell,  elongate 

and  cylindrical.     Plates  oval,  imbricating  in  a  regular  manner. 
From  four  to  six  large,  long  spines  are  developed,  representing 
<i::^3;SJ^Xlt;?Qf=r^  prolongations  of  some  of  the  lateral  plates.       Habitat  among 

\V^^^^^-«-<.i23>^  sphagnum.     Length  104  to  128^- 

^»^  Fig.  336.     Euglypha  brachiata.      X  i8o.     (After  Leidy  ) 

132  (131)     Spines  usually  absent,  scattered  when  present. 

Euglypha  alveolata  Dujardin  1841. 
Shell  ovoid,  elongated,  very  slightly  compressed  if  any.       Plates 
round  or  oval,  imbricating,  presenting  a  regular  hexagonal  design. 
Nucleus    large,    spherical;     contractile    vacuoles   two    in     number. 
Pseudopodia  numerous,  long  and  straight.     .\  common  species  in  the 
f^^^r^i^T^  ooze  of  ponds,  among  algae  and  mosses.     Length  45  to  100  n. 

Fig.  337.    Euglypha  alveolata.     X  375-     (Original,  from  a  prepared  mount.) 

133  (126)     Aperture  oval 134 

134  (135)     Plates  bordering  aperture  denticulate. 

Euglypha  ciliata  Ehrenberg  1848. 

Shell  compressed,  elongate-oval.  Plates  oval  or  round,  imbricated. 
Needle-like  spines  are  produced  from  the  entire  surface  or  in  a  line 
around  the  lateral  border  of  the  shell.     Habitat  sphagnum.      Length 


40  to  90  M. 

Fig.  338.     Euglypha  ciliata.     X  250.     (After  Penard.) 

135  (134)     Plates  bordering  aperture  lobed.      Euglypha  compressa  Carter  1864. 

Shell  greatly  compressed,  formed  of  elliptical  plates,  imbricating 
and  presenting  a  hexagonal  design.  Numerous  spines,  fusiform  in 
shape,  are  produced  from  the  lateral  border  of  the  shell.  Habitat 
sphagnum.     Length  70  to  132  /i. 

Fig.   339.     Euglypha  compressa.      X  225.     (After  Leidy.) 

136  (121)     Margin  of  aperture  not  dentate.     Shell  oval,  compressed. 

Placocista  Lcidy. 

Representative  species Placocista  spinosa  Lcidy  1874. 

This  species  may  be  known  by  the  long,  awl-shaped  spines 
which  are  movably  articulated  in  a  line  about  the  lateral  border 
of  the  shell.  Plates  oval,  imbricating  in  a  regular  manner.  Habi- 
tat sphagnum.     Length  100  to  136  n. 

Fig.  340.     Placocista  spinosa.      X  170.     (After  Leidy.) 


137  (120)     Aperture  not  terminal 138 

138  (143)     Shell    elongate-oval,   usually   compressed;     aperture   subtcrminal. 

Plates  rounded Trinema  Dujardin   .    .      130 


139  (140)     Oral  extremity  broad. 


Trinema  camplanatiim  Penard  1800. 


This  species  is  short  and  broad,  the  anterior  end  usually  as  broad 
as  the  posterior  extremity.  Aperture  oval.  Habitat  mosses.  Length 
30  to  40  n. 

Fig.  341.     Trinema  camplanatum.      X  500.     (After  Penard.) 

140  (139)     Oral  extremity  narrow 141 


232  FRESH-WATER   BIOLOGY 

141  (142)     Plates  distinct,  large  size.  .    .    .   Trincma  cnchelys  Ehrenberg  1836. 

The  aperture  is  circular  in  this  species  and  surrounded  by  a  num- 

^/'^    ^'  "    »^ her  of  rows  of  very  minute  chitinous  plates.     Pseudopodia  very  tine 

c'^.      ;  ■  :  .    'v^  iind  long,  usually  few  in  number.     This  is  the  most  common  species 

^^^i^ -'       /        '  of  the  genus  and  is  found  everywhere  among  mosses.     Length  40  to 

/  100  n. 

Fig.  342.     Trinema  enchclys.      X  310.     (After  Penard.) 

142  (141)     Plates  indistinct,  small  size.     .    .    .     Trincma  lineare  Penard  1890. 

,  ,  The  plates  of  this  small  form  are  indistinct  except  about  the  edges, 

/  where  they  may  appear  as  minute  undulations.     The  aperture  is  round. 

j^  Habitat  as  other  species.     Length  16  to  26  m- 

^j^^v^;^  Pig.  343.     Trinema  lineare.     X  500.     (After  Penard.) 

43  (138)     Shell  shaped  as  Trinema;   aperture  subterminal;  plates  elongate. 

Corythion  Taranek. 
Representative  species Corythion  dubiiim  Taranek  1882. 

In  this  species  the  shape  of  the  aperture  is  characteristic,  its  border  rep- 
resenting two  unequal  arcs  placed  together,  the  anterior  one  the  longer. 
The  plates  are  close  together  but  not  overlapping.  Habitat  mosses. 
Length  35  to  40  m- 

Fig.  344.     Corythion  diibium.      X  375-     (After  Penard.) 

144  (2)     Pseudopodia  usually  anastomosing 145 

145  (158)     Pseudopodia  very  delicate,  usually  finely  branched. 

Subclass  Foraminifera    .    .      146 

146  (147)     Body  without  a  covering;    pseudopodia  formed  from  any  part  of 

the  surface Biomyxa  Leidy. 

Representative  species Biomyxa  vagans  Leidy  1875. 

The  body  moves  slowly  but  continuously,  no  distinction 
^  between  ectoplasm  and  endoplasm  being  observed.     Pseu- 

dopodia long,  branching  and  anastomosing,  always  chang- 
ing.     A   granular   nucleus   and  a  number  of   contractile 
V  <£TS-;^''"^^:::-__.__^  '^'^.cuoles  are  present.     Habitat  sphagnous  swamps.     Large 

'°_^<s'.'o(      ^^>>.^  individuals  may  measure  480  ^  between  the   tips  of  the 

pseudopodia. 

'\  P~~^,   N       ^  Fig.  345.     Biomyxa  vagans.      X  65.     (After  Penard.) 

147  (146)     Body  with  a  distinct  covering 148 

148  (153)     Pseudopodia  extending  from  more  than  one  aperture.     .    .    .     149 
149(152)     Envelop  elongate,  compressed.      .   .   Amphiirema  Archer  .    .      150 

150  (151)     Envelop  transparent,  with  no  foreign  particles  attached. 

Amphitrema  jlaviim  Archer  1878. 

Pseudopodia  straight,  unbranched,  extending  from  the  opposite 
poles  of  the  envelop.  Protoplasm  always  enclosing  chlorophyl. 
Nucleus  single.  One  or  more  contractile  vacuoles.  Habitat 
mosses.     Length  45  to  55  ix. 

Fig.  346.     Amphitrema  flavum.      X  255.     (After  Penard.) 

151  (150)     Envelop  with  foreign  particles  attached.    • 

Amphitrema  wrightianum  Archer  1870. 

In   this  species  the   apertures  at  opposite  poles  are  sur- 
rounded   by    short    collars.      Chlorophyl    always    present. 
•gr,""®*"*  "o  E- Pseudopodia  often  branched.     Nucleus  single.      Contractile 


vacuoles  one  or  more.     Habitat  mosses.     Length  65  to  70  /x. 
Fig.  347.     Amphiirema  wrighlianum.     X  215.     (After  Penard.) 


AMOEBOID    PROTOZOA    (SARCODINA) 


233 


152  (149) 


Envelop  spherical Diplophrys  Barker. 

Representative  species Diplophrys  archer i  Barker  1868. 

In  this  species  the  pseudopodia,  which  are  long  and  branched,  extend 
from  opposite  poles  of  the  envelop.  The  protoplasm  always  encloses 
a  large  spherical  globule  usually  yellow  or  brown  in  color.  A  nucleus 
and  one  or  more  contractile  vacuoles  are  present.  Habitat  sphagnum. 
Diameter  8  to  20  /x. 

Fig.   348.     Diplophrys   archeri.      X  1200.     (.'\fter   Penard.) 

153(148)     Pseudopodia  extending  from  a  single  aperture 154 

154  (155)     Envelop  very  flexible,  changeable  in  shape. 

Lieberkuhnia  Claparede  and  Lachmann. 
Representative  species.    .    .  Lieberkuhnia  wageneri  C.  and  L.  1858. 


The  envelop  is  normally  pyriform  but  changeable  in  shape. 
Pseudopodia  long,  anastomosing,  extending  from  a  protoplasmic 
peduncle  at  the  aperture.  Nuclei  as  many  as  200.  Contractile 
vacuoles  numerous.     Habitat  mosses.     Length  96  /i> 

Fig.   349.    LieberkUh'iii    wageneri.      X  130.     (After   Penard.) 


155  (154) 

156  (157) 


Envelop  rigid  or  slightly  flexible 156 

Body  filling  the  envelop Gromia  Dujardin. 

Representative  species Gromia  fluviatil is  T>w]diX(]\n  i^^i. 

Envelop  spherical  or  ovoid,  seldom  changing  shape.     The  outer 

surface  of  the  envelop  is  covered  by  a  delicate  sheath  of  proto- 

/     ".!^  plasm  in  which  minute  granules  circulate.     Pseudopodia  numerous, 

''..:_^  anastomosing.     Habitat  among  aquatic  plants.     Diameter  90  to 

.     -  250  n.     This  species  is  identical  with  Gromia  terricola  Leidy. 

--;.""  Fig.  350.     Gromia  fluvial  His.     X  25.     (After  Leidy.) 


157  (156)     Body  not  filling  the  envelop Microgromia  R.  Hertwig. 

Representative  species.    .    .   Microgromia  social  is  R.  Hertwig  1S74. 

Envelop  rigid  with  a  short  neck.  Pseudopodia  long,  anastomosing,  aris- 
ing from  a  peduncle  at  the  aperture.  Sometimes  colonies  are  formed. 
Habitat  standing  water.  Length  20  m-  Conn  reports  a  form  from  Con- 
necticut which  he  refers  to  this  species  with  some  doubt  as  to  its  identity. 


Fig.  351. 


Microgromia  socialis.    cv,  contractile  vacuole;  n,  nucleus. 
(After  Hertwig.) 


X  545. 


158  (145)     Pseudopodia  ray-like,  soft,  and  anastomosing  when  touching. 

Subclass  Proteomyxa   .    .      1 50 


159  (160)     Body  amoeboid;  endoplasm  colorless.  .     .    Nuclear ia  Cienkowsky. 
Representative  species.  .    .    .  Nuclearia  simplex  Cienkowsky  i^b^. 

Body  normally  spherical  but  capable  of  changing  shape.  Pseudopodia 
arising  from  all  parts  of  the  body.  Nucleus  central,  contractile  vacuoles 
more  than  one.  Diameter  20  to  50  m-  Reported  by  Conn  from  Connecti- 
cut. 

Fig.  352.    Nuclcaria  simplex.     X  250.     (.Vfter  Cona.) 


234  FRESH-WATER    BIOLOGY 

i6o  (159)     Body  amoeboid;  endoplasm  red  or  brown. 

Vampyrella  Cienkowsky. 
Representative  species.  .    .    Vampyrella  lateritia  Cienkowsky  1865. 

Body  spherical  or  elongated.  Pscudopodia  arising  from  all  parts  of  the 
body  or  from  one  point.  The  nucleus  and  contractile  vacuole  usually  con- 
cealed by  the  contents  of  the  endoplasm,  A  gelatinous  sheath  sometimes 
surrounds  the  body.  Habitat  among  algae  up)on  which  it  feeds.  Diameter 
25  to  80  n. 

Fig.    353.     Vampyrella    lateritia.      X  250.     (After  Conn.) 


161  (i)     Pseudopodia  with  axial  filaments Class  Actinopoda. 

Fresh-water  species  included  in  one  subclass. 

Subclass  Heliozoa    .    .      162 
No  central  capsule  between  endoplasm  and  ectoplasm.     Pscudopodia  ray-like. 

162  (165)     With  no  external  envelop  ....   Order  Aphrothoracida   .    .      163 

163  (164)     Nucleus  single Actinophrys  Ehrenberg. 

Representative  species Actinophrys  sol.  Ehrenberg  1830. 


Body  spherical  with  protoplasm  highly  vacuolated.  Usually 
one  contractile  vacuole  which  rises  and  pushes  out  the  surface  as 
a  rounded  globule  before  bursting.  Pseudopodia  extending  from 
all  parts  of  the  body.  Habitat  pond  water  among  aquatic  plants; 
very  common.     Diameter  40  to  50  //. 

Fig.  354.    Actinophrys  sol.  cv,  contractile  vacuole.     X  245.     (After  Leidy.) 


164  (163)     Nuclei  many Actinosphaeriiim  Stein. 

Representative  species. 

Actinosphaerium  eichhornii  Ehrenberg  1840. 

Protoplasm  vacuolated  with  very  large  vacuoles  about  the 
periphery.  Nuclei  scattered  throughout  the  endoplasm.  Pseudo- 
podia extending  from  all  parts  of  the  body.  One  or  more  con- 
tractile vacuoles.  Habitat  among  aquatic  plants.  Not  common. 
Average  diameter  200  to  300  n.  Some  have  reported  individuals 
over  1000  M  in  diameter. 

Fig.  355.     Actinosphaerium   eichhornii.    cv,  contractile  vacuole.      X  40. 
(After  Leidy.) 

With  an  external  envelop 166 

167)     Envelop  gelatinous,  without  plates  or  spicules. 

Order  Chlamydophora. 

One  genus  reported  in  North  America.      .    .    .   Adinolophus  Schultze. 
With  a  pedicel. 
Representative  species.     .    .   Actinolophus  minutus  Walton  1905. 

Pseudopodia  very  short,  extending  from  all  parts  of  the  body.  Nucleus  single,  in 
the  posterior  region.  Contractile  vacuole  not  observed.  Diameter  of  body  with  en- 
velop 12  M-  Length  of  pedicel  70  /i.  Habitat  river  water.  Described  by  Walton 
from  Ohio.  This  genus  is  introduced  provisionally.  Further  knowledge  is  needed 
concerning  it,  as  certain  species  referred  to  the  genus  show  marked  affinities  with 
Sucloria. 
Fig.  356.     Actinolophus  minulus.     cv,  contractile  vacuole;  ».  nucleus.     X  350.     (After  Walton.) 


AMOEBOID    PROTOZOA    (SARCODINA) 

167  (166)     Envelop  with  more  or  less  closely  united  spicules. 


235 
168 


168  (175)     With  a  thick  protoplasmic  envelop  in  which  are  imbedded  skeletal 
elements  in  the  form  of  spicules  or  plates. 

Order  Chalarothoraca    .    .      169 

169(172)     Skeletal  elements  loosely  connected i^q 


170  (171)     Spicules  chitinous,  radiating  between  the  pseudopodia. 

Hekrophrys  Archer. 
Representative  species.  .    .    .    Hekrophrys  myriopoda  Archer  1869. 

In  this  species  the  envelop  is  mucilaginous,  its  outer  border  pre- 
senting a  villous  appearance  due  to  the  arrangement  of  the  spicules. 
Ray-like  pseudopodia  penetrate  the  envelop.  This  organism  is 
known  to  take  possession  of  spicules  from  species  of  related  genera, 
probably  from  discarded  skeletons,  and  make  them  a  part  of  its 
own  envelop.  Endoplasm  usually  green  with  symljiotic  algae. 
Nucleus  single.  A  contractile  vacuole  is  not  always  observed. 
Habitat  marshes  and  standing  water.     Diameter  70^. 

Fig.  357.     Heterophrys  myrioPoda.     x  190.     (After  Penard.) 


171 


(170)     Spicules  siliceous,  scattered  through  the  envelop  and  surrounding 
the  bases  of  the  pseudopodia.    .    .    .   Raphidiophrys  Archer. 
Representative  species. 

Raphidiophrys  ekgans  Hertwig  and  Lesser  1874. 

The  spicules  are  semicircular,  with  their  convex  surfaces 
toward  the  body  and  pseudopodia.  Nucleus  single.  One 
contractile  vacuole.  Chlorophyl  sometimes  present.  Often 
numbers  of  these  individuals  are  grouped  into  colonies,  joined 
by  protoplasmic  processes.  Habitat  among  aquatic  plants. 
Diameter  30  m. 

R.  viridis  Archer  diflfers  from  R.  ekgans  in  the  fusiform  spic- 
ules and  the  constant  presence  of  symbiotic  algae. 

Fig.  358.     Raphidiophrys  ekgans.     X  150.     (After  Leidy.) 


172  (169)     Skeletal  elements  closely  united,  forming  a  compact  envelop.     173 


173  (174)     Spicules  siliceous,  globular,  completely  surrounding  the  body. 

Pompholyxophrys  Archer. 
Representative  species.  .    .  Pompholyxophrys  piinicca  Archer  1869. 

The  spicules  usually  in  three  rows  about  the  body.  Endoplasm  re<l- 
dish.  Nucleus  spherical,  large.  No  contractile  vacuole.  PscudojxKlia 
very  fine  and  indistinct.  Habitat  among  aquatic  plants  in  ponds  antl 
in  swamps.  Diameter  25  to  30  /i.  Leidy  records  this  species  from 
New  Jersey  as  Uyalolampe  Jeneslrata  Greeff. 

Fig.  359.     Pompholyxophrys  punicea.      X  200.     (After  Penard.) 


236  FRESH-WATER    BIOLOGY 

174  (173)     Spicules  siliceous,   in  the  form  of  plates  and  delicate  radiating 

spines Acanthocystis  Carter. 

Representative  species.  .    .     Acanthocystis  chaetophora  Leidy  1874. 


The  skeletal  plates  are  oval,  arranged  tangentially.  The 
spinous  rays  are  of  two  lengths,  the  long  ones  acutely  forked, 
the  short  ones  widely  forked  at  the  distal  extremities.  Nucleus 
large,  usually  no  contractile  vacuole.  Endoplasm  green  in 
color  from  enclosed  chlorophyl.  Habitat  among  aquatic 
plants.     Diameter  of  body  50  to  60  m- 

Fig.  360.     Acanthocystis  chaetophora.      X  250.     (After  Leidy.) 


^M^MW^- 


175  (168)     With  a  solid  envelop,  perforated  for  the  pseudopodia.     Sometimes 
stalked Order  Desmothoraca. 

One  genus  reported  in  North  America.    .    .    .      Clathrulina  Cicnkowsky. 

Envelop  with  a  stalk. 
Representative  species Clathrulina  elegans  Cienkowsky  1867. 


Envelop  more  or  less  chitinous,  perforated  by  numerous  large,  irreg- 
ular openings.  Protoplasm  not  filling  the  envelop.  Nucleus  single. 
One  or  more  contractile  vacuoles.  Pseudopodia  very  delicate,  appar- 
ently without  a.Kial  filaments.  Habitat  sphagnous  swamps  and  among 
aquatic  plants;  very  common  in  some  localities.  Diameter  of  envelop 
60  to  90  M- 

Fig.    361.     Clathrulina  elegans.     X  130.     (After  Leidy.) 


IMPORTANT  REFERENCES  ON   PROTOZOA,   ESPECIALLY 
SARCODINA 

BuTSCHLi,  O.     1883.     Protozoa.     In  Bronn's  Klassen  and  Ordnungen  des 

Thierreichs,  vol.  i,  pt.  1-3.     Leipzig. 
Calkins,  G.  N.     1901.     The  Protozoa.     New  York. 

1909.     Protozoology.     New  York. 
Cash,  J.,  and  Hopkins,  J.     1 905-1 909.     The  British  Fresh-water  Rhizopoda 

and  Heliozoa.     2  parts.     Ray  Society,  vol.  75. 
COCKERELL,  T.   D.  A.     1911.     The  Fauna   of  Boulder  County,   Colorado. 

Univ.  Colo.  Studies,  8:  227-256. 
Conn,  H.  W.     1905.     A  Preliminary  Report  on  the  Protozoa  of  the  Fresh 

Waters  of  Connecticut.     State   Geol.  and  Nat.  Hist.  Survey,  Bull.  2; 

69  pp.,  34  Pl. 


AMOEBOID    PROTOZOA    (SARCODINA)  237 

Edmondson,  C.  H.     1906.     The  Protozoa  of  Iowa.     Proc.  Davenport  Acad. 

Sci.,  II :   1-124;  29  pi. 
191 2.      Protozoa   of   High  Mountain  Lakes   in    Colorado.      Univ.    Colo. 

Studies,  9:  65-74. 
Heaipel,  a.    1898.   A  list  of  the  Protozoa  and  Rotifera  Found  in  Illinois  River 

and  Adjacent  Lakes  at  Havana,  111.     Bull.  111.  State  Lab.  Nat.  Hist.,  5: 

301-388;  5  figs. 
Landacre,  F.  L.     1908.     Protozoa  of  Sandusky  Bay  and  Vicinity.     Ohio 

Acad.  Sci.,  4:  421-472. 
Leidy,  Jos.     1879.     Fresh-water  Rhizopods  of  North  America.     U.  S.  Geol. 

Surv.  Territ.,  vol.  12;  324  pp.,  48  pi. 
Penard,  E.     1902.     Faune  rhizopodique  du  bassin  du  leman.     714  pp.,  figs. 

Geneve. 

1904.  Les  Heliozoaires  d'eau  douce.     341  pp.,  figs.     Geneve. 

1905.  Les  Sarcodines  des  grand  lacs.     133  pp.,  figs.     Geneve. 

1911.  Rhizopodes  d'eau  douce.  British  Antartic  Expedition,  1907-9,  i: 
203-262.     (Includes  a  Kst  of  Rhizopods  from  Canada.) 

Wailes,  G.  H.  191 2.  Fresh-water  Rhizopods  and  Heliozoa  from  the  States  of 
New  York,  New  Jersey,  and  Georgia,  U.  S.  A.;  with  Supplemental  Note 
on  Seychelles  Species.    Jour.  Linnean  Soc,  Zoology  32:  121-161;  i  pi. 

Wailes,  G.  H.,  and  Penard,  E.  191 1.  Rhizopoda.  Proc.  Roy.  Irish  Acad., 
Clare  Island  Survey,  Part  65;  64  pp.;  6  pi. 


CHAPTER   IX 
FLAGELLATE    AND    CILIATE    PROTOZOA 

(mastigophora  et  infusoria) 

By  H.  W.  conn  and  C.  H.  EDIMONDSON 

Professor  of  Biology,  Wesleyan\U niversity  Assistant  Professor  of  Zoology,  University  of  Oregon 

By  early  observers  the  term  Infusoria  was  applied  to  all  minute 
organisms  found  in  water,  including  not  only  unicellular  animals 
but  many  minute  plants  and  not  a  few  multicellular  animals,  as 
rotifiers,  sponges,  etc.  Later  the  term  was  restricted  to  those  one- 
celled  animals  which  are  commonly  found  in  standing  water  and 
which  move  by  means  of  long  whip-like  processes  called  flagella 
or  by  shorter,  hair-like  structures  called  cilia. 

At  the  present  time  the  flagellated  forms  are  included  under  the 
subphylum  Mastigophora  and  those  possessing  ciHa,  throughout 
their  entire  existence  or  during  their  embryonic  stage  only,  are 
grouped  under  the  subphylum  Infusoria.  Mastigophora  and 
Infusoria  are  of  almost  universal  distribution,  occurring  in  fresh 
and  salt  water,  abundant  in  clear  pools  and  streams  as  well  as 
in  stagnant  bodies  of  water  and  also  in  infusions  of  plant  or  animal 
macerations.  Some  are  parasitic,  Hving  upon  or  within  the  bodies 
of  other  animals. 

In  the  Mastigophora  flagella  are  the  characteristic  structural 
features.  These  structures  are  slender,  flexible,  whip-Hke  processes 
drawn  out  from  the  body,  commonly  at  one  end.  The  flagellum 
when  single  is  usually  directed  forward,  and  by  a  lashing  movement, 
a  corkscrew  twisting,  or  a  mere  vibration  of  its  free  distal  end 
draws  the  body  forward.  Flagella  may  be  numerous  and  often 
one  or  more  are  directed  backward  or  trail  at  the  side  in  addition 
to  those  extended  in  advance. 

That  a  close  relationship  exists  between  flagella  and  pseudopodia 
is  easily  observed  in  a  number  of  forms.    Some  low  flagellates 

238 


FLAGELLATE   AND   CILLVTE   PROTOZOA  239 

possess  well-defined  pseudopodia,  and  the  flagella  of  these  forms  have 
the  appearance  of  permanent,  specialized  pseudopodia  endowed 
With  the  power  of  vibration.  The  interchanging  of  pseudopodia 
and  flagella  has  been  referred  to  in  the  case  of  Vampyrella  under 
Sarcodina.  The  origin  of  the  flagellum  has  been  traced  in  some 
forms  to  the  region  of  the  nucleus,  which  may  be  considered  as 
evidence  in  favor  of  its  homology  with  the  axial  supports  of 
pseudopodia. 

Cilia,  which  are  the  conspicuous  and  for  diagnosis  the  special  struc- 
tural feature  of  the  cilia tes,  as  contrasted  with  flagella,  arc  short, 
hair-like  processes.  They  arise  from  the  ectoplasm,  not  origina- 
ting from  the  deeper  regions  of  the  body  as  do  flagella.  Cilia  may 
be  evenly  distributed  over  the  surface  of  the  animal  or  restricted 
to  certain  regions  or  zones.  Often  fusion  of  cilia  takes  place  form- 
ing vibrating  membranelles  or  large  bristle-like  cirri  or  setae.  By 
tufts  of  cilia  certain  forms  may  be  temporarily  attached  to  supports. 
Suctoria,  in  transition  from  the  embryonic  stages  to  the  adult,  lose 
the  covering  of  cilia  which  is  replaced  by  hollow  tentacles,  capable 
of  extension  and  retraction.  The  tentacles  may  be  pointed  or  dis- 
tinctly capitate,  the  prey  being  pierced  by  them  and  its  protoplasm 
drawn  through  the  hollow  tubules  into  the  body  of  the  suctorian. 

In  Mastigophora  and  Infusoria  the  protoplasm  is  similar  in 
structure  to  that  of  lower  Protozoa,  being  alveolar  in  character. 
However,  in  these  groups,  the  protoplasmic  contents  of  the  body 
are  not  arranged  in  zones  to  the  extent  found  in  Sarcodina.  Great 
variation  exists  in  the  consistency  of  the  body  both  in  flagellates 
and  in  ciliates.  In  some  the  body  is  soft  and  flexible,  the  ectoplasm 
permitting  rapid  changes  in  shape  or  even  the  formation  of  pseud- 
opodia; others  are  enclosed  by  inflexible  membranes,  sheaths,  or 
well-defined  plates.  Cup-like  loricae  are  sometimes  developed, 
to  the  inner  surface  of  which  the  animal  may  be  fixed,  from  which 
it  may  project,  and  into  which  it  may  retract.  In  a  few  oi  the 
flagellates  a  delicate  collar  is  formed  about  the  base  of  the  tlagellum. 
The  collar  is  very  transparent,  variable  in  size,  and  capable  of  being 
retracted  into  the  body  protoplasm  like  a  pseudopodium. 

Many  flagellates  and  ciliates  are  free  swimming,  while  some  may 
be  temporarily  fixed  by  cilia  or  flagella  or  by  the  adherence  of  a 


240  FRESH-WATER   BIOLOGY 

surface  to  some  support.  Others  are  attached  by  stalks  or  pedicels 
which  may  be  rigid,  flexible  or,  in  some  forms,  as  Vorticella,  may 
contract  spirally.  Special  organs  of  defense  are  provided  in  a  few 
flagellates  and  many  ciliates  in  the  form  of  trichocysts  or  stinging, 
thread-like  structures.  In  at  least  one  genus  of  flagellates,  Poly- 
krikos,  the  stinging  threads  are  highly  specialized,  resembling 
nematocysts  of  Coelenterata.  As  in  Sarcodina,  one  or  more  con- 
tractile vacuoles  are  usually  present  in  the  flagellates  and  ciliates, 
their  function  being  similar  in  all  Protozoa. 

Nuclei  are  present  in  all  Mastigophora  and  Infusoria  but  con- 
siderable structural  variation  exists  with  respect  to  them  in  these 
two  groups.  In  some  flagellates  the  nucleus  consists  of  scattered 
or  grouped  particles  of  chromatin  without  a  nuclear  membrane, 
while  in  many  of  the  higher  Infusoria  it  consists  of  a  highly  differ- 
entiated, branched  structure.  Infusoria  differ  from  other  Proto- 
zoa, with  a  few  possible  exceptions,  in  the  possession  of  two  kinds 
of  nuclei  in  each  cell,  a  macronucleus  and  a  micronucleus,  the 
former  being  concerned  with  the  vegetative  functions  and  asexual 
division,  the  latter  with  sexual  division.  The  macronucleus  is  the 
larger  and  often  varies  greatly  from  the  regular  spherical  t>^e;  the 
micronucleus  is  usually  very  small,  spherical,  and  in  close  contact 
with  the  macronucleus.  In  but  one  flagellate,  Polykrikos,  has  this 
differentiation  into  two  nuclei  been  found.  In  the  key  which 
follows,  wherever  the  term  nucleus  is  mentioned,  reference  is  made 
to  the  macronucleus.  In  many  forms  of  Mastigophora  and  In- 
fusoria as  well  as  Sarcodina,  the  nucleus  encloses  a  spherical  body 
which  functions  as  a  division  center.  During  the  resting  stage  of 
the  cell  the  division  center  resembles  a  nucleolus  in  appearance,  but 
during  mitosis  it  elongates,  forming  a  spindle,  and  indirect  division 
comparable  to  that  in  the  Metazoa  occurs  in  some  of  the  more 
complex  forms. 

The  endoplasm  of  many  Mastigophora  encloses  colored  corpuscles 
or  chroma tophores,  green,  yellow,  and  brown  being  the  prevailing 
colors.  The  chromatophores  themselves  often  enclose  deeply 
staining  pyrenoid  bodies  which  probably  have  to  do  with  the  con- 
struction of  starch.  Other  inclusions  as  oil  droplets,  paramylum 
granules,  allied  to  starch,  and  pigment  spots  are  common  in  those 


FLAGELLATE   AND    CILLVTE    PROTOZOA  241 

forms  containing  chromatophores.  The  red  ''eye-spot"  is  usually 
located  at  the  anterior  end  of  the  body  near  the  base  of  the  flagellum 
and  probably  functions  as  a  sense  organ,  being  stimulated  by  rays 
of  light.  Chromatophores,  oil  droplets,  and  pigment  spots  may 
sometimes  be  found  in  Infusoria  but  are  much  less  common  than 
among  the  flagellates. 

Generally  speaking,  the  physiological  processes  in  Mastigophora 
and  Infusoria  are  carried  on  precisely  as  in  Sarcodina.  The  pres- 
ence of  chlorophyl  in  some  of  the  flagellates  makes  possible  the 
synthesis  of  food  from  inorganic  elements,  but  in  many  of  these 
forms  and  in  nearly  all  of  the  ciHates  distinct  mouths  are  developed, 
sometimes  permanently  open  and  sometimes  open  only  while  food 
is  being  ingested.  The  symbiotic  relationship  exists  with  algae 
in  some  species  of  ciKates  also.  Among  Mastigophora  food  is 
often  whipped  down  by  the  flagellum  to  the  soft  ectoplasm  at  its 
base  where  ingestion  takes  place.  The  dehcate  collars  present  in 
some  flagellates  assist  in  food  getting.  Among  ciliates  the  vibrat- 
ing ciHa,  membranelles,  and  membranes  serve  to  draw  food  toward 
the  animal  by  arousing  currents  of  water.  In  Suctoria  the  tentacles 
are  organs  for  securing  food,  their  distal  extremities  being  provided 
with  openings  through  which  the  protoplasm  of  the  prey  is  drawn. 
Respiration  and  excretion  are  similar  processes  in  all  Protozoa. 
The  contractile  vacuoles  assist  in  the  excretion  of  waste  fluids  and 
probably  of  gases.  In  some  Infusoria  there  are  deflnite  points  on 
the  surface  where  waste  solids  pass  from  the  body. 

Among  the  Mastigophora, longitudinal  fission  is  the  predominating 
method  of  reproduction,  only  a  few  forms  dividing  transverse!}'. 
Usually  the  chromatophores, ''eye-spot"  and  pyrenoids,  if  present, 
divide  as  well  as  the  nucleus  during  reproduction.  The  flagellum 
sometimes  divides  longitudinally,  and  in  other  forms  is  cast  oil, 
new  flagella  being  developed  as  the  cells  separate.  In  some  cases 
the  "eye-spot,"  pyrenoids,  and  flagella  arc  duplicated  before  a 
division  of  the  ceH  commences.  Many  colonial  forms  of  Masti- 
gophora illustrate  a  highly  specialized  ty-pc  of  cell  division  similar 
to  that  shown  in  a  metazoan  ovum.  Among  Infusoria  simjile 
division  is  the  predominating  method  of  reproduction.  Division 
may  be  longitudinal,  transverse,  or  diagonal,  both  nuclei  dividing 


242  FRESH-WATER   BIOLOGY 

during  the  process,  new  stmctures  such  as  mouth  parts  and  con- 
tractile vacuoles  usually  being  formed  as  division  goes  on.  The 
production  of  swarm  spores  is  common  among  the  flagellates,  occur- 
ring either  in  the  free  swimming  or  encysted  condition  and  develop- 
ing into  the  adult  either  directly  or  after  the  fusion  of  two  of  them 
has  taken  place.  Swarm  spores  are  produced  in  a  few  species  of 
ciliates  during  encystment. 

Conjugation  occurs  in  both  Mastigophora  and  Infusoria.  In 
some  cases  the  fusion  is  permanent;  in  others  it  is  temporary,  the 
cells  separating  after  an  interchange  of  micronuclear  material. 
Conjugation  may  often  be  followed  by  either  encystment  or  the 
production  of  swarm  spores,  or  both.  Gametes  of  unequal  size  are 
frequently  produced,  in  some  cases  union  between  two  small  gametes 
taking  place,  in  others  a  large  and  a  small  one  uniting.  Among 
VorticelHdae  there  is  a  complete  fusion  of  the  free-swimming  micro- 
gamete  with  the  fixed  macrogamete.  In  some  of  the  more  compH- 
cated  flagellates,  as  Volvox,  phenomena  closely  resembHng  sexual 
reproduction  occur;  sex  cells  are  differentiated  from  somatic 
cells,  ova  and  sperm  are  developed,  and  new  colonies  are  produced 
as  a  result  of  fertilization,  Encystment  occurs  in  Mastigophora 
and  Infusoria  as  in  Sarcodina,  the  condition  sometimes  being  pre- 
ceded by  conjugation  or  followed  by  the  formation  of  swarm 
spores. 

In  general,  methods  of  collecting,  studying  and  preserving 
Sarcodina  may  be  employed  for  Mastigophora  and  Infusoria. 
However,  these  latter  are  often  free-swimming,  swift-moving  forms, 
and  before  any  satisfactory  study  of  them  can  be  made  their  move- 
ments must  be  retarded.  An  aqueous  solution  of  gelatin  will  check 
the  movements  without  kiUing  the  animals  if  a  solution  of  the  right 
consistency  is  used  and  this  may  be  obtained  by  trial.  Egg  albumen 
may  be  substituted  for  gelatin.  A  drop  of  very  dilute  methyl 
alcohol  added  to  the  water  containing  Protozoa  will  usually  nar- 
cotize them.  Evaporation  of  water  from  under  the  cover  glass  will 
gradually  retard  their  movement^  but  the  larger  forms  will  soon 
be  crushed  by  the  weight  of  the  cover  unless  the  latter  is  supported 
by  wax  feet,  bits  of  paper,  or  very  thin  glass.  Fine  capillary  tubes 
broken  into  short  pieces  make  useful  rollers  on  which  the  cover 


FLAGELLATE  PROTOZOA  (MASTIGOPHORA) 


243 


glass  may  be  supported  and  the  protozoan,  if  under  the  proper 
pressure,  may  then  be  rotated  for  study  from  various  aspects. 

KEY   TO    NORTH   AMERICAN    FRESH-WATER    MASTIGOPHORA 

I  (131)     Flagellated  forms  with  animal  characteristics  predominating. 

Class  Zoomastigophora    .    .      2 

Confessedly  a  poor  definition,  but  no  better  can  be  given.  The  beginner  will  often  be  in 
doubt  whether  forms  under  consideration  are  flagellated  animals  (Mastigophora),  or  flagel- 
lated plants  (unicellular  algae),  or  less  frequently  flagellate  stages  (spores)  of  Protozoa  and 
Protophyta.  Even  authorities  are  not  in  agreement  regarding  the  position  which  should  be 
assigned  to  specific  forms;  thus  the  Volvocina  are  included  in  both  Protophyta  and  Protozoa 
in  this  book. 


2(118)     Without  protoplasmic  collars.     .    .     Subclass  Lissoflagellata   .    .       3 

3  (36)     Very  plastic,  often  producing  pseudopodia.    Order  Monadida   .    .       4 

4  (15)     Not  forming  colonies  and  without  lorica c 


5  (12)     Pseudopodia  present;  flagella,  one  or  two. 

Family  Rhizomastigidae 

6  (9)     Flagellum  single 


7  (8)     Pseudopodia  lobe-like  or  pointed,  sometimes  branched. 

Mastigamoeba  Schultze. 
Representative  species Mastigamoeba  longifilum  Stokes  1886. 

Body  very  changeable  in  shape,  often  producing  distinct 
pseudopodia;  movements  usually  slow,  repent,  but  sometimes 
the  animal  glides  forward  rapidly  without  pseudopodia  being 
formed.  Flagellum  long,  very  active.  Nucleus  small,  near 
the  anterior  extremity;  contractile  vacuole  single,  anterior  in 
position.  Length  12  to  30 /i.  Standing  water,  among  decaying 
vegetation. 

Fig.  362.     Mastigamoeba  longifilum.     x  1000.     (After  Conn.) 

8  (7)     Pseudopodia  ray-like,  often  capitate Actinomonas  Kent. 

Representative  species Actinomonas  vernalis  Stokes  1885. 


Body  subspherical,  changeable  in  shape,  free  swimming  or 
temporarily  attached  by  a  short  stalk.  Pseudopodia  few,  radi- 
ating from  any  part  of  the  periphery,  simple  or  branched. 
Nucleus  subcentral;  contractile  vacuoles  several.  Diameter 
about  20  n.     Shallow  ponds  in  early  spring. 


Fig.  363. 


Actinomonas  vernalit.     cv,  contractile  vacuole;  n,  nucleus. 
X  600.      (After  Stokes.) 


More  than  one  flagellum 10 


244 


FRESH-WATER  BIOLOGY 


lo(ii)     Pseudopodia  ray-like  with  swellings  along  their  course.     Flagella 

directed  forward .     Acinetactis  Stokes. 

Representative  species Acinetactis  mirabilis  Stokes  1886. 


Body  subsphcrical,  soft,  and  plastic.  Short,  lobate  pseudopodia 
often  in  addition  to  capitate  rays.  Flagella  subequal  arising  at 
some  distance  from  each  other.  Nucleus  central;  contractile  vacu- 
oles two.     Diameter  about  1 2  m-     Stagnant  pond  water. 


Fig.  364.     Acinetactis  mirabilis.      X  700.     (After  Stokes.) 


11(10)     Pseudopodia  lobe-like.     Flagella  two,  one  trailing.     Cercobodo  Kvaas. 
Representative  species Cercobodo  sp. 


Species  not  determined. 

Fig.  365.     Cercobodo  sp.     X  1250.     (After  Conn. 


12  (5)     Plastic  but  not  forming  pseudopodia.     Flagellum  single. 

Family  Cercomoxadidae 


13 


13  (14)     With  a  posterior  tail-like  filament Ccrcomonas  Dujardin. 

Representative  species.  .    .     Cercomonas  longicaudata  DuisLvdm  1S41. 

Body  elongate-ovate,  fusiform,  terminating 
posteriorly  in  a  long,  tail-like  filament  about 
c    o  twice  the  length  of  the  body.    Nucleus  spher- 

ical,  subcentral.     Length    10  fx.     Vegetable 
infusions. 

Fig.  366.     Cercomonaslongicaudata.    a;,  contractile 
vacuole;  »,  nucleus       X  1200.     (After  Stein.) 


14  (13)     Without  a  tail-like  filament Oikomonas  Kent. 

Representative  species Oikomonas  steinii  Kent  1880. 


Body,  in  motile  condition,  exceedingly  plastic  with  a  single 
flagellum  at  the  anterior  end  and  a  lip-like  extension  which  as- 
sists in  taking  food;  in  sedentary  state,  pyriform  and  attached 
by  posterior  extremity.  Nucleus  posteriorly  located.  Length,- 
when  contracted,  about  20  to  30  tx.   Vegetable  infusions.    Social. 


Fig.  367. 


Oikomonas  steinii.    cv,  contractile  vacuole;  n,  nucleus. 
X  440.     (After  Blochmann.) 


FLAGELLATE   PROTOZOA    (MASTK;OPHORA) 


245 
16 


15(4)     Often  forming  colonies  and  often  with  lorica 

16  (21)     Lorica  present Family  Bikoecidak  17 

17  (20)     Not  forming  colonies 18 

18  (19)     Body  attached  in  lorica  by  thread-like  peduncle;    with  peristome 
process.     Two  flagella Bicosoeca  James-Clark. 

Representative  species Bicosoeca  lepteca  Stokes  1885. 


/ 


Lorica  subcylindrical  with  a  very  short  neck  in  front;  drawn  out  to  an  acute 
point  where  attachment  is  made  with  the  pedicel.  Body  ovate,  ol)liquely 
truncate  in  front  and  projecting  slightly  beyond  the  margin  of  the  lorica  when  fully 
extended.  Flagella  unequal.  Nucleus  near  the  middle  of  the  body;  two  con- 
tractile vacuoles.  A  chestnut-brown  color  of  the  lorica  indicates  old  age.  Length 
of  lorica  15  to  18  m-     Pond  water  among  algae. 


Fig.  368.     Bicosoeca  lepteca.    cv,  contractile  vacuole;  n,  nucleus.     X  840.      (.\fter  Stokes.) 


Body  not  attached  by  thread-like  peduncle,  no  peristome  process. 

Flagellum  single Codonoeca  James-Clark. 

Representative  species Codonoeca  inclinata  Kent  1880. 


Lorica  ovate,  attached  obliquely  to  a  pedicel  twice  its  length.  Body  attached 
to  the  posterior,  inner  surface  of  the  lorica  without  a  peduncle.  Not  projecting 
beyond  the  margin  of  the  lorica.  Flagellum  extending  considerably  beyond 
the  aperture.  A  nucleus  and  a  contractile  vacuole  in  the  posterior  regi(jn  of 
the  body.     Length  of  lorica  15  m-     Pond  water. 


Fig.  369.    Codonoeca  inclinata.    cv,  contractile  vacuole.     X  810.     (.\fter  Kent.) 


20  (17)     Forming  colonies,  with  peristome  projection. 

r.^./^  Slylohryon  de  Fromentel. 

~        Representative  species.    .    .    ^/y/oftryo/z />t'//(;/(i//<m  Dujardin  1838. 


Each  lorica  wineglass-shaped,  pointed  posteriorly,  attached  to  a  pKxliccl 
which  arises  from  within  the  cavity  of  the  associated  lorica.  Body  plastic. 
Flagella  two,  unequal  in  length.  Length  of  lorica  },o  to  50  m-  I'i>nd  water. 
Often  subdividing  by  spores. 


Fig.  370.    Stylobryon  pciiolatum.  cv,  contractile  vacuole;  «,  nucleus.   X  75-  (After  Kent 


246  FRESH-WATER   BIOLOGY 

21  (16)     Without  lorica;  one  or  more  llagella. 

Family  Heteromastigidae   .    .     22 

22  (29)     Not  forming  colonies 23 

23  (26)     Flagellum  single 24 

24  (25)     Flagellum  directed  forward Leptomonas  Kent. 

Representative  species Leptomonas  sp. 

Body  pointed  anteriorly  and  very  flexible.  Flagellum  long  and  active. 
Often  parasitic.  Fig.  371  represents  a  form  reported  by  Conn,  taken  from  a 
watering  trough,  and  assigned  to  this  genus  with  some  doubt. 

Species  not  determined. 

Fig.  371.     Leptomonas  sp.     X  875.     (After  Conn.) 


25  (24)     Flagellum  trailing Rhynchomonas  Klebs. 

Representative  species Rhynchomonas  nasula  Klebs  1886. 


Body  ovate,  slightly  compressed,  anterior  end  prolonged 
into  a  movable  process.  Mouth  near  the  anterior  end. 
Nucleus  central.  Contractile  vacuole  anterior.  Fresh 
water. 


Fig.  372.     Rhynchomonas  nasula.     X  1500-     (After  Conn.) 


26  (23)     Two  or  more  flagella 27 

27  (28)  Body  free  or  attached  by  an  attenuated  posterior  end;  spherical  to 
ovate,  with  one  chief  flagellum  and  one  or  two  secondary 
ones.     Moderately  flexible Monas  Ehrenberg. 

Representative  species M<?wa5/wi(/a  Dujardin  1841. 

W^^-o°yy^A       Fig.  373.    Monas  fluida.     ct,  contractile  vacuole;  m,  nucleus;  5,  stigma;  w,  mouth. 
"[iavi^^S  X  1000. 


FLAGELLATE  PROTOZOA  (MASTIGOPHORA) 


247 


28  (27)     Free,  like  Monas,  but  with  the  anterior  end  ol^Hque. 

Physomonas  Kent. 
Representative  species Physomonas  elongala  Stokes  icS86. 


Body  elongate-ovate,  changeable  in  shape;  free-swimming  or  temporarily 
attached  by  a  very  short  pedicel.  Flagella  two,  unequal.  Contractile 
vacuole  anterior  in  position.     Length  about  1 2  n.     Swamp  water. 

Fig.  374.     Physomonas  elongata.     cv,  contractile  vacuole;  n.  nucleus 
X  1000.     (After  Stokes.) 


29  (22)     Forming  colonies.     Two  flagella -^o 

30(33)     One  zooid  upon  the  end  of  each  branch 31 

31(32)     Pedicel  rigid.      . Deudromomis  Stein. 

Representative  species Dendromonas  virgaria  Weisse  1845. 


Body  of  zooid  pyriform,  compressed,  with  an  anterior, 
lip-like  projection  from  the  base  of  which  arise  the  two 
unequal  flagella.  Nucleus  single;  contractile  vacuole  one 
or  two.  Colony  branching  dichotomously.  .\  colony  may 
include  over  one  hundred  zooids.  Length  of  zooid  8  to  10  u. 
Pond  water. 


Fig.  375.    Dendromonas  virgaria.    Colony  X  160;  single  zooid  X  935  , 
(After  Blochmann.) 


32(31)     Pedicel  flexible Ramosoiiema  Kent. 

Representative  species Ramosoncnia  laxum  Kent  1871. 

Zooids  pyriform,  compressed,  obliquely  truncate  anteriorly.     Pedicel 

very  slender,  threadlike.      A  colony  may  include  as  many  as  twenty  or 

XWlVym^/      "i^       more  zooids.     Length  of  zooids  8  m-     Pond  water. 

K^UuT  r    ■      Fig.  376.    Ramosonema  laxum.    cf,  contractile  vacuole;  n,  nucleus.  Colony  X  350; 

single  zooid  X  1000.     (After  Kent.) 

3i  (30)     Many  zooids  upon  each  branch 34 

34  (35)     Stalk  short,  branching  dichotomously  once  or  twice. 

Ccplhdothamuiiim  Stein. 
Representative  species.  .      Cephalotliamniitm  cacspitosum  Kent  1880. 

Zooids  irregularly  pyriform,  in  clusters  of  two  or  three 
or  as  many  as  si.x  or  eight  on  the  summit  of  a  simple  or 
slightly  branched  pedicel.  Pedicel  very  short.  Length 
of  zooid  about  6  m-     Fresh  water,  attached  to  Cyclops. 

Fig.  377.  Cephalothamniumcacspitoium.    X  875.   i.Uter  Conn.) 


248 


FRESH-WATER   BIOLOGY 


35  (34)     Stalk  long,  stout,  greatly  branched.  Anthophysa  Bory  de  St.  Vincent. 
Representative  species Anthophysa  vegetans  M.\i\[er  I'jZt. 

Bodies  attached  in  rosette-like  clusters,  each  zooid  pyriform 
in  shape,  ohUqucly  truncate  in  front,  with  two  lla^ella  of  un- 
equal length.  Clusters  attached  to  a  branched  pedicel  or 
free  swimming,  moving  through  the  water  in  a  rolling  motion. 
In  older  stages  the  pedicel  becomes  dark  brown  in  color. 
Length  of  zooid  5  to  10  m-     In  stagnant  water. 

Fig.  378.     Anthophysa  vegetans.      X  500.     (.\fter  Miiller.) 


36  (3)     Sometimes  plastic  but  not  producing  pseudopodia 37 


37  (60)     Chromatophores  not  present;  flagella  often  numerous. 


38 


38  (49)     Flagella  usually  two,  one  usually  trailing;  very  minute  forms. 

Order  Heteromastigida    .    .     39 


39  (40)     Flagella  three  in  number,  one  directed  forward.     .    .   Elvirea  Parona. 
Representative  species Elvirea  cionae  Parona  1886. 

Body  ovate  to  elongate,  laterally  compressed.  The  shorter 
flagellum  directed  forward.  Mouth  and  nucleus  anterior. 
Fresh  water. 

Fig.  379.     Elvirea  cionae.     x  1200.     (After  Conn.) 


40  (39)     Flagella  two  in  number 41 

41  (42)     Both  directed  forward Dinomonas  Kent. 

Representative  species Dinomonas  vorax  Kent  1880. 

Body  persistent  in  shape,  subpyriform,  widest  posteriorly, 
slightly  curved.  Flagella  siibequal,  longer  than  the  body. 
Length  15  ^l.     Hay  infusions. 

Fig.  380.     Dinomonas  vorax.     X  1000.     (After  Conn.) 

42  (41)     One  flagellum  trailing,  the  other  directed  forward 43 


43  (46)     Body  spiral  or  oblique 44 

44  (45)     Body  not  spiral,  anterior  end  obhque;  very  flexible. 

PhyUomitus  Stein. 
Representative  species.  .    .    .      PhyUomitus  amylophagus  Klebs  1886. 

.~  \--'o'(^  "-"*'«» v-V'.'".Sf3  Fig.  381.  PhyUomitus  amylophagus.   X  137  = 

:^f^_2^  \J,jf^^^X2):£^  (After  Conn.) 


FLAGELLATE  PROTOZOA  (MASTIGOPHORA) 


249 


45  (44)     Body  spiral,  elongated. 
Representative  species. 


Spiromonas  Perty. 

.    .   Spiromonas  angnsta  Dujardin  1841, 

Body  five  or  six  times  as  long  as  broad.  Fla- 
gella  subequal,  as  long  as  the  body,  one  directed 
forward;  body  sometimes  temfKjrarily  attached 
by  one.     Length  10  m-     Hay  infusions. 

Fig.  382.    Spiromonas  angusla.  X  1000.    (After  Conn.) 
There  is  doubt  as  to  the  identity  of  Conn's  form. 


46  (43)     Body  neither  spiral  nor  oblique 47 


47  (48)     Kidney-shaped  to  spherical;    flagella  arising  from  a  ventral  depres- 
sion, one  trailing.     Food  absorbed  by  a  dorsal  vacuole. 

Pleuromonas  Perty. 
Representative  species Pleuromonas  jaculans  Fcrty  1852. 


Body  kidney-shaped,  very  small;  sometimes  attached  by  the  pos- 
terior flagellum.     Contractile  vacuole  anterior;   nucleus  posterior. 

Length  5  to  9  m-      Stagnant  water  and  infusions.      Movements 
jerking  and  leaping. 

Fig.  383.     Pleuromonas  j ocularis.      X  looo.     (After  Conn.) 


48  (47)     Pear-shaped  to  spindle-shaped;    flagella  arising  from   the  anterior 
end,  one  trailing.     Food  not  taken  in  by  a  dorsal  vacuole. 

Heteromita  Dujardin. 
Representative  species Heteromita  ovata  Dujardin  1841. 

Body  ovate,  widest  posteriorly.  Flagella  unequal,  the 
trailing  one  twice  as  long  as  the  anterior  one.  Length 
25  to  40  ix.     River  water  with  aquatic  plants. 

Fig.  384.     Fleteromita  ovata.      X  500.     (.Alter  Conn.) 


49  (38)     Flagella  usually  numerous,  frequently  arranged  in  groups. 

Order  Phytomastigida 


50 


50  (53)     Flagella  two  in  number. 


51  (52)     Body  expanded  into  two  wings;  flagella  long. 

Trcpomonas  Dujardin. 
Representative  species Trcpomonas  agilis  Dujardin  1841. 

Very  irregular  in  shape,  difTerent  ajipcarances  being  presented 
from  different  points  of  view.  The  broad,  wing-like  lateral  lobes 
curve  backward  nearly  to  the  middle  of  the  bo<ly.  Length  20  m. 
Pond  water. 

Fig.  385.     Trcpomonas  agilis.     X  450.     (.\fter  Conn.) 


250  FRESH-WATER   BIOLOGY 

52  (51)     Body  not  laterally  expanded,  sometimes  attached  by  a  stalk.     Flagella 

arising  from  the  anterior  end.      .    .    AmpJiimojias  Du}a.rdm. 

Representative  species Amphimonas  globosa  Kent  1880. 


Body  subspherical,  attached  by  a  filamentous  pedicel.  Flagella  equal,  twice  the 
length  of  the  body.     Diameter  1 2  n.     Pond  water. 

Fig.  386.     Amphimonas  globosa.      X  875,     (After  Kent.) 

Conn  reports  a  form,  found  abundantly  in  the  fresh  waters  of  Connecticut,  which 
he  assigns  to  this  genus,  with  some  doubt.  Although  never  attached  by  a  pedicel, 
the  two  equal  flagella  would  seem  to  place  it  here. 


53  (50)     Flagella  four  in  number 54 

54(55)     With  a  deep,  vertical  furrow Collodictyon  Ca.TiGT. 

55  (54)     Without  a  vertical  furrow 56 

56  (57)     With  three  flagella  directed  forward,  one  trailing.     Body  pear-shaped, 

rounded  in  front,  acute  behind.    .   Trichomastix  Blochmann. 
Representative  species Trichomastix  sp. 

American  species  observed  have  not  been  de- 
termined. 

Fig.  387.    Trichomastix  sp.    X  7S0.    (After  Conn.) 

57  (56)     With  all  four  flagella  directed  forward 58 

58  (59)     Body  ellipsoidal,   with  two  thread-like   processes   at  the  posterior 

end Hexamitd  Dujardin. 

Representative  species Hexamita  inflata  Dujardin  1838. 


Body  plastic,  posterior  end  bifid,  giving  rise  to  the  trailing,  flagella-like 
processes  by  means  of  which  it  may  be  temporarily  fixed.  Length  10  to 
15  ti.     Pond  water  and  infusions. 


Fig.  388.     Hexamita  inflata.      X  875.     (After  Coon.) 


59  (58) 


60  (37) 

61  (87) 

62  (69) 

63  (68) 

64  (65) 


65  (64) 


FLAGELLATE   PROTOZOA    (MASTIGOPHORA)  251 

Body  obovate,  obliquely  truncate  in  front;  or  subpyriform  or  sub- 
spherical  with  a  rounded  front Tetramitiis  Perty. 

Representative  species Tetramitus  variabilis  Stokes  i^^b. 

Body  changeable  in  form.  Fiagella  subequal,  inserted  near  the  middle  of  the  an- 
terior border.  Endoplasm  granular.  Contractile  vacuoles  two,  near  the  front 
border.  Food  received  at  any  portion  of  the  surface.  Length  18  to  25  m-  Stand- 
ing water  with  decaying  vegetation. 

Fig.  389.     Tetramilus  variabilis.     X  250.     (After  Stokes.) 

Chromatophores  usually  present.     Fiagella  one  or  two. 

Order  Euglenida   .    .     6 1 

Elongated  forms  usually  with  pointed  posterior  ends.     Chromato- 
phores usually  green.     Paramylin  bodies  present. 

Family  Euglenidae  .    .     62 

Naked  or  with  very  thin  cuticle 63 

Flagellum  single 64 

Attached  by  a  branched  stalk,  usually  surrounded  by  a  jelly-like  en- 
velop  Colaciuni  Ehrenbcrg. 

Representative  species Colaciuni  stein ii  Kent  1880. 


So  far  as  has  been  determined,  no  members  of  this  genus  have  been  reported  in 
North  America.  Several  species  have  been  reported  in  Europe.  Usually 
attached  to  Cyclops  or  other  fresh-water  crustaceans. 

Fig.  390.     Colaciuni  steinii.      X  350.     (.^fter  Kent.) 


Not  attached  and  not  surrounded  by  a  jelly-like  envelop.     Large 
forms,  spindle-shaped,  usually  green,  with  an  eye-spot. 

Euglena  Ehrenbcrg  .    .     66 


66  (67)     Body  rounded  anteriorly,  surface  smooth. 

Euglena  viridis   Ehrenbcrg  1830. 


Body  usually  rounded  anteriorly  with  a  colorless,  tail-like  iwsterior  pro- 
longation. Surface  smooth.  Nucleus  central;  contractile  vacuole  anterior. 
Length  50  to  75  n.  Common.  The  chlorophyl  may  at  times  be  lost  and 
the  species,  no  doubt,  may  then  exist  on  organic  substances. 


Fig.  391. 


Euiilena  viridis.     cv,  contractile  vacuole;   n,  nucleus;  pant,  paramylum; 
st,  stigma.      X  400.     (After  Blochmann.) 


67  (66)     Body  cylindrical;  surface  beaded.     Euglena  spirogyra  Ehrcnhcrg  1S30 


392.     Euglena  spirogyra.      X  500-    (After  Conn.) 


Body  elongate,  cylindrical,  with  a 
jxjinted,  tail-like  prolongation.  IVriplury 
covered  by  oblicjue  rows  of  minute  l>cad- 
like  elevations.  Color  bright  green. 
Nucleus  central,  with  an  clongate<i  starch- 
like body  anterior  and  jxistcrior  to  it. 
Kye-spot  near  the  base  of  the  llagcllum. 
Length  100  to  200  n.     Among  algae. 


252  FRESH-WATER   BIOLOGY 

68  (63)     Flagella  two;   body  spindle-shaped  when  extended;   chromatophores 

disk-shaped Eutreptia  Perty. 

Representative  species Eutreptia  viridis  Perty  1852. 

_  Body  very  changeable  in  form.       Flagella  equalling  the 

body  in  length.    Eye-spot  present.    Length,  when  extended, 
100  /x.     Pond  water. 

Fig.  31)3.    Eutreptia  viridis.      X  500-    (After  Conn.) 

69  (76)     With  a  thick  cuticle  or  lorica 7° 

70  (76)     Lorica  present 71 

71  (72)     Lorica  beaker-shaped  or  tube-shaped Ascoglena  Stein. 

72  (71)     Lorica  spherical  or  cylindrical,  smooth  or  spiny. 

Trachelomonas  Ehrenberg   .    .      73 

73  (74>  75)     Lorica  smooth,  colorless    .    .    Trachelomonas  lagenella  Stein  1878. 

Lorica  colorless,  oval  or  elliptical,  smooth.     An  obliquely  projecting  neck. 
Length  20  to  35  m-     Fresh  water. 

Fig.  394.     1  rachelomonas  lagenella.      X  600.     (After  Stein.) 

74  (73,  73)    Lorica  spinous,  brown.     .    .    .   Trachelomonas  hispida  Stein  1878. 

Lorica  elongate-oval,  with  ends  broadly  rounded.  Surface  cov- 
ered with  minute,  sharp-pointed  spines.  A  short,  tube-Hke  neck 
sometimes  present  Brown  in  color.  Length  30  to  36  n.  Pond 
water,  with  other  species  of  the  genus. 

'nvOTf       ^FZ^"^^^  Fig.  395.     Trachelomonas  kispida.     X  400.     (After  Conn.) 

75(73.74)    Lorica  smooth,  brown.   .    Trachelomonas  volvocina  Ehrenberg  iS2,3- 

Lorica  nearly  spherical,  surface  smooth,  usually   without  a 
neck.     Flagellum  long.     Color  brown.      Diameter  30  m-     Very 
^^        -        "V^  I     y  common  among  algae  and  other  aquatic  plants. 

Fig.  396.     Trachelomonas  volvocina.     X  450.     (After  Edmondson.) 

76(69)     With  a  thick  cuticle  but  no  lorica 77 

77  (78)     Not  flattened,  ellipsoidal,  with  a  pointed  caudal  process. 

Chloropeltis  Stein. 
Representative  species Chloropeltis  hispidula  Stein  1878. 

Surface  of  the  body  ornamented  with  mi- 
nute spines  arranged  in   longitudinal   rows. 
4r     ■  't'^   y^     \  CV'  Endoplasm  green,  with  an  eye-spot.     Length 

55  p.     Fresh  water,  among  diatoms. 

Fig.  397-     Chloropeltis  hisptdula.     X  600.    (After 
Conn.) 

78  (77)     Flattened 79 


FLAGELLATE    PROTOZOA    (MASTIGOPHORA)  253 

79  (84)     Posterior  border  acute  or  with  a  caudal  appendage 80 

80  (81)     Ellipsoidal,  slightly  flattened;    posterior  end  acute.     Longitudinally 

or  spirally  marked Lepocindis  Perty. 

Representative  species Lepocindis  sp. 


This  genus  is  very  closely  related  to,  if  not  identical  with,  the  preceding 
one.  The  form  here  represented  is  assigned  to  this  genus  by  Conn,  with 
some  doubt.     Species  not  determined. 

Fig.  398.     Lepocindis  sp.      x  1000.     (After  Conn.) 


Round  to  pear-shaped,  asymmetrical,  much  flattened;  caudal  process 
present Phacus  Nitzsch   .    .     82 

Caudal  process  moderate;  not  large. 

Phacus  pleuronectes  Nitzsch  181 6. 

Tail-like  projection  usually  curved.  Surface  longitudinally  striateci. 
Endoplasm  green,  enclosing  one  or  more  large,  amylaceous  bodies.  Flagel- 
lum  arises  from  a  cleft-like  mouth  on  the  anterior  border.  Length  25  to 
75  M-     Among  aquatic  plants. 

Fig.  399.     Phacus  pleuronectes.     X  450.     (After  Conn.) 

83  (82)     Caudal  process  long;  size  conspicuous. 

Phacus  longicaudus  Ehrenberg  1838. 

Recognized  by  its  large  size  and  long  caudal  pro- 
jection. Body  frequently  twisted  on  its  longitudinal 
axis.     Length  100  n. 

Fig.  400.     Phacus  longicaudus.     x  310.     (.Aifter  Conn.) 

84  (79)     Posterior  end  evenly  rounded 85 

85  (86)     Resembling  Phacus  but  without  caudal  appendage. 

Cydaiiura  Stokes. 
Representative  species Cydanura  orhiciilata  Stokes  1S86. 

Body  ovate  or  suborbicular,  thick,  compressed,  with  a  longitudmal 
keel  across  the  right-hand  side.  Color  green.  Contractile  vacuole 
and  eye-spot  anteriorly  placed.  Length  about  50  /i.  Stagnant  pond 
water. 

Fig.  401.     Cydanura  orbiculata.      X  3^5-     (After  Stokes. J 

86  (85)     Oval  in  outline,   rigid,   flattened.     Chromatophores  green,   two  in 

number,  lateral  in  position.     .    .    .    Cryptoglcua  Ehrenberg. 

Representative  species Cryptoglena  pigra  EhTcnhcig  \^^i. 

Flagellum  single,  short.  Chromatophores  band-like,  following  the 
contour  of  the  body.  \  scarlet  eye-six)t  near  the  anterior  extremity. 
Length  1 2  ti.     Fresh  water. 

Fig.  402.     Cryptoglena  pigra.      X  1500.     (After  Conn.) 

87  (61)     Colorless  forms  without  eye-spots.     Often  very  plastic 88 

88  (loi)  Body  elongate,  usually  with  striped  membrane.     Nutrition  sapro- 

phytic.    Flagella  usually  two.     Family  Astasiidae  .    .     89 


2  54  FRESH-WATER    BIOLOGY 

89  (94)     Body  flexible;  one  or  two  flagella 90 

90  (93)     Flagella  two 91 

91  (92)     Secondary  flagellum  very  small,  directed  backward.    .   Astasia  Stein. 

Representative  species \  stasia  trichophora  Ehrenberg  1830. 

/yTj^^~^^—~r^~y-^.r~—.^ Body     elongate,     usually    wider    posteriorly. 

t>>Pi^;^^^^£^s^^  Primary  flagellum    very   thick   at   the   base  and 

^i^^^^=^=^^^^^  long.      Nucleus  central;    contractile  vacuole  an- 

FiG.  403.      Astasia  trichophora.      X  410.  teriorly  located.     Length,  when  extended,  30  to 

(Alter  Conn.)  60  m      Common  among  diatoms  and  algae. 

92  (91)     Secondary  flagellum  about  half  as  long  as  the  primary;   both  flagella 

directed  forward Distigma  Ehrenberg. 

Representative  species Distigma  proteus  Ehrenberg  1830. 

Body  very  plastic;  when  contracted,  distended  in  one 
/  ^^''      or  two  regions.     Endoplasm  with  dark-colored  corpuscles. 

^^_^__^^<^^^^^::^^^j^-^  Nucleus  central ;  contractile  vacuole  in  the  anterior  region. 

^^^;ssss=*ss^^*^^^^^^^v_^^  Length,  when  e.xtended,  95  /x.     Pond  water. 

*       "^  Fig.  404.    Distigma  proteus.    cv,  contractile  vacuole;  n,  nucleus; 

ph,  pharynx.      X  33°      (After  Stein.) 

93  (90)     Flagellum  single;   body  elongate,  tapering  posteriorly.     A  long  tubu- 

lar pharynx Atractonema  Stein. 

Representative  species Atractoiuma  tortuosa  Stokes  1885. 

Body  flexible  but  persistent  in  shape,  colorless, 

enclosing   oblong  dark-bordered    corpuscles.      Fla- 

^,.^^^55.^^^^  ^<''o'^^3~-^2-^         gellum  about  half  as  long  as  the  body.     Movements 

<i^^^^-'-^^^^>>___^.,('^^         rotary  on  the  long  axis.     Length  50  to  80  n.     In 

^""^^^^^S^  vegetable  infusions. 

Fig.  405.     Atractonema  tortuosa.    X  625.    (After  Stokes.) 

94  (89)     Body  not  flexible 95 

95  (98)     With  longitudinal  or  spiral  ridges 96 

96  (97)     Elongate  or  crescentic,  with  four  longitudinal  ridges;    flagella,  two, 

unequal Sphenomonas  Stein. 

Representative  species.    .    .  Sphenomonas  quadrangular  is  Stein  1878. 


Body  subfusiform,  with  the  ridges  fopming  a  quadrate  outline  in  cross  sec- 
tion. Long  flagellum  stout,  four  times  the  length  of  the  shorter  one.  A 
large  amylaceous  corpuscle  usually  enclosed  in  the  endoplasm.  Length  40  m- 
Fresh  water. 


Fig.  406.     Sphenomonas  quadrangularis.      X  400.     (After  Biitschli.) 


97  (96)     Nearly  ellipsoidal,  with  many  spiral  ridges.     .   Tropidoscyphus  Stein. 

98  (95)     Without  ridges 99 


FLAGELLATE  PROTOZOA  (MASTIGOPHORA) 


:>:) 


99  (loo)     Resembling  Sphenomonas,  but  without  ridges;  flagella  two,  unequal. 

Clostonema  Stokes. 
Representative  species Clostonema  socialis  Stokes  1886. 


Body  fusiform,  with  a  short,  rounded  posterior  prolongation.  Primary  flagel- 
lum  as  long  as  the  body;  secondary,  about  one-fourth  as  long.  A  long,  pha- 
ryngeal passage  present.     Length  about  20  m-     In  standing  water. 

Fig.  407.     Clostonema  socialis.      X  600.     (After  Stokes.) 


100  (99)     Resembling  Clostonema,  but  with  a  single  flagellum. 

Menoidium  Perty. 
Representative  species. 

Menoidium  pellucidum  Perty  1852. 
Body  lunate,  obliquely  truncated  at  the  anterior  extremity.  Pos- 
terior end  rounded.  The  short  side  of  the  body  thin  and  sharp,  the 
long  side  rounded.  Flagellum  equalling  the  body  in  length.  One  or 
more  amylaceous  corpuscles  usually  present.  Length  40  to  60  m- 
Fresh  water. 

Fig.  408.     Menoidium  pellucidum.     X  500.     (After  Senn.) 


loi  (88)     Body  rigid  or  plastic,  usually  symmetrical;  one  or  two  dissimilar 
flagella  deeply  sunk  in  the  body.     Nutrition  holozoic. 

Family  Peranemidae  .    .    102 

102  (109)     Body  plastic 103 

103  (108)     One  flagellum 104 


104  (105)  Oval,  flattened,  very  flexible;   distinct  pharynx  and  rod-like  organ 

back  of  the  mouth Peranema  Dujardin. 

Representative  species. 

Peranema  trichophorum  Ehrenberg  1838. 


Cuticle  finely  marked  spirally.      Flagellum  very  long,  vibratilc  at  the  tip 
only.     Nucleus  central. 


Fig.  409.     Peranema  trichophorum.      X  250.     (.\fter  Conn.) 


Conn  reports  a  number  of  undetermined  forms  which  bear  considerable 
resemblance  to  the  above  species  and  should,  without  doubt,  be  assigned 
to  the  genus  Peranema. 


105  (104)     Flask-shaped;  neck-like  anterior  end  with  elongated  phar>'nx  and 
rod-like  organ io6 


256 


FRESH-WATER   BIOLOGY 


io6  (107)     Without  sand  grains  attached Urccolus  Mereschkowsky. 

Representative  species Urccolus  cyclostomum  Stein  1878. 


Anterior  extremity  oblicjuely  truncate  with  an  expanded  rim  about  the 
mouth.  Pharynx  nearly  reaching  the  posterior  extremity  with  its  distal  end 
dilated.  Surface  usually  spirally  marked.  Flagellum  about  as  long  as  the 
body.  Length  50  m-  Fresh  water.  Identical  with  Phialonema  cyclostomum 
Mereschkowsky. 


Fig.  410.     Urceolus  cyclostomum.     X  500.     (After  Conn.) 


107  (106)     With  sand  grains  attached Urceolopsis  Stokes. 

Representative  species Urceolopsis  sabulosa  Stokes  1886. 


Body  flexible  and  elastic,  with  a  short,  anterior,  neck-like  prolongation. 
Usually  densely  covered  with  sand  grains.  Movements  are  rapid,  the  body 
being  held  at  an  angle  with  the  anterior  end  downward.  The  long  flagellum 
\ibrates  strongly  at  its  tip.  Food  particles  are  drawn  into  the  oral  aperture 
with  considerable  force.     Length  20  ^u.     Among  algae. 


Fig. 


Urceolopsis  sabulosa.      X  625.     (After  Stokes.) 


108  (103)     Two  flagella,  one  trailing;  mouth  depression  obHque. 

Heteronema  Dujardin. 
Representative  species.    .   Heteronema  acus  Ehrenberg  1840. 


Body  very  plastic,  fusiform  when  extended.  Primar>'  flagellum  as 
long  as  the  body  and  twice  as  long  as  the  secondar>%  trailing  one. 
Nucleus  central;  contractile  vacuole  in  the  anterior  extremity.  Length, 
extended,  50  m-     Fresh  water. 


Fig.  412.        Heteronema  acus.      X  500.     (After  Conn.) 

Numerous  other  forms  reported  by  Conn  should,  without  doubt,  be 
assigned  to  this  genus.     The  species  are  undetermined. 


109  (102)     Body  rigid no 

no  (hi)     One  flagellum;  body  flattened,  usually  furrowed  and  keeled. 

Pctalomonas  Stein. 
Representative  species.  .    .   PetaJomonas  pkurosigma  Stokes  1887. 

Body  ovate,  the  posterior  end  pointed;  lateral  borders  sigmoid.  Dorsal 
and  ventral  surfaces  each  traversed  by  a  narrow,  longitudinal  furrow.  Length 
IS  to  20  M-     Standing  pond  water. 


Fig.  413.     Pctalomonas  pleurosigma.     X  625      (After  Stokes.) 


FLAGELLATE   PROTOZOA    (MASTIGOPHORA)  257 

III  (no)     Two  flagella,  unequal 112 

112(113)     Body  with  spiral  ridges Tropidoscyphus  Stem. 

113  (112)     Body  without  spiral  ridges 114 

114  (115)     Trailing  flagellum  very  prominent,  curving  around  the  anterior 

end Anisoncma  Dujardin. 

Representative  species.      .    .    .     Anisonema  acinus  V>\i]diX<\\\\  i?>^i . 

ys'^^'-^r'^-^^.^^  Body  wider  posteriorly,  flattened  ventrally;  anterior  vi- 

fii^~^  ■ -'^^^vv^^  bratile  flagellum  short.      Mouth  near  the  base  of  the  an- 

^^jggliaS^r"^-''^^-  terior  flagellum.    Length  25  m.    Among  diatoms.    Common. 

Fig.  414.   Anisonema  acinus.    X  scxd.  Jhe  genus  Metanema  Klebs  resembles  Anisonema  but  is 

(After  Conn.)  flexible. 

115(114)     Trailing  flagellum  not  prominent 116 


116  (117)     Primary  flagellum  carried  obliquely  forward,  vibratile  only  at  its 
end.       Body   ovate    or    angular   with    dorsal   side   concave. 

No  protrusile  pharynx Notosolenus  Stokes. 

Representative  species  .    .  Notosolenus  orbicularis  Stokes  1884. 


Body  with  a  broad,  shallow,  dorsal  concavity;  the  ventral  surface  convex. 
Movements  somewhat  eccentric,  the  convex  surface  usually  directed  down- 
ward. Nucleus  to  the  left  of  the  center  of  the  body.  Contractile  vacuole 
near  the  anterior  end.     Length  10  to  12  /i.     Bottom  of  shallow  ponds. 


Fig.  415.     Notosolenus  orbicularis.      X  looo.     (After  Conn.) 


117  (116)     Primary  flagellum  not  carried  obliquely  forward;    pharynx  pro- 
trusile.    A  strong  furrow  on  the  ventral  surface. 

Entosiphon  Stein. 
Representative  species.  .    .  Entosiphon  sukatus  Stein  1S78. 

Body  oval,  flattened;  anterior  border  oblique,  with  a  concavity  at  the 
bottom  of  which  is  the  mouth  leading  into  a  long  tubular  phar>'nx. 
Nucleus  posterior.  Contractile  vacuole  anterior.  Length  22  ti.  Pond 
water,  among  aquatic  plants. 

Fig.  416.     Entosiphon  sukatus.     X  500.     (.\fter  Conn. 


118(2)     With  protoplasmic  collars.    .    .      Subclass  Choanoflagellata  .    .      119 
119(122)     Not  forming  colonies 120 


58 


FRESH-WATER    BIOLOGY 


120(121)     No  lorica,  with  or  without  a  stalk. Mo>iosiga  Kent. 

Representative  species Monosiga  ovata  Kent  1880. 


Body  obovate,  the  broader  end  posterior;  with  a  rigid  pedicel  nearly 
equal  to  the  body  in  length.  Length  of  body  about  6  m-  Reported  by 
Conn  from  the  fresh  waters  of  Connecticut. 

Fig.  417.     Monosiga  ovala.      X  looo.     (After  Conn.) 


121  (120)     With  lorica,  with  or  without  a  stalk.  .    .    Salpingoeca  James-Clark. 
Representative  species .    .    .    .     Salpingoeca  convallaria  SiQin  iS-jS. 


\ 


Lorica  campanulate,  pointed  posteriorly,  slightly  constricted  anteriorly. 
Pedicel  very  slender  and  short.  Zooid  nearly  filling  the  lorica.  Length  of 
lorica  IS  to  25  M-     Attached  to  Epistylis. 

Fig.  418.     Salpingoeca  convallaria.     X  600.     (After  Kent.) 


122(119)     Forming  colonies 123 

123  (128)     Without  stalks 124 

124(127)     Colonies  enclosed  in  a  gelatinous  mass 125 

125  (126)     Forming  a  flat  colony  in  an  irregular  jelly.    .  Proterospongia  Kent. 

Representative  species.    .    .    .     Proterospongia  haeckeli  Kent  1880. 

Zooids  pyriform,  plastic;  collar  long,  each  zooid  bearing  a  single  fiagel- 
lum.  Colony  may  contain  as  many  as  fifty  or  sixty  zooids,  but  often  not 
more  than  six  or  eight.  The  gelatinous  support  very  transparent. 
Length  of  zooid  8  n.     Fresh  water. 

Fig.  419.     Proterospongia  haeckeli.     X  37S- 

126  (125)     Colony  disk-shaped  or  arising  from  a  funnel-like,  open  jelly  tube. 

Phalanslerium  Cienkowsky. 
Representative  species.     .    .      Phalansterium  digitatum  Stein  1878. 

NX        "N\     jg^ra       ^^       z'      X'  Zooids  ovate,  plastic.      Flagellum  two  or  three 

VX        \>ni.«R»fB      KA  ^"^i,^  times  the  length  of  the  body.     Jelly  mass  coarse, 

i'y.'^ftt  granular,  digitiform,  and  often  branching.     Length 

of  zooid  18  y..     Fresh  water. 

Fig.  420.      Phalansterium    digitatum.       X    400-     (After 
ButschU.) 


FLAGELLATE   PROTOZOA    (^IASTIGOPHORA) 


259 


127(124)     Colony  free,  not  enclosed  by  jelly H irm id i inn  Vciiy. 

Representative  species Hirmidium  inane  Perty  1852. 

As  many  as  eleven  individuals  may  be  included  in  the  colony.  Un- 
der the  name  Desmarclla  irregularis,  Stokes  describes  a  form  with  fifty 
individuals.  Length  of  body,  reported  by  Stokes,  8  to  1 2  p.  Pond 
water. 

Fig.  421.    Hirmidium  inane.    Colony  X  155;  single  zooid  X  325.     (After  Stein.) 

128  (123)     With  Stalks \    .     129 

129  (130)     Stalk  simple;  many  individuals  borne  at  the  end  of  the  stalk. 

Codosigd  James-Clark. 
Representative  species.    .    .    .      Codosiga  hotrytis  Ehrcnberg  1838. 


Bodies  ovate;  pedicel  slender,  rigid.  Flagellum  long.  Collar 
equalling  the  body  in  length.  Length  of  zooid  10  to  15  n.  Attached 
to  aquatic  plants. 

Kent  reports  that  previous  to  encystment  the  collars  and  flagella 
of  this  species  may  be  withdrawn  into  the  protoplasm  of  the  Ixxlies. 
while  the  latter  become  covered  with  radiating  pseudopodia.  Occa- 
sionally the  pseudopodia  are  produced  while  the  collar  is  still  ex- 
tended.    Spores  are  formed  during  encystment. 

Fig.  422.    Codosiga  botrytis.     x  350.     (After  Kent.) 


130  (129)     Stalk  branched,  with  single  individuals  or  groups  on  the  end  of 

each  branch Codonocladiiim  Stein. 

Representative  species.   .    Codonocladium  umbeUatiim  Tatem  1868. 


Kent  would  refer  this  species  to  the  genus  Codosiga,  in  which 
genus  some  forms  possess  zooids  with  short  pedicels  attached  to  the 
end  of  the  main  stalk. 


Fig.  423.     Codonocladium  umbellatum.     X  500.     (.^fter  Conn.) 


131  (i)     Plant  characteristics  evident;  chromatophorcs  usually  present;  often 

producing  colonies.  Class  Phytomastigophora   .    .      i  w 

132  (205)     Body   without  a  shell   formed  of  plates;  (.hroniatophores  yellow. 

brown,  or  green.    .    .    .      Subclass  Phytoflagellata    .    .      13.? 

133  (164)     Chromatophorcs  usually  yellow  or  brown. 

Order  Chrysoflagellida   .    .      134 

134  (137)     Body  usually  naked  but  may  be  enclosed  in  a  jelly  mass  during 

resting  stages U5 


26o  FRESH-WATER   BIOLOGY 

135  (136)     Flagellum  single;  two  chromatophores.    .  Chromulina  Cienkowsky. 

Chrysomonas    Stein  is  very   closely   related   to   this 
genus.     Under  the  name  Chrysomonas  pulchra  Stokes 
-      describes  a  species  as  follows:    Body  elongate-ovate  or 
obovate,   somewhat   flexible,  three    times    as   long   as 
broad,  tapering   and    slightly    constricted    posteriorly, 
curved  toward  one  side  anteriorly.     Frontal  border  ob- 
liquely excavate.       Surface  covered  with  minute  hemi- 
FiG.  424.    Chrysomotun;  pulchra.     X  400.   spherical  elevations.     Flagellum  scarcely  equalling  the 
(After  Stokes.)  j^^^jy  j^  length.     Nucleus  ovate.    Contractile  vacuoles 

two,  anterior.    Length  35  to  40  m-    Color  green.    Marsh 
water. 

1^6(1^0     Flagclla   two;  two  chromatophores.    .    .    .    Ochr omonas  Wysoizki. 
Representative  species Ochromonas  sp. 

Species  not  identified. 

Fig.  425.     Ochromonas  sp.      X  1000.     (After  Conn.) 

137  (134)     Body  enclosed  by  a  membrane  or  lorica 138 

138  (157)     With  a  membrane ^39 

139  (146)     Not  forming  colonies 140 

140  (141)     With  a  close-fitting  membrane  of  plates;  flagellum  single. 

Mallomonas  Perty. 
Representative  species Mallomonas  sp. 


Body  elongated,  enclosed  by  a  membrane  of  overlapping 
plates  which  bear  long,  slender  spines.  Two  elongated,  yel- 
lowish-green chromatophores  are  within  the  body. 

Species  not  determined. 

Fig.  426.     Mallomonas  sp.      X  500-     (After  Conn.) 


141  (140)     With  a  firm  cuticle;  two  flagella 142 

142  (145)     Without  chromatophores i43 

143  (144)     Body  oval,   truncate  or  concave  anteriorly,  enclosing  refractive 

bodies Cyathomonas  de  Fromentel. 

Representative  species.   .   Cya//jowf)wa5/rw«ca/ade  Fromentel  1874. 

^.qrasr-^^  De  Fromentel  identified  six  or  eight  species,  several  of  which  are 

^^rg^'-r\  but  slightly  distinguished  from  each  other.     Length  12  to  20  /x. 

^«*^^ll  r^*^^^  Fresh  water. 

^^•JfiSaatf-^  Fig.  427.    Cyalhomonas  truncata.     X  1200.     (After  Conn.) 


FLAGELLATE  PROTOZOA  (MASTIGOPHORA) 


261 


144  (143)     Shaped  as  Cyathomonas,  but  with  pharynx  and  without  refractive 

bodies Chilomonas  Ehrenberg. 

Representative  species.  .    Chilomonas  Paramecium  Ehrenberg  1831. 


Body  elongatc-oval,  anterior  margin  with  a  lip-like  projection.  Flagelia 
subequal  in  length.  Endoplasm  usually  enclosing  dark-colored  corpuscles. 
Length  25  to  40  m-     Stagnant  infusions;  very  common. 


Fig.  428.     Chilomonas  Paramecium.      X  350.     (.\fter  Conn.) 


145  (142)     With   two   brown   or   green   chromatophores.     Shaped   as    Chilo- 
monas       Cryptomonas  Ehrenberg. 

Representative  species.     .   Cryptomonas  ovata  YAircnhtrg  1831. 

ChIoroph>l  bands  two  in  number,  extending  longitudinally  through  the 
body.     Length  50  m-     Among  algae. 

Fig.  42g.     Cryptomonas  ovala.      X  350.     (.After  Conn.) 


146  (139)     Forming  colonies 147 

147  (154)     Individuals  imbedded  in  a  gelatinous  mass 148 


148  (149)  Spherical  colonies;  individuals  usually  with  two  yellow  chroma- 
tophores and  eye-spot.  Free-swimming.  Flagelia  two,  un- 
equal        Uroglena  Ehrenberg. 

Representative  species Uroglena  americana  Qdl^ms  i^(M. 


Cells  very  numerous,  arranged  around  the  periph- 
ery of  a  gelatinous  mass.  Posterior  ends  of  the 
cells  rounded,  with  no  means  of  connection  with 
each  other  except  by  the  matrix. 

Sometimes  found  in  reservoirs,  causing  the  water 
to  have  a  fishv  taste. 


Fig.   430.     Uroglena  americana.      Individual   cells  X  1500. 
(After  Conn.) 


149(148)     Not  colored 150 

150  (151)     Colonies  of  dichotomously  branching  lubes.     .     ClaJomonus  Stein. 


262  FRESH-WATER  BIOLOGY 

151(150)     Colonies  not  of  branching  tubes 152 

152  (153)     Colony  in  a  gelatinous  mass;  variable  in  shape,  thread-like,  discoi- 
dal   or   round,   hollow  or  sac-like.      Individuals  with    tw^o 

equal  flagella Spongomonas  Stein. 

Representative  species Spongomonas  discus  Stein  1878. 


Colony  discoidal,  gelatinous  mass  granular;  zooids  subspheroidal. 
Flagella  two  or  three  times  the  length  of  the  body.  Length  of 
zooids  8  Ai.     Fresh  water. 


Fig.  431.     Spongomonas  discus.     X  lOO.     (After  Biitschli.) 


1 53  (152)     Colony  formed  of  jelly-like  tubes,  closely  approximated;  individuals 

as  in  Spongomonas Rhipidodendron  Stein. 

Representative  species. 

Rhipidodendron  splendidum  Stein  1878, 

Tubules  forming  an  erect  branching  colony.  Zooids  ovate  or  ellipti- 
cal, usually  in  the  distal  extremity  of  the  tubules.  Flagella  equal,  twice 
the  length  of  the  body. 

The  tubes  being  hollow  are  probably  secreted  or  excreted  from  the 
entire  surfaces,  rather  than  the  posterior  extremities  of  the  zooids. 
The  tubes  are  usually  rusty-brown  in  color  and  have  a  granular  appear- 
ance. Sometimes  as  many  as  two  hundred  tubes  are  bound  together 
in  one  mass. 

Length  of  body  12  //.     Fresh  water. 

Fig.  432.     Rhipidodendron  splendidum.     X  250.     (After  Stein.) 


154(147)     Individuals  not  imbedded  in  a  gelatinous  mass 155 


155  (156)  Forming  spherical  colonies.  About  fifty  individuals  held  loosely 
together,  each  with  a  delicate  membrane,  often  spiny.  Fla- 
gella two,  unequal Synura  Ehrenberg. 

Representative  species Synura  uvella  Ehrenberg  1833. 


Membranes  pyriforn,,  often  with  pKJSterior  stalk-like  pro- 
jections; surfaces  spiny.  Zooids  nearly  filling  membranes. 
Color  bands  two,  extending  along  the  lateral  borders.  Length 
of  body  30  fi.     Pond  water. 


Fig.  433.    Synura  uvella.     X  6cx3.     (After  Conn.) 


FLAGELLATE  PROTOZOA  (MASTIGOPHORA) 


263 


156  (155)     Forming  annular  colonies;    individuals  closely  united.      Flagella 

two,  unequal Cycloncxis  Stokes. 

Representative  species.      .    .    .     Cycloncxis  annularis  Stokes  1886. 


From  ten  to  twenty  zooids,  not  in  contact  in  older  colonics,  leav- 
ing a  central,  circular  space.  Zooids  obovate,  about  twice  as  long 
as  broad.     Length  of  zooid  10  to  15  m-     Marsh  water. 


Fig.  434.    Cycloncxis  annularis.     X  625.     (After  Conn.) 


tXjx 


157  (138)     With  a  lorica 158 


158  (163)     Not  forming  colonies 159 


159  (162)     Lorica  sessile 160 


160  (161)     Lorica  beaker-shaped;  usually  with  a  peristome  process. 

Epipyxis  Ehrcnberg. 
Representative  species.     .    .    .  Epipyxis  utriculus  Ehrcnberg  1838. 


Lorica  is  truncate  or  slightly  everted  anteriorly,  widest  centrally  and  pointed 
posteriorly.  Body  occupies  about  one-half  the  cavity  of  the  lorica.  and  is  at- 
tached by  a  thread-like  pedicel  to  one  side  of  the  lorica.  An  eye-spot  usually 
present.     Nucleus  central;   contractile  vacuole  anterior. 

Length  of  lorica  about  40 /x.     Attached  to  water-plants. 

Fig.  435.     Epipyxis  utriculus.     X  650.     (After  Stein.) 


161  (160)     Lorica  urn-shaped.    . 
Representative  species. 


Chrysopyxis  Stein. 

Chrysopyxis  urceolata  Stokes  1886. 


Zooid  occupying  the  center  of  the  lorica,  but  in  no  way  attached  to  it. 
Flagella  two,  long,  diverging.  Yellow  chromatophores  often  present.  Nu- 
cleus centrally  located;  contractile  vacuole  ixisterior.  Length  of  lorica  \2  fx. 
Attached  to  algae. 

Fig.  436.    Chrysopyxis  urceolata.     x  uoo.     (After  Stokes.) 


264 


FRESH-WATER   BIOLOGY 


162(159)     Lorica  with  a  pedicel Dere pyxis  Stokes. 

Representative  species.      .    .    Derepyxis  amorpha  Stokes  1885. 


Lorica  flask-shaped.  Pedicel  about  one-tenth  as  long  as  the  lorica. 
Zooid  occupying  the  center  of  the  lorica,  subspherical,  with  the  front  border 
pointed.  Endoplasm  with  two  greenish-yellow  color  bands.  Length  of  lorica 
25  to  30  M-     .Attached  to  algae. 


Fig.  437.     Derepyxis  amorpha.     X  looo.     ^ After  Stokes.) 


163  (158)     Forming  colonies;  loricae  beaker-shaped.     One  primary  and  one 

secondary  flagellum Dinobryon  Ehrenberg. 

Representative  species.        .    Dinobryon  sertularia  Ehrenberg  1838. 


Loricae  joined  to  each  other  without  separate  pedicels, 
the  younger  individuals  being  attached  by  their  posterior  ends 
to  the  inner,  anterior  edges  of  the  older  loricae.  Zooids  at- 
tached to  the  bottoms  of  the  loricae  by  transparent,  elastic 
ligaments.  Chromatophores  and  eye-spot  present.  Length 
of  lorica  20  n.     Pond  water. 

Fig.  438.     Dinobryon  sertularia.     X  750-     (After  Conn.) 


164  (133)     Chromatophores  green Order  Chloroflagellida    .    .      165 

165(168)     Flagella  four;  not  forming  colonies 166 

166  (167)     Body  enclosed  by  a  lorica Tetraselmis  Stokes. 

Representative  species.    .    Tetraselmis  limnetis  Stokes  1887. 


Lorica  broadly  oval,  zooid  nearly  filling  the  lorica,  green  in  color. 
Flagella  exceeding  the  lorica  in  length.  An  amylaceous  corpuscle  pos- 
teriorly located.     Length  of  lorica  15  /u.     Pond  water. 


Fig.  439.     Tetraselmis  limnetis.     X  840.     (After  Stokes.) 


FLAGELLATE  PROTOZOA   (MASTIGOPHORA)  265 

167  (166)     Body  not  enclosed  by  a  lorica Carter ia  Diesing. 

168  (165)     Flagella  usually  two;  often  forming  colonies 169 

169  (180)     Not  forming  colonies 170 

170(177)     Body  with  closely  attached  cuticle 171 

171  (172)     Usually  without  chromatophores;   occasionally  a  colored  eye-spot. 

Ellipsoidal,  two  contractile  vacuoles.    .    Polytoma  Ehrenberg. 

Representative  species Polytoma  uvella  Ehrenberg  1838. 


Flagella  two,  equal,  longer  than  the  body,  both  extending  forward 
with  loop-like  flexures  at  their  bases.  Endoplasm  usually  granular. 
Length  20  to  30  m-     Animal  macerations. 

Fig.  440.     Polytoma  uvella.     x  iioo.     (After  Conn.) 


172  (171)     With  chromatophores 173 


173  (174)     Chromatophores  numerous;  one  flagellum  trailing 
Representative  species.    .    .    . 


Treymnia  Stokes. 
Trentonia  jiagellata  Stokes  1886. 


Body  ovate,  the  anterior  border  oblique 
and  somewhat  bilobate,  the  posterior  ex- 
tremity obtusely  pointed.  Flagella  sub- 
equal  in  length,  one  extending  forward, 
often  rapidly  and  spirally  vibrating. 
.  Mouth  and  pharynx   conspicuous.      Nu- 

nc. 441.    Trentonta  jiagellata.    X  400.    (After  Stokes.;       merous  green   chromatophores.      Length 

60  AX.     Pond  water. 

174  (173)     Chromatophores  few,  sometimes  wanting 175 


175  (176)     Spherical  or  elliptical,   with  one  large  chromatophoro.     An  eye- 
spot  present Chlaviydomoiias  Ehrenberg. 

Representative  species. 

Chlamydomonas  pulvisculus  Ehrenberg  1883. 


Fig.  442.     Chlamydomcnas  pulvhculu'i.      X  looo      (.\(tcr  Coon.) 


266 

176  (i75) 


177  (170) 

178(179) 

179  (178) 

180  (169) 

181  (186) 

182  (185) 

183  (184) 

184  (183) 

^ 

185  (182) 

FRESH-WATER   BIOLOGY 

Elongate,   spindle-shaped;     chromatophores   two,    ribbon-shaped; 

eye-spot  obscure Chlorangium  Stein. 

Representative  species. 

Chlorangium  slentorinum  Ehrenberg  1838. 

Flagella  terminal,  subequal.  Attached  during  the  sedentary  stage  by  a 
short,  thick  pedicel,  singly  or  in  groups  up  to  ten  or  tvvelve  zooids.  Length 
24  M-     Pond  water,  often  attached  to  various  Entomostraca. 

Fig.  443.     Chlorangium  slentorinum.     X  375-     (After  Stein.) 

Cuticle  separated  from  body  mass 178 

Cuticle  smooth Haemotococcus  Agardh. 

Cuticle  rough Coccomonas  Stein. 

Forming  colonies 181 

Colonies  plate-like  with  flagella  upon  one  face  only 182 

Colonies   in  a   four-sided    plate   with   envelop   closely   adherent. 
Cells  four  or  sixteen Gonium  Miiller  .    .    183 

Four  cells Gonium  sociale  Dujardin  1838. 

Sixteen  cells Gonium  pectomle  MiiWer  lyy^t- 

In  this  species  each  of  the  sixteen  cells  of  the  colony  produces  a 
daughter  colony  of  sixteen  cells.  As  the  daughter  colonies  develop,  a 
secondary  shifting  of  the  cells  takes  place  resulting  in  individuals  of 
the  adult  colonies  lying  in  one  plane. 

Fig.  444.     Gonium  pedorale.     X  350.     (After  Stein.) 

Colonies  in  a  rounded  plate  with  envelop  swollen,  oval,  or  spherical. 

Stephanosphaera  Cohn. 
Representative  species.    .    .    Stephanosphaera  pluvialis  Cohn  1853. 


Cells  four  or  eight,  ovoid  or  spindle-shaped, 
with  numerous  processes. 

This  form  represents  a  transition  from  a 
rosette  arrangement  of  cells  to  a  spherical 
aggregate,  the  units  being  arranged  in  a 
rosette  but  surrounded  by  a  common  gelati- 
nous envelop. 


Fig.  445.  Stephanosphaera  pluvialis.  /I  .copula- 
tion of  gametes;  ^,  spore  formation;  C,  cells  with 
protoplasmic  processes;  D,  colony  of  eight  cells. 
A  X  1325;  B,C,DX  425.       (After  Hieronymus.) 


186  (181)     Colonies  spherical,  ellipsoidal,  or  flattened,  with  flagella  not  confined 

to  one  face ^87 

187  (190)     Colonies  with  cells  crowded  together 188 


FLAGELLATE   PROTOZOA    (MASTIGOPHORA) 


267 


188  (189)     Colony  ellipsoidal  or  spherical  with  cells  reaching  toward  the  center. 

Pandorina  Bory  de  Saint  Vincent. 
Representative  species. 

Pandorina  morum  Bory  de  Saint  Vincent  1824. 


Cells  sixteen  or  thirty-two;  enclosed  within  a  definite 
membrane  which  does  not  touch  the  surface  of  the  indi- 
viduals.    Each  cell  bears  two  Ion«  llagella. 
> 

Fig.  446.  Pandorina  morum    cf,  contractile  vacuole;  i/,  stigma. 
X  250.     (After  Pringsheira.) 


189  (188)     Colony  ellipsoidal  with  sixteen  cells  in  four  rows  around  a  longi- 
tudinal axis.     Each  cell  bears  four  flagella. 

Spondylomorum  Ehrenberg. 
Representative  species. 

Spondylomorum  quaternarium  Ehrenberg  1848. 

Reproduction  occurs  by  the  cells  of  the  colony  separating  and 
each  individual  building  up  a  new  colony  by  cell  division. 

Colonies  often  produced  in  large  numbers  in  pond  water. 
Movements  rapid,  rotating  on  the  long  a.xis.  (ireen  in  color. 
Very  favorable  conditions  are  necessary  in  order  that  the  llagella 
may  be  seen  and  counted. 

Fig.     447.     Spondylomorum    quaternarium.     n,     nucleus;     o,    stigma. 
X  600.     (After  Stein.) 


190  (187)     Colonies  with  cells  not  crowded  together  and  not  reaching  toward 

the  center iqi 

191  (194)     Colonies  spherical,  ellipsoidal,  or  flattened,  with  cells  uniform  in 

size IQ2 


192  (193)     Colony  spherical  or  ellipsoidal;    poles   not   difTcrentiatetl  by  ar- 
rangement or  size  of  cells.     No  tails  present. 

Eudorina  Ehrenberg. 
Representative  species.    .    .    .     Eudorina  clcgans  YMri^nhcTg  I'^^i. 


Cells   sixteen,    thirty-two.   or   sixty-four;     arranged  around  the 
periphery  of  the  jelly  mass  but  not  in  contact  with  each  other. 
Each  cell  bears  two  flagella. 

Fig.  448.     Eudorina  eUgans.      X  250.     (From  a  specimen.) 


268 


FRESH-WATER   BIOLOGY 


193  (192)     Colony  flattened,  horseshoe-shaped,  with  poles  differentiated  by 
arrangement  of  cells.     Tails  at  posterior  end. 

Platydorina  Kofoid. 
Representative  species Platydorina  caudata  Kofoid  1899. 

Colony  slightly  twisted  in  a  left  spiral.  Cells  sixteen  or 
thirty-two  imbedded  in  a  transparent,  gelatinous  matrix  and 
surrounded  by  a  distinct  sheath. 

Each  cell  has  two  llagella,  an  eye-spot,  a  nucleus,  and  a 
single  chromatophore.  Tails,  in  sixteen  cell  colonies,  are 
three  in  number;  in  thirty-two  cell  colonies  five  tails  are 
present.  Movement  by  rotation  on  the  longitudinal  axis. 
Length  150 /x.     Plankton  of  rivers  and  lake's. 

Fig.  449.     Platydorina  caudata.      X  185.     (After  Kofoid.) 


194  (191)     Colonies  spherical  or  elHpsoidal;   cells  differentiated  as  to  size  and 

function i95 

195  (198)     No  protoplasmic  processes  connecting  the  cells.     Small  vegetative 

cells  at  the  anterior  pole,  large  gonidial  cells  at  the  posterior 
pole Pleodorina  Shaw   .    .      196 


[96  (197)     Cells  sixty-four  or  one  hundred  and  twenty-eight,  about  equally 
divided  between  large  and  small. 

Pleodorina  calif  or  nica  Shaw  1893. 


Colony  spherical,  with  gonidial  cells  two  or  three 
times  the  size  of  the  vegetative  cells.  Cells  bifiagel- 
late,  not  in  contact  with  each  other. 

Reproduction  asexual,  by  gonidial  cells,  in  this  and 
other  species  of  the  genus. 

Found  in  ponds,  ditches,  and  streams. 

Fig.  450.     Pleodorina  calif  arnica.      X  300-     (After  Shaw.) 


197  (196)     Cells   thirty-two,  rarely  sixteen  or  sixty-four.     Vegetative  cells, 
four  in  number.    .    .     Pleodorina  illinoisensis  Kofoid  1898. 


Colony  ellipsoidal  with  cells  arranged  in  five  circles; 
the  polar  circles  with  four  cells  each,  the  other  three 
circles  with  eight  cells  each.  The  gelatinous  sheath 
enclosing  the  colony  is  of  two  layers. 

Gonidial  cells  much  larger  than  vegetative  cells,  the 
latter  always  directed  forward  during  movement. 

Each  cell  with  two  flagella,  an  eye-spot,  a  nucleus, 
and  a  single  chromatophore. 

Average  length  113  /x-     Plankton  of  rivers. 

Fig.  451.     Pleodorina  illinoisensis.     X  200.     (After  Kofoid.) 


FLAGELLATE   PROTOZOA    (mASTIGOPHORA)  269 

198  (195)     Protoplasmic  processes  connecting  cells  usually  distinct.       Polos 

of  colony  not  differentiated  by  arrangement  of  vegetative 
and  gonidial  cells Volvox  Leeuwenhoek   .    .      199 

199  (204)     Colonies    with   distinct   protoplasmic   processes    connecting    the 

cells 200 

200  (203)     Protoplasmic  processes  very  stout 201 

201  (202)     Colonies  dioecious Volvox  pcrglobator  Powers  1908. 

•■"■^®<:^^0  0^^'^^^''-  Colonies  often   exceeding   i   mm     in   diameter.      Ova  or 

.^I^^^^^Q  e  0 '  <3 "^t^^i  oosperms  not  infrequently  numbering  several  hundred  in  a 

•o«'0^'5  G>^^0l®'^.^li^=  colony.     Very  common  in  the  United  States. 

'•■^0  0'^ Q^^^^  o  0.'^%^^  Fig.  452.    Volvox  per glohator.    Colony  with  eight  daughter  coenobia. 

'•.0 G  ®  ■  o^^S®  Q  ^i>.ci^^j?  Cilia  and  protoplasmic  processes  not  shown.      X  50.      (From  a 

■■^oZors^  ^  'o<^'&^^  prepared  mount). 

•n.oQ  <a  .©.??•• 

202(201)     Colonies  monoecious Fo/z^o-r  g/o6a/(?r  Leeuwenhoek  1788. 

The  common  European  species.  About  one-half  the  size  of  the  preceding  species,  and  con- 
taining fewer  reproductive  cells.  This  species  probably  occurs  in  the  United  States  but,  if  so, 
in  much  less  abundance  than  Volvox  perglobator. 

203  (200)     Protoplasmic  processes  slender.   .      Volvox  aureus  Ehrenberg  1838. 
A  typical  European  species  but  probably  occurring  in  the  United  States  also.    Diameter 

about  850  (1. 


204  (199)     Colonies  apparently   without  protoplasmic   processes   connecting 
the  cells Volvox  spermatosphara  Powers  1908. 


Monoecious  forms  with  ripe  sperms  arranged  in  bundles 
of  32,  grouped  in  sperm  spheres  in  the  colonies  Mature 
colonies  often  exceed  600  m  in  diameter.  Widely  dis- 
tributed in  the  United  States. 


Fig.  453.  Volvox  spermatosphara.  Colony  with  two  daughter 
coenobia,  five  egg  cells  and  one  sphere  of  sperm  bundles. 
X  80.    (From  a  specimen.) 


205  (132)     Usually  with  an  outer  membrane  or  shell  in  the  form  of  plates; 

body  usually  furrowed;   flagclla  two.     Usually  colored. 

Subclass  Dinoflagellida    ,    .      206 

206  (209)     Without  a  membrane  around  the  body 207 


207  (208)  Cross  furrow  extending  only  around  the  left  side;  a  longitudinal 
furrow  extending  from  the  central  end  of  the  cross  furrow  to 
the  under  part  of  the  body Uemidinium  Stein. 


270  FRESH-WATER   BIOLOGY 

208  (207)     Cross  furrow  extending  entirely  around  the  body;  often  flattened. 

Gymnodinium  Stein. 
Representative  species.     .    Gymnodinium  fuscum  FAircnherg  1838. 


Body  oval,  compressed,  pointed  anterioriy.     Color  light  brown.     An 
eye-spot  reported  by  Perty.     Length  60  to  80  n.     Fresh  water. 

^^C^  Fig.  454.     Gymnodinium  fuscum.      X  325.     (After  Blochmann.) 


209  (206)     With  a  membrane  around  the  body 210 

210(211)     Membrane  delicate,  homogeneous;  body  without  processes,  often 

flattened Glenodinium  Ehrenberg. 

Representative  species. 

Glenodinium  pidvisculus  Ehrenberg  1838. 


Fig.  455.     Glenodinium  pulvisculus.      X  500      (After  Stein.) 


211  (210)     Membrane  of  distinct  plates 212 

212  (213)     Plates  without  horn-Hke  processes,  polygonal,  21  in  number. 

Peridiniiim  Ehrenberg. 
Representative  species. 

Peridiniiim  tahulatmn  Ehrenberg  1838. 

Body  ovate,  with  convex  dorsal  and  concave  ventral  surface.  Plates 
showing  a  delicate  reticulate  structure  under  high  magnification.  Color 
yellow,  green,  or  brown.     Length  45  to  60  m-     Fresh  water. 

Fig.  456.     Peridinium  tabulatum.     X  320.     (After  Stein.) 

213(212)     Plates  with  long,  horn-like  processes Ceratium  ^chx^nk. 

Representative  species.     .    .    .    Ceratium  hirundiftella  MuIIgt  ij^G. 

Body  somewhat  quadrilateral,  the  anterior  segment 
bearing  two  nearly  straight  processes  and  the  posterior 
segment  a  single  short  one.  Color  brown  or  green. 
Length  go  to  170  ij.     Freshwater. 

Fig.  457.     Ceratium  hirundinella.     X  325.     (After  Stein.) 


CILIATE    PROTOZOA    (INFUSORIA) 


271 


INFUSORIA 

I  (208)     Cilia  present  during  all  stages  of  existence.    .    .    Class  Ciliata   .    .     2 
2(127)     Body  usually  uniformly  covered  with  cilia 3 

3  (104)     Cilia  similar  or  slightly  lengthened  about  the  mouth;  no  adoral  spiral 

zone Order  Holotricha   .         4 

4  (59)     Without  an  undulating  membrane  about  the  mouth.     Moutli  closed 

except  when  taking  food.       Suborder.  Gymnostomina  .    .     5 

5  (6)     With  a  shell  of  numerous  plates  arranged  in  zones  around  the  body. 

Ciha  projecting  between  the  plates.     .    .    .     Coleps  Nitzsch. 
Representative  species Coleps  hirtus  Ehrenberg  1838. 


Ovate,  persistent  in  shape.  Mouth  terminal,  bordered  by  tooth-like 
processes,  and  surrounded  by  cilia  larger  than  those  of  the  general 
surface.  Posterior  border  usually  bearing  spines.  Length  60  /i-  Pond 
water  and  old  infusions. 


Fig.  458.     Coleps  hirtus.     X  250.     (After  Conn.) 


0  (5)     Without  a  shell 7 

7  (12)     With  tentacle-like  processes  in  addition  to  the  cilia 8 

8  (9)     Tentacle  process  single. Ileonema  Stokes. 

Representative  species Ileonema  dispar  Stokes  1885. 


Body  flask-shaped,  flexible;  flattened  ventrally,  convex  dorsally,  the 
latter  surface  bearing  a  row  of  short,  hair-like  setae.  Tentacle-like  proc- 
ess thick  at  the  base,  twisted,  with  a  filamentous  distal  half.  Nucleus 
subcentral;  contractile  vacuole  posterior.     Length  1 20  m-    Among  algae. 


Fig.  459.     Ileonema  dispar.      X  185.     (After  Stokes.) 


9  (8)     Tentacle  processes  more  than  one 10 

10  (11)     Tentacles  very  long  and  numerous,  extending  between  the  cilia. 

Actinoholus  Stein. 
Representative  species [ct'uioboliis  radians  Stein  1867. 


Body  ovate  or  subglobosc.  the  anterior  extremity  pro- 
duced as  a  snout-like  projection  which  carries  the  mouth 
and  bears  the  retractile  tentacles  and  cilia.  Nucleus 
band-like;   contractile  vacuole  large. 

Fig.  460.  Actinobolus  radians.  Figure  reprcsentinK  indiviilual 
with  mouth  downward.  Dimensions  undetermined.  (.■Vftir 
Calkins.) 


272  FRESH-WATER   BIOLOGY 

11  (lo)     Tentacles  short,  few  in  number,  extending  from  about  the  mouth. 

Mesodinium  Stein. 
Representative  species. 

Mesodinium  pulex  Claparede  and  Lachmann  1858. 

Body  turbinate,  conical,  and  tapering  anteriorly.     A  wreath  of  strong  cilia  on 

a  constriction  halfway  between  the  middle  of  the  body  and  the  base  of  the 

-jr/ ,  1 1 1 V v^     snout-like  proboscis.     According  to  Claparede  and  Lachmann  three  long  stylate 

^//  W  V\     processes  e.xtend  in  front  of  the  mouth.     Length  15  /i.      Habitat,  reported  by 

Claparede  and  Lachmann,  salt  water. 

Fig.  461.     Mesodinium  pulex.      X  8io.     (After  Kent.) 

12  (7)     Without  tentacle-like  processes 13 

13  (34)     Body  round,  or  ovate,  or  elongate  in  outhne,  symmetrical.      .    .      14 

14  (15)     Cilia  of  body  confined  to  two  (rarely  one)  many-rowed  crowns  or 

circles.     Body  thimble-shaped,  with  broad  end  forward,  from 
the  flattened  center  of  which  rises  an  elevation  bearing  the 

mouth  at  the  apex Didiniiim  Stein. 

Representative  species Didinium  nasutum  Miiller  1786. 

Body  oval,  broadly  rounded  posteriorly.  One  wreath  of  cilia  near  the 
base  of  the  proboscis,  the  other  posterior  to  the  middle  of  the  body. 
Nucleus  band-like.  Contractile  vacuole  posterior.  Length  100  to  175  m- 
Among  decaying  vegetation. 

Fig   462.    Didinium  nasutum.    t:,  contractile  vacuole.     X  95.     (.\fter  Blochmann.) 


15  (14)  Cilia  not  limited  to  two  crowns  or  circles i6 

16  (27)  With  pharynx  absent  or  slightly  developed 17 

17  (22)  Anterior  end  rounded,  not  oblique 18 

18  (21)  Without  a  terminal  bristle 19 

19  (20)     Ellipsoidal  to  ovate,  rounded  at  both  ends.      Mouth  anterior,  leading 

into  a  short  pharynx.     Uniform  ciliation. 

Holophrya  Ehrenberg, 
Representative  species Holophrya  sp. 

Species  not  determined. 

Fig.  463.     Tlolophrya  sp.      X  300.     (After  Conn.) 


20  (19)     Elongated,  cylindrical,  narrow  in  front,  mouth  terminal  or  subter- 

minal.     No   pharynx.      Cilia   longer   at   the   anterior  end. 

Nucleus  divided  into  small  pieces.  .    .  C//«n/z'fl  Quenncrstedt. 

Representative  species Chaenia  teres  Dujardin  1841. 

Forms  observed  from  the  fresh  waters  of  Connecticut  are 
^■^■^        provisionally  placed  here. 

Fig.  464.     Chaenia  teres.     X  350.     (After  Conn.) 


21   (l8) 


22  (17) 

23  (24) 


24  (23) 

25  (26) 


CILIATE   PROTOZOA    (INFUSORIA)  273 

With  a  terminal  bristle.     Similar  to  Holophrya  in  shape. 

Urotricha  Claparecle  and  Lachmann. 
Representative  species. 

Urotricha  Jar  eta  Claparede  and  Lachmann  1858. 

Body  obliquely  striated;  posterior  bristle  obliquely  directetl 
when  at  rest.  Progression  by  slow  forward  movement  or  sud- 
den leaps  to  one  side.  Mouth  on  a  small  circular  {)r()mincnce 
at  the  anterior  end.  Length  20  ^l.  Pond  water.  Bulanlozoon 
of  Stokes  agrees  with  this  genus  except  that  only  the  anterior 
two-thirds  is  ciliated. 

Fig.  465.     Urotricha  farcta.      X  435-     (After  Conn.) 

Anterior  end  oblique ' 2,5 

With  a  spiral  series  of  long  ciHa  on  either  side  of  a  ridge  extending 
from  the  anterior  border  to  the  posterior  extremity. 

Perispira  Stein. 

Representative  species Perispira  strephosoma  Stokes  1886. 

Body  elongate-ovate.  Cilia  of  the  general  surface  very  fine. 
Protoplasm  filled  with  dark-colored  corpuscles.  Length  80  ^. 
Standing  water  with  sphagnum. 

Fig.  466.     Perispira  strephosoma.     X  280.     (After  Stokes.) 

Without  a  spiral  series  of  cilia 25 

Elongated,  with  mouth  slightly  on  one  side;   uniform  ciliation.     Nu- 
cleus single Enchdys  Hill. 

Representative  species Enchelys  pupa  Ehrenberg  1836. 

iP^^^'*'^;^  Body  inflated,  slender  anteriorly.      Often  colored  green. 

•J?-^IiP^^?!te«;£.  Length  about  200  m-     Stagnant  water. 

Fig.  467.     Enchelys  pupa.      X  150.     (After  Conn.) 


26  (25)     Elongate,  sac-like,  mouth  occupying  the  oblique  surface.     Pharynx 

slightly  developed,   sometimes  with  rods.     Nucleus  bead- 
like Spathidium  Dujardin. 

Representative  species.    .    .    .      Spathidiiwi  spatliula  Dujardin  1S41. 
^^niimiiiiijM^^^a^,,.^^^^^^^^^^.^  Very  difficult  to  distinguish  from  forms  of  the  genus 

:^CCCJM$^''-^'C^^f/  Enchelys. 

Fig.  468.     Spathidium  spathula.     X  250.     (.\fter  Conn.) 

27  (16)     With  pharynx  well  developed 28 

28  (33)     Body  greatly  elongated 29 

29  (32)     Body  flattened 30 

30  (31)     Flask-shaped  with  an  elongated  ncck-likc  anterior  end.      Proboscis 

short,    retractile.     Mouth    terminal    leading    into    a    long 

pharynx.    .    .    .    rmc/zf/^^/j/a'/Z/^m  Claparetle  and  Lachmann. 

Representative  species.  .     Trachelophyllum  tachyblastiim  Stokes  1884. 

Body  eight  or  ten  times  as  long  as  broad;  neck  slender; 

'■>^^^,^^;_w-:-_i^..,_^^^^^  pharyngeal  passage  indistinct,  narrow,  longitudinally  stri- 

_2^^|^^^^^^i??t:^2j:gs^^        ate.      Cilia  of    surface    long,    vibrating    indeix-ndently. 

''^^^^^^^^^ffT'^^S^^^^^^        Nuclei  two,  subcentral.      Contractile  vacuole  ix)sterior. 

^^Tf./^-   ^^      ^^  Length,  extended,  120  to  150 /!•    Bottom  of  shallow  ptKils. 

Fig.  469.   Trachelophyllum  tachyblastum.  cr,  contractile  vacuole; 

macn,  macronuclcus.     X  250-     (After  Stokes.) 


^74 
31  (3o) 


FRESH-WATER  BIOLOGY 

Long,  ribbon-like;  no  proboscis.  ^Mouth  terminal  with  an  evident 
pharynx.  Nucleus  in  the  posterior  third  of  the  body  and  a 
row  of  minute  vacuoles  near  one  side.   .  Flcxiphylliim  Conn. 

Representative  species Flcxiphylliim  elongatum  Conn  1905. 


Fig.  470. 


Flexiphyllum  elongatum. 
Conn.) 


X  220.     (After 


32  (29)     Body  not  llattened;    with  a  long,  highly  contractile  neck;    a  plug- 

like projection  carrying  the  terminal  mouth  which  is  sur- 
rounded by  a  crown  of  long  cilia.      Body  longitudinally  or 

spirally  striated Lacrymaria  Ehrenberg. 

Representative  species Lacry;;wrw  o/or  Miiller  1786. 

A  common  species  found  in  pond  water.  Its 
swan-like  appearance  was  suggested  to  the  early 
observers  by  its  graceful  movements,  as  it  swims 
about  extending  its  neck  here  and  there  in  search  of 
food.  Length,  neck  contracted,  50  to  70  m- 
Fig.  471.  Lacrymaria  olor.  cv,  contractile  vacuole;  n,  nu- 
cleus. E.xpanded.  X  50.  (After  Blochmann.)  Con- 
tracted.     X  200.     (After  Conn.) 

33  (28)     Body  not  elongated,  spherical  to  ovate;   anterior  end  not  oblique. 

Mouth  terminal  or  subterminal,  pharynx  usually  with  rods. 

Nucleus  ovate  to  ribbon-like.      .    .    .     Prorodon  Ehrenberg. 

Representative  species Prorodon  ovum  Ehrenberg  1833. 


Body  oval,  evenly  rounded  at  both  ends;  mouth  eccentric,  open- 
ing into  a  conical  phar>^nx  which  leads  far  into  the  body.  Rods  of 
pharynx  conspicuous.  Cilia  of  posterior  border  longer.  Nucleus 
spherical,  central.  Contractile  vacuole  posterior.  Length  125  m- 
Pond  water. 


Fig.  472.     Prorodon  ovum,     ct),  contractile  vacuole;  macn,  macro- 
nucleus;  mien,  micronucleus.      X  170.     (After  Blochmann) 


34  (13)     Body  asymmetrical  with  dorsal  side  arched 35 


35  (48)     Mouth  subterminal  or  terminal,  body  greatly  elongated. 


36 


36  (43)     Mouth  usually  open,  pharynx  often  rod-like 37 


37  (42) 

38  (39) 


Mouth  subterminal. 


38 


Anterior  end  hook-like,  bent  to  the  left;  elongated,  flattened,  leaf- 
hke.  \'entral  surface  flat  with  ciliated  ribs;  dorsal  surface 
curved,  without  cilia.  Mouth  on  the  left  anterior  edge,  lead- 
ing into  a  pharynx Loxodes  Ehrenberg. 

Representative  species Loxodes  rostriim  MiiWer  lySd. 

The  body  of  this  species  is  highly  vesicular.      Nuclei 
'^Pi^'^'^*"?^---'^^''-  '    ^^y  ^^  two  or  more.     Wrzesniowski  has  demonstrated  a 

l5>^!^^^^J^.'^C;^^^  racemose  system  of  nuclei.     Length  250  to  400  /!•     At  the 

*^%ii^^^^5S^^^  bottom  of  old  infusions. 

Fig.  473.     Loxodes  rostrum.     X  250,     (After  Conn.) 


39  (38)     Anterior  end  not  hook-like 40 


CILIATE   PROTOZOA    (INFUSORIA) 


Rcprcscntati 


275 

40  (41)     Body  not  elongated;    spherical  to  ovate,  slightly  flexible;    a  short 
proboscis  at   the  base  of  which  is  the  mouth.      Pharynx 

with  rods Trachdiiis  Schrank. 

"'"'"'"  species Trachelius  ovum  YMxiinhiixg  1^7,^. 

Neck  highly  flexible.  Mouth  circular;  pharynx  with  rods. 
Nucleus  central;  contractile  vacuoles  numerous.  Endoplasm 
at  the  inner  end  of  the  pharynx  usually  spreads  out  into  four 
or  five  broadly  diverging  ramifications.  Length  500^.  J."— "<- 
water. 

Fig.  474.     Trachclius  ovum,      x  85.     (After  Blochmann.) 


T'resh 


41  (40)     Body  greatly  elongated,  band-Hke,  very  flexible;  proboscis  long  with 
mouth  at  the  base  and  a  row  of  long  cilia  along  its  ventral 

side Dilcptus  Dujardin. 

Representative  species.    Dilcptus  gigas  Claparede  and  Lachmann  1858. 

c>v  Body  somewhat  compressed,  often  with  a  pointed, 

j)  tail-like  prolongation.  A  prominent  shoulder  or 
hump  often  indicates  the  position  of  the  mouth. 
Nucleus  moniliform,  very  long.  Contractile  vacuoles 
numerous  in  a  dorsal  row.  Trichocysts  on  the  ven- 
tral surface  of  the  neck.  Length  500  to  800  n.  Pond 
water. 

Fig.  475.     Dileptus  gigas.     x  no.     f.\fter  Conn.) 

Mouth  terminal;    body  elongated  with  a  long  proboscis.     Nucleus 

double Lionotopsis  Conn. 

Representative  species Lionotopsis  anser  Conn  1903. 


Fig.  476.     Lionotopsis  anser.      X  230.     (.^ftcr  Conn.) 


43  (36)     Mouth  usually  closed;  pharynx  when  present,  without  rods.   .    .     44 

44  (45)     With  a  broad  hyaline  border;  body  flattened;  proboscis  short,  mouth 

on  the  left  side.     Trichocysts  well  developed  on  the  right 

side Loxophyllum  Dujardin. 

Representative  species Loxophyllum  rostratum  Cohn  1866. 

Anterior  extremity  prolonged  into  a  dorsally  re- 
flected, uncinate  rostrum.  Cilia  of  anterior  region 
longer.  Middle  of  the  dorsal  border  crenulate,  the  row 
of  trichocysts  extending  from  this  region  forward 
nearly  to  the  tip  of  the  rostrum.  Nuclei  multiple, 
central;  a  number  of  contractile  vesicles  {X)sterior. 
Length  190  m-  Recorded  by  Conn  from  the  fresh 
waters  of  Connecticut. 


Fig.  477.   Loxophyllum  rostratum. 
(After  Conn.) 


45  (44) 

46  (47) 


Without  a  broad  hyaline  border 46 

Body  flattened,  elongated  with  an  acute  proboscis  at  the  base  of 
which  is  the  mouth.     Nucleus  single  or  double. 

.1  mp/iilcptus  Ehrenberg. 
Representative  species {mpliilcpliis  guttn  Cohn  iS,66. 

Mouth  about  one-third  the  length  of  the  body  from  the 
anterior  end.  Pharynx  a  short  smooth  tube.  Cilia  ev(^n  all 
^=?^,iii^  over  the  body.  Nucleus-like  corjiusclos  scattcre<l  throughout 
the  cortical  region.  Contractile  vacuole  single,  posterior. 
Length  125  n.  Reported  by  Conn  from  Connecticut.  Cohn 
reports  the  species  from  salt  water. 

Fig.  478.    Amp/tileplus  gutta.     X  335.     (After  Conn.) 


276  FRESH-WATER    BIOLOGY 

47  (46)     Body  flattened  ventrally,  convex  dorsally.     With  a  long  neck  and 

usually  a  tail-like  prolongation  both  of  which  are  hyaline. 
Mouth  a  slit  at  the  base  of  the  neck,  often  invisible.  Nuclei 
usually  two;   contractile  vacuole  posterior. 

Lio)iotus  Wrzesniowski. 
Representative  species Lionotus  urzcsniowskii  Kent  1882. 

■^■^~^'"~~^-~^        Fk;.  479.     Lionotus  wrzesniowskii.     cv,  contractile 
5-     ^.jc^    -  vacuole.      X  125.     (After  Kent.) 

48  (35)     ^louth  usually  somewhat  posterior,  and  often  with  a  pharynx;  body 

oval  or  kidney-shaped 49 

49  (50)     Body  completely  ciliated,  cylindrical  to  ovate,  rounded  posteriorly. 

Mouth  about  one-third  of  the  way  from  the  anterior  end; 

pharynx  with  rods Nassula  Ehrenberg. 

Representative  species Nassula  oniata  Ehrenberg  1838. 

Ifl^^l^  Usually  some  shade  of  red  or  brown  in  color.      Nucleus 

_  '  W''"^^^  large,  spherical,  posteriorly  located.      Contractile  vacuole 

0'  -^  '0K-^ri^^  single.     Length  200  m-     Among  algae 

Fig.  480.      Nassula  ornaia.     In  act  of  feeding.       X  325.     (After 
Conn.) 


50  (49)     Body  not  completely  ciliated;  cilia  ventral  only 51 

51  (56)     Body  flattened 52 

52  (55)     Mouth  in  the  anterior  half  of  the  body 53 

53  (54)     Body  with  convex  dorsal  and  flattened  or  slightly  concave  ventral 

surface.    Pharynx  with  rods Chilodon  Ehrenberg. 

Representative  species Chilodon  cucullulus  Miiller  1 786. 

o  The  lip-like  extension  prominent,  a  groove  leading  from  it  to  the 

mouth.  Nucleus  oval  near  the  inner  end  of  the  pharynx.  Contractile 
vacuoles  numerous.  Length  125  to  200  m-  Stagnant  water  and  among 
algae. 


Fig.  481.     Chilodon  cucullulus.     cv,  contractile  vacuole;   macn,  macronucleus; 
mic,  micronucleus.       X  no.     (After  Blochmann.) 

54  (53)     Body  with  ridges  on  dorsal  and  ventral  surfaces,  crenate  in  cross 

section,  pharynx  with  rods Chilodonopsis  Conn. 

Representative  species Chilodonopsis  crenida  Conn  1905. 


Fig.  482.     Chilodonopsis  crenula.      X  335.     (After  Conn.) 


55  (52)     Mouth  in  the  posterior  half  of  the  body Opisthodon  Stein. 

56  (51)     Body  not  flattened 57 


CILIATE   PROTOZOA    (INFUSORIA)  277 

57  (58)     Body  purse-shaped Phascolodon  Siein. 

58  (57)     Body  ovate  or  nearly  spherical  in  outline  with  a  slight  lip  at  the 

anterior  end.     Mouth  at  the  base  of  the  lip  with  no  evident 

pharynx.     Cilia  ventral  in  six  rows.  .    .    .   Ilcxotricha  Conn 

Representative  species Hcxotricha  globosa  Conn  u)os. 


Fig. 


h.     nexotricha  globosa.     Lateral  and  end  views,     cv,  contractile 
vacuole;   m,  mouth,      x  335-     (After  Conn.) 


.SO 


Oo  (87) 

61  (70) 

62  (65) 

63  (64) 


Usually  with  an  undulating  membrane  or  membranes  about  the  mouth 

Mouth  always  open.    .    .    .  Suborder  Trichostomma   .    .     60 

Peristome  usually  absent;  with  or  without  undulating  membranes.     61 

Without  an  undulating  membrane;  pharynx  present 62 

One  or  two  broad  zones  of  strong  cilia  about  the  body;  with  a  tail- 
like tuft  of  cilia 5, 

Two  broad  zones  of  strong  cilia  about  the  body.  Body  cylindrical, 
with  mouth  posterior  leading  into  a  short  pharynx.  An- 
terior part  of  the  body  uniformly  ciliated.  A  band  of 
strong  cilia  near  the  middle  and  posterior  end. 

^  .  Urocentrum  Nitzsch. 

Representative  species Urocentrum  turbo  ^m\ev  l^?>6. 


Body  broadly  rounded  anteriorly,  rounded  or  truncate  posteriorly 
Movement  by  a  rotation  on  the  long  axis  or  swiftly  darting  from  side 
to  sidle.  Contractile  vacuole  posterior  with  the  band-like  nucleus 
curved  about  it.     Length  100  n.     Pond  water. 

Fig.  484.    Urocentrum  turbo,  cv,  contractile  vacuole;  n,  nucleus     X  200 
(After  Kent.) 


64  (63)  With  an  oblique  circle  of  strong  cilia  near  the  anterior  end.  Body 
somewhat  pyriform,  rigid,  finely  ciliated.  Two  groove-like 
canals  encircling  the  body.  I\Iouth  ver^tral,  posterior  to 
the  grooves  and  leading  into  a  short  pharynx. 

CalccolHs  Diesing. 
Representative  species.  .    .  Calceolus  cypripcdiiim  James-Clark  1866. 


Color  light  brown.     \'crv  similar  in  movement  to  i'rocnilrum  turbo. 
Length  80  to  160  ^.     Fresh  water. 

Fig.  485.   Calceolus  cypripedium.   cv,  contractile  vacuole;  moiH,  macronucleus 
X  200.     {.After  Kent.) 


278 


FRESH-WATER    BIOLOGY 


65  (62)     No  zones  of  strong  cilia  about  the  body 66 

66  (67)     Mouth  covering  the  whole  oblique  anterior  end.     Body  usually  oval 

or  purse-shaped Lciicophrys  Ehrenberg. 

Representative  species Lciicophrys  palula  Ehrenberg  1838. 


Body  oval;  pharynx  tubular,  curved.  Nucleus  banil- 
like,  central.  Contractile  vacuole  posterior.  Length  200  m- 
.\mong  algae. 

Fig.  486.     Leucophrys  patula.      X  150.     (After  Kent.) 


67  (66)     Mouth  at  some  distance  from  the  anterior  end 68 

68  (69)     Body  ellipsoidal,  ciliation  regular,  mouth  a  crescent-shaped  or  spiral 

slit  leading  into  a  pharynx.      .    .    .    Ophryoglena  Ehrenberg. 
Representative  species Ophryoglena  atra  Ehrenberg  1838. 

Body  with  posterior  extremity  pointed.  Endoplasm  usually 
opaque,  with  a  dark  blue  pigment  spot  in  the  anterior  region. 
Nucleus  round,  posterior;  contractile  vacuole  central.  Length  125 
to  150  n.     Stagnant  water. 

Fig.  487.     Ophryoglena  atra.     cv,  contractile 'vacuole;  macn,  macronucleus. 
X  200.     (After  Kent.) 


69  (68)  Body  laterally  compressed,  ovate,  with  the  dorsal  surface  rounded. 
]\louth  one-third  of  the  distance  from  the  anterior  end,  with 
a  few,  long,  fine  cilia  on  its  superior  wall  or  roof. 

Colpoda  Miiller. 
Representative  species Colpoda  canipyla  Stokes  1886. 


Length  of  body   55/1 
leaves. 


Standing   water  with   dead 
Fig.  488.     Colpoda  campyla.     X  600.     (After  Conn.) 


70(61)     With  one  or  more  undulating  membranes 71 


71  (76)     One  membrane  present. 


72  (75)     Mouth  not  terminal. 


73  (74)     Body  not  flexible;    mouth  lateral,  triangular,  following  a  small  peri- 
stome and  with  an  undulating  membrane  in  front.     Body 
similar  to  Colpoda,  but  less  compressed.    .    Colpidium  Stein. 
Representative  species Colpidium  striatum  Stokes  1886. 

Body  twice  as  long  as  broad,  striated  longitudinally,  an- 
terior extremity  curved  ventrally.  Nucleus  subcentral; 
contractile  vacuole  posterior,  often  leaving  several  small 
vacuoles  after  contraction.     Length  50  fi.     Infusions. 


^Mjjl)^^?^*^^^ 


f^^'""''^-^' 


Fig.  48y.     Colpidium  striatum.     X  500.     (After  Edmondson.) 


CILIATE   PROTOZOA    (INFUSORIA) 


279 


74  (73)  Body  very  flexible  and  changeable  in  shape.  Ovate,  covered  with 
fine  ciUa,  with  a  long  bristle  extending  from  the  posterior 
border.  Mouth  ventral  with  a  vibratile  and  retractile  hood- 
like velum Saprophilus  Stokes. 

Representative  species Saprophilus  agilatus  Stokes  1887. 

Body  twice  as  long  as  broad,  compressed,  obliquely  truncate  in  front; 
cilia  very  short  and  fine.  Body  longitudinally  striate.  Nucleus  sub- 
central.  Contractile  vacuole  posterior.  Length  of  body  35  to  45  n. 
Infusions  containing  animal  matter. 

Fig.  490.     Saprophilus  agilalus.     x  390.     (After  Stokes.) 


75  (72)     Mouth  terminal  with  a  delicate  membrane.      Body  ovate,  elastic; 

anterior  extremity  obliquely  truncate.  .    .    Trichoda  Miiller. 

Representative  species Trichoda  pur  a  Ehrenberg  1838. 

Length  40  m-      Often  found  abundantly  in  old  infusions  of  pond 
water.     Swift  moving,  usually  rolling  on  its  long  axis. 


Fig.  491.     Trichoda  Pura.     macn,  macronucleus.     X  400.     (.^fter  Kent.) 


76  (71)     Two  membranes  present 77 

77  (78)     Body  elongated,  rounded  in  front,  contracting  into  a  tail  behind. 

One  side  somewhat  flattened,   the  other  convex.     Mouth 

triangular,  near  the  anterior  end Dallasia  Stokes. 

Representative  species Dallasia  froutata  Stokes  1886. 

Body  five  times  as  long  as  broad,  ventral 
surface  convex,  dorsal  slightly  concave:   taper- 
,^„^^         ing  posteriorly  to  a  retractile  tail-like  prolonga- 
^^^^^.-^  >^  ^-^J^        tion.      Anterior    extremity    narrow.       Mouth 

^ll^\  ^  .,__    jM^'~~  obliquely  placed  on  the  ventral  surface.    Length 

'*'^'  "       '^  150  M-     Still  water,  with  aquatic  plants. 

Fig.  492.    Dallasia  frontata.   X  335-    (After  Conn.) 


78  (77)     Body  not  contracting  into  a  tail 79 

79  (84)     With  a  long,  posterior  bristle 80 

80  (83)     Without  a  spiral  row  of  long  cilia 81 


81  (82)  Body  ovate,  slightly  compressed,  broader  behind;  ventral  surface 
straight,  dorsal  surface  curved.  Mouth  near  or  anterior 
to  the  middle,  with  an  extensile  membrane.  Cilia  densely 
arranged  in  a  furrow  in  front  of  the  mouth. 

Uroncma  Dujardin. 
Representative  species Uroncma  marinum  Dujardin  1841. 

The  cilia  are  exceedingly  vibratile,  their  movements  being  ir- 
regular and  independent.  Nucleus  central.  Contractile  vacu- 
ole posterior.  Length  so  n.  Fresh  water,  often  associated  with 
Cyclidium  but  not  so  numerous. 

Fig.  493.     Uroncma  marinum.     X  400-     (After  Kent.) 


28o 


FRESH-WATER    BIOLOGY 


82  (81) 


83  (80) 


84  (79) 

85  (86) 


Body  elongate,  nearly  cylindrical,  the  anterior  extremity  truncate 
and  slightly  curved;  a  short,  curved  seta  borne  on  either 
side  near  the  anterior  end.  A  long,  straight  bristle  extend- 
ing from  the  posterior  end Loxocephaliis  Kent. 

Representative  species Loxocephaliis  granulosus  Kent  1882. 

Endoplasm  granular,  mouth  on  the  obhque  anterior  bor- 
"""',""M<(/f'fnr  (ler  although  quite  indistinct.     Nucleus  spherical,   central, 

p^      p.        ^jfe.         Contractile  vacuole  jiosterior.      Length  40  to  70  n.      Often 
^      ^  -<^         abundant  among  decaying  vegetable  matter.       Conjugation 

readily  occurs  in  infusions. 
Fig.  494.    Loxocephalus  granulosus.     X  375.    (After  Edmondson.) 

Like  Uro)icma,  but  with  an  anterior,  spiral  row  of  long  cilia. 

Dexiotricha  Stokes. 
Representative  species Dexiotricha  plagia  Stokes  1885. 

Body  about  three   times  as  long  as  broad,  bearing  minute 
hemispherical  protuberances.     Cilia  setae-like;   a  row  of  flexible 
^/^p<<r,         setae  extending  from  the  margin  of  the  mouth  obliquely  across 
<rs        "^^^        ^^^  right-hand  side  of  the  anterior  half  of  the  body.      Nucleus 
l~ilnrTTX^^        subcentral;   contractile  vacuole  posterior.     Length  60 /*•      Pond 
water. 

Fig.  495.     Dexiotricha  plagia.     X  315.     (After  Stokes.) 

Without  a  posterior  bristle 85 

Ellipsoidal  to  elongate,  somewhat  acute  behind.  Mouth  lateral, 
surrounded  by  a  furrow  which  extends  backward.  Pharynx 
short  with  rods Frontonia  Ehrenberg. 

Representative  species Frontonia  Iciicas  Ehrenberg  1838. 


Body  elongate-oval,  wider  anteriorly.  Mouth  a  slit  anterior  to  the 
middle  of  the  body.  Cilia  fine,  in  longitudinal  rows.  Contractile 
vacuoles,  usually  two.  Trichocysts  numerous.  Length  250  to  300  m- 
Stagnant  water. 


Fig.  496.     Frontonia  leucas. 
V,  vacuole. 


canal;    N,  macronucleus;  «,  micronucleus; 
X  165.     (After  Calkins.) 


86  (85)     Ovate,  flattened,  rounded  at  each  end.     Mouth  triangular  or  crescent- 
shaped,  lateral,  in  front  of  the  middle  of  the  body. 

Glaucoma  Ehrenberg. 
Representative  species.    .    .    .    Glaucoma  scintillans  Ehrenberg  1830. 


The  vibratile  membranes  extending  around  the  mouth  pre- 
senting a  bilabial  appearance.  Nucleus  large,  central.  Con- 
tractile vacuole  posterior.     Length  75  /i.     Infusions. 


Fig.  41)7.     Glaucoma  scintillans.     cv,  contractile  vacuole;  macn,  macro- 
nucleus;  mien,  micronucleus.      X  350.     (.\fter  Blitschli.) 


-^^^m^\> 


CILIATE   PROTOZOA    (INFUSORIA)  281 

87  (60)     With  a  well-developed  peristome gg 

88  (loi)     Mouth  not  posterior  to  the  middle  of  the  body gg 

89  (98)     Not  surrounded  by  a  lorica  or  gelatinous  sheath qo 

go  (91)     Peristome  oblique.     Body  elongated,  slightly  flattened,  rounded  at 

both  ends  or  slightly  truncated  in  front.     Mouth  followed 

by  a  short  pharynx;  ciliation  regular.    .    Paramoecium  Stein. 

Representative  species.    .    .  Paramoecium  caudatum  Ehrenberg  1858. 

^^^^  Perhaps  the  most  famihar  cih'ated  protozoon  known. 

^^^^^^^^gj^*.|pj^^  Body  with  a  large  central  macronucleus  and  a  small 

^^t'^'^%/'^r   ■'    '  '■'  ^^'"^0'^^^  micronucleus,    and    a   contractile    vacuole   in  either 

4^^^^^-!:.     '^■■^^i^-     *'*'^^  extremity.      Abundantly   supplied   with   trichocysts. 

^'^^^^^■^^^T^^^^'"''''^^'^        Length  variable,  average  250  ^l.     Everywhere  in  in- 

-<»'*:'«aKSiift,Aaiii'.j  - ;:-:-  -  fusions. 

Fig.  498.     Paramoecium  caudatum.     X  170.    (.^fter  Conn.) 

91  (90)     Peristome  not  oblique 02 

92  (97)     With  one  or  more  membranes  well  developed  in  the  peristome.  .     93 

93  (94)     Peristome  very  broad  and  conspicuous,  occupying  the  entire  right 

side.     Body  oval,  flattened  ventrally,  convex  dorsally;    an- 
terior end  oblique,  posterior  end  acute.     A  tuft  of  long  cilia 

extends  from  the  posterior  end Lcmbadion  Perty. 

Representative  species Lembadion  bullinum  Perty  1849. 


Nucleus  elongated,  curved  in  the  posterior  region  on  the  left  side;  con- 
tractile vacuole  opposite  the  nucleus.  When  stimulated  the  animal  swims 
rapidly  backward  rotating  on  its  long  axis.  Length  50  to  100  m-  Among 
aquatic  plants  in  pond  water. 

Hymenostoma  Stokes  differs  from  Lembadion  in  the  more  posterior,  ven- 
tral position  of  the  mouth,  the  greater  length  of  the  adoral  cilia,  the 
abruptly  narrowing  membrane  and  the  double  contractile  vacuole. 

Fig.  499.     Lembadion  bullinum.     macn.  macronucleus;  mien,  micronucleus.      x  250. 
(.\fter  Blochmann.) 


94  (93)     Peristome  not  broad  and  conspicuous 95 

95  (96)     Without  a  long,  posterior  bristle.     Peristome  parallel  to  the  right 

side  with  a  large  projecting  membrane.     Body  oval,  fat- 
tened dorso-ventrally.     Cilia  very  long. 

Plciironcma  Dujardin. 
Representative  species.  .    .    .     Pleuroncma  chrysalis  Ehrenberg  1838. 


Cilia  in  length  nearly  one-half  the  diameter  of  the  body.  stifTcnetl, 
setae-like.  Nucleus  central;  contractile  vacuole  anterior.  Length 
75  to  125  fx.  Fresh  water.  Stokes  rccogni/.es  two  separate  gen- 
era, II istriohalantidium.  with  long  setose  bristles  among  the  cilia 
over  the  whole  body,  and  Bothrostoma,  with  a  long  terminal  tuft 
of  cilia.      Biitschli  places  them  both  under  Phuroncma. 


Fig.  500.    Pleuroncma  chrysalis,    wdcw,  macronucleus;  miV«,  micronucleus. 
X  225.     (.^Ucr  Blochmann.) 


282 


FRESH-WATER   BIOLOGY 


96  (95)     Like  Pleuroncma  but  with  a  shorter  peristome  and  one  or  more  long 

posterior  bristles Cyclidium  Ehrenberg. 

Representative  species.  .    .    .      Cyclidium  glaucoma  Ehrenberg  1838. 


mm///'-^>- 


m 


-^ 


'''//liil^m^ 


Cilia  long  and  rigid,  in  longitudinal  rows.  Nucleus  central; 
contractile  vacuole  posterior.  Length  20  /i.  Very  abundant  in 
stagnant  water. 

Fig.  SOI.     Cyclidium  glaucoma.     X  625.     (After  Edmondson.) 


97  (92)  Without  an  oral  membrane.  Body  ovate;  mouth  ventral  at  the 
posterior  end  of  a  longitudinal  groove  which  bears  on  its 
right-hand  border  a  row  of  large,  arcuately  curved  setose 
cilia  diminishing  in  length  toward  the  mouth.  A  long 
bristle  extending  from  the  posterior  end  of  the  body. 

Ctcdoclema  Stokes. 
Representative  species.  .    .    .    Ctedoctema  acanthocrypta  Stokes  1884. 


Often  very  abundant  among  fresh-water  algae. 
Trichocysts  are  numerous  and  very  stout.  Length 
of  body  25  M- 


Fig.  502.    Ctedoctema  acanthocrypta.    X  875.    (After  Stokes.) 


98  (89)     With  a  lorica  or  gelatinous  sheath 99 

99(100)     Enclosed  in  a  lorica.     Animal  similar  to  P/ewr<7W^ma.    Lorica  oblong- 
ovate,  hyaline,  with  tapering  extremities,  the  terminal  aper- 
tures about  half  as  wide  as  the  center  of  the  sheath.     Animal 
very  active  within  the  lorica.  ....   Calyptotricha  Phillips. 
Representative  species.      .    .    .    Calyptotricha  inhaesa  Stokes  1885. 


Kellicott  reports  this  species  from  Ontario.     Length  of  lorica  180  to  200  m- 
Enclosed  animal  30  m-     Attached  laterally  to  algae. 

Fig.  503.     Calyptotricha  inhaesa.     X  100.     (After  Kellicott.) 


Enclosed  in  a  gelatinous  sheath  to  which  the  animal  is  not  attached. 
Body  ovate;  mouth  ventral,  at  the  end  of  a  groove  on  the 
margin  of  which  is  a  series  of  strong  cilia.  A  tuft  of  long, 
curved  cilia  extends  from  the  anterior  extremity. 

Cyrtolophosis  Stokes. 
Representative  species.    .    .    .    Cyrtolophosis  miicicola  Stokes  1885. 

,  _  _ .,  A  strange  form  not  uncommon  among  algae.    When  the  animal 

comes  to  rest,  a  transparent,  sticky  substance  seems  to  be  exuded 
from  the  body  which  becomes  granular,  due  to  excreta,  bacteria 
and  other  foreign  bodies  which  adhere  to  it.  When  disturbed 
the  animal  glides  out  of  its  covering  and  another  is  constructed. 
A  temporary  colony  may  be  built  up  by  the  adherence  of  several 
gelatinous  sheaths.     Length  of  body  25  /i. 

Fig.  504.     Cyrtolophosis  mucicola.     X  875.     (After  Stokes.) 

Mouth  at  the  posterior  end  of  the  body 102 


100  (99) 


CILIATE   PROTOZOA    (INFUSORIA)  283 

102  (103)  Body  flattened,  oval,  with  spiral  furrows.  Peristome  with  a  vi- 
brating membrane  posterior  leading  into  the  mouth.  A 
tuft  of  long  bristles  at  the  posterior  end  of  the  body. 

Cinctochilum  Perty. 
Representative  species. 

Cinetochilum  margaritaceum  Ehreni^erg  1838. 

Contractile  vacuole  posterior,  opposite  the  mouth,  with  nucleus  an- 
terior to  it.     Length  30  ix.     Very  common  in  pond  water. 

Fig.  505.     Cinetochilum  margaritaceum.     x  scxj.     (After  Butschli.) 


103  (102)     Body  neatly  oval,  ventral  surface  flat,  ciliated;    dorsal  surface 

curved,  with  three  longitudinal  grooves.     Mouth  posterior 
on  the  left  side,  with  a  small,  vibrating  membrane. 

Microthorax  Engelmann. 
Representative  species.  .    .    Microthorax  sulcatus  Engelmann  1862. 

Associated  with  the  preceding  species.     Length  40  to  60  n. 
Fig.  506.     Microthorax  sulcatus.     X  310.     (After  Kent.) 

104  (3)     An  adoral  zone  present  consisting  of  ciha  fused  together  into  mem- 

branellae Order  Heterotricha   .    .     105 


105(120)     With  a  uniform  covering  of  cilia 106 

106(115)  Peristome  not  confined  to  the  anterior  border  of  the  body.    .  107 

107  (112)     Peristome  a  long,  narrow  furrow 108 

108(111)     With  an  undulating  membrane 100 


109  (no)     Body  flattened,  narrow  and  hook-like  in  front.     Mouth  near  the 
middle  of  the  body  at  the  end  of  the  narrow  peristome. 
Membranellae  on  the  left  wall  of  the  peristome,  on  the  right 
an  undulating  membrane.     Colored.    .      BUpharisma  Perty. 
Representative  species.  .    .     Blepharisma  later itia  Ehrenberg  1838. 


Body  usually  truncate  behind;  nucleus  in  the  anterior  half  of  the  body.     Contrac- 
tile vacuole  posterior.     Color,  peach-bloom.     Length  150 /i.    .\mong  aquatic  plants. 

Fig.  507.     Blepharisma  lalcritia.     X  180.     (.\fter  Stein.) 


284 

no  (109) 


FRESH-WATER    BIOLOGY 

Body  spiral,  cylindrical,  somewhat  pointed  at  both  ends,  but  con- 
tractile; peristome  spiral  with  the  mouth  near  the  middle 
of  the  body.  Membranellae  on  the  left  side  of  the  peri- 
stome, a  membrane  on  the  right  side. 

M  do  pus  Claparede  and  Lachmann 

Representative  species Meio pus  sigmoides  MiXWer  ijSO. 


Cilia  usually  longer  at  the  posterior  end.  A  mass  of  dark  pigment  gran- 
ules in  the  anterior  extremity.  Nucleus  oval,  central:  contractile  vacuole 
posterior.  Length  100  to  200  u.  At  the  bottom  of  infusions.  Metapides 
acuminata  Stokes  diflfers  from  the  above  species  in  the  posterior,  tail-like 
prolongation  from  which  extend  a  number  of  long  bristles.  It  is  also 
smaller  in  size. 


\ 


-CV 


Fig.  508.     Metopus  sigmoides. 


CV.  contractile  vacuole;  tnacn,  macronucleus.     X  220. 
(After  Stein.) 


(108) 


Without  an  undulating  membrane.  Body  greatly  elongated,  cyl- 
indrical, contractile.  Peristome  reaching  to  the  middle  of 
the  body.  Strong  membranellae  on  the  left  side  of  the  peri- 
stome.   Body  spirally  striated.  .    .   Spirostomum  Ehrenberg. 

Representative  species.  .  Spirostomum  ambiguum  Ehrenberg  1835. 

Body  ten  to  fifteen  times  as  long  as 
broad,  but  readily  contracting  into  a  short 
spiral  body.     Nucleus  moniliform.     Con- 
tractile vacuole  posterior,  extending  for- 
ward as  a  canal.      Extended  body  may 
...      reach  2800  m  in  length.     Common  among 
Fig.  509.    Spirostomum  ambtguum.  ct,  contractile  vacuole;   oQuatic  olants 
tnacn,  macronucleus.     X  30.     (After  Kent.)  ^  ^ 


2(107)     Peristome  a  broad  triangular  area,  deeply  sunken 113 


113  (114)  With  an  undulating  membrane  on  the  right  side  of  the  peristorne. 
Body  cylindrical  or  purse-shaped,  sometimes  contractile. 
Peristome  broad  in  front  extending  one-third  the  length  of 

the  body Condylostoma  Dujardin. 

Representative  species Condylostoma  patens  M\i\\qv  I'j^G. 


Body  broadly  ovate,  widest  posteriody.  Peristome  broadly  triangular, 
extending  about  half  the  length  of  the  body.  Nucleus  moniliform;  con- 
tractile vacuole  irregular.     Length  200  m-     Stagnant  water. 


Fig.  510.     Condylostoma  patens,     macn,  macronucleus;  u,  undulating  membrane. 
X  105.     (After  Kent.) 


CILIATE   PROTOZOA    (INFUSORIA) 


28  = 


14  (113) 


Without  an  undulating  membrane  in  the  peristome.     Body  purse- 
shaped,  oblique  in  front;  peristome  funnel-shaped,  open 
mg  on  the  ventral  side  by  a  slit  reaching  as  far  as  the 
middle  of  the  body.     Membranellae  on  the  left  side  of 

the  peristome Bursaria  Muller. 

Representative  species. 

Bursaria  truncatclla  Muller  1786. 

Nucleus  band-like;   contractile  vacuoles  numerous.     Length  500 
to  700  n.     Pond  water. 


Fig.  51 


Bursaria  truncatella.    cv,  contractile  vacuole:  tnacn  macronucleus 
X  35-     (After  Kent.) 


Peristome  confined  to  the  anterior  border  of  the  body,  with  its 
plane  nearly  at  right  angles  to  the  longitudinal  axis  of  the 
body ,j6 


115  (106) 

116(119)     Posterior  end  not  produced  into  a  tail-like  process 117 

117  (118)     Body  purse-shaped,  slightly  flattened,  anterior  end  oblique. 

Peristome  enclosing  most  of  the  anterior  end  of  the  body. 

Climacostomum  Stein. 

118  (117)     Body  funnel-shaped  when  extended,  fixed  or  free-swimming,  some- 

times enclosed  in  a  jelly-like  lorica.  Peristome,  the  ante- 
rior expanded  surface  with  a  spiral  row  of  strong  cilia 
around  its  border;  the  left  end  of  the  spiral  being  the  lower, 
leading  into  the  mouth  and  short  pharynx.  Surface  fmelv 
ciHate  sometimes  bearing,  in  addition,  long  slender  bristles.' 

Stcntor  Oken. 
Representative  species.     .   Stcntor  polymorphiis  Muller  1786. 

Body  usually  containing  a  cortical  layer  of  chlorophyl  granules. 
Nucleus  moniliform.  Length,  extended,  1200  n.  Among  aquatic  plants 
and  in  infusions.  Sometimes  found  in  gelatinous  masses  on  leaves  and 
roots  of  water  plants. 

Another  fresh-water  form,  S/enlor  coerulcus  Ehrenberg.  blue  in  color. 
is  also  common. 


Fig.  512. 


Stentor  polymorphus.     cv,  contractile  vacuole;    macn,  macronucleus 
X  30.     (.After  Kent.) 


119  (116)  Posterior  end  produced  into  a  tail-like  process;  anterior  region 
helmet-like,  rounded  anteriorly  with  a  free  posterior  margin. 
Mouth  ventral  in  a  ciliated  groove.  Cilia  extending  from 
the  mouth  in  a  spiral  across  the  anterior  border  and  around 
the  free  margin  of  the  anterior  portion. 

Ciuiiomorpha  Perty. 
Representative  species.    Caowmorplia  mcdiisula  Perty  i84(). 


Movements   swift,   rotating  on  the   long   axis 
100  to  130  M.     Standing  water. 


Loncrth.    with   fail. 


Fig.  513.     Caenomorplia  meJusula.      X  200      u\UerMein.) 


120(105)     Cilia  restricted  to  certain  limited  areas  or  zonts 121 

121  (124)     Body  not  in  a  lorica 1^2 


286  FRESH-WATER    BIOLOGY 

122  (123)     Equatorial  region  of  the  body  bearing  a  circle  of  long,  fine  bristles. 

Body  spheroidal  with  a  spiral  wTeath  of  strong  cilia  about 
the  anterior  border.     Mouth  anterior,  marginal. 

Ualtcria  Dujardin. 
Representative  species Ilallcria  grandinella  MiXWer  1^86. 

,  Nucleus  round,  central,  with  contractile  vacuole  near.     Moving  by  a 

rotary  motion  accompanied  by  sudden  leaps.     Length  25  m-      Common 
(^;^  in  pond  water. 

Fig.   514.     Ualteruj  grandinella.     cv,  contractile  vacuole;    macn,  macronucleus. 
X  400.     (After  Kent.) 

123  (122)     Without  long,  fine  bristles,  otherwise  very  similar  to  II alter ia. 

Strombidium  Claparede  and  Lachmann. 

v.,V;-,i(.i«//tfi/  Representative  species.      .    Strombidium  claparedii  Kent  1882. 


Body  somewhat  elongate,  tapering  posteriorly.      Length   80  m-      Pond 

Fig.    515.     Strombidium   claparedii.      cv,   contractile   vacuole;  n,   nucleus.      X  loo. 
(After  Kent.) 

124  (121)     Body  in  a  lorica.     . 125 

125  (126)  Lorica  mucilaginous,  attached  to  some  support.  Body  ovate  to 
pyriform,  attached  in  the  lorica  by  a  pedicel.  Mouth  ante- 
rior, surrounded  by  a  wreath  of  long  cilia. 

Tintinnidium  Kent. 
loij^  Representative  species.    .  Tintinnidium  fluvidtilisSte'miS6'j.      I 

fvV? "!'!.:.  The  lorica   has  an  uneven  surface,  frequently  with  incorporated  foreign 

particles.       Body  sometimes  attached  to  the  bottom,  sometimes  to  the  side 
of  the  lorica.      Length  of  lorica  125  n.     Attached  to  aquatic  plants. 

Fig.  516.     Tintinnidiutn  fluvialilis.      X  200.     (After  Entz.) 


126(125)     Lorica  chitinous;  Otherwise  as  rm/t7i;z/(f/ww.    .    .      Tintinnus  Fo\. 
127(2)     Body  not  uniformly  covered  with  cilia 12S 

128  (169)     CiUa   setae-like,  usually  Hmited   to   the   ventral  surface.     Dorsal 

surface  sometimes  with  bristles.     Body  flattened. 

Order  Hypotricha   .    .      i2<) 

129  (130)     Ventral  side  uniformly  ciliate,  except  sternum;  a  group  of  stronger 

cilia  behind  peristome  and  near  posterior  end. 

Trichogaster  Sterki. 

130(129)  Ventral  surface  not  uniformly  ciliate 131 

131  (166)  Many  border  cilia 13- 

132  (157)  Ventral  cilia  numerous,  in  rows 133 

133  (152)  Ventral  cilia  bristle-like 134 

134  (143)  Usually  more  than  two  rows  of  ventral  cilia 135 

135  (140)  Five  or  more  rows  of  ventral  cilia 136 


CILIATE    PROTOZOA    (IXFUSORIA) 


287 


Fig.  517.     Urostyla  Irichogaster. 
Conn.) 


136  (137)     Peristome  with  an  undulating  membrane,  body  flexible.     Three  or 

more  frontal  styles.  Five  to  twelve  anal  styles  in  an  oblique 
row  extending  to  the  left.     Peristome  an  elongated  triangle. 

Urostyla  Ehrenberg. 
Representative  species Urostyla  Irichogaster  Stokes  1885. 

Yentral  surface  with  closely  approximated  rows 
of  fine  cilia.  Anal  styles  ten  or  twelve  in  number. 
Nucleus  single,  according  to  Stokes.  Contractile 
vacuole  single,  to  the  left  of  the  peristome. 
Length  250  to  300  n.  Vegetable  infusions. 
Hemiciplostyla  Stokes  agrees  with  Urostyla,  but 
has  no  anal  styles. 
X  1 50.  (After  Conn  found  two  nuclei  in  his  form  and  states  that 
it  may  be  a  variety  of  Urostyla  grandis  Ehrenberg. 

137  (136)     Peristome  without  an  undulating  membrane 138 

138  (139)     Elongate,  rounded  at  both  extremities,  not  flexible;    five  nearly 

straight  rows  of  ventral  cilia.  Peristome  on  the  right-hand 
margin,  extending  back  of  the  middle,  with  a  row  of  long 
cilia  or  membranellae.     Nuclei  four  to  six  in  number. 

Homostyla  Conn. 
Representative  species Homostyla  elliptica  Conn  1905. 


Fig.  518.     Homostyla  elliptica.     X  325.    (.After  Conn.) 


139  (138)  Kidney-shaped,  with  six  obHque  rows  of  ventral  cilia,  the  posterior 
row  the  stronger.  No  frontal,  ventral,  or  anal  styles.  Border 
cilia  forming  a  complete  row  around  the  periphery.  Peri- 
stome reaching  to  the  middle  of  the  body.  External  para- 
sites on  Hydra Kerona  Ehrenberg. 

Representative  species Kerona  pcdkulus  yWiWur  I'l^b. 


Fig.  519.     Kerona  pediculus.      X  250.     (After  Stein.) 


140  (135)     Less  than  five  row^s  of  ventral  cilia 141 

141  (142)     Body  elongated  anteriorly  into  a  neck;  rounded  behind,  very  con- 

tractile. Peristome  narrow,  extending  to  or  beyond  the 
middle.  Membranellae  long.  Two  or  three  oblique  rows 
of  ventral  setae.     No  frontal  or  anal  styles. 

Stichotricha  Perty. 

Representative  species Stichotricha  sccumla  Perty  1849. 

_______  Marginal  setae  long  and  slender.     Nuclei  two.  with 

^rf^=7^ ■, ' -  ^  ■  \-~.-^rr-^ry:rKP'::!'—^     the  contractile  vacuole  between.     Often  a  mucilaginous 
^^<i'<£?<^y<''1^''-^\'*''C-.-;'^^.,,^^^      sheath  is  secreted  by  the  animal,  from  which  it  may 
'^^sss^^^ir^?:^,  ;  project  the  anterior' half  of  the  body  or  may  entirely 

vacate  it  and  swim  freely  in  water.      Length  about 
200  M-     Among  sphagnum. 

Fig.  520.    Stichotricha  secunJa.     X  23s-     (After  Comi.) 


288  FRESH-WATER   BIOLOGY 

142  (141)     Body  elliptical  to  ovate,  flexible.     Three  unequal  rows  of  ventral 

cilia;    frontal  styles  numerous.     No  anal  styles.     Marginal 

setae  uninterrupted Eschamustyla  Stokes. 

Representative  species.     .    .  Eschaneiistyla  hrachytona  Stokes  1886. 

Anterior  extremity  slightly  curved  to  the  left  with  a  con- 

^^-TjaabUL-l ^'VS'-l'fi'^-"«t^.  striction   beneath   the  front  border.      Frontal  styles  about 

-■jiir^'ViPm^  -^ "  qM- "--^^g^Ji^r-.     twenty-five  in  oblique  rows.      Nucleus  not  observed.     Con- 

j^^^Sa^^is^^^qBaflJ^^     tractile  vacuole  canal-like  along  the  left-hand  border.    Length 

"^^riU^lil  1iliiiii^*'"~'T IT  about  200  M-     Standing  water  with  dead  leaves. 

Fig.  521.     Eschaneuslyla  brachylona.      X  200.     (After  Stokes.) 

143  (134)     One  or  two  rows  of  ventral  cilia 144 

144  (145)     One  row  of  about  seven  large  ventral  cilia.     Long  border  and  anal 

cilia ■  Balladina  Kowalewsky. 

145  (144)     Two  rows  of  ventral  cilia;  body  not  elongated  in  front.      .    .      146 

146  (151)     Body  prolonged  posteriorly  into  a  tail-like  process 147 

147  (150)     Body  not  flask-shaped 148 

148  (149)     No  anal  styles;    body  narrow,  elongated,  sometimes  contractile. 

The  border  setae  pushed  in  on  the  ventral  surface. 

Uroleptus  Stein. 
Representative  species Uroleptus  musculus  MUUer  1786. 

Body  slightly  elastic;  tail-like  process  short,  conical.     An- 
-  -   -—^       terior  end  curved  slightly  to  the  left,  the  posterior  to  the 
i:=i:i^^       right.     Frontal  styles  three  or  four.     Length  200  m-     Among 
aquatic  plants. 

Fig.  522.     Uroleptus  musculus.     X  150.      (After  Conn.) 

149  (148)     With  a  row  of  seventeen  anal  styles  upon  the  left  side.     In  other 

respects  hke  Uroleptus Amphisia  Sterki. 

150  (146)     Body  flask-shaped,  otherwise  very  similar  to  Uroleptus. 

Platytrichotus  Stokes. 
Representative  species.     .     Platytrichotus  opisthobolus  Stokes  1886. 

Frontal  styles  five.    Nucleus  single,  posterior.    Contractile 

\acuole  single.      The  posterior  tip  of  the  body  is  changeable 

in  form.     It  may  be  bifid,  truncate,  or  rounded.     Long  hispid 

•^^^^'^^^^''^fuij^^u^^^         bristles  are  developed  from  the  dorsal  surface.     Length  190  /i. 

Among  sphagnum. 

Fig.  523.     Platylrichoius  opisthobolus.      X  200.     (After  Stokes.) 

151  (147)     Body  not  prolonged  into  a  tail-like  process.     Elongated,  rounded  at 

both  ends.     With  two  uninterrupted  rows  of  cilia  on  the 

ventral  surface Holosticha  Wrzesniowski. 

Representative  species Holosticha  vernalis  Stokes  1887. 

Frontal  styles  five  or  six.     Anal  styles  from  five  to  eight, 
TS''^''^*-^*,.,^  usually  branched.      Dorsal  bristles  numerous.      Nuclei  two; 

^^^^■^^^^^^        contractile  vacuole  central.     Length   190  n.     Shallow  pools, 
observed  with  algae. 

Fig.  524.     Uolosticha  vernalis.      X  225.     (After  Conn.) 

152(133)     Ventral  cilia  setae-like,  often  in  interrupted  rows 153 

153(156)     Ventral  setae  in  more  than  one  row 154 


CILIATE   PROTOZOA    (INFUSORIA) 


289 


154  (155) 


Body  elongate-oval,  with  five  to  eight  frontal  styles;  ventral  setae 
usually  arranged  in  two  or  more  rows,  the  inner  rows  having 
but  few  setae.  Anal  styles  five  or  six,  two  of  which  are  near 
the  posterior  border Plciirotricha  Stein. 

Representative  species.  .    .   Pleurolrichalanceolata¥j\\vQr\hcTg\9>T,^. 

Somewhat  resembling  Stylonychia  but  without  caudal  setae  and 
with  anal  styles  arranged  in  two  groups.  Nuclei  two  in  number, 
one  in  front  of  the  apex  of  the  peristome.  Length  250  m-  Among 
algae. 

Fig.  525.     Pleurotriclia  lanceolate.      X112.     (After  Edmondson.) 


155  (154) 


Body  somewhat  rectangular  in  outline  with  slightly  rounded  ends. 
Three  or  four  obHque  rows  of  ventral  setae  running  from 
left  to  right,  and  three  rows  parallel  to  the  peristome  Ijorder. 
Anal  styles  five  or  six.     Border  ciha  uninterrupted. 

Onychodromiis  Stein. 

Representative  species Onychodromiis  grandis  Stein  1859. 

Body  not  flexible.  Frontal  styles  from  sixteen  to 
twenty-eight,  in  three  rows.  Anal  styles  from  five  to 
seven.  Nuclei  usually  four.  Length  100  to  300  ti. 
Onychodromopsis  flexilis  Stokes  differs  from  Stein's  form 
in  having  a  soft,  flexible  body. 


Fig.  526.    Onychodromus  grandis.     x  125.     (After  Conn.) 


156  (153)  Ventral  setae  in  one  obHque  row.  Body  elongate-oval.  Five  or 
six  frontal  styles  and  as  many  anal.  Peristome  triangular, 
curved,  with  an  undulating  membrane. 

Gastrostyla  Engelmann. 
Representative  species.   .    .    .    Gastrostyla  steinii  Engelmann  i86-\ 

Body  evenly  rounded  at  each  extremity.      Three  very 

large  frontal  styles  near  the  border.      Anal  styles  five, 

^    ==^^        i^    ^"   obHque   row,   not    projecting    beyond   the   border. 

Nuclei  four.       Contractile  vacuole  near  the  middle  of  the 

v>\N        body  on  the  left  side.     Length  250  m-     Fresh  water. 

Fig.  527.    Gastrostyla  steinii.     X  125.     (.\fter  Edmondson.) 

157(132)     Ventral  cilia  few,  not  in  rows 158 

158(165)     Not  produced  posteriorly  into  a  tail-hke  process 15Q 

159  (162)     Body  flexible 160 

160  (161)     Border  cilia  uninterrupted.     Narrow,  elliptical,  rounded^  at  both 

ends.     Five  ventral  setae  and  five  anal  styles.     No  caudal 
bristles.     Inner  right  wall  of  peristome  bent  toward  outer 

left  wall Oxytricha  Ehrenberg. 

Representative  species.     .    .    .     Oxytricha  pell ioftelld  MiJUleT  lySe. 

^^^^^^^^^'^'^'^^'^^^^'r^  Marginal  setae  set  well   in  on   the  ventral  surface. 

■-■o'^-Q-;  .'    -^^b^/  .Anal  styles  arising  near  the  iiosterior  lK)rdcr  and  vx- 

'"     '^^*^<^^  tending' nearly  their  entire  length  beyond  it.       Nuclei 

*i;^tf^^!^^P  two.     Contractile  vacuole  on  the  left  side.     Length  So 

^^'^ii^iic--''^     \im\  j.^^  jQQ  ^      Common  in  infusions  and  fresh  water. 

Fig.  528.    Oxytricha  peUionella.     X  335.  Opisthotricha    Kent   resembles   Oxytri<h<i    in    general 

(After  Conn.)  characteristics  but  has  three  caudal  setae. 


290 

i6i  (160) 


162  (159) 

163  (164) 


macn 


FRESH-WATER   BIOLOGY 

Border  cilia  interrupted  at  the  posterior  end.  Frontal  styles, 
eight  or  ten.  Five  ventral  setae  and  five  anal  styles.  No 
caudal  bristles.     Dorsal  hispid  setae  usually  present. 

T  achy  soma  Stokes. 

Representative  species.     .    .    .     Tachysoma  parvistyla  Stokes  1887. 

Body  narrow  anteriorly   forming   a   neck-like  region.     Ten 
frontal  styles.     Marginal  setae  scarcely  projecting  except  pos- 
teriorly.    Dorsal  setae  minute.     Styles  in  this  form  are  very 
^yyyJ;:>'+r^^^^^^         small.     Length  Oo  m-     Shallow  pools  in  early  spring. 

Fig.  529.     Tachysoma  parvistyla.     X  450.     (After  Stokes.) 

Body  not  flexible 163 

With  caudal  setae.  Elongate-oval  in  shape  with  eight  frontal,  five 
ventral  setae,  and  five  anal  styles.  Caudal  setae  usually 
three,  long.  Peristome  triangular,  with  an  undulating  mem- 
brane; the  inner  wall  bent  away  from  the  outer  wall. 

Stylonychia  Stein. 

Representative  species.     .    .    .    Stylonychia  notophora  Stokes  1885. 


Front  border  obliquely  truncate  on  the  left  side.  Peristome 
extending  nearly  to  the  middle  of  the  body.  Caudal  setae 
widely  separated.  Nuclei  two.  Length  120  to  160  m-  Pond 
water. 

Fig.  530.     Stylonychia  notophora.     cv,  contractile  vacuole;  macn,  macro- 
nucleus.      X  300-     (After  Conn.) 


164  (163)     Without  caudal  setae;  with  inner  wall  of  peristome  bent  toward  the 

outer  wall.     Like  Stylonychia  in  other  respects. 

Histrio  Sterki. 
Representative  species Histrio  erethisticus  Stokes  1887. 

Frontal  styles  nine;  anal  styles  five,  stout,  rigid.  Mar- 
ginal setae  uninterrupted.  Length  150/1-  Shallow  pools, 
with  algae. 

Fig.  531.     Histrio  erethisticus.     X  200.     (After  Conn.) 

165  (158)     Produced  posteriorly  into  a  tail-like  process.     Body  flexible,  with 

eight  ventral  setae  and  five  anal  styles  at  the  base  of  the  tail. 

Urosoma  Kowalewsky. 
Representative  species Urosoma  sp. 

Form  doubtful  as  to  species. 

■^^^^^vrr^^^         Fig.  532.     Urosoma  sp.    X  335-  (After  Conn.) 

166  (131)    Border  cilia  few  or  none 167 


CILIATE   PROTOZOA    (INFUSORIA)  291 

167  (168)  No  caudal  setae.  Body  rounded  or  oval,  dorsal  surface  usually 
furrowed.  Peristome  in  the  posterior  region  in  the  left- 
lateral  border,  its  right  border  prolonged  into  a  triangular, 
lip-like  extension.  Usually  three  frontal  styles,  four  or  five 
ventral  setae,  and  five  or  more  anal  styles. 

Aspidisca  Ehrenberg. 
Representative  species Aspidisca  coslataT>\i),}iTdm  i^^i. 


Dorsal    surface    with    five    or    si.x    furrows. 
Length  35  n.      Common  in  infusions. 


Nucleus    band-like. 


Fig.  533.     Aspidisca  costata.     x  500.     (After  Conn.) 


[68  (167) 


me^n 


Caudal  setae  usually  four  in  number.  Body  oval,  with  dorsal 
convex  surface  furrowed.  Peristome  broad,  on  the  left 
side,  extending  backward  to  or  beyond  the  middle  of  the 
body.  Frontal  styles  six  or  eight,  a  few  scattered  ventral 
setae,  and  five  anal  styles Euplotcs  Stein. 

Representative  species Euplotes  char  on  Miiller  1786. 


Frontal  styles  seven;  ventral  setae  three.  Nu- 
cleus band-like.  Length  80  ^.  Pond  water.  Dif- 
fering from  Euplotcs  patella  Ehrenberg  by  its  smaller 
size  and  greater  number  of  frontal  styles. 


Fig.  534.  Euplotes  cliaron.  \'entral  view  and  individual 
in  process  of  division.  a\  contractile  vacuole;  macn, 
macronucleus.      X  300.     (After  Kent.) 


169  (128)     Cilia  usually  limited  to  the  adoral  zone,  sometimes  with  additional 
rings  of  cilia.     Body  cup-like  or  cylindrical. 

Order  Peritricha    .    .      170 

170(193)     No  lorica  present 171 

171  (180)     Without  a  stalk 172 

172  (175)     With  a  permanent  secondary  ring  of  cilia  at   the  posterior  end 

enclosing  an  adhesive  disk 173 

Body  short,  barrel-shaped,  with  the  posterior  end  discoidal,  the 
inner  border  of  which  is  sujiported  by  a  horny  ring,  the 
peripheral  zone  of  which  is  radially  striated  and  denticu- 
late; the  outer  border  surrounded  by  a  wreath  of  cilia. 
Adoral  zone  extends  spirally  around  the  llattened  end. 
Mouth  eccentric.     Parasitic  forms.    .     .      Triihodimi  Stein. 

Representative  species.    .    .    Trichodiiia  pcdicidus  Ehrenberg  1S30. 

Commonly  observed  gliding  up  and  down  on  the  tentacles 
of  fresh-water  Hydra.     Height  of  body  70  m. 

Fig.  53 s.    Tricluidina  pediiulus.    Individuals  adherent  lo  tcnt.icic  of 
Uydra.     X  50.     (After  Kent.) 


173  (174) 


292 


FRESH-WATER   BIOLOGY 


174  (173)     Identical  with  Trichodina,  except  that  the  chitinous  ring  is  not 
denticulate Urccolaria  Stein. 


175(172)     Without  a  permanent  secondary  ring  of  ciha 176 

176  (177)     With  two  rings  of  stiff,  spinous  processes.   .    .    Hastatdla  Erlanger. 
Representative  species Hastatella  radians  Erlanger  1890. 


Fig.  536.    nastalella  radians.     mac«,  macronucleus.     X  500.     (.^fter 
Erlanger.) 


m^n 


177  (176)     Without  rings  of  stiff,  spinous  processes 178 


178  (179)     Posterior  end  elongated,  usually  attached;    peristome  slightly  de- 
veloped.    Ciliated  disk  small.     .    .    .   Scyphidia  Lachmann. 
Representative  species Scyphidia  frotnentellii  Kent  1S8  2. 


Body  truncate  anteriorly;  stalk-like  appendafije 
longitudinally  striated.  Length,  extended,  80  n. 
On  water  snails. 


Fig.  537.    Scyphidia  fromentellii.   ci;,  contractile  vacuole;  n, 
nucleus.     X  2CX3.     (After  Kent.) 


'^  ^ 


179  (178)     Posterior  end  not  elongated;  attached  or  free.     Cylindrical  when 
extended.     Ciliated  disk  small. 

Gerda  Claparede  and  Lachmann. 
Representative  species Gerda  sigmoides  Kellicott  1885. 


Anterior  region  narrowed,  usually  curved.  Surface  finely  striated  trans- 
versely. Nucleus  not  observed.  Length,  extended,  150  m-  Adherent  to 
fresh-water  plants. 


Fig.  538.     Gerda  sigmoides.     x  160.     (After  Kellicott.) 


180(171)     With  a  stalk.    : 181 

181  (186)     Stalk  unbranched 182 


CILIATE   PROTOZOA    (INFUSORIA) 


182  (183)  Stalk  retractile.  Body  bell-shaped,  cuticle  often  ringed.  A  series 
of  strong  cilia  encircle  the  central,  elevated  ciliary  disk. 
Mouth  eccentric  between   the  peristome  and  ciliary  disk. 

Nucleus  band-like,  curved Vorticella  Ehrenijerg. 

Representative  species.    .    .    Vorticella  campanula  Ehrenberg  1838. 


Body  broadly  campanulate,  greatly  dilated  anteriorly,  surface  smooth. 
Stalk  thick,  five  or  six  times  the  length  of  the  body.  Endoplasm  often 
opaque  with  granules.     Length  of  body  150  m.     Pond  water.     Social. 


Fig.  539.     VorHcella  campanula.     X  50.     (.\fter  Kent.) 


183  (182)     Stalk  not  retractile 184 


184  (185)     With  an  operculum.     Body  ellipsoidal  to  ovate;    the  ciliary  disk 
upon  a  stalk,  closing  Kke  a  lid.     Nucleus  short  or  band-like. 

Pyxidiiun  Kent. 
Representative  species Pyxidium  ramosiun  Stokes  1887. 


Body  vasiform,  widest  cehtrally;  surface  smooth.  Ciliary  disk  slightly 
exserted  with  two  circles  of  long  fine  cilia.  Pedicel  very  short.  Length  of 
body  about  100  m-     Pond  water  on  rootlets  of  Lemna. 


Fig.  540.     Pyxidium  ramosum.      X  335.     (After  Conn. 


[85  (184)     Without  an  operculum.     Body  elongate-ovate  with  surface  usu- 
ally transversely  striate,  stalk  short.    .    .   Rhabdostyla  Kent. 
Representative  species R/iabdosiyla  vcnialis  Stokes  1887. 


Body  widest  centrally,  constricted  below  the  ix?ristomc  border.  Ciliary 
circles'two.  Nucleus  band-like.  Length  50 /i.  .\ttach.-.|  t.^  (\rlnM  and 
Cypris  in  early  spring. 

Fig.  541.     Rhabdoslyla  vernalis.     cr,  contractile  vacuole.     X  OOo.    (.-KftiT  ^(tokes.) 


:86  (181)     Stalk  branched i^7 


294 


FRESH-WATER    I^IOLOGY 


187  (190)     Stalk  retractile. 


188  (189)  Zooids  contracting  independently.  Bodies  bell-shaped.  Central 
muscle  interrupted  at  the  union  of  the  stalk  and  the  branch. 
Ciliated  spiral  forming  about  one  and  a  half  circles.  Nu- 
cleus horseshoe-shaped Carchcsium  Ehrenberg. 

Representative  species.  .    .    .       Carchcsium  polypinum  Kent  1882. 


Colonics  often  reachinj?  a  height  of  one-eighth  of  an  inch.  At- 
tached to  the  under  surfaces  of  stones  or  floating  sticks  in  fresh- 
water pools  or  running  streams.  The  colony  may  be  the 
temporary   host   of   Amphileptus   meleagris.     Length   of   zooids 

Some  interesting  work,  has  been  done  on  the  nucleus  of  this 
species  by  Miss  M.  Greenwood.  (The  Journal  of  Physiology, 
Vol.  XX,  pp.  427-454.)  It  was  found  that  the  normal  activity 
causes  a  drain  on  the  organism  which,  if  not  offset  by  sufficient 
repair  due  to  the  lack  of  nutrition,  results  in  the  more  fluid  char- 
acter of  the  macrosomes  of  the  nucleus. 


Fig.  542. 


Carchcsium  polypinum. 
macn.  macronucleus. 


Terminal  branch  with  two  zooids; 
X  300.     (After  Kent.) 


(188)     Zooids  contracting  together.     Bodies  very  similar  to  Carchcsium 
but  central  muscle  continuous,  causing  all  of  the  zooids  to 

contract  together Zocthamnium  Stein. 

Representative  species.     .    .    .     Zocthamnium  adamsi  Stokes  1885. 


Bodies  about  twice  as  long  as  broad,  tapering  to  the 
pedicel;  finely  striated  transversely.  Length  of  zooids 
60  M-  Reported  from  Niagara  River.  Attached  to 
algae. 


Fig.  543.     Zoethamnium 
macronucleus. 


cv,  contractile  vacuole;    macn, 
100.     (After  Stokes.) 


190  (187)     Stalk  not  retractile ,    . 191 


CILIATE   PROTOZOA    (INFUSORIA) 

bell-shaped,  usi 
road.     Stalk  cc 

Representative  species. 


29: 


191  (192)     ^-^--^ben^^haM^^^  transversely  striated;    peristomal  disk 

broad.     Stalk  contaniuig  a  canal  but  no  muscle. 


I?.-     ,■    .       Epistylis  EhrcnheTR. 
J^pislyhs  jlavicans  Ehrcnberg  1830. 


stoI''''ir^Klf'  "".Y  ^'^  [J'«tinP:"ished  by  the  fact  that  the 

ftee-sw,mm,nK    microgamrtes   with    attache      macro™ 
metes  ,s  common.     Length  of  zooids  200  to  U^      \? 

orS'^iteTrciol*"^'  ^'°"-'  ^'^•'  ■"  --inl  -earns 


Fig.  544.    Epistylisflavicans.    macg,  macrogamete-  mice 
microgamete.     x  25.     (After  Kent.)  ^' 


19.  (.91)     ^^^-,^~^^^^  ,,k  ,ot  broad   elevated  a  con- 

Representative  species.  • : : ;  o^.../../.,/.^S:k:'S:. 


asbn?a?teT'"°\^''-  '"'?'^'  'f  *  ""1  ^"''^^^'  ^^out  three  times 
fnlH™  f  -I  -^J  '''"  contracted,  zooids  are  thrown  into  transverse 
n  front  Pr°n^  l"''  bear  longitudinally  plicate,  snout-like  projec  ioTs 
Siln     ■'  ■  ,P™^«P'^f  "1  enclosing  green  corpuscles.     Cil.arv  circles  two 

to  twenf;^'  l?nl'ti'T  h1'"'"^'-  ^"?^'^  '"  ^^^^"^  «^«"P^  o!  from  en 
\JZTl^'  I  .  ^^^  °^  ^°'^>'  ^50  M.  Height  of  colony  2  5  mm  At- 
tached to  plants  m  pond  water.  ' 


Fig.  545.     Opcrciiiaria  plicaltUs.      x  25.     (Aiicr  btokes.> 


^93  (170)     Withalorica. 


10} 


194  (197)     Lorica  gelatinous. 


10- 


296 


FRESH-WATER   BIOLOGY 


195  (196)  Animals  growing  in  clusters,  attached  or  free-floating,  enclosed  in 
a  mucilaginous  jelly.  Zooids  attached  to  a  branching  stalk, 
each  secreting  a  jelly-like  tube  which  may  remain  distinct 
or  fuse  with  its  neighbor  forming  a  jelly  mass.  Zooids 
similar  in  anatomy  to  Vorticella.     Usually  green. 

Ophrydium  Ehrenberg. 
Representative  species.  •.    .   Ophrydium  eichhornii  Ehrenberg  1838. 

Bodies  very  plastic,  finely  striate  transversely.  Clusters  hemispherical,  of 
closely  approximated  individuals.  Some  colonies  may  include  as  many  as  one 
hundred  zooids,  although  this  large  size  is  uncommon. 

Division  of  the  body  has  been  observed  to  take  place  in  a  transverse  direction, 
which  is  a  rare  occurrence  in  this  family. 

The  anterior  portion  swims  away  and  settles  down  to  form  a  new  colony,  or 
probably  conjugates  with  some  fi.\ed  zooid.  Length  of  expanded  zooids  250  to 
500  n.     Fresh  water. 


Fig.  546.     Ophrydium  eichhornii 


a\  contractile  vacuole; 
(After  Kent.) 


I,  macronucleus.     X  $o. 


'  )6  (195) 

197  (194) 

198  (205) 

199  (202) 

200  (201) 


Animals  solitary;  similar  in  other  respects  to  Ophrydium. 

Ophridinopsis  Kent. 

Lorica  chitinous 198 

Lorica  not  decumbent • 199 

Lorica  sessile 200 

Lorica  with  a  hinge-like  valve  that  closes  the  opening  when  the 
body  retracts.  Lorica  elongate,  subcylindrical.  Body 
elongate  with  ciliary  system  as  Vorticella. 

Thuricola  Kent. 

Representative  species Thuricola  valvata  Wright  1858. 


Lorica  four  or  five  times  as  long  as  broad,  with  the  valve  at  some  dis- 
tance from  the  aperture.  Length  of  lorica  i20m-  Fresh  water;  also 
reported  from  salt  water.  In  Thuricolopsis  Stokes  the  lorica  is  provided 
with  a  support  for  the  valve.     Otherwise  as  Thuricola. 


Fig.  547.     Thuricola  valvata.     X  150.     (After  Kent.) 


201  (200)     Lorica  without  a  valve. 
Representative  species. 


Vaginicola  Claparede  and  Lachmann. 
Vaginicola  leptosoma  Stokes  1885. 


Lorica  broadly  vasiform,  twice  as  long  as  broad,  inflated  posteriorly.  Zooid 
elongate,  projecting  one-third  its  length  beyond  the  lorica.  Peristome  twice  as 
broad  as  the  body.  Surface  transversely  striate.  Length  of  lorica  120 /x. 
Pond  water. 

Fig.  548.     Vaginicola  leptosoma.    ct,  contractile  vacuole.     X  no.     (After  Stokes.) 

202  (199)     Lorica  with  a  pedicel 203 


CILIATE   PROTOZOA    (INFUSORIA) 


297 


203  (204)     Without    an  operculum.      Zooid  like  Thuricola;    adherent  to  the 
bottom  of  the  lorica  in  a  sessile  manner  or  united  by  a  con- 
tinuation of  the  supporting  pedicel.    .  Cothurnia  Ehrenlierg. 
Representative  species Cothurnia  plectoslyla  Stokes  1885. 


TTldCn 


Lorica  curved,  two  and  one-half  times  as  long  as  broad,  finely  striate 
longitudinally,  also  with  transverse  markings.  Divided  posteriorly 
into  two  unequal  parts  by  a  curved,  chitinous  partition  to  which  the 
zooid  is  attached.  Zooid  not  protruding  much  beyond  the  aperture 
when  extended;  transversely  striate.  Length  of  lorica  iio/x.  Marsh 
water. 


Fig. 


54Q.     Cothurnia  plectoslyla.     cv 
X  250. 


contractile  vacuole,  macn,  raacronucieus 
(After  Stokes.) 


204  (203)     With  an  operculum  of  chitin  developed  beneath  the  peristome  and 
closing  the  lorica  when  the  animal  is  retracted. 

Pyxicola  Kent. 
Representative  species Pyxicola  cartcri  Kent  1882. 


Lorica  subcylindrical,  three  times  as  long  as  broad,  anterior  margin 
slightly  oblique,  walls  undulate.  Pedicel  very  short.  Zooid  extending 
beyond   the   aperture.     Length  of  lorica  90  /u.     Fresh  water. 


Fig.  550.     Pyxicola  carleri.     X  270.     U^fter  Kent.) 


205  (198)     Lorica  decumbent 206 

206  (207)     Animal  adherent  to  the  posterior  extremity  of  the  lorica. 

Plat y cola  Kent. 
Representative  species Platycola  decumhcns  Kent  1882. 

Lorica  oval,  depressed.  Zooid  extending  considerably 
beyond  the  aperture,  the  exserted  portion  being  at  right 
angles  to  the  portion  within  the  lorica.  Length  of  lonca 
QO  n.     Fresh  water. 

Fig.  551-     Platycola  decumbens.      X  200.     (.After  Kent.) 

207  (206)     Animal  adherent  to  one  side  of  the  lorica  which  often  has  a  valvular 

aperture.     Zooid  adherent  to  the  margin  of  the  aperture. 

Lagenophrys  Stein 
Representative  species.     .    .    .    Lagenophrys  vaginocola 'Sic'm  \^>,\ 

Lorica  elongate  with  two  semilunar,  lip-like  processes  partially  closini:  tin- 
aperture.  The  processes  are  raised  when  the  zooid  is  extcn<lc<l  and  lowcrctl 
when  it  is  retracted.  Zooid  adherent  by  its  narrow  peristome  to  the  ctlgc  of 
the  aperture.  Length  of  lorica  70  m-  Freshwater.  5/y/<j/k-(/ra  Kellicolt  diflcrs 
from  Lagenophrys  in  having  an  erect  lorica  with  a  ^K-dicei. 

Fig.  552.     Lagenophrys  vaginocola.     X  210.     (.\iter  Maupas.) 


!98 


FRESH-WATER   BIOLOGY 


208  (i)     Cilia  present  during  embryonic  stage  only.     Tentacles  in  adult. 

Class  Suctoria    .    .      209 

209  (210)     Tentacles  branched.     Animals  solitary,  sessile,  discoidal,  or  sub- 

spherical,   with   the   sfirface  of   the  integument   indurated. 
Tentacles  flexible,  non-contractile,  finely  perforate  at  their  ex- 
tremities.   Increasing  by  gemmation.    .    Dcndrocometcs '>At'm. 
Representative  species.  Dendfocometes  paradoxus  Sie'm  1851 

Tentacles  equal  in  length  to  the  diameter  of  thh  body, 
usually  five  or  less  in  number.  The  distal  terminations 
of  the  tentacles  are  capable  of  great  expansion  and,  by 
means  of  these,  other  Protozoa  are  captuicd  and  the  pio- 
toplasm  of  their  bodies  absorbed  into  the  body  of  the 
host.  Nucleus  subtriangular.  Diameter  of  body  8c  ^i. 
Fresh  viatei,  sometimes  attached  to  Gammarus  pulcx,  a 
fresh-water  shrimp. 

Fic.  SSZ-     Dcndrccometti  paradoxus.     X  170.      (After  Stein.) 

210(200)     Tentacles  unbranched,  contractile 211 

211  (220)     Without  a  lorica 212 

212(213)  With  a  stalk.  Body  spherical  or  pear-shaped.  Tentacles  knobbed, 
scattered,  or  in  groups.  In  some  species  the  animal  may 
become  detached  from  the  stalk  and  live  a  free  life. 

Podophrya  Ehrenberg. 
Representative  species Podophrya  fixa  ^ixiWQX  !']'&(). 

Stalk  slender  but  rigid.  Tentacles  slender, 
scattered  over  the  surface  of  the  body,  usually 
not  longer  than  the  diameter  of  the  body.  Nu- 
cleus oval,  central.  Contractile  vacuoles  often 
two.  Diameter  of  body  55  m-  Attached  to  aquat- 
ic plants. 

Fig   554.     Podophrya fixa.     Active  individuals.     X  210. 
(After  Conn.)     Cyst.     X  230.     (Alter  Edmondson.) 

213(212)     Without  a  stalk 214 

214  (215)  Forming  colonies.  Animals  fused,  forming  an  erect,  branching 
colony.  Several  colonies  may  be  connected  by  a  creeping 
stolon.     Suctorial,  capitate  tentacles  borne  on  the  ends  of 

the  branches Dendrosoma  Ehrenberg. 

Representative  species.    .    .     Dendrosoma  radians  Ehrenberg  1838. 


Stolon  repent,  giving  rise  to  a  number  of  erect  branches 
tapering  distally,  themselves  often  branched.  Nucleus  ribbon- 
like, ramifying  into  the  branches.  Contractile  vacuoles  nu- 
merous. Height  of  colony  1000  to  2500  n.  Attached  to 
aquatic  plants. 

Fig.  555.     Dendrosoma  radians.     X  30.     (After  Blochmann.) 


215  (214)     Not  forming  colonies 216 


2i6  (217) 

217  (216) 

218  (219) 


219  (2] 


CILIATE   PROTOZOA    (INFUSORIA)  299 

Tentacle  one,  consisting  of   a  single,  movable   anterior  process. 
Parasitic  on  Cyclops Rhyncheta  Zenker. 

Tentacles  numerous 218 

Body  spherical,  never  fixed;    knobbed   tentacles  arising  from  all 

sides Sphaerophrya  Claparede  and  Lachmann. 

Representative  species.  .    .    .     Sphaerophrya  magna  MdiUpdiS  i?>'S>i. 

/:.*■ 

Tentacles  not  exceeding  fifty  in  number:  when  fully  extended, 
equal  in  length  to  the  diameter  of  the  body.  Reproduction  has 
been  observed  to  take  place  by  transverse  division.  Diameter 
of  body  40  ju.     Freshwater. 

Fig.  556.     Sphaerophrya  magna.      X  500.     (After  Conn.) 

Body  irregular;    knobbed  tentacles  arising  from  the  lobes  of  the 

margin  of  the  body.     Attached  by  the  broad,  lower  surface. 

Trichophrya  Claparede  and  Lachmann. 

Representative  species Trichophrya  sinuosa  Stokes  1886. 

Body  flattened  with  lobed  margins.     Usually  not  more  than  five 
\|/^6f  clusters  of   tentacles.      Nucleus  branched.      Contractile  vacuoles 

.3m^^  ,  numerous.     Length  55  m-     Attached  to  aquatic  plants 

\^/\\\\v^  Fig.  557.     Trichophrya  sinuosa.     X  125.     (.\fter  Stokes.) 


220(211)     With  a  lorica 221 

221  (224)     Lorica  sessile ^^^ 

222  (223)     Usually  cup-shaped  or  subspherical ;  tentacles  suctorial,  sometimes 

in  groups Solenophrya  Claparede  and  Lachmann. 

Representative  species Solenophrya  pera  Stokes  1SS5. 

Lorica  irregularly  cubical  or  satchel-shaped,  hyaline,  widest  at  the  base 
of  attachment,  narrowing  anteriorly,  with  the  sides  somewhat  concave. 
Zooid  oval,  not  attached  to  bottom  of  lorica.  Tentacles  arising  from  the 
entire  frontal  border.  Two  individuals  often  in  the  same  lorica.  Height 
of  lorica  40  m-  Width  and  length  nearly  the  same  as  height.  Attached  to 
p.\  aquatic  plants  in  standing  water. 

Fig.  558.    Solenophrya  pera.     X  225.     (After  Stokes.) 

223  (222)     Posterior  end  of  the  body  prolonged  into  a  projection.     Attached 

to  Epistylis.     Two  to  five  long,  simple  tentacles. 

Urnula  Claparede  and  Lachmann. 


300  FRESH-WATER   BIOLOGY 

224  (221)  Lorica  with  a  stalk.  Body  may  or  may  not  fill  the  lorica.  The 
end  of  the  lorica  may  be  open  or  provided  with  slit-like 
openings  through  which  the  tentacles  extend.  Tentacles 
suctorial,  knobbed,  scattered,  or  in  groups. 

Acineta  Ehrenberg. 
Representative  species Acineta  fluviatilis  Stokes  iSSs- 


Lorica  subtriangular,  compressed,  very  delicate,  widest  an- 
teriorly, tapering  to  the  attachment  with  the  stalk.  Stalk 
shorter  than  the  lorica.  Two  anterolateral  openings  for  the 
tentacles.  Zooid  usually  filling  the  lorica.  Length  of  lorica 
40  to  80  n.     Attached  to  aquatic  plants. 

Fig.  559.     Acineta  flmiatilis.     X  3i5-     (After  Stokes.) 


IMPORTANT  REFERENCES  ON  MASTIGOPHORA  AND  INFUSORIA 

See  list  of  general  works  under  Sarcodina,  p.  236;  also  the  following: 
Dangeard,    p.   a.     1902.     Recherches  sur  les  Eugleniens.      Le   Botaniste, 

8:97-357;  4Pl.,  53  figs. 
Kent,  S.     1880-1882.     A  Manual  of  the  Infusoria.     3  vols.     London. 
KoFOiD,   C.   A.     1898.     Plankton   Studies,   II.     Bull.   111.   State   Lab.   Nat. 

Hist.,  5:  273-300;   12  pi. 
1899.     Plankton  Studies,  III.     Bull.  111.  State   Lab.    Nat.  Hist.,   5:419- 

440;   I  pi. 
Palmer,   T.   C.     1905.     Delaware  Valley  Forms  of  Trachelomonas,     Proc. 

Acad.  Nat.  Sci.,  Phila.,  57:  665-675;   i  pi. 
Powers,  J.  H.     1907.     New  Forms  of  Volvox.     Trans.  Amer.  Micr.  Soc. 

27:123-149;   4  pi. 
1908.     Further  Studies  on  Volvox,  with  Descriptions  of  Three  New  Species. 

Trans.  Amer.  Micr.  Soc,  2?)'.  141-176;  4  pi. 
Roux,  J.     1901.     Faune  Infusorienne  des  eaux  stagnantes  des  environs  de 

Geneve,  149  pp.,  8  pL,  4to.,  Geneve. 
Stokes,  A.  C.     1888.     A  Preliminary  Contribution  Toward  a  History  of  the 

Fresh  Water  Infusoria  of  the  United  States.    Jour.  Trenton  Nat.  Hist. 

Soc,  1:71-344;   13  pi. 


CHAPTER   X 
THE    SPONGES   (PORIFERA) 

By  EDWARD  POTTS*  Meadville,  Pa. 

The  zoophytes  or  plant  animals  of  the  old  zoologists  or,  as  they 
are  now  more  correctly  designated,  the  separate  groups  of  sponges 
and  coelenterates,  are  represented  in  the  fresh  waters  of  North 
America  through  a  very  narrow  range  both  of  genera  and  species. 
Sponges  alone  constitute  the  topic  of  this  chapter.  The  student  of 
fresh-water  sponges  must  not  expect  to  find  them  resembling  in  ap- 
pearance the  familiar  forms  of  commerce,  which  in  fact  are  exclu- 
sively of  marine  origin.  Nor  should  he  look  for  shapeless  masses  of 
jelly;  such  may  be  found,  but  they  are  not  sponges.  Yet  as  animal 
organisms,  sponges,  whether  fresh-water  or  marine,  are  essentially 
alike.  Infinitely  variable  in  form  and  external  appearance  and  in 
the  character  and  constituents  of  their  skeletal  structure,  the  vital 
parts  that  have  clothed  them,  or  do  still  clothe  them  if  examined 
in  life,  are  composed  alike  of  protoplasm  or  sarcode.  This  forms 
the  delicate  tissues,  structureless  except  when  viewed  through 
powerful  lenses,  and  builds  up  the  inert  framework  whether  it  con- 
sists of  tough  elastic  fibers,  as  in  the  commercial  sponge,  or  is  the 
fairy-like  structure  of  flint  or  lime  belonging  to  other  sponges 
found  in  the  ocean,  or  forms  skeletons,  as  in  our  fresh-water  forms 
so  far  as  known,  always  of  silex.  The  active  life  work  of  sponges 
it  is  impossible  to  see  with  the  naked  eye  and  very  difficult  to  study 
even  under  the  microscope.  Certain  collared  cells  by  means  ot 
waving  flagella  feed  the  sponge,  reject  intrusive  matter,  and  create 

*  The  death  of  Mr.  Potts  just  after  the  first  manuscript  of  the  chapter  liad  been 
submitted  laid  upon  me  the  duty  of  bringing  it  into  conformity  with  the  other  chapters 
of  the  book  without  his  help.  I  have  endeavored  to  do  this  with  the  least  possible 
change  from  the  original.  To  make  sure  that  no  error  was  committed  in  the  priKcss 
I  secured  the  aid  of  Dr.  N.  Annandale,  Calcutta,  India,  for  whose  kind  assistance  I 
am  deeply  indebted.  For  the  present  form  of  the  key  Mr.  Potts  is  in  no  wise  responsible. 
I  am  also  indebted  to  Professor  Frank  Smith  for  valuable  unpublished  data  in  regard 
to  distribution.  — Henry  B.  Ward. 

301 


302  FRESH-WATER   BIOLOGY 

the  currents  that  traverse  the  canals  of  the  body.  While  the 
action  of  these  fiagella  is  invisible  to  the  unaided  eye,  their  effect 
may  be  seen  if  some  finely  divided  carmine  is  added  to  the  water. 
The  particles  are  sucked  into  the  little  pores  over  the  surface  and 
after  long  wandering,  having  proved  indigestible,  are  ejected  from 
the  larger  orifices. 

The  skeleton  of  these  siliceous  sponges,  the  only  part  that  can  be 
easily  preserved  for  study,  is  composed  of  spicules  or  little  needles 
of  "hydrated  silica  (opal),  averaging  about  one  one-hundredth  of  an 
inch  in  length,  fasciculated  or  bound  together  side  by  side,  but  break- 
ing joints,  to  form  threads  of  considerable  thickness  along  the  princi- 
pal lines  of  the  sponge  growth  but  thinner  in  the  connecting  hnks 
that  make  the  interspaces.  The  binding  material  along  these 
threads  is  not  strong  and  its  composition  is  not  certainly  known. 
The  terminal  spicules  projecting  around  the  sponge  uphold  the 
filmy  dermis  a  little  above  the  firmer  body  of  the  sponge.  Where 
the  larger  channels  unite  to  form  the  efferent  osteoles  the  out- 
flowing currents  stretch  this  dermis  into  little  cylindrical  tubes  or 
towers,  technically  called  chimneys,  with  terminal  openings  through 
which  one  may  often  see  rejected  particles  shot  out  as  from  the 
crater  of  a  volcano. 

A  few  fresh-water  sponges  in  some  situations  seem  to  be  essen- 
tially perennial;  others  die  in  hot  countries  at  the  onset  of  the  sum- 
mer season,  or  among  us  at  the  coming  of  winter,  or  are  broken 
up  by  floods,  floating  ice,  etc.,  so  that  for  a  season  they  disappear 
from  view.  The  ordinary  annual  revival  of  sponge  life,  the  growth 
after  winter  or  after  a  period  of  desiccation,  is  provided  for  by  the 
germination  of  many  seed-like  bodies,  called  gemmules;  these  may 
generally  be  found  when  the  sponge  matures,  fixed  as  a  pavement 
layer  at  the  base  of  the  sponge  or  distributed  amongst  its  tissues. 
The  living  cells  enclosed  in  these  are  protected  by  a  firm  chitinous 
coat  or  shell  that  is  again  surrounded  by  a  crust  composed  of 
minute  air  cells,  which  float  the  gemmules  and  promote  their  distri- 
bution to  distant  places.  A  variety  of  minute  spicules  is  normally 
found  embedded  in  this  crust  as  described  under  individual  species 
in  the  key. 

Whenever  the  favorable  season  arrives,  that  is  in  most  regions 


THE   SPONGES    (PORIFERA)  303 

when  spring  comes  or  when,  in  dry  regions,  the  occasional  floods 
reach  them,  the  gemmules  in  the  pavement  layers  are  supposed  to 
germinate  where  they  were  deposited;  the  floating  kinds,  set  adrift, 
lodge  upon  any  suitable  surface  and  begin  their  seasonal  growth. 
Each  gemmule  is  provided  with  a  foramen,  or  a  foraminal  aperture, 
sometimes  plain,  but  often  more  or  less  tubular,  through  which 
the  growing  cells  usually  escape  by  amoeboid  action  and  appear 
as  a  delicate  creamy  film  surrounding  the  gemmule.     Sometimes, 
however,  they  escape  by  the  rupture  of  the  whole  gemmule.     Where 
this  is  part  of  a  pavement-layer  or  one  of  a  group  of  detached  gem- 
mules  the  escaping  currents  flow  together  as  a  filmy  mass,  sometimes 
rounded  up  like  a  small  pea,  otherwise  as  a  spreading  film  or  Hke 
the  wandering  trail  of  slime  left  by  one  of  the  larger  snails.     The 
appearance  of  the  young  spicules  is  nearly  coincident  with  the 
escape  of  the  cells  and  they  at  once  begin  to  arrange  themselves 
according  to  the  habit  of  the  species,  forming  a  network  over  the 
supporting  surface,  upon  which  is  built  a  superstructure  suggesting 
that   of   our  modern  steel-framed  buildings.     Special   interspaces 
become  the  chambers  fined  with  the  coHared  flagellate  cells  already 
mentioned.     The  action  of  these  flagella  creates  currents  of  water 
flowing  in  through  myriads  of  almost  invisible  pores  in  the  cover- 
ing, bearing  food  particles  to  nourish  the  growing  sponge  and  then 
carrying  off  and  discharging  useless  matter  through  the  larger  canak 
by  the  efferent  osteoles  already  mentioned. 

The  study  of  fresh-water  sponges  should  begin  here  and  foDow 
the  cycle  of  growth  from  gemmule  to  gemmule,  watching,  if  it  be 
possible,  even  the  development  within  their  own  especial  cells  of 
the  various  classes  of  spicules,  observing  in  the  autumn  the  gradual 
gathering  together  of  the  germ  cefis  before  they  are  shrouded  in 
chitin  or  committed  to  the  waters  within  their  floating  crusts. 
Under  favorable  conditions  and  constant  as  well  as  careful  control 
much  of  this  work  may  be  made  independent  of  the  seasons,  after 
germinating  the  fresh  gemmules  in  shallow  glass  dishes  at  home, 
and  in  a  small  way  afford  excellent  opportunity  for  study;  but  it 
will  not  be  found  practicable  to  grow  sponges  in  aquaria  excepting  as 
small  fragments  in  very  large  bodies  of  water  or  in  vessels  in  which 
the  water  is  constantly  or  frequently  renewed. 


304  FRESH-WATER  BIOLOGY 

Those  who  wish  to  gather  specimens  for  their  cabinets  or  design 
to  determine  genera  and  species  must  await  the  maturity  of  the 
various  specimens.  Observation  seems  to  make  it  probable  that 
the  rarer,  filmy  sponges  complete  their  growth  and  mature  their 
gemmules  earher  than  the  more  lusty,  massive  forms.  The  gem- 
mules  of  the  former  have  often  been  seen  in  August  or  September 
resting  in  slender  lines  upon  standing  or  floating  timbers  from 
which  the  rest  of  the  sponge  has  disappeared,  though  the  coarser 
forms  are  frequently  immature  late  in  November.  These  dates 
hold  true  for  the  northern  United  States  generally  and  would  of 
course  vary  in  other  parts  of  the  world;  but  there  are  undoubtedly 
individual  regions  of  extreme  or  atypical  climatic  conditions  within 
our  own  area  where  the  sponge  calendar  when  worked  out  will  show 
a  distinctly  individual  aspect. 

A  hint  as  to  hopeful  localities  for  collecting  may  suffice.  Do  not 
waste  time  in  hunting  along  sluggish  streams  or  in  shallow,  muddy 
ponds,  where,  even  if  the  sponges  start  to  grow,  they  will  soon  be  j 
suffocated  by  gravitating  particles  of  earthy  matter.  A  reserva-  \ 
tion  should  perhaps  be  made  in  favor  of  the  lower  sides  of  floating 
timbers  that  have  long  lain  in  the  water,  since  here  gravity  protects 
instead  of  injures  the  sponges.  Only  one  other  caution  seems  neces- 
sary. As  all  known  fresh-water  sponges  are  siKceous  the  student 
Vill  probably  fail  to  find  them  in  waters  strongly  impregnated  with 
carbonate  of  Hme,  though  they  are  recorded  from  such  places. 

Perfect  drying  is  to  be  recommended.  The  proper  classification 
can  be  as  readily  determined  from  dry  as  from  fresh  sponges  and 
it  is  only  when  a  specimen  has  some  novel  character  or  specific 
form  that  it  is  worth  while  to  preserve  it  in  alcohol.  When  a 
wrapper  is  necessary  for  transportation  or  otherwise,  be  sure  to 
use  soft  paper,  rather  than  cotton  or  sawdust. 

Other  features  having  proved  indeterminate  or  unreliable,  the 
system  is  based  upon  the  shapes  and  positions  of  the  minute  spicules 
found  embedded  in  the  gemmule  crust.  As  these  can  only  be  sat- 
isfactorily seen  when  the  impenetrable  crust  is  made  transparent 
or  removed,  three  microsHdes  from  each  specimen  must  be  pre- 
pared to  determine  the  forms  of  the  skeleton,  the  dermal  or  flesh, 
and  the  gemmule  spicules. 


THE   SPONGES    (PORIFERA)  305 

Provide  a  half  dozen  or  more  short  test  tubes  with  a  stand  made 
by  boring  holes  of  suitable  diameter  in  a  piece  of  inch  board. 
First  make  sure  that  you  have  in  hand  parts  of  the  same  sponge 
only.  Place  in  the  first  tube  a  dozen  or  more  clean  gemmules, 
some  of  them  cut  in  half  with  a  sharp  knife,  and  about  an  equal 
bulk  from  the  remainder  of  the  sponge;  cover  with  a  few  drops  of 
strong  nitric  acid  that  has  been  previously  brought  to  a  boil  in 
another  tube  and  set  aside,  the  purpose  being  to  corrode  away  the 
crust  but  not  the  chitin  of  the  gemmules.  In  a  few  minutes,  when 
most  of  the  gemmules  incline  to  settle  at  the  bottom,  pour  off  the 
acid  into  the  next  tube,  wash  carefully  with  several  lots  of  pure  water, 
replace  it  with  alcohol  and  set  the  tube  aside  to  settle.  Put  into 
the  acid  in  the  second  tube  a  small  quantity  of  all  parts  of  the 
sponge,  adding  more  acid  if  necessary,  and  boil  carefully  over  a 
spirit  lamp  to  thorough  disintegration.  When  that  is  effected  till 
this  tube  also  with  water  and  set  it  aside  to  settle.  The  smaller 
spicules  settle  very  slowly.  It  may  be  well  to  shake  the  tube  a  Httle 
in  order  to  separate  the  darker  particles  from  the  pure  white.  When 
the  mass  has  settled,  carefully  pour  off  the  water  with  the  impuri- 
ties, wash  the  residue  with  fresh  water  and  let  it  stand,  after  which 
a  mount  may  be  made  from  this  tube.  Spread  the  spicules  evenly 
and  not  too  thickly  on  a  slide,  and  let  them  dry  thoroughly  before 
adding  balsam  and  a  cover  glass.  This  amount  ^vill  of  course  fur- 
nish an  epitome  of  the  sponge  but  will  not  show  the  exact  relations 
of  the  minor  spicules  to  the  gemmules.  This  can  only  be  seen  after 
two  or  more  applications  of  alcohol  to  the  first  tube  have  removed 
the  acid  mixture;  to  keep  out  the  air,  cover  with  benzol  until  fully 
ready  for  the  balsam.  Distribute  a  few  of  the  gemmules,  with  some 
spicules,  upon  a  second  slide  and  mount  in  balsam  before  the  air 
penetrates  them.  A  fragment  of  the  dry  filmy  dermis  mounted  in 
balsam  will  determine  the  presence  or  absence  of  dermal  spicules 
and  fix  positively  the  standing  of  the  sponge  according  to  the  key. 

If  all  the  smaller  spicules  distinguished  by  this  process  arc  accr- 
ates,  that  is,  more  or  less  cylindrical,  whether  straight  or  cur\'ed, 
smooth  or  spined,  pointed  or  abruptly  terminated,  the  specimen 
under  examination  may  unhesitatingly  be  placed  in  the  genus  Spon- 
gilla.     All  others,  unless  entirely  novel,  will  show  some  modification 


3o6 


FRESH-WATER    BIOLOGY 


of  the  birotulate  form,  i.e.,  two  little  wheels  or  rotules  connected  by 
a  shaft,  and  on  the  numerous  variations  of  these  parts  depends  the 
position  of  the  species  in  the  key. 

KEY  TO  NORTH  AMERICAN   FRESH-WATER   SPONGES 

I  (12)     Gemmules  with  acerate  spicules  only.  .    .   Spongilla  Lamarck     .    .     2 

SpongilHdae  with  long  spindle-shaped  skeleton  spicules,  macroscleres.  having  pointed  or 
rounded  ends,  and  often  also  with  minute  simple  flesh  spicules,  or  microscleres.  Gemmules 
naked,  or  with  external  air-cell  layer  containing  rhabdi,  or  rod-like  spicules. 


2  (5)     Sponge  branching 

Abnormal  forms  of  S.  lacustris  occur  in  which  there  are  no  branches. 


3  (4)     Flesh  spicules  smooth Spongilla  aspinosa  Potts  1880. 

Sponge  evergreen,  encrusting,  thin,  sending  out  numerous  long, 
slender  waving  branches  from  a  relatively  thick  basal  membrane. 
Gemmules  few,  in  scattered  branches.  Skeleton  spicules  smooth, 
straight  or  slightly  curved,  rather  abruptly  pointed.  Dermal  spic- 
ules minute,  smooth,  straight  or  curved,  slender,  gradually  pointed. 
From  clear  standing  water  in  New  Jersey  and  Virginia. 


Fig.  560.  Spicules  of  Spongilla  aspinosa.  Four  types  of  spicules  figured 
here:  ordinary  skeleton  spicules  abruptly  pointed  at  both  ends;  skeleton 
spicule,  acute  or  rounded  at  one  end;  malformations  of  skeleton  spicules, 
with  processes  at  or  near  one  end;  small  smooth  dermal  spicules;  globular 
or  discoidal  masses  of  sUica  frequently  observed  in  this  species.  X  loo. 
(After  Potts.) 


o\^ 


4  (3)     Flesh  spicules  spined Spongilla  lacustris  (Linnaeus)  1745. 

Branches  cylindrical  or  tapering,  and  rigid.     Prefers  rapidly  running  water.     Very  abun- 
dant.    Gemmules  either  apparently  wanting  or  abundant  throughout  the  sponge,  with  or 
without  a  granular  crust.     Skeleton  spicules  smooth.    Dermal  spicules  pointed  spined  acer- 
ates.      Gemmule  spicules  whether  few  or  many  generally  cylin- 
drical, more  or  less  curved,  rather  sparsely  spined.     From  Boston, 
Mass.,  to  McDonald  Lake,  Alaska,  in  an  infinite  number  of  situa- 
tions and  variety  of  forms.     The  variety  paupercula  Bowerbank, 
made  an  independent  species  Spongilla  paupercula  by  Carter,  "  is 
perhaps  that  one  of  this  group  of  synonyms  about  whose  identity 
with  S.  lacustris  there  may  be  most  hesitation.    Its  character  is  some- 
what anomalous,  as  its  locahty  and  associations  are  peculiar.    Grow- 
ing originalli'  in  the  ponds  and  reservoirs  tributary  to  the  Boston 
Water  supply,  Bailey  wrote  in  1856  that  it  grew  abundantly  in  the 
waterpipes  by  which  the  city  was  supplied  with  water  from  a  small 
Fig  s6i  Skeleton  and  gem-    '^^^•"     ^^^  minute  acerate^  were  said  to  have  been  smooth  which 
mule    spicules   of   Spon-    would  separate  it  clearly  from  S.  lacustris,  but  Potts  was  unable  to 
gilla  lacustris,  var.   mon-    secure  material  from  the  original  locality  which  bore  out  the  con- 
towa.  X 100.  (After  Potts.)     tention. 


5  (2)     Sponge  without  branches 6 


6  (9)     Gemmules  in  layers  or  groups 7 


THE   SPONGES   (PORIFERA) 


307 


7  (8)     Tubules  of  gemmules  turned  upward  or  outward  from  the  groups. 

Spongilla  fragilis   Leidy  1851. 

Sponge  encrusting  in  subcircular  patches,  thin  at  edges,  occasionally  one  or  more  inches 
thick  near  the  middle.  In  the  most  varied  situations,  apparently  preferring  standing  water, 
though  also  in  running  water.  Abundant.  Gemmules  abundant,  primarily  in  one  or  more 
pavement  layers.  Also  in  compact  groups  surrounded  by  a  cellular  parenchyma  charged  with 
subcylindrical  spined  acerates.  Skeleton  spicules  smooth,  slightly  curved,  rather  abruptly 
pointed.    True  dermals  wanting.    Found  in  most  of  the  United  States. 


A  B 

Fig.  562.  Spongilla  fragilis.  A.  Section  of  group  of  gemmules;  a,  curved  foraminal  tubules,  always  out- 
ward; 6,  envelop  with  acerate  spicules.  X  12.  B.  Three  types  of  spicules  figured  here:  skeleton  spicules, 
smooth,  abruptly  pointed;  variable  parenchymal  spicules,  subcylindrical,  subspined:  spined,  spherical 
forms  frequently  seen  throughout  the  species.     X  loo.     (After  Potts.) 

8  (7)     Tubules  of  gemmules  turned  inwards  in  the  groups. 

Spongilla  igloviformis  Potts  1887. 
Sponge  brown,  thin,  encrusting.  Gemmules  in  compact  hemispherical  groups  of  eight  to 
twelve  or  more,  resting  on  the  flat  side,  surrounded  by  a  parenchyma  of  unequal  cells,  chargerl 
with  numerous  coarsely  spined  spicules  nearly  as  long  as  the  rather  few,  less  strongly  spined 
skeleton  spicules.  On  "the  lower  side  of  timbers  in  cedar  swamps,  New  Jersey.  S.  mackayi, 
described  by  Carter  from  Newfoundland,  may  belong  here. 


Fig.  563.  Spongilla  igloviformis.  A.  Lateral  view  of  dome-shaped  group  of  gemmulp.  (Foraminal 
tubules  open  inward  and  are  invisible,)  X  25.  B.  Two  types  of  spicules  figured  here:  skeleton  spicules, 
weakly  spined;  "parenchymal  spicules"  nearly  equally  long,  but  more  spmous.     X  100.     (Alter  t'otts.) 

9  (6)     Gemmules  not  in  layers  or  groups i° 

10(11)     Dermal  spicules  birotulate.    .    .    .     Spongilla  novae-tcrrae  Votts  iSS6. 

Sponge  encrusting,  gemmules  rather  numercnis,  very  large,  crust 
absent  or  inconspicuous.  Skeleton  spicules  relatively  few,  slender, 
gradually  pointed,  smooth  or  microspmed.  Dermal  spicules  very 
abundant,  minute,  birotulate.  Gemmule  spicules  smooth  or  irregu- 
lar, furnished  with  long  spines,  frequently  located  near  the  e.vtremi- 
ties.  Placed  by  some  in  genus  Ephydalia.  tound  only  in  shallow 
water  of  lakes  in  Newfoundland  (4^°  N.  L.). 

Fig.  564.  Spicules  of  Sponiilla  novae-terrac.  Representing  the  slender, 
smooth  or  sparsely  microspmed  skeleton  spicules;  the  dermal  spicules  birot- 
ulates  of  unequal  size;  and  the  spinous  gemmule  spicules.  X  100. 
(After  Potts.) 


V^ 


3o8 


FRESH-WATER   BIOLOGY 


11  (lo)     Dermal  spicules  acerate S pongilla  wagneri  Votts  iSSg. 

Gemmules  abundant.  Skeleton  spicules  long,  robust,  smooth.  Dermal  spicules  very 
numerous.  Gemmule  spicules  spined,  long,  curved.  Spines  most  numerous  at  extremities. 
Recorded  only  from  brackish  water  of  southwestern  Florida. 

No  figure  yet  published. 

12  (i)     Gemmule  spicules  of  birotulate  type,  more  or  less  modified. 

Sub-family  Meyeninae  Vejdovsky  .    .     13 

13  (47)     Apertures  of  gemmules  not  provided  with  filamentous  appendages     14 
14(46)     Rotules  of  gemmule  biro tulates  nearly  equal 15 

15  (37)     Gemmule  birotulates  of  a  single  class 16 

16  (19)     Margins  of  rotules  entire,  i.e.,  smooth,  not  serrate. 

Trochospongilla  Wejdovsky  .   .     17 

17  (18)     Skeleton  spicules  smooth.   .  Trochospongilla  leidyi  (Bowerbank)  1863. 

Sponge  of  a  peculiar  light  gray  or  drab  color,  encrusting  thin,  persistent.  Gemmules  numer- 
ous, each  surrounded  by  a  capsule  of  skeleton  spicules.  Skeleton  spicules  short,  smooth, 
robust.  Dermal  spicules  wanting.  Gemmule  spicules  short,  birotulate,  margins  entire  and 
exflected.  From  Louisiana  as  well  as  original  field  of  discovery  near  Philadelphia.  Generally 
distributed  in  the  Illinois  River  from  the  mouth  to  La  Salle  according  to  F.  Smith. 


Fig.  565.  Trochospongilla  leidyi.  A.  Upper  surface  of  portion  of  a  layer  of  gemmules,  each  of  which  is 
surrounded  by  a  lattice  capsule  (c)  of  spicules  resembling  those  of  the  skeleton;  at  the  summit  an  open 
space  around  the  foramina!  aperture  (a),  more  than  one  being  sometimes  present.  X  so.  B.  Four  types 
of  spicules  figured  here:  smooth  skeleton  spicules,  abruptly  pointed;  same,  with  rounded  terminations; 
short  birotulates  with  entire  margins;  same  with  rotule  twisted  or  exflected;  face  of  rotule;  group  of 
rotules  as  they  appear  upon  the  surface  of  the  gemmules.     X  loo.     (After  Potts.) 

18  (17)     Skeleton  spicules  strongly  spined. 

Trochospongilla  horrida  (Weltner)  1893. 


Sponge  encrusting,  white,  gray,  yellow,  or  brown. 
No  gemmule  spicules  except  birotulates  which  are 
smooth-margined,  low,  small.  Lives  in  standing  or 
flowing  water.  Rare.  F.  Smith  found  one  specimen 
each  in  the  Illinois  River  near  Starved  Rock  and  in  the 
Big  Muddy  River  in  southern  Illinois. 


Fig.  566.  Trochospongilla  horrida.  Spinous  skeleton  spic- 
ules. X  180.  Birotulate  gemmule  spicules.  X400.  (After 
W.  Kiikenthal.) 


THE   SPONGES    (PORIFERA) 


309 


19  (16)     Margins  of  rotules  serrated  or  incised.    .   Ephydatia  Lamouroux.  .  20 

Spongillidae  with  gemmule  spicules  of  the  birotulate  type  that  are  uniform  or  variable  in 
length  but  not  definitely  of  two  classes,  long  and  short,  and  that  have  finely  or  deeply  cut 
margins. 

20  (35,  36)     Dermal  spicules  if  present  neither  birotulate  nor  stellate.    .    .    21 


21  (22)     Rays  and  spines  of  birotulates  subdivided  and  microspincd. 

Ephydatia  subdivisa  (Potts)  1887. 

Sponge  massive,  encrusting,  compact.  Gemmules  few.  Skeleton 
spicules  smooth  or  microspined,  abruptly  pointed.  Birotulates  very 
numerous,  robust,  shafts  frequently  spined;  rays  short  but  subdi- 
vided.    I'^rom  St.  Johns  River  near  Palatka,  Florida. 

Fig.  567.  Spicules  of  Ephydatia  subdivisa.  Three  types  of  spicules  figured 
here:  smooth  and  spined  skeleton  spicules;  long,  massive  geramule  birotu- 
lates, spined  and  subspined;  rotules  of  same.     X  loo.     (After  Potts.) 


22  (21)     Rays  and  spines  of  birotulates  entire 23 


23  (24)     Margins  of  rotules  very  finely  serrate 

0/ 


Ephydatia  millsii  (Potts)  1887, 


Sponge  encrusting.  Gemmules  small.  Skeleton  spicules  nearly 
straight,  slender,  rather  abruptb'  pointed,  entirely  microspined. 
Gemmule  birotulates  very  numerous,  very  symmetrical,  their  shafts 
usually  smooth.  Rotules  sometimes  microspined.  From  Sherwood 
Lake,  near  Deland,  Florida. 


Fig.  568.  Spicules  oi  Ephydatia  millsii.  Three  tjTDCS  of  spicules  figured 
here:  microspined  skeleton  spicule;  mature  gemmule  birotulates  with  smooth 
shafts;  probably  immature  forms  with  less  notching  on  the  rotules;  face 
of  rotulates  lacinulate  or  delicately  notched,  and  without  rays.  X  loo. 
(After  Potts  J 


24(23)  Margins  of  rotules  coarsely  dentate 25 

25  (32)  Length  of  birotulates  not  more  than  twice  the  diameter  of  rottiles.   .  26 

26  (31)  Shafts  of  birotulates  generally  smooth 27 

27  (30)  Skeleton  spicules  smooth 28 


28  (29)     Shafts  of  birotulates  much  longer  than  diameter  of  rotules. 

Ephydatia  Jul  id!  His  (auctorum) . 

Sponge  sessile,  massive,  rarely  throwing  out  short  branches  an  inch  or  less  in  length.  Pre- 
fers standing  water.  No  vesicular  cells  in  parenchyma.  Gemmules  numerous  throughout. 
Skeleton  spicules  smooth.  Dermal  spicules  wanting.  Rotules  of  gemmule  spicules  not  deeply 
indented.  Numerous  varieties  the  occurrence  of  which  in  North  America  has  not  been  accu- 
rately recorded.  The  form  which  Potts  describes  as  present  generally  throughout  the  eastern 
and  middle  United  States  is  declared  by  Weltner  to  be  Ephvdatia  miUleri,  the  secon.l  following 
species.  The  true  E.flmiatilis  is  found  in  Michigan  and  Illinois,  and  is  fairly  common  though 
not  so  abundant  as  E.  mulleri  {fide  F.  Smith). 


3IO 


FRESH-WATER   BIOLOGY 


29  (28)     Shafts  of  birotulates  slightly  if  any  longer  than  diameter  of  rotules. 

Ephydatia  japonica  (Hilgendorf)  1882. 

Much  like  E.  fluinalUis.  Dermal  spicules  wanting.  Birotulates  with  smooth  shaft,  short, 
never  forming  more  than  a  single  layer  on  the  gemmule.  Rotules  deeply  indented.  Gem- 
mule  with  short,  straight,  broad,  very  delicate  foraminal  tubule.  In  Potomac  River,  near 
Washington,  D.  C. 


Fig.  569.     Ephydatia  japonica. 


% 


H 


^    ^      ^^  . 


Gemmule,  X  i8;  birotulates,  X  120;  skeieton'spicules,  X  120. 
(After  Annandale.) 


30  (27)     Skeleton  spicules  microspined  except  at  tips. 

Ephydatia  miilleri  (Lieberkiihn)  1856. 

Sponge  cushionlike,  rarely  branched.  Vesicular- cells  abundant 
in  the  parenchyma.  Dermal  spicules  wanting.  Shafts  of  gemmule 
birotulates  not,  or  barely,  longer  than  diameter  of  rotules.  Rotules 
deeply  indented.  Eastern  and  Central  United  States;  Nova  Scotia; 
Newfoundland;  Vancouver  Island.  Found  by  F.  Smith  at  Douglas 
Lake,  Mich.,  and  Tolland,  Col. 

Fig.  570.  S'^\cn\t?,oi  Ephydatia  miilleri.  Three  types  of  spicules  figured 
here:  skeleton  spicules,  X  120;  birotulate  gemmule  spicules;  same  mal- 
formed; group  of  rotulae;  single  rotules  showing  an  ordinary  distribution  of 
the  rays.     X  250.     (After  Potts.) 


31   (26) 


Shafts  of  birotulates  with  enormous  spines. 

Ephydatia  rohnsta  (Potts)  li 


Sponge  massive,  encru.sting,  thin.  Gemmules  scarce.  Skeleton 
spicules  pointed,  smooth.  Birotulates  large,  generally  malformed. 
Shafts  abounding  in  spines  as  long  as  rays  of  the  rotules.  Collected 
near  Susan ville,  California.    Perhaps  only  a  variety  of  E.  fluvialilis. 


Fig.  571.  Spicules  oi  Ephydatia  robusta.  Three  types  of  spicules  figured 
here:  smooth  skeleton  spicules;  coarsely  spined  gemmule  birotulates;  single 
rotules;  exceedingly  misshapen  forms.     X  100.     (After  Potts.) 


32  (25)     Length  of  birotulates  more  than  twice  the  diameter  of  the  rotules. 


33 


33  (34)     Birotulates  two  or  three  times  longer  than  the  diameter  of  the  rot- 
ules  Ephydatia  subtilis  Weltner  1895. 

Sponge  thin,  encrusting.  Skeleton  needles  extremely  slender,  scantily  covered  with  short 
spines.  Dermal  spicules  wanting.  Gemmules  small,  spherical;  foramen  a  simple  pore,  or  a 
very  short  tube.  Birotulates  delicate,  slender,  of  variable  length;  shaft  thin,  smooth,  long. 
Rotules  small,  split  nearly  to  the  center,  with  10  to  20  blunt  rays.     Kissimee  Lake,  Florida. 

No  figure  yet  published. 


THE   SPONGES    (PORIFERA)  '  ^jj 

34  (33)     Birotulates  many  times  longer  than  diameter  of  rotules. 

Ephydatia  crater ijor mis  (Potts)  1882. 

Sponge  encrusting,  thin.     Gemmules  small,  white  very  numern.,..      Pro      1  ,  ' 

mules  extremely   thick,   the  foraminal   tubes  in  a  Vr'?f?rZT  M  P^anular  crust  of  gem- 

which  may  be  the  same  as  this  species     The  d^sprfSinn  "  '/     ^  ' 
ulates^w.th  short  hooked  ra?s;  suppSd^i^ii'  K"  T^'' ^Mill 


35  (20,  36)     Dermal  spicules,  minute  birotulates. 

Ephydatia  everetti  (Mills) 


[884. 


36  (20, 


Sponge  green  consisting  entirely  of  slender  filaments  little  more 
than  a  sixteenth  of  an  inch  in  diameter.  Gemmules  few  but  ^?u 
smnofh^'n^'^  a  thick  crust.  Skeleton  spicules  slender!  cyHndrkd' 
S?  I^erma  spicules,  minute  birotulates  with  slender  cyhndncai 
shafts  and  cap-like  rotules  notched  into  five  or  six  hooks  GemmS 
formed'oTfi"''-"  '^^-  '^""^-^^''^  ^^afts  smooth  and  blender; To^ules 
iTr  rA  K-  ^^'^^  ^''''^\'  ^^'^"^ved.  acuminate  hooks.  In  cdd 
water,  Berkshire  County,  Mass.,  and  Nova  Scotia. 

u  ^^^"  ^^^-  u  Spicules  of  Ephydatia  everetti.     Four  tynes  of  snirnlp.;  f,cn,r.A 
formed  of  hooked  rays;  minute  dermal  birotulates.     X  100      (After  Potts  ) 

35)     Dermal  spicules  stellate      Dosilia  Grv^y. 

Only  species  yet  reported  m  the  United  States. 

Dosilia  palmer i  (Potts)  1885. 
Sponge  massive,  subspherical,  lobate.  Skeleton  spicules  spar«;elv 
microspined,  curved,  gradually  pointed.  Dermal  spicules  star- 
shaped,  consisting  of  a  variable  number  of  arms  of  various  lengths 
radiating  froni  a  large  smooth  globular  body;  arms  spined  through- 
out. Gemmule  birotulates  with  long  spined  shafts,  rotules  notched 
i^rom  Colorado  River,  60  miles  below  Fort  Yuma,  attached  to 
pendent  branches  flooded  bv  spring  freshets.  •iii'icnea  to 

In  the  opinion  of  Annandale,  Potts'  var.  pdmeri  is  a  different 
species  from  Carter  s  /^/wm^^o  from  India.  He  has  seen  types  of 
both  and  is  confident  both  belong  to  DosUia 


Spicules  oi  Dosilia  palmeri.     Five  types  of  spicules  figured 

lule 


rotules  of  same,  irregularly  notched;  substellate  dermal  spicules;  imperfect 
Xi^      (ASerPottsT      ^'''°  '''^''   amorphous  " Scotch  terrier  '  forms. 


37  (15)     Gemmule  birotulates  of  two  distinct  classes t^^ 

38(41)     Dermal  spicules  stellate Aster omeycn ia  Xnus^udviXc.    .     39 

thf?o?m  of^antSerl!"''^'''^^^  ^^"'"'"''  'P^'"'"'  ^^  '^°  ^^'''"'^  ^^^^  ^°^  ^'^^  microsderesin 


312 


FRESH-WATER   BIOLOGY 


39  (40)     Terminal  spines  of  longer  gemmule  spicules  with  a  simple  curve. 

Asteromeyenia  plumosa  (Weltner)  1895. 

Sponge  massive,  though  brittle  and  friable. 
Skeleton  spicules  slender,  smooth,  sharply  pointed 
at  both  ends,  nearly  straight.  Shaft  of  long  birot- 
ulates  almost  smooth,  slender,  straight;  rotules 
a  circle  of  curved  hooks,  joined  at  the  base. 
Short  birotulates  with  stouter  shafts,  profusely, 
irregularly,  and  strongly  spined;  rotules  not  mark- 
edly convex  in  profile,  irregularly,  narrowly,  and 
deeply  serrated.  Free  spicules  very  minute, 
abundant,  resembling  those  of  Dosilia.  Gem- 
mules  large,  spherical,  with  single,  very  small 
aperture  having  short,  straight  foraminal  tubule. 
From  Pinto  Creek,  Kinney  County,  Tex.,  and 
Shreveport,  La.;  one  specimen  measured  29  X 
25  cm. 


Fig.  575.  Asteromyenia  plumosa.  ^ ,  gemmule  show- 
ing aperture  in  center,  X  35 ;  ^.  short  birotulates,  X  1 20; 
C,  long  birotulates,  X  120;  Z),  free  microscleres.  X  120; 
£,  skeleton  spicule,  X  120.      (After  Annandale.) 


40  (39)     Terminal  spines  of  longer  gemmule  spicules  distinctly  recurved. 

Asteromeyenia  radiospiculata  (Mills)  if 


Resembles  A.  plumosa.  In  profile  the  rays  of  the  longer 
gemmule  spicule  have  almost  the  form  of  a  J.  Ohio  and  Illi- 
nois. At  Granite  City,  111.,  specimens  were  taken  from  settling 
tanks  of  the  city  water  works,  measuring  42  x  12x8  cm. 


Fig. 576. 
mount.) 


Spicules  ot  Asteromeyenia  radiospiculata.     X  100.    (From 


41  (38)     Dermal  spicules  acerate  if  present. 


Heteromeyenia  Potts   .    .42 


SpongilHdae  producing  gemmules  with  birotulate  spicules  of  two  distinct  classes,  long  and 
short.     Margins  of  rotules  not  smooth  but  dentate  or  incised. 


42  (43)     Rotules  of  gemmule  spicules  of  smaller  class  finely  serrated. 

Heteromeyenia  ryderi  Potts 


.2. 


Sponge  massive,  often  hemispherical.  Gemmules  numerous,  crust 
thick,  foramina  short  and  inconspicuous.  Skeleton  spicules  grad- 
ually pointed,  entirely  spined  except  at  the  tips.  Dermal  spicules 
wanting.  Shafts  of  long  birotulates  spined,  rotules  of  three  to  six 
short  recurved  hooks,  sometimes  umbonate.  Rotules  of  small  birot- 
ulates nearly  as  great  in  diameter  as  the  length  of  their  shafts. 
Shafts  smooth  or  with  few  spines.  Shallow  flowing  water,  Florida 
to  Nova  Scotia,  and  inland  at  least  as  far  as  Iowa. 

Fig.  577.  Spicules  of  Heteromeyenia  ryderi.  Four  types  of  spicules 
figured  here:  skeleton  spicule;  long  gemmule  birotulates.  hooked  and 
spined;  short  birotulates;  surface  of  rotules,  margins  lacinulate,  surface 
microspined  or  granulated;  spherical  amorphous  spicule.  X  loo.  (After 
Potts.) 


43  (42)     Rotules  of  gemmule  spicules  of  small  class  coarsely  serrate. 


44 


THE   SPONGES    (PORIFERA) 


313 


44  (45)     Rotules  of  gemmule  spicules  of  small  class  regular  mushroom-shaped, 
shafts  usually  smooth.   .  Heteromeyeniarepens  Potts  iSSo. 

Sponge  encrusting,  thin.  Gemmules  not  abundant.  Skeleton 
spicules  rather  slender,  sparsely  microspined,  gradually  pointed 
Dermal  spicules  nearly  straight,  entirely  spined.  Gemmule  birotu- 
lates  of  longer  class  comparatively  few;  shafts,  smooth  or  with  one 
or  a  few  conspicuous  spines  often  irregularly  bent.  Rotules  dome- 
shaped,  rays  incurved  like  fish  hooks.  Small  birotulates  very  nu- 
merous, about  two-thirds  the  length  of  the  large  ones  Quiet 
almost  stagnant  water,  New  Jersey,  Pennsylvania,  and  Michigan.  ' 

Fig  578.  Spicules  of  E eteromeyenia  repens.  Five  types  of  spicules 
figured  here:  microspined  skeleton  spicules;  gemmule  birotulates  of  the 
longer  class,  with  recurved  hooked  rays;  birotulates  of  the  shorter  class 
with  less  pronounced  rays;  rotules  of  same;  small  dermal  spicules,  coarsely 
spined;  amorphous  spicule.     X  100.     (After  Potts  ) 


45  (44)     Rotules  of  gemmule  spicules  of  small  class  very  irregular,  shafts 
abundantly  spined.     Heieromeyenia  argyrosperma  Potts  1880. 

Sponge  minute,  encrusting,  gray.  Gemmules  abundant  and 
large.  Foraminal  tubules  somewhat  prolonged.  Skeleton  spicules 
rather  slender,  cylindrical,  abruptly  pointed,  sparsely  spined 
Dermal  spicules  apparently  wanting.  Shafts  of  long  birotulates 
sparsely  spined.  Rays  of  rotules  few,  long,  stout,  and  clawlike 
Short  birotulates  much  smaller,  abundantly  spined.  From  Penn- 
sylvania, New  Jersey,  New  England  States,  and  Nova  Scotia 
Found  by  F.  Smith  at  Douglas  Lake,  Mich. 

Fig.  57g.  Spicules  of  H eteromeyenia  argyrosperma.  Three  types  of 
spicules  figured  here:  sparsely  microspined  skeleton  spicules;  gemmule 
birotulates  of  the  longer  class  with  one  to  three  hooked  rays;  spined  birot- 
ulates of  the  shorter  class.     X  100.     (After  Potts.) 


46  (14)     Rotules  of  gemmule  spicules  unequal,  the  proximal  being  larger. 

Tubella  Carter. 
Only  North  American  species  known. 

Tubella  pennsylvanica  Potts  1882. 

Sponge  minute,  encrusting,  on  stones  or  timbers  in  shallow  water. 
Gemmules  very  numerous,  small.  Skeleton  spicules  very  variable 
in  length  and  curvature,  entirely  spined;  spines  large,  conical.  Der- 
mal spicules  wanting.  Birotulates  of  gemmules  numerous  with  a 
large  rotule  next  to  the  coat  and  a  small  distal  rotule,  varying  from 
the  diameter  of  the  shaft  to  that  of  the  pro.^imal  rotule.  Margin  of 
large  rotule  usually  entire  but  margin  of  small  often  angular  and 
notched.  Shaft  smooth.  Averse  to  light  and  found  as  a  rule  under 
stones  and  roots.  Eastern  United  States  generally.  Found  by  F 
Smith  at  Rhinelander,  Wis.,  and  Douglas  Lake,  Mich. 

Fig.  580.  Spicules  of  Tubella  pennsylvanica.  Two  types  of  spicuks 
figured  here:  spined  skeleton  spicules;  gemmule  "inaequibirotulates."  or 
trumpet-shaped  spicules;  group  of  rotules  seen  from  above,  showing  the 
relative  sizes  of  the  rotules;  surface  of  single  large  rotule.  X  loo.  (.•\fter 
Potts.) 


47  (13)     Apertures  of  gemmules  prolonged  and  divided  into  filamentous  ap- 
pendages  Carter  ins  Potts  .    .   4S 

Gemmules  possess  a  long  foraminal  tubule,  the  outer  end  of  which  carries  an  irregularly 
lobed  disc  or  is  provided  with  long  filaments.  Not  recognized  as  a  separate  genus  by  some 
recent  authors  (see  Annandale,  1909),  but  distributed  among  the  preceding  genera. 


314 


FRESH-WATER   BIOLOGY 


48  (49,  50)     Foraminal  tubule  very  long  and  slender,  tendrils  short,  irregu- 
larly waving C ar terius  tubisperma  MiWs  iSSi. 

Sponge  massive.  Gemmules  numerous.  Length  of  foraminal  tubule  one-half  to  once  diam- 
eter of  gemmule.  Skeleton  spicules  rather  slender,  gradually  pointed,  sparsely  spined.  Der- 
mal spicules  long,  slender,  entirely  spined.  Gemmule  birotulates  abundant,  irregular  in  length, 
suggesting  genus  Ueteromeyenia,  shaft  smooth  or  with  one  or  more  spines,  rotules  arched,  rays 
numerous,  long,  incurved.  Assigned  by  Annandale  to  genus  Heteromeyenia.  In  Niagara  River, 
N.  Y.,  Massachusetts,  and  Michigan. 


Fig.  581.  Carierius  tubisperma.  A.  Partial  section  of  gemmule;  (a),  Foraminal  aperture  prolonged 
into  a  long  tubule  flaring  and  funnel-shaped  at  its  extremity  and  divided  into  several  short  tendrils  {d) 
or  cirrous  appendages,  (b) .  birotulate  spicules.  X  50.  (After  Potts.)  B.  Three  types  of  spicules  figured 
here:  skeleton  spicules;  gemmule  birotulates;  face  of  rotule;  long  spined  slender  dermal  acerates.  X  100. 
(After  Potts.) 


49  (48,  50)     Foraminal  tubule  shorter;    tendrils,  one  or  two,  enveloping  the 
tubule C  ar  terius  latitenta  Fotts  iSSi. 

Sponge  often  encrusting  stones  in  rapidly  running  water.  Gemmules  numerous.  Cirrous  ap- 
pendages at  first  flat  and  ribbon-like,  becoming  slender  and  rounded,  and  occasionally  subdivid- 
ing. Skeleton  spicules  smooth:  or  sparsely  microspined,  gradually  pointed.  Dermal  spicules 
long,  entirely  spined.  Birotulates  stout,  shafts  with  numerous  long  pointed  spines.  Rays  of 
rotules  deeply  cut  and  sometimes  recurved.  Annandale  believes  this  and  the  following  species 
should  be  assigned  to  Ephydatia.    In  Pennsylvania,  western  New  York,  and  Illinois  River. 


Fig.  582.  Carterius  latitenia.  A.  Partial  section  of  gemmule;  (a),  foraminal  tubule  short;  (6),  birotu- 
late spicules;  {d),  one  or  two  long  and  broad,  ribbon-like  cirrous  appendages.  X  3°-  (After  Potts.)  B. 
Three  tyjies  of  spicules  figured  here:  skeleton  spicules;  gemmule  birotulates  vanable  m  length;  face  ol 
rotule;  spined  dermals.     Xioo.     (After  Potts.) 


THE   SPONGES   (PORIFERA) 


315 


50  (48,  49)     Foraminal  tubule  still  shorter;    tendrils,  three  to  five,  very  long 
and  slender Carterius  tenosperma  Potts  1880. 

Sponge  forming  irregular  masses  creeping  upon  and  around  water  plants  and  roots,  less  fre- 
quently encrusting  stones.  Gemmules  rather  numerous.  Foraminal  tubules  about  one  fourth 
the  diameter  of  the  gemmules.  Tendrils  as  much  as  half  an  inch  long.  Skeleton  spicules  slen- 
der, very  sparsely  microspined.  gradually  pointed.  Dermal  spicules  slender,  nearly  straight, 
entirely  spined.  Birotulates  with  cylindrical  shafts,  abundantly  spined,  rotules  often  irregular. 
New  Jersey  and  Eastern  Pennsylvania. 


Fig.  583.  Carterius  tenosperma.  A.  Section  of  gemmule,  (a),  short  tubule;  (d) ,  long,  slender  cirrous 
appendages.  X35-  B.  Three  types  of  spicules:  skeleton  spicules;  spined  gemmule  birotulates  with 
burr-like  rotules;  ends  of  same;  long,  spinous,  acerate  dermal  spicules.     X  lOO.     (After  Potts.) 


IMPORTANT   REFERENCES    ON   FRESH-WATER   SPONGES 

Annandale,  N.     1909.     Report  on  a  Collection  of  Fresh-water  Sponges  from 
Japan.     Annot.  Zool.  Japon.,  7:    105-112,  pi.  2. 
1909a.     Fresh- water  Sponges  in  the  Collection  of  the  United  States  Na- 
tional Museum.     Part  II.     Specimens  from  North  and  South  America. 
Proc.  U.  S.  Nat.  Mus.,  37:  401-406. 

1910.  Fresh-water  Sponges  in  the  Collection  of  the  United  States  National 
Museum.  Part  IV.  Note  on  the  Fresh-water  Sponge  Ephydatia  japon ica, 
and  its  Allies.     Proc.  U.  S.  Nat.  Mus.,  38:  649-650. 

191 1.  Fresh-water  Sponges  in  the  Collection  of  the  United  States  National 
Museum.  Part  V.  A  New  Genus  proposed,  with  Eeteromeyenia  radio- 
spicidata  Mills  as  Type.     Proc.  U.  S.  Nat,  Mus.,  40:  593-594. 

1911a.     Fresh-water  Sponges,  Hydroids  and  Polyzoa.    Fauna  British  India. 
251  pp.,  5  pi. 
Carter,  H.  J.     1881.     History  and  Classification  of  the  Known  Species  of 

Spongilla.     Ann.  Mag.  Nat.  Hist.,  (5),  7:  77-107,  pi.  5-6. 
Potts,  Edward.     1883.     Our  Fresh-water  Sponges.     Amer.  Nat.,  17:  1203-6. 
1887.     Fresh-water  Sponges;  a  Monograph.     Proc.  Acad.  Nat.  Sci.,  Phila., 

39:  158-279,  pi.  5-12. 
1890.     Fresh- water   Sponges.      Microscope,    10:    140-143,    1 61-163,    193- 
196,  257-263,  307-310;  pi.  5-6. 
Weltner,  W.     1895.     Spongillidenstudien  III.     Katalog  und  Verbreitung  der 
bekannten  Susswasserchwamme.  Arch.  f.  Naturges.,  (pt.  I),  61:  1 14-144. 


CHAPTER  XI 

HYDRA    AND    OTHER    FRESH-WATER 
HYDROZOA 

By   frank    smith 

Professor  of  Zoology  and  Curator  of  the  Museum,  University  of  Illinois 

The  student  of  the  animal  life  of  the  sea  is  continually  in 
contact  with  a  great  variety  of  organisms  which  have  radial  sym- 
metry and  are  often  striking  in  appearance,  diversity,  and  abun- 
dance. These  were  formerly  included  in  a  great  group,  Radiata, 
but  are  now  separated  into  two  very  distinct  branches  (phyla), 
the  Coelenterata  and  Echinodermata.  The  latter  phylum,  which 
includes  the  well-known  starfishes  and  sea  urchins,  is  wholly  un- 
represented in  fresh  water,  while  the  former,  which  includes  the 
hydroids,  jellyfishes,  and  corals,  with  thousands  of  species  in  the 
seas  of  to-day,  has  in  fresh  water  scarcely  a  dozen  species  and 
these  are  relatively  insignificant  in  appearance.  The  fresh-water 
Coelenterata  are  all  included  in  the  class  Hydrozoa,  and  hydra  is 
the  only  one  which  is  abundant,  widely  distributed,  and  well 
known  to  the  ordinary  student  of  zoology.  Because  of  its  abun- 
dance it  is  the  type  form  commonly  used  in  zoology  classes  as  an 
introduction  to  a  knowledge  of  the  phylum. 

Among  the  more  obvious  structural  or  morphological  characters 
of  hydra  is  the  sac-like  body  with  the  capacious  chamber  which 
is  at  the  same  time  body  cavity  and  digestive  cavity  and  of  which 
the  mouth  is  the  only  opening  to  the  exterior.  The  animal  is 
attached  by  one  end  and  at  the  other  shows  the  mouth  surrounded 
by  a  circle  of  tentacles  which  are  evaginations  of  the  body  wall 
and  are  hollow,  their  cavities  being  continuous  with  the  digestive 
cavity.  The  body  wall  as  well  as  that  of  the  tentacles  is  com- 
posed of  two  cellular  layers,  the  ectoderm  and  entoderm,  sep- 
arated by  a  thin,  noncellular  mesogloea  and  bounded  externally 
by  a  deUcate  cuticula.  In  some  species  there  is  an  obvious  dis- 
tinction between  an  adoral  part  of  greater  diameter  and  more 

316 


HYDRA   AND    OTHER    FRESH-WATER    HYDROZOA  317 

granular  opaque  entoderm,  and  a  narrowed  paler  aboral  part 
which  is  termed  the  stalk.  In  other  species  designated  in  the 
key  as  "  not  stalked,"  there  is-  no  clearly  marked  division  into 
such  regions.  Highly  contractile  fibers  formed  by  certain  cells  in 
both  ectoderm  and  entoderm  may  bring  about  either  a  great 
elongation  of  the  body  and  tentacles  to  thread-like  proportions  or 
their  contraction  to  an  almost  globular  form.  Certain  kinds  of 
ectoderm  cells,  which  are  most  abundant  in  the  adoral  half  of  the 
body,  especially  in  the  tentacles,  give  rise  to  the  characteristic  ne- 
matocysts  or  ^'  nettling  cells  "  of  difTercnt  shapes  and  sizes.  These 
contain  a  fluid  secretion  which  passes  out  through  a  thread-like 
extension  of  the  sac  wall,  that  is  forced  out  when  the  cell  is  stimu- 
lated. The  combined  action  of  a  number  of  these  nematocysts 
on  the  small  organisms  encountering  them  results  in  the  loss  of 
activity  or  even  death  of  the  organisms  and  so  permits  their  cap- 
ture and  appropriation  as  food  by  the  hydra, 

Spermaries  and  ovaries  develop  in  the  ectoderm  layer  and  at  a 
time  of  year  which  seems  to  be  fairly  constant  for  a  given  species 
but  differs  in  different  species.  After  fertilization  the  ovum  passes 
through  the  early  stages  of  development  while  still  in  the  ovary 
and  becomes  enclosed  by  a  chitinous  envelop  which  has  a  charac- 
teristic shape  and  surface  for  each  species.  This  en\elop  which 
often  is  spiny  is  referred  to  in  the  key  as  the  embryonic,  chitinous 
membrane.  In  some  species  the  embryos  are  freed  from  the  parent 
organism  and  drop  to  the  bottom,  while  in  others  they  are  fastened 
by  the  parent  to  the  substratum  to  which  it  adheres.  The  develop- 
ment is  direct.  In  one  species  {Hydra  oligactis)  the  individuals  are 
said  to  be  of  separate  sexes,  or  dioecious,  but  in  others  hermaphro- 
ditism prevails.  Asexual  reproduction  by  budding  is  the  preva- 
lent mode  of  multipHcation  and  very  rarely  the  formation  of  two 
individuals  by  a  process  of  fission  has  been  observed. 

Hydra  has  long  been  an  object  of  interest  and  experiment  because 
of  its  notable  powers  of  regeneration  and  form  regulation  and  there 
is  now  an  extensive  literature  dealing  with  these  phenomena. 

Hydra  individuals  ordinarily  maintain  an  independent  existence 
but  in  various  related  groups  colonies  which  often  include  many 
individuals  arise  by  asexual  reproduction.     In  some  such  colonies, 


3l8  FRESH- WATER    BIOLOGY 

besides  hydra-like  forms  or  hydranths,  another  type  of  individuals 
is  produced  which  become  medusae  and  separate  from  the  colony 
as  free-swimming  forms  that  develop  germ  cells  which  in  turn  pro- 
duce a  generation  of  individuals  of  the  hydranth  type.  In  other 
colonial  forms  the  germ  cells  are  formed  by  individuals  that  re- 
main as  members  of  the  colony.  All  the  species  of  Hydrozoa 
which  have  a  complex  colonial  organization  are  with  one  exception 
marine. 

In  the  fresh-water  colonial  hydroid  Cordylophora,  many  of  the 
individuals  or  zooids  are  nutritive  and  provide  food  for  the  colony 
and  by  budding  increase  its  size  while  other  individuals  form  germ 
cells;  there  are  no  medusae  formed.  Among  the  obvious  structural 
features  in  which  this  form  differs  from  hydra  are  the  following: 
the  tentacles  are  not  hollow  but  the  entoderm  forms  a  core  of  large 
cells  which  occupies  all  the  space  enclosed  by  the  ectoderm  and 
mesogloea;  the  tentacles  are  more  numerous  than  in  hydra  and  are 
irregularly  distributed;  the  cuticula  is  thick  and  forms  a  support- 
ing skeleton  for  the  colony. 

Four  genera  of  fresh-water  Hydrozoa  form  free-swimming  me- 
dusae. Two  of  these  occur  in  Africa  but  the  two  following  genera 
are  each  known  in  North  America  and  Europe. 

Edward  Potts  first  discovered  the  Microhydra  and  it  has  been 
studiM  chiefly  by  him.  The  hydranth  form  has  no  tentacles  and 
it  lives  independently  or  forms  simple  colonies  of  two  or  three 
individuals.  The  medusae  have  been  seen  by  him  to  arise  by 
budding  from  hydranths  but  have  not  been  observed  when  older 
than  a  stage  attained  two  or  three  days  after  being  freed.  They 
have  but  eight  tentacles  and  no  marginal  sense  organs. 

Craspedaciista  was  first  found  in  the  Regent's  Park  Gardens, 
London,  England,  in  1880,  and  its  only  occurrence  in  North  Amer- 
ica thus  far  recorded  was  in  Washington,  D.  C,  in  1907  (Hargitt). 
Only  its  medusa  stage  is  known  with  certainty  but  what  is  supposed 
to  be  the  hydranth  form  is  very  similar  to  that  of  Microhydra. 
The  medusa  has  more  than  eight  tentacles  and  has  marginal  sense 
organs. 

The  hydra  is  usually  found  adhering  firmly  by  the  base  to  sub- 
merged objects  over  which  it  moves  slowly  and  may  be  found  at 


HYDRA   AND    OTHER    FRESH-WATER   HYDROZOA  319 

various  distances  from  the  surface,  but  not  infrequently  is  sus- 
pended from  the  surface  film  or  even  drifts  about  unattached 
and  thus  often  becomes  a  component  of  the  plankton.  The  hydras 
multiply  so  rapidly  when  conditions  are  favorable  that  they  often 
take  heavy  toll  from  the  plankton  organisms,  especially  the  ento- 
mostracans  and  small  worms.  Since  they  are  probably  little  used 
as  food  by  animals  useful  to  man  and  since  they  compete  with 
young  lish  for  food,  their  economic  relations  to  man  are  unfavor- 
able. 

The  most  favorable  conditions  for  Cordylophora  are  in  brackish 
water  and  there  it  attains  most  luxuriant  development  but  it 
thrives  also  in  fresh  water,  although  the  colonies  are  there  less 
stalwart  and  the  ascending  branches  are  usually  not  more  than 
half  as  large  as  in  colonies  from  brackish  water.  It  was  first  known 
as  a  brackish  water  form  from  Europe  and  its  appearance  in  fresh 
water  is  of  comparatively  recent  date.  It  has  been  known  for  a 
number  of  years  in  the  United  States,  near  the  Atlantic  Coast,  where 
it  occurs  in  both  brackish  and  fresh  water.  The  first  recorded 
appearance  in  the  Mississippi  Valley  was  in  the  Illinois  River  in 
1909,  but  it  is  now  known  in  several  states  of  that  region. 

This  form  is  a  plankton  feeder  and  thus  competes  with  young 
fish  for  food.  Its  most  vigorous  colonies  are  found  where  there  is 
considerable  current  and  in  company  with  Bryozoa  it  not  infre- 
quently invades  the  pipes  of  water  systems,  impedes  the  flow,  and 
at  times  vitiates  the  water  itself.  ]\{icrohydra  is  found  associated 
with  bryozoans  on  the  surface  of  stones  in  running  water  near 
Philadelphia,  and  is  apparently  not  an  abundant  form. 

In  the  search  after  hydra  if  pond-lily  leaves  and  coarse  sub- 
merged vegetation  be  collected  from  bodies  of  water  in  which 
hydra  occurs,  and  allowed  to  stand  a  few  hours  or  days  in  glass 
jars,  specimens  are  likely  to  be  found  attached  to  the  vegetation 
or  to  the  sides  of  the  jar  or  even  suspended  from  the  surface  film. 
Hydra  may  be  kept  in  good  condition  for  long  periods  of  time  in 
well  aerated  aquaria,  if  suppHed  with  suflicient  food,  preferably 
small  entomostracans  and  worms.  At  the  proper  season  and  tem- 
perature they  may  reproduce  sexually  as  well  as  by  budding. 
For  ordinary  purposes  a  corrosive  sublimate  and   acetic   acid 


320  FRESH-WATER   BIOLOGY 

mixture  either  hot  or  cold  gives  sufficiently  good  results  as  a  fixa- 
tive, but  for  certain  cytological  studies  special  methods  are  recom- 
mended; for  these  one  must  consult  the  literature. 

Occurring  most  frequently  attached  to  submerged  sticks  or  twigs 
Cordylophora  may  also  be  looked  for  on  the  submerged  surfaces  of 
walls  and  piers  and  also  on  stems  of  coarse  vegetation.  Fixation 
may  be  accomplished  as  with  hydra. 

It  has  recently  been  shown  that  the  Linnaean  systematic  names 
in  common  use  for  species  of  Hydra  must  be  dropped  for  the  earlier 
ones  of  Pallas.  Recent  Hterature  which  deals  with  the  results 
obtained  by  several  investigators  who  have  worked  on  Hydra 
shows  such  conflicting  views  concerning  the  status  of  certain  sup- 
posed species  of  this  genus,  that  any  classification  or  key  deaHng 
with  them  must  be  regarded  as  tentative.  The  chief  difficulty  is 
with  Hydra  oligactis  Pallas  {H.  fusca  L.),  which  by  some  is  beHeved 
to  have  been  applied  in  the  past  to  two  specifically  distinct  forms 
while  others  uphold  a  contrary  view. 

The  treatment  of  the  species  of  Hydra  in  the  following  key  is 
based  chiefly  on  the  papers  of  Brauer,  Downing,  and  KoeKtz. 

KEY  TO  NORTH-AMERICAN   FRESH-WATER  HYDROZOA 

1  (lo)     Hydranths  with  tentacles;  no  free  swimming  medusae  at  any  stage  of 

the  life  history 2 

2  (9)     Tentacles  in  a  circle  about  the  oral  end;    do  not  form  true  colonies; 

have  power  of  slow  locomotion.  .  .    Hydra  Linnaeus  .    .      3 

3  (6)     Body  not  definitely  stalked;    extended  tentacles  not  very  much  longer 

than  the  body 4 

4  (5)     Green;    three  kinds  of  nematocysts;    embryonic  chitinous  membrane 

spherical,   with  minute  elevations;    spermaries  limited   to 

oral  third  of  body;  sexual  activity  more  frequent  in  summer. 

Hydra  viridissima  Pallas  {H.  viridis  L.)  1766. 

5  (4)     Pale  yellow,  gray,  or  brown;    four  kinds  of  nematocysts,  diameter  of 

largest  0.0105-0.013  mm.;  embryonic  chitinous  membrane 
spherical,  with  coarse  branched  pointed  spines;  spermaries 
only  on  distal  third;  sexual  activity  more  frequent  in  sum- 
mer  Hydra  vulgaris  VdiWdiS  {H.  grisea'L.)  1766. 

6(3)     Body  definitely  stalked;  extended  tentacles  much  longer  than  body.   .     7 


HYDRA   AND   OTHER    FRESH-WATER   HYDROZOA 


321 


7  (8)  Gray,  brown,  or  reddish;  three  kinds  of  nematocysts;  diameter  of 
largest  less  than  0.0105  mm. ;  embryonic  chitinous  membrane 
spherical,  with  very  short  spines;  spermaries  on  any  part 
of  body  except  the  stalk;  sexual  activity  more  frequent  in 
winter Hydra  oligactis  VdXldiS  {H.  fuscal^.)  1766. 


By  some  it  is  claimed  that  //.  oligactis  is  strictly  dioe- 
cious and  is  in  this  way  distinct  from  the  following 
species. 


Fig.  584.     Hydra  oligactis.     (a)  Nematocysts.     (b)  Embryonic 
chitinous  membrane.     X  47-     (-'^fter  Brauer.) 


(7)  Gray  or  brown;  four  kinds  of  nematocysts,  diameter  of  largest  less 
than  o.oi  mm.;  embryonic  chitinous  membrane  plano-con- 
vex, with  only  convex  side  covered  with  spines;  spermaries 
limited  to  the  oral  third  of  the  body;  sexual  activity  more 
frequent  in  autumn Hydra  polypus  Linnaeus  i-js^- 


Besides  the  diflferences  between  H.  oligactis  and  77.  polypus 
mentioned  above  the  latter  is  said  to  be  somewhat  smaller  and 
to  have  somewhat  shorter  tentacles  than  the  former.  By  some 
the  vaHdity  of  any  of  the  diflfering  characters  mentioned  above 
is  disputed,  with  the  possible  exception  of  the  difference  in  the 
number  of  different  kinds  of  nematocysts. 

H.  pallida  Beardsley,  a  very  pale  form  in  Colorado,  and  H. 
corala  Elrod,  a  very  large  red  form  in  Montana,  may  prove  to 
belong  to  the  species  listed  above,  as  similar  variations  of  them 
are  known  to  occur  in  Europe. 


Fig.  58^^.  Hydra  polypus,  (a) 
Nematocysts.  (6)  Embry- 
onic chitinous  membrane. 
X  36.    (After  Brauer.) 


(2)     Tentacles  irregularly  scattered  on  the  body  of  the  hydranth;   form  true 
colonies Cordylophora  Allman. 


But  one  species,  C.  lacustris  Allman,  which 
occurs  in  fresh  water  near  Philadelphia.  Pa., 
and  near  Woods  Hole,  Mass.  It  has  recently 
been  found  in  the  Illinois  River  at  Havana, 
and  by  Mr.  W.  Donaldson  in  the  Mississippi 
River  at  Granite  City  and  East  St.  Louis,  111., 
in  the  Arkansas  River  at  Little  Rock,  Ark., 
and  in  the  Red  River  at  Shreveport,  La. 


Fig.  586.  Cordylophora  lacustris.  (a)  A  branch  from 
a  colony.  About  twice  as  larpe  as  is  common  in  fresh 
water,  (b)  Female  reproductive  zooids  with  embryos 
in  different  stages  of  development.  X  20.  (Alter 
Schulze.) 


10  (i)     Hydranths without  tentacles;  free  swimming  medusae  are  formed . 


322 


FRESH-WATER   BIOLOGY 


11  (12)     Hydranth  form  most  frequently  seen;  medusae  rarely  found  and 

have  but  eight  tentacles Microhydra  Potts. 

But  one  species,  M.  ryderi  Potts, 
first  described  from  near  Philadel- 
phia, Pa.,  but  since  then  found  in 
different  localities  in  Europe.  The 
medusae  have  been  seen  only  when 
in  a  very  early  stage  and  the  adult 
stages  are  not  known. 

Fig.  587.    Microhydra  ryderi.    (a)  Young 
medusa.       X  40.       (After     Moore     from 
Potts.)       (b)    Hydranths     and     embryo. 
^  J  X  22.     (After  Ryder  from  Potts.) 

12  (11)     Hydranth  form  rarely  seen;  medusae  have  more  than  eight  tentacles. 

Craspedacusta  Lankester. 

But  one  species,  C.  sowerbyi  Lankester,  known  in  Europe 
and  America.  Found  only  in  aquaria  according  to  earlier 
records,  but  large  numbers  were  collected  by  Professor  H.  Gar- 
man  in  September,  1916,  in  a  creek  near  Frankfort,  Kentucky, 
the  first  record  of  their  occurrence  in  other  than  artificial  sur- 
roundings. A  second  species,  C.  kawaii  Oka,  has  been  found  in 
a  river  of  China. 

Fig.  588.     Craspedacusta  sowerbyi.      X  about  4.     (After  Hargitt.) 

Limnocnida  Giinther  is  the  only  other  known  genus  of  fresh-water  medusae  and  its 
distribution  so  far  as  recorded  is  limited  to  the  Eastern  Hemisphere.  Limnocnida 
tanganyicae  (Bohm)  1883  is  found  in  Africa;  Limnocnida  indica  Annandale  1912,  in 
India;  Limnocnida  rhodesia  Boulenger  191 2,  in  southern  Africa. 


IMPORTANT   REFERENCES   ON   FRESH-WATER  HYDROZOA 

Brauer,  a.     1909.     Die  Benennung  und  Unterscheidung  der  Hydra- Arten. 

Zool.  Anz.,  33:  790-792. 
Downing,  E.  R.     1905.     The  Spermatogenesis  of  Hydra.    Zool.  Jahrb.,  Anat., 

21:  379-426. 
Hargitt,  C.  W.     1908.     Occurrence  of  the  Fresh-water  Medusa,  Limnoco- 

dium,  in  the  United  States.     Biol.  Bull.,  14:  304-318. 
Nutting,  C.  C.     1901.     The  Hydroids  of  the  Woods  Hole  Region.     U.  S. 

Fish  Com.  Bull,  for  1899:  327. 
Potts,  E.     1906.     On  the  Medusa  of  Microhydra  ryderi  and  on  the  Known 

Forms  of  Medusae  inhabiting  Fresh  Water.     Quar.  Jour.  Mic.  Sci.,  50: 

623-633;  2  pi. 
Smith,  F.     1910.    Hydroids  in  the  Illinois  River.    Biol.  Bull.,  18:  67-68. 


CHAPTER   XII 

THE    FREE-LIVING    FLATWORMS 

(TURBELLARIA) 

By  CAROLINE  E.  STRINGER 

Bead  of  the  Department  of  Biology,  Omaha  High  School 

The  Turbellaria  or  free-living  flatworms  are  among  the  most 
interesting  of  the  simply  organized  animals  because  of  the  re- 
markable variety  shown  in  their  reactions  and  behavior.  They 
are  to  be  found  both  in  fresh  and  salt  water  and  sometimes  in 
moist  places  on  land.  The  fresh-water  forms  are  common  in 
ponds  and  streams  ahnost  everywhere.  Many  of  the  smaller 
forms  resemble  infusoria  in  their  minute  size,  shape,  and  mo\e- 
ments.  The  larger  Turbellaria  are  more  readily  recognized  as 
worms  but  are  often  confused  with  leeches  which  they  resemble 
superficially  in  color  and  form,  although  they  are  easily  distin- 
guished by  their  head-like  anterior  end,  non-segmented  body,  and 
lack  of  posterior  adhesive  sucker. 

Probably  the  first  attempt  to  describe  one  of  this  group  dates 
back  to  1744  when  Trembley  included  in  his  memoir  on  Hydra 
what  was  undoubtedly  a  planarian.  As  early  as  1776  O.  F. 
MuUer  separated  the  Turbellaria  and  Nemertinea  from  the  para- 
sitic Trematoda,  but  it  was  not  until  1831  that  Ehrenberg  gave 
to  these  animals  the  name  Turbellaria  because  of  the  tiny  cur- 
rents in  the  water  created  by  the  delicate  cilia  which  cover  the 
body.  Much  confusion  existed  in  their  classification  until  the 
appearance  of  Lang's  work  on  structure  and  relationships  in  1S81 
and  in  the  next  year  of  L.  von  Graff's  monograph  on  the  Rhab- 
docoelida.  Since  then  considerable  attention  has  been  given  to  the 
morphological  and  physiological  as  well  as  to  the  systematic  study 
of  the  group. 

Flatworms  may  be  either  cylindrical,  thread-Hke,  spindle-shaped, 
or  more  or  less  flattened  and  leaf-like.  They  range  in  length 
from  a  fraction   of    a  millimeter   to   several    centimeters.       The 


324  FRESH-WATER   BIOLOGY 

larger  fresh-water  forms  are  usually  inconspicuously  colored,  gray, 
brown,  or  blackish  or  are  entirely  free  from  pigment.  The  smaller 
forms  are  often  brilliantly  colored,  yellow,  orange,  red,  or  rose; 
and  a  few  appear  green  due  to  the  zoochlorellae  or  symbiotic 
one-celled  plants  which  live  within  the  mesenchyma.  The  color 
is  more  or  less  affected  by  the  food  contained  in  the  intes- 
tine. This  is  especially  true  of  the  non-pigmented  or  very  trans- 
parent forms  and  in  many  cases  examination  with  a  lens  will  be 
necessary  to  show  whether  pigment  is  actually  present  or  not. 

The  anterior  end  is  often  modified  so  as  to  suggest  the  form 
of  a  head,  either  by  the  presence  of  the  various  special  sense 
organs,  a  pair  of  lobes  or  cephalic  appendages,  or  by  a  groove 
or  constriction  separating  it  from  the  rest  of  the  body.  Eyes 
may  or  may  not  be  present.  If  present,  the  usual  number  is  two, 
though  some  forms  have  four  and  one  genus  of  planarians, 
Poly  cells,  is  characterized  by  the  possession  of  a  large  number 
of  eyes.  Accessory  eyes  or  pigment  spots  are  common  among 
certain  species.  The  normal  eyes  are  usually  bean-shaped  and 
are  black  in  color  although  there  are  many  exceptions.  Acces- 
sory eyes  are  usually  more  or  less  irregular  in  shape  as  well  as  in 
position. 

A  pair  of  sensory  pits  occurs  in  the  anterior  region  in  many 
forms.  These  may  be  round,  oblong,  or  sHt-shaped,  and  very 
shallow  or  deeply  sunken.  They  are  connected  with  special 
brain  gangHa,  are  usually  provided  with  long  ciha,  and  are  re- 
garded as  olfactory  organs.  A  few  forms  possess  a  statocyst 
(otocyst)  or  balancing  organ.  It  consists  of  a  membranous  sac 
filled  with  a  fluid  in  which  a  strongly  light-refracting  statoHth 
(otolith)  is  suspended.  The  non-pigmented,  light-refracting  organs 
found  in  Stenostomum  posterior  to  the  brain  and  connected  with 
it  by  nerves  are  of  three  types.  They  may  consist  (i)  of  a  va- 
riable number  of  spherical  bodies  arranged  in  the  form  of  a 
convex  organ,  the  so-called  saucer-shaped  or  pateUiform  organ, 
(2)  of  a  vesicle  which  contains  a  strongly  Hght-refracting  lens- 
shaped  body  on  its  wall,  or  (3)  of  a  hollow  capsule-like  vesicle. 

The  epidermis  consists  of  a  single  layer  of  ciliated  cells.  The 
dlia    are   conspicuous    in    the    rhabdocoels,    which    are    enabled 


THE   FREE-LIVING  FLATWORMS    (TURBELLARIA)  325 

thereby  to  move  freely  through  the  water,  and  to  the  unaided 
eye  look  much  Hke  infusoria.  Planarians  have  a  uniform  glidin<^ 
movement  but  do  not  swim  about  unsupported.  In  addition  to 
the  ciKa,  remarkably  long  sensory  hairs  are  present  in  a  few  forms. 
The  Turbellaria  are  richly  suppHed  with  various  kinds  of  glands. 
Slime  glands  occur  all  over  the  body  and  are  especially  numerous 
near  the  anterior  and  posterior  ends.  Other  glands  form  the 
rod-shaped  bodies  or  rhabdites  which  are  either  homogeneous 
and  uniformly  hght-refracting  (rhabdoids),  or  consist  of  a  hyaline 
outer  layer  enclosing  a  fine  granular  substance  (rhammites).  The 
former  are  extremely  variable  in  shape  (spindle-,  egg-,  rod-,  or 
club-shaped)  and  originate  either  in  dermal  gland  cells  or  in  sin- 
gle-celled glands  witliin  the  mesenchyma,  especially  in  the  anterior 
end  where  the  tracts  through  which  they  pass  to  the  surface  may 
appear  as  conspicuous  fines.  The  rhammites  are  found  onh'  in 
the  mesenchyma.  Still  other  glands  produce  the  pseudo-rhab- 
dites  which  are  irregular  in  shape,  granulated  in  structure,  and 
have  a  low  light-refracting  power.  A  few  forms  have  nematocysts, 
or  stinging  cells,  similar  to  those  of  the  coelenterates,  in  place 
of  rhabdites.  Adhesive  cells  and  adhesive  papillae  are  present 
in  many  forms,  especially  at  the  posterior  end  of  the  body. 
The  external  openings,  mouth,  genital  pore,  and  excretory  pores, 
are  extremely  variable  in  position. 

In  place  of  the  usual  body  cavity  of  liigher  ammals,  the  space 
between  the  body  and  internal  organs  is  filled  with  a  peculiar 
connective  tissue  called  mesenchyma  (parenchyma).  In  the 
smaller  forms  this  tissue  consists  of  a  few  scattered  suspensory 
strands  and  the  space  between  is  filled  vdih  fluid.  In  others 
there  is  a  network  which  encloses  spaces  filled  with  lluid  and  richly 
supplied  with  cells.  The  cells  may  be  vacuolated  or  otherwise 
modified.  The  musculature  includes  bands  of  circular,  longitudi- 
nal, and  diagonal  muscles  in  the  body  wall.  There  are  also  mus- 
cles which  extend  through  the  mesenchyma  or  connect  with  the 
internal  organs.  The  digestive  apparatus  includes  the  mouth, 
pharynx,  and  intestine,  all  of  which  play  an  important  ]xirt  in 
classification  and  furnish  a  ready  means  of  distinguishing  the  two 
great  groups  of  fresh-water  Turbellaria. 


326  FRESH-WATER    BIOLOGY 

In  rhabdocoels  (Fig.  589J  which  include  smaller  forms,  the  mouth 
may  be  placed  at  the  anterior  end  or  at  various  points  on  the 
ventral  surface.  The  pharynx  is  represented  by  three  general 
types,  simple,  bulbous,  and  pUcate.  In  the  bulbous  t>pe  a  muscu- 
lar membrane  divides  the  pharynx  from  the  surrounding  mesen- 
chyma;  the  phcate  form  does  not  have  the  dividing  membrane, 
but  consists  of  a  cylindrical  tube  lying  within  a  phar>Tigeal  cavity 
which  opens  to  the  exterior  through  the  mouth.  The  simple  and 
plicate  types  of  pharynx  lie  more  or  less  lengthwise  and  the  organ 
appears  as  a  tube  parallel  with  the  surface  of  the  body.  The 
bulbous  pharynx  is  more  variable  and  includes  three  types,  the 
rosette-shaped,  the  cask-shaped  (dolioHform) ,  and  the  variable. 
The  intestine  has  the  form  of  a  simple  sac;  it  consists  of  a  blind 
cyUndrical  tube,  median  in  position.  It  is  sometimes  provided 
with  short  lateral  diverticula.     The  walls  are  thin. 

In  triclads  (Fig.  590)  the  mouth  is  on  the  ventral  surface  usu- 
ally just  posterior  to  the  middle  of  the  body.  The  pharyngeal 
region  ordinarily  shows  externally  about  the  middle  of  the  body, 
either  as  a  more  heavily  pigmented  or  as  a  hghter  colored  area. 
The  pharynx  is  a  cyhndrical,  very  muscular  tube  which  hes  within 
the  pharyngeal  ca\dty  except  when  protruded  while  feeding. 
In  a  single  genus,  Phagocata,  there  are  many  pharyngeal  tubes 
instead  of  one.  The  intestine  is  thin-walled  as  in  the  rhabdo- 
coels but  has  three  main  branches,  a  single  one  extending  forward, 
and  two  passing  back,  one  on  either  side  of  the  pharynx  to  the 
posterior  end  of  the  body.  Numerous  lateral  diverticula  are 
found  especially  in  the  anterior  region.  These  may  anastomose 
with  each  other  or  remain  distinct. 

The  protonephridial  system  (water-vascular  system  or  simple 
kidney)  possesses  one,  two,  or  four  principal  canals,  with  a  general 
antero-posterior  direction.  The  number  and  position  of  the  open- 
ings is  variable.  The  nervous  system  includes  two  principal  brain 
gangha  and  two  main  longitudinal  nerves  with  numerous  lateral 
branches.  In  many  forms  the  longitudinal  nerves  may  be  seen  as 
two  light  lines  on  the  ventral  surface. 

Reproduction  is  both  sexual  and  asexual.  The  Turbellaria 
are  hermaphroditic  with  the  female  organs  distinct  from  the  male. 


THE   FREE-LIVING  FLATWORMS    (TURBELLARIA)  327 

Both  sets  of  organs  have  a  common  genital  pore  or  are  provided 
with  separate  external  openings.  In  many  cases  the  male  organs 
mature  earlier  than  the  female  and  degenerate  as  the  latter  develop 
so  that  a  study  of  various  stages  of  growth  is  necessary  to  give 
complete  knowledge  of  the  organs.  The  rhabdocoels  show  great 
diversity  in  structure  ranging  from  those  with  simple  ovaries  and 
testes  to  those  with  an  elaborate  system  of  accessory  glands  and 
ducts  that  much  resemble  those  of  the  triclads.  The  male  copu- 
la tory  apparatus  or  cirrus  is  often  remarkably  complex  and  may, 
as  in  Dallyellia,  present  the  chief  characters  for  identification  of 
species. 

Some  rhabdocoels  produce  two  kinds  of  eggs,  the  thin-walled 
transparent  summer  eggs  which  may  undergo  development  within 
the  body  of  the  parent,  and  the  thick-walled  winter  eggs  which  have 
a  hard,  brown  shell  and  develop  in  the  outer  world.  In  other 
species  only  the  hard-shelled  eggs  are  produced.  In  the  Catenuli- 
dae  asexual  reproduction  by  the  formation  of  buds  or  zooids  at 
the  posterior  end  of  the  body  is  met  with  commonly.  More  than 
one  bud  may  be  produced  before  separation  takes  place. 

Planarians  (Fig.  590)  show  less  variation  in  the  structure  of 
the  sexual  organs.  The  testes,  usually  numerous,  lie  both  above 
and  below  the  digestive  tract  and  extend  from  anterior  to  posterior 
end.  The  seminal  vesicle  opens  into  the  muscular  bulb-like 
cirrus,  the  apex  of  which  projects  into  the  male  genital  atrium, 
which  in  turn  leads  into  the  common  atrium.  Two  ovaries  are 
placed  far  forward.  The  numerous  yolk  glands  open  into  the 
oviducts  as  they  pass  back  and  either  unite  to  form  a  common 
duct  which  enters  the  genital  atrium  or  open  separately  into  the 
posterior  part  of  the  uterine  duct.  Fertilization  apparently  occurs 
in  the  uterus  which  lies  just  back  of  the  pharynx. 

Some  triclads  manifest  only  sexual  reproduction;  others  have 
regular  alternating  periods  of  sexual  and  asexual  reproduction; 
while  a  number  do  not  have  a  definite  life  cycle  since  sexual  ma- 
turity occurs  at  irregular  intervals  and  often  only  among  a  limited 
number  of  individuals.  In  these  forms  reproduction  is  ordinarily 
asexual.  Dendrocoelum  lacteum  attains  sexual  maturity  and  de- 
posits its  cocoons  during  the  winter  months.     Li  Planaria  maculata 


328  FRESH-WATER    BIOLOGY 

and  Planaria  agilis  sexual  organs  begin  to  develop  early  in  the 
autumn  and  mature  in  the  spring.  After  the  cocoons  are  depos- 
ited the  reproductive  organs  degenerate  and  reproduction  is  again 
carried  on  by  transverse  division  into  two  pieces  with  subsequent 
regeneration  of  the  missing  parts  in  each  piece.  The  division 
plane  in  most  planarians  passes  just  back  of  the  pharynx.  In 
Planaria  velata  there  is  a  division  into  pieces  of  various  sizes 
which  encyst  in  a  slime  layer  in  response  to  unfavorable  con- 
ditions. This  slime  layer  hardens  into  a  shell-like  covering. 
Entire  animals  may  also  encyst.  Asexual  reproduction  among 
planarians  may  occur  at  any  time  of  the  year  and  in  many  species 
is  the  usual  method  of  propagation.  The  factors  which  control 
the  development  of  sexual  maturity  are  not  fully  understood 
although  the  food  supply  unquestionably  plays  an  important  part. 

Turbellaria  undergo  no  metamorphosis  during  development  but 
emerge  from  the  egg,  resembling  the  parent  except  in  the  lack 
of  sexual  organs.  In  viviparous  forms  the  young  develop  within 
the  mesenchyma  of  the  parent  and  make  their  way  to  the  exterior 
through  the  body  wall  in  the  posterior  region. 

Flatworms  are  extremely  responsive  to  external  influences  and 
the  larger  forms  especially  give  interesting  and  specific  reactions 
to  various  kinds  of  stimuh.  If  a  dish  in  which  they  are  quietly 
gliding  about  is  jarred  even  very  shghtly,  it  will  cause  them  to 
stop  and  contract  until  quiet  is  restored,  or  if  at  rest  and  the  dish 
is  moved  they  respond  by  becoming  active  as  soon  as  the  disturb- 
ance ceases.  Violent  disturbance  induces  a  highly  excited  condi- 
tion with  a  loss  of  their  more  delicate  reactions.  After  being 
disturbed  the  animals  continue  moving  about  for  some  time,  this 
period  depending  on  the  strength  of  the  stimulus  and  the  physi- 
ological condition  of  the  animal.  Naturally  it  depends  also  upon 
the  species  since  some  are  more  active  than  others.  They  come 
to  rest  in  some  sheltered  spot,  normally  in  groups.  Light  plays 
an  important  part  in  determining  their  resting  place  as  they  show 
decided  negative  photokinesis .  The  length  of  time  of  the  resting 
period  varies  greatly.  The  animals  are  much  more  active  at 
night  than  in  day  time;  this  is  probably  due  to  their  feeding 
habits. 


I 


THE    FREE-LIVING   FLATWORMS    (TURBELLARIA)  329 

If  the  worm  is  in  a  normal  condition  a  delicate  mechanical 
stimulus  induces  a  positive  reaction,  i.e.,  the  animal  pauses  mo- 
mentarily, then  turns  towards  the  source  of  the  stimulus  and 
glides  forward  in  that  direction.  A  negative  reaction  is  usually 
given  in  response  to  a  strong  mechanical  stimulus.  In  this  case 
the  animal  turns  away  from  the  source  of  the  stimulus.  The 
positive  and  negative  reactions  are  given  not  only  in  response  to 
weak  and  strong  mechanical  stimuli  but  to  changes  in  tempera- 
ture and  to  various  chemical  stimuli.  The  food  reaction  is  essen- 
tially a  positive  one.  If  food  is  placed  in  a  dish  where  planarians 
are  gHding  about,  as  they  pass  near  enough  to  receive  the  stimulus 
supplied  by  the  juices  of  the  tissues,  they  give  a  positive  reaction 
similar  to  that  following  delicate  mechanical  stimuli.  This  reac- 
tion brings  them  to  the  food  and  as  they  pass  over  it  the  anterior 
end  closes  over  the  food  as  if  testing  it.  This  process  completed, 
the  animal  moves  ahead  sufficiently  to  bring  the  mouth  opening 
over  the  food.  The  pharynx  is  extruded  and  the  feeding  process 
begins.  An  interesting  reaction  is  given  where  a  planarian  falls 
dorsal  side  down,  as  it  rights  itself  by  forming  a  more  or  less 
complete  spiral. 

There  is  a  constant  secretion  of  slime  over  the  entire  body  and 
especially  on  the  ventral  surface.  Irritation  causes  an  increase  in  the 
quantity  discharged.  The  sKme  layer  and  rhabdites  probably  serve 
the  purpose  of  protection  to  some  extent  and  aid  in  holding  the  prey. 

Some  Turbellaria  occur  in  shallow  quiet  pools  only;  others 
in  larger  ponds,  lakes,  or  rivers,  while  a  few  species  seem  to  prefer 
swiftly  flowing  spring-fed  brooks  and  streams.  They  are  found 
not  only  in  all  kinds  of  water  but  under  varying  temperature 
conditions  as  well,  since  they  may  be  collected  during  the  winter 
from  beneath  the  ice  and  also  are  found  in  hot  springs  with  a 
temperature  of  47°  C.  They  collect  on  the  under  side  of  stones, 
sticks,  and  leaves,  conceal  themselves  among  algae  and  in  (lel)ris, 
or  cHng  to  the  stems  of  Chara,  CeratophyUunu  and  other  h>-dro- 
phytic  plants.  Certain  forms  are  found  near  the  surface  in  com- 
paratively open  water,  and  others  in  the  mud  or  sediment  at 
the  bottom  of  ponds  or  lakes.  Peat  bogs  and  swampy  places 
often  furnish  a  large  number  of  forms. 


330  FRESH-WATER   BIOLOGY 

The  regions  occupied  by  different  species  of  planarians  are  ap- 
parently determined  by  temperature  and  food  supply  to  a  very 
great  extent.  Those  species  which  are  adapted  to  low  tempera- 
tures become  sluggish  and  inactive  in  higher  temperatures,  or 
the  reverse,  and  so  will  be  less  Hkely  to  find  food  than  forms 
especially  adapted  to  that  temperature.  If  the  food  supply  is 
limited  this  will  necessarily  lead  to  a  crowding  out  of  those  less 
perfectly  adapted  to  the  environment.  The  development  of  any 
one  species  in  a  particular  region  is  consequently  limited  by  com- 
petition with  other  species  already  established  in  the  area.  In 
some  cases  two  or  more  species  may  be  found  in  almost  equal 
numbers  in  the  same  pond  as  Planaria  maculata  and  Dendrocoelum 
lacteum.  In  such  cases  a  variety  of  food  usually  seems  to  be 
abundant,  thus  reducing  the  competition  which  would  otherwise 
lead  to  the  eUmination  of  the  weaker.  Cannibahsm  sometimes 
occurs  among  individuals  of  the  same  species  when  food  is  scarce 
and  different  species  are  especially  likely  to  prey  upon  each  other. 
Planaria  agilis  is  a  voracious  feeder,  and  will  exterminate  a  culture 
of  Planaria  velata  or  Planaria  maculata  in  a  comparatively  short 
time  even  if  other  food  is  provided.  This  may  account  in  part 
for  the  fact  that  certain  species  are  always  found  alone. 

Ordinarily  a  pond  or  stream  shows  no  evidence  of  the  presence 
of  Planaria  even  though  large  numbers  of  them  may  be  hidden 
away  under  stones  or  leaves.  However,  one  sometimes  finds 
them  moving  restlessly  about  in  great  masses,  either  all  in  one 
general  direction  or  in  disorder.  Voigt  has  conducted  some  inter- 
esting experiments  with  European  forms  under  natural  conditions 
which  would  indicate  that  these  apparently  concerted  movements 
are  the  result  of  a  response  to  some  stimulus  which  may  promise 
food,  and  cannot  be  regarded  as  indicating  the  possession  of  any 
inherited  tendency  toward  periodical  wanderings.  The  marine 
Turbellaria,  like  the  fresh-water  forms,  hide  under  stones  and 
among  seaweeds.  Some  find  shelter  within  the  shells  of  molluscs 
and  a  few  are  parasitic. 

The  land  planarians  are  in  general  characteristic  of  tropical 
and  sub-tropical  regions  where  they  attain  a  considerable  length 
and  are  usually  brilUantly  colored.     In   this  country  one  may 


THE  FREE-LIVING   FLATWORMS    (TURBELLARIA)  331 

sometimes  find  them  in  greenhouses  and  gardens,  under  flower 
pots  or  boxes,  in  moist  woods  under  bark  and  old  logs,  or  in  any 
moist  sheltered  place.  They  are  easily  overlooked  because  of  the 
similarity  in  their  appearance  to  young  snails. 

Rhabdocoels  are  especially  abundant  in  pools  or  ponds  which 
contain  much  algal  or  other  vegetation.  A  lens  is  often  neces- 
sary to  distinguish  them  from  other  minute  organisms.  They 
may  be  collected  by  means  of  a  Birge  net  or  other  apparatus  used 
in  collecting  small  animals  or  simply  by  gathering  carefully  plant 
material,  sediment,  or  debris  from  the  ponds  where  they  live 
and  exposing  this  material  in  shallow  dishes  in  the  laboratory. 
The  larger  triclads  are  easily  collected  as  they  cling  to  the  stone 
or  leaf  which  conceals  them  when  it  is  lifted  from  the  water  and 
they  may  then  be  removed  with  the  point  of  a  knife,  or  washed 
off  into  a  large-mouthed  jar.  When  algae  or  debris  which  con- 
tains them  is  disturbed,  they  contract,  remain  motionless  until 
the  disturbance  ceases,  and  then  come  to  the  surface  and  crawl 
about  excitedly,  thus  being  easily  picked  up  with  a  large-mouthed 
pipette. 

Most  Turbellaria  are  easily  kept  in  cultures  if  the  water  is  kept 
pure.  Rhabdocoels  should  have  a  supply  of  unicellular  and  tila- 
mentous  algae  such  as  diatoms,  Spirogyra,  etc.,  and  small  animals 
like  rotifers,  Crustacea,  and  insect  larvae,  as  they  use  both  plant 
and  animal  food.  Planarians  are  largely,  if  not  entirely,  carnivo- 
rous and  thrive  in  aquaria  which  are  supplied  with  running  water 
so  that  they  may  be  given  a  constant  supply  of  food.  If  this  is 
not  possible,  they  may  be  kept  in  ordinary  aquarium  jars  or  shal- 
low dishes  with  or  without  algae.  They  will  live  for  weeks  with- 
out food  but  become  greatly  reduced  in  size.  They  take  food 
readily,  especially  at  night,  and  should  be  fed  once  or  twice  a 
week  on  earthworms,  snails,  liver,  or  almost  any  soft  fleshy  animal 
tissue.     The  water  should  be  changed  after  each  feeding. 

Small  forms  are  easily  studied  under  the  microscope  if  slightly 
compressed  by  the  cover  glass  through  the  absorption  of  the 
surplus  water  with  filter  paper.  A  few  quince  seeds  added  to 
the  water  are  of  great  assistance  as  they  form  a  jelly  which  re- 
tards movement  without  injury  to  the  animal.     Cells  or  hollow 


332  FRESH-WATER  BIOLOGY 

slides  are  convement  for  work  with  large  forms.  Anesthesia  may 
be  induced  by  the  use  of  a  solution  of  one-tenth  of  one  per  cent 
of  chloretone,  or  even  less  with  some  species.  For  preservation 
hot  corrosive  subhmate  may  be  used,  or  a  cold  solution  of  the 
subHmate  to  which  five  per  cent  of  glacial  acetic  acid  has  been 
added.  Lang's  fluid,  Chichkoff' s  mixture,  and  30%  HNO3  fol- 
lowed after  one  minute  with  70%  alcohol,  are  all  useful  kilhng 
reagents.  Formol  is  useful  for  preservation  of  external  characters 
since  the  animals  retain  their  shape  and  color  in  it  better  than 
in  most  reagents.  The  larger  planarians  are  especially  valuable 
for  study  in  laboratories  where  attention  is  given  to  animal  be- 
havior. Certain  forms  also  afford  excellent  training  in  exactness 
of  observation. 

The  lack  of  well  defined  and  unvarying  external  characteristics 
makes  it  difficult  to  identify  many  Turbellaria.  A  large  part  of 
the  material  ordinarily  collected  is  sexually  immature  whereas,  as 
has  been  noted  above,  a  knowledge  of  the  structure  of  the  sex 
organs  is  necessary  in  certain  genera  for  identification.  Preserved 
material  if  immature  is  especially  difficult  to  identify  since  the 
body  becomes  distorted  in  shape  and  the  color  is  usually  so 
modified  as  to  be  unrehable.  The  differences  in  color  and  form 
between  several  of  the  species  of  planarians  while  definite  are 
so  sHght  as  to  be  apparent  only  after  a  comparison  of  Hving 
material.  In  other  cases  there  is  a  wide  variation  in  color  be- 
tween individuals  of  the  same  species. 

Until  comparatively  recently  descriptions  of  many  species  of 
Turbellaria  were  extremely  meager.  The  confusion  which  has 
arisen  as  a  result  is  due  to  the  lack  of  conspicuous  external  char- 
acteristics which  would  serve  for  identification. 


THE    FREE-LIVING   FLATVVORMS    (TURBELLARIA) 


333 


KEY  TO  NORTH  AMERICAN  FRESH-WATER  TURBELLARIA 


Including  the  Land  Planarians 

I  (78)     Intestine  a  single  blind  tube,  median  in  position. 

Order  Rhabdocoelida  .    .     2 

The  intestine  consists  of  a  simple  rod-shaped  or  sac  cavity  which  rarely  has  lateral  diverticula 
and  never  is  divided  into  two  distinct  post-pharyngeal  branches.  Mostly  small  forms,  never 
more  than  a  few  millimeters  in  length.  The  following  figures  (Figs.  589  and  590)  facilitate  a 
comparison  of  structure  in  the  two  great  orders,  Rhabdocoelida  and  Tricladida  (p.  354). 


Fig.  589.  Structure  of  a  Rhabdocoel. 
Dalyellia  rossi.  Compressed,  ad,  atrial 
glands;  be,  bursa  copulatrix;  bst,  duct  lead- 
ing from  bursa  copulatrix;  ch,  chitinous 
part  of  the  male  copulatory  organ;  da,  in- 
testine; dg,  duct  of  yolk  gland;  ge,  ovary; 
go,  genital  pore;  mgc,  male  genital  canal; 
mph,  retractor  muscles  of  pharynx;  ph, 
pharynx;  pp,  cirrus;  pr,  reddish  reticu- 
lar pigment;  pz,  yellow  pigment  cell;  r?, 
receptaculum  seminis;  sph,  sphinctor 
muscle  of  the  uterus;  (e,  testes;  vd.  vas  de- 
ferens; vs,  seminal  vesicle;  vi,  yolk  gland;  z, 
esophageal  cells;  e,  eye;  u,  uterus.  X 
50.     (After  von  Graff.) 


Fig.  590.    Structure  of  a  Triclad. 

Diagram  of  a  Planarian.  ag, 
genital  atrium;  aw.  eye;  com,  cross 
commissures  of  nervous  system; 
d',  anterior,  and  d",  posterior 
branches  of  intestines;  do,  yolk 
gland;  ex.  excretory  canal;  cxp,  ex- 
cretory pore;  gl,  brain;  gp,  genital 
pore;  In,  longitudinal  nerve;  m, 
mouth;  od,  oviduct;  od',  common 
oviduct;  ov,  ovary;  p,  cirrus;  pit, 
pharynx;  pht,  phar>-ngeal  pocket; 
te,  testes;  ut,  uterus;  utd,  uterine 
duct;  vd,  vas  deferens.  (After 
Bohmig.) 


2  (77)     Pharynx  simple,  cask-shaped  or  rosctte-shapcd.     Connective  tissue  of 
body  cavity  poorly  developed. 

Suborder  Rhabdocoela   .    .     3 

The  mesenchyma  often  consists  of  but  a  few  strands  of  connective  tissue  and  contains  large 
spaces  filled  with  a  perivisceral  fluid. 


3  (30)     Reproductive  organs  simple. 


Female  organs  consist  of  ovary  only. 
Section  Hysterophora  .    . 


These  forms  possess  no  accessory  female  organs,  i.e.,  no  separate  yolk  glands,  uterus,  female 
copulatory  apparatus,  etc.  Asexual  reproduction  among  rhabdocoels  is  found  only  in  this 
section  of  the  order. 


334 


FRESH-WATER    BIOLOGY 


4  (27)     Pharynx  simple 5 


5  (20)     Protonephridia  with  one  principal  branch,  median  dorsal  in  position. 

Family  Catenulidae  .    .     6 

Without  eyes  but  with  ciHated  pits,  non-pigmented  light-refracting  organs,  and  in  one  genus 
a  statocyst.  The  mouth  lies  on  the  ventral  side  of  the  anterior  end.  The  pharynx  opens  into 
the  anterior  end  of  the  intestine.  Asexual  reproduction  by  budding,  thus  forming  chains  of 
zooids,  known  for  most  species.  Testes  in  front  of  ovary.  Both  testes  and  ovary  may  consist 
of  one  or  more  lobes. 


6  (7)     With  one  statocyst  and  pre-oval  circular  groove Catenula. 

But  one  species  supposed  to  occur  in  America. 

Catenula  lemnae  (Anton  Duges)  1832. 


Length  of  single  specimen  i  mm.  Rarely  2  to  4  or 
8  zooids  in  a  chain.  Delicate,  white  thread-like.  Head 
region  set  off  by  a  circular  groove  lined  with  long  cilia. 
Intestine  short  and  not  continuous  through  chain  of 
zooids. 

Graflf  regards  the  European  species  C.  lemnae  as  prob- 
ably identical  with  the  species  which  was  collected  in 
the  vicinity  of  Philadelphia  and  very  incompletely  de- 
scribed by  Leidy  under  the  name  Anortha  gracilis. 
Until  further  collections  of  the  Philadelphia  form  have 
been  made  this  must  of  necessity  be  a  matter  open  to 
question,  and  C.  lemnae  be  admitted  to  the  Hst  of  Ameri- 
can species  tentatively. 


Fig.  sqi  .  Catenula  lemnae.  {A )  anterior  end :  J,  brain;  eg,  cili- 
ated groove;  w,  mouth;  s/,  statocyst.  X  75.  (After  von  Graff.) 
{B)  Chain  of  two  zooids.     X  30.     (After  Mrazek.) 


7  (6)  Without  statocyst  or  pre-oral  circular  groove.     With  ciliated  pits.   .       8 


8(19)     Ciliated  pits  well  developed.    Without  proboscis.    Stenostomum  .    .       9 


9  (18)     Head  region  not  at  all  or  only  slightly  set  off  from  rest  of  body.   .     10 


10  (17)     Integument  colorless ii 


11(14)     Wall  of  digestive  tract  free  from  pigment.  ...       12 


THE   FREE-LIVING  FLATWORMS    (TURBELLARIA)  335 

12  (13)  Anterior  end  bluntly  pointed,  ciliated  pits  about  as  far  from  end  of 
body  as  width  of  body  at  that  point.  Posterior  end  taper- 
ing uniformly  to  a  blunt  point. 

Stenostomum  leucops  (Anton  Duges)  1828. 


Length  of  single  individuals  0.5  to  1.5  mm.  .Asex- 
ual reproduction  by  budding  2  to  4  zooids  common, 
rarely  9  zooids.  Intestine  continuous  through  zooids. 
Rhabdites  small,  numerous.  Two  patelliform  organs 
which  consist  of  numerous  spherical  bodies.  Male 
sexual  organs  mature  in  August,  female  in  September. 
At  this  time  the  animal  becomes  large,  sluggish,  and 
somewhat  reddish-brown  in  color.  The  six-lobed 
ovary  lies  under  the  intestine.  The  oval-shaped 
testes  which  consist  of  many  closely  compacted  lobes, 
lie  above  the  pharynx  and  open  into  the  seminal 
vesicle  which  leads  through  a  short  canal  to  the 
opening  on  the  dorsal  surface.  Abundant  on  plants 
in  quiet  water  such  as  small  lakes  or  ponds.  Mass  . 
N.  Y.,  111.,  Mich.,  Neb. 


WV 


Op 


Fig.  592.  Stenostomum  leucops.  (A)  dorsal  view  of  anterior  end:  b,  brain;  m,  mouth;  k,  protonephrid- 
lum;  phd,  pharyngeal  glands;  do,  patelliform  organ;  cp,  ciliated  pit.  X  200.  (5)  Entire  worm,  cp, 
ciliated  pit;  c,  cilia;  b,  brain;  m,  mouth;  ph,  pharynx;  in,  intestine;  wv,  protonephridium;  op,  external 
pore  of  protonephridium.     X  100.     (After  Ott.) 

13  (12)     Anterior  end  very  bluntly  rounded  with  ciliated  pits  very  near  the  end. 
Posterior  end  of  body  narrow  and  forming  a  long  slender  tail, 
somewhat  spatulate  in  shape,   except   where   division  has 
recently  taken  place,  in  which  case  the  tail  is  shorter  and 
more  pointed.    .    .    .    Stenostomum  spcciosum  Stringer  19 13. 
Length  2.25  mm.     A  large  rhabdocoel  which  moves  rather  slowly  and  very  gracefully.     The 
ciliated  pits  are  placed  close  to  the  blunt  anterior  end,  much  farther  forward  than  in  S.  leucops, 
also  are  deeper  and  narrower  than  in  the  latter  form.     The  mouth  is  about  as  far  from  the  an- 
terior end  as  the  diameter  of  the  body  at  that  point,  and  is  surrounded  by  glands.     The  pharjnx 
has  delicate  longitudinal  striations.     The  intestine  shows  many  large  highly  refractive  color- 
less bodies,  probably  fat  globules.     Nothing  definite  can  be  said  of  the  light-refracting  organs 
which  were  difficult  to  identify  because  of  the  unusual  size  of  the  animal.     .\  few  specimens 
collected  from  pond  with  S.  leucops.     Lincoln,  Neb. 


Fig.  593.     Stenostomum  speciosum.    cp.  ciliated  pit;  6,  brain;  ph.  pharjnx;  m,  mouth  with  surrounding 
glands;   e.  egg.     X  45-     (Original  ) 

14(11)     Wall  of  digestive  tract  pigmented 15 


33^ 


FRESH- WATER   BIOLOGY 


15  (16)     Pharynx  yellowish-brown.     Intestine  except  gland  cells  bright  yellow. 

Stenostomum  tenuicauda  von  Graff  191 1. 


Length  in  cliain«;  of  4  zooids  1.5  mm.  Slender.  Posterior  end  tapering 
to  a  slender  tail  (i  to  ^^  of  entire  length).  Point  of  tail  set  with  adhesive 
cells.  Integument  colorless  and  contains  masses  of  small  rhabdites  measuring 
up  to  4JM.  in  length.  Excretorj^  pore  nearer  to  intestine  than  end  of  body. 
Two  pateUiform  organs  12  m  across  and  composed  of  loosely  joined  spherical 
bodies.     Rochester  and  Cold  Spring  Harbor,  Long  Island,  N.  Y. 


-ep 


Fig.  594.    Stenostomum  tenuicauda.    An  undivided  chain  of  four  zooids:  rh,  rhabdites; 
ig,  intestinal  glands;  ep,  excretory  pore;  ph  I,  II,  pharynx.     X  4°-     (After  von  Graff.) 


1 6  (15)     Intestine  yellowish-green  between  the  round  glistening  oil  drops. 

Stenostomum  agile  (Silliman)  1885. 


Length  of  single  individual  0.75  mm.  Chains  of  two  zooids  measure  i  .5  mm., 
those  of  five,  4  mm.  Light-refracting  organs  lens-shaped.  Rhabdites  small. 
Posterior  end  bears  adhesive  cells.  Pharynx  long  and  provided  with  glands 
throughout  its  entire  length.  Sexual  organs  similar  to  5.  leucops.  Monroe 
Co.,  N.  Y. 

Fig.  595.  Stenostomum  agile.  {A)  Anterior  end  extended;  wgr,  ciliated  pit;  lo,  lens- 
shaped  organ;  f5c/i,  protonephridium;  jj/i,  pharynx;  rfa,  intestine;  g,  brain.  X  65.  (5) 
Lens-shaped  organ.    X  125.     (After  von  Graff.) 


^H^    a 


17  (10)     Integument  bright  yellow. 


Stenostomum  grande  (Child)  1902. 


Length  of  chains  of  4  to  6  zooids  2  to  2.2  mm.  Pre-oral  region,  especially 
the  rounded  beak-like  portion,  white.  Integument  bright  yellow,  pharynx 
somewhat  darker  yellow,  intestine  deep  orange-yellow.  Rhabdites  small, 
especially  numerous  in  anterior  end. 

Two  patelliform  organs  composed  of  about  25  spherical  bodies.  Posterior 
portion  of  nearly  cyhndrical  muscular  pharynx  sometimes  shows  folds  as  a 
result  of  contraction.  Intestine  slightly  lobed.  Rochester,  N.  Y.  Brackish 
water,  Falmouth,  Mass. 

Fig.  596.  Stenostomum  grande.  {A)  Anterior  end:  wgr,  ciliated  pit;  so,  patelliform 
organ;  ph.  pharynx;  da,  intestine.  (5)  posterior  end:  ed,  excretory  pore.  X  55-  (After 
von  Graff.) 


THE  FREE-LIVING  FLATWORMS    (TURBELLARIA)  337 

'enostomiim  coluber  Leydig  1854. 


18  (9)     Head  region  distinct  from  rest  of  body 


Length  6  mm.  Width  about  one-thirtieth  the  length.  Very 
slender,  white  thread-like  with  snake-like  movements.  Head  region 
broader  than  the  rest  of  the  body  with  blunt  point  at  anterior  end. 
Posterior  end  abruptly  rounded.  Asexual  reproduction  not  known. 
Brackish  water,  Falmouth,  Mass. 

Fig.   597.     Stenostomum  coluber.     Anterior  end:  wj,  mouth;  ^  pharynx-  in 
intestine;   ov,  egg  (?);   ns,  protonephridium.     X  20.     (After  Leydig.)      ' 


A  club-shaped  proboscis  is  present. 

RhyncJwscolex. 
Rhynchoscolex  simplex  Leidy  185 1. 


-    (8)     Ciliated  pits  shallow. 

Only  one  species. 

Length  4  to  7  mm.  Color  yellowish-white  opaque.  Anteriorly  abruptly  attenuated  into  a 
long  cylindrical  clavate  proboscis;  anterior  end  abruptly  narrowed,  obtusely  rounded  Pro- 
boscis shows  longitudinal  and  numerous  transverse  marks.  Mouth  ventral,  at  the  base  of  the 
proboscis.  Intestine  straight  and  capacious.  A  small  wriggling  worm  found  among  yellowish 
fragments  of  vegetable  matter  and  confervae  at  the  bottom  of  clear  brooks  in  the  vicinity  of 
Philadelphia. 

Von  Grafif  regards  the  European  species  R.  vejdovski  Sekera  1888  as  probably  identical  with 
this  American  form. 

20  (5)     With  two  lateral  branches  of  the  protonephridium. 

Family  Microstomidae     .    .     21 

Mouth  a  longitudinal  sUt  on  ventral  surface,  intestine  occasionally  with  side  lobes.     Proto- 

nephridial  branches  open  in  anterior  end.     Testes  and  ovary  either  paired  or  unpaired,  with  two 

ventral  sexual  pores,  the  male  posterior  to  the  female.     With  or  without  eyes  and  ciliated  pits. 

21  (24)     The  intestine  extends  dorsally  and  anteriorly  beyond  the  junction 

with  the  pharynx Subfamily  AIicrostominak. 

Only  one  genus Microstomum   .    .     22 

22  (23)     With  two  reddish-yellow  pigmented  eye  spots. 

Microstonmm  lineare  (Miiller)  1773. 


Length  of  single  individuals  1.8  mm.  In  chains 
up  to  18  zooids  with  a  length  of  9  to  11  mm. 
Slender.  Very  active.  Color  yellowish  to  grayish- 
brown,  rarely  rose-colored,  with  the  intestine 
always  darker  than  the  body.  Pre-oral  portion  of 
intestine  short.  Two  small  ciliated  pits.  Nettle 
cells  or  nematocysts  in  place  of  rhabdites. 
Male  sexual  organs  with  {xiired  testes;  slender 
chitinous  spicule  of  copulatorj*  organ  with  curved 
Doint.  Ovary  unpaired  and  median  in  position. 
Hi  fresh  and  brackish  water.  Monroe  Co.  and 
Ontario  Beach,  N.  V.;  West  Twin  Lake  and 
Round  Lake,  Mich. 


Fig.  598.  Microstomum  lineare.  M  )  anterior  jxirtion 
of  a  chain:  e,  eyes;  r/>,  ciliated  pit;  ai.  pre-<>r.il  por- 
tion of  intestine;  m,  mouth;  oe,  esophagus.  X  lo. 
(After  von  Grafl.)  (B)  Chitinous  portion  of  cirrus. 
Much  enlarged,     (.^fter  SchuJlze.) 


338  FRESH-WATER   BIOLOGY 

23  (22)     Without  eyes Microstomum  candatum  Leidy. 

^p-'-t-M^--^/? 


Length  1.5  to  3  mm.  Commonly  in  chains  of  2  to  8  zooids. 
Nematocysts  in  place  of  rhabdites.  Color  of  integument  white,  in- 
testine yellow.  Ciliated  pits  directly  dorsal  to  mouth.  Pre-oral 
portion  of  intestine  short.  Anterior  end  bluntly  rounded.  Poste- 
rior end  narrower,  bluntly  pointed,  tail-like,  elevated.  In  standing 
water  and  small  brooks,  Monroe  Co.,  N.  Y.;  near  Philadelphia,  and 
in  West  Twin  Lake,  Charlevoix,  Mich. 


Fig.  599.    Microstomum  caudatum.    b,  brain;  ph,  pharynx;  cp,  ciliated 
pit.    (After  Silliman.) 


24  (21)     Pharynx  opens  into  anterior  end  of  the  intestine,  which  has  short 

lateral  diverticula Subfamily  Macrostominae. 

Only  one  genus Macrostommn  .    .     25 

25  (26)     Chitinous  portion  of  copula tory  organ  a  broad  straight  funnel  with 

the  slender  point  bent  at  a  right  angle  or  nearly  so  and 
bearing  on  its  convex  side  the  small  opening.  Vesicula 
seminahs  and  vesicula  granulorum  connected  by  a  narrow 
tube.     .    Macrostomum  appendiculatum  (O.  Fabricius)  1826. 


This  is  the  form  known  as  M.  hystrix  Oersted 
1843.  Length  2  mm.  Unpigmented,  transparent. 
Body  flattened  especially  at  the  ends.  The  spatulate 
posterior  end  set  with  adhesive  papillae.  Rhabdoids 
and  long  sensory  hairs  conspicuous.  Two  eyes, 
black.  Protonephridial  tubes  open  on  median  dorsal 
side  back  of  the  slit-like  mouth.  Testes  and  ovary 
both  paired.  Asexual  reproduction  not  known.  In 
running  and  standing  water.  Monroe  Co.,  N.  Y.;  Lin- 
coln, Neb. 


Fig.  600.  Macrostomum  appendiculatum.  (A)  Entire 
worm:  b,  brain;  e,  eye;  ph,  pharynx;  di,  diverticulum  of 
intestine;  i,  intestine;  ie,  testes;  vd,  vas  deferens;  vg, 
ductus  seminalis;  vs,  seminal  vesicle;  vg,  vesicula  granu- 
lorum; ch,  chitinous  spicule  of  cirrus;  $  and  9  <  ™^^^ 
and  female  genital  pores;  on,  ovary.  X  35-  (After  von  Graff.) 
(B)  Chitinous  spicule  enlarged.     X  3So.     (After  Luther.) 


THE   FREE-LIVING   FLATWORMS    (TURBELLARIA) 


3  39 


26  (25)  Chitinous  spicule  of  cirrus  a  straight  narrow  tube  tapering  to  a 
somewhat  variably  curved  point.  Vesicula  seminalis  and 
vesicula  granulorum  separated  by  a  short  constriction. 

Macrostomum  sensitivum  (Silliman)  1885. 


Length  1.5  mm.  Color  grayish- 
white.  Intestine  yellowish.  Broad- 
est through  middle.  Posterior  end 
narrowed.  Rhabdites  present  in  in- 
tegument in  large  numbers,  either 
singly  or  in  twos  and  threes.  Rhab- 
dite  tracts  conspicuous  in  anterior 
end.  Intestine  with  lateral  diver- 
ticula. Protonephridium  communi- 
cates through  a  pore  with  mouth 
cavity.  Chitinous  organ  somewhat 
variable.  Monroe  Co.,  N.  Y.;  brack- 
ish water,  Falmouth,  Mass. 


Fig.  601.  Macrostomum  sensitivum.  {A)  Anterior  end:  6, 
brain;  e,  eye  with  lens;  k,  protonephridium  which  opens 
through  the  pore  {p)  into  the  mouth  cavity;  sh,  sensory 
hairs.  X  150.  (After  Silliman)  (B)  Male  copuiatory  organ 
subjected  to  pressure.  (C)  Male  copulatory  organ  not  under 
pressure:  w,  vesicula  seminalis;  ig,  vesicula  granulorum;  ch, 
chitinous  point.     Much  enlarged.     (B,  C,  after  von  GraflF.) 


27  (4)     With  a  long  cylindrical  bulbous  pharynx.   .    Family  Prorhynchidae. 

The  pharynx  is  remarkably  large.  The  mouth  is  in  the  anterior  end.  Testes  with  numerous 
follicles.  Ovary  not  paired.  Two  sexual  pores,  the  female  pore  on  the  ventral  side.  The  male 
sexual  organs  open  near  the  mouth  or  unite  with  it. 


Only  one  genus Prorhynchus  M.  Schultze 


28 


28  (29)     Without  eyes. 


Prorhynchus  stagnalis  M.  Schultze  185 1. 


Length  to  6  mm.,  commonly  much  smaUer.  White,  thread-like.  Two  cili- 
ated pits.  With  numerous  pear-shaped  glands  in  the  mtegument.  1  haryn.x 
about  I  of  total  length  of  body.  Protonephridium  with  four  prmcipal  branches, 
two  dorsal  and  two  ventral.  Chitinous  portion  of  cirrus  straight  and  stiletto- 
shaped.     Monroe  Co.,  N.  Y.;  brackish  water,  Falmouth,  Mass. 

Fig.  6c2.  Prorhynchus  stagnalis.  ch,  chitinous  stUetto;  p6  bulb-like  cirrus;  vs.  -^mi- 
nal  vesicle;  ds,  ductus  seminalis;  t,  testis  follicle;  otx;mng  of  male  sexual  organ>  into 
pharyngeal  pocket;  oi»,  ovary;  e,  mature  egg.    X  i5-     t.\Uer  von  uraa.j 


-ov 


340 


FRESH-WATER   BIOLOGY 


29  (28)  With  two  very  small  eyes,  yellowish  by  transmitted  light,  whitish  by 
reflected  light,  lying  just  before  the  brain  in  the  widest  re- 
gion of  the  pharynx.    .    Prorhynchus  applanatus  Kennel  1888. 

Length  4  mm.  White.  Body 
much  flattened  at  both  ends. 
Pharynx  very  muscular.  In- 
testine a  slender  straight  tube 
with  one  diverticulum  extend- 
ing anteriorly  under  the  phar- 
ynx and  numerous  slender  very 
closely  set  lateral  diverticula. 
Greenhouse,  University  of  Ne- 
braska, Lincoln,  Neb. 


Fig.  603.    Prorhynchus  applanatus .   From  life.    X  20.    (After  Kennel.) 


30  (3)  Female  sexual  organs  divided  into  ovary  and  yolk  glands.     Male  sex 
organs  complex Section  Lecithophora  .    .      31 

Ovary  in  general  small  and  simple.  Yolk  glands  extremely  variable,  elongated,  lobed,  or 
forming  a  network  which  anastomoses.  Chitinous  portion  of  male  copulatory  organ  very 
complicated  and  variable  in  form. 


31  (74)     Proboscis  either   lacking  entirely  or  if  present  without  a  definite 
sheath Subsection  Liporhynchia  .    .     32 

This  division  contains  the  greater  part  of  the  fresh-water  Turbellaria. 


32  (61)  With  a  cask-shaped  pharynx  parallel  to  the  ventral  surface  or  slightly 
inclined  and  with  the  end  directed  forward.  But  one  genital 
pore Family  Dalyellidae  .    .     2>2> 

With  the  exception  of  the  genus  Opistomum,  which  is  not  represented  in  this  country,  the 
pharynx  is  typically  cask-shaped  and  opens  into  the  anterior  end  of  the  intestine.  The  genital 
pore  opens  on  the  ventral  surface  posterior  to  the  mouth.  Ovary  simple.  Yolk  glands  variable, 
female  receptaculum  seminis  and  a  simple  uterus  are  present.  Testes  always  paired.  Chitinous 
portion  of  male  copulatory  organ  often  very  complex.  Pigment  eyes  usually  present,  but 
without  other  sense  organs.  Protonephridium  consists  of  two  principal  branches  which  open 
on  the  ventral  surface.     Rhabdoids  and  glands  of  integument  prominent. 


33  (60)     Without  a  separate  pocket  for  the  chitinous  part  of  the  cirrus.  .     34 


34  (59)     Sexual  pore  in  posterior  third  of  body.     The  paired  yolk  glands  un- 
branched  and  separate.    .    Dalyellia  Fleming  1822    .    .     35 

This  is  the  one  commonly  known  as  Vortex  Ehrenberg  183 1. 


THE    FREE-LIVING   FLATWORMS    (TUR  BELL  ARIA) 


341 


35  (36)     The  chitinous  portion  of  the  male  copulatory  organ  is  represented 
merely  by  the  chitinous  tube  of  the  ductus  ejaculatorius. 

Daly  cilia  incrmis  von  Graff  191 1. 


Length  0.6  mm.  Flattened.  Posterior  end 
modified  into  a  kind  of  adhesive  disk.  Color 
white  by  reflected  light.  Intestine  very 
broad  and  yellow  in  color.  Eyes  dul^  yellow. 
Accessory  pigment  spots  irregularly  groui)ed 
near  the  eyes.  The  locomotor  movements 
are  very  quick.     Rochester,  N.  Y. 


Fig.  604.  Dalyellia  inermis.  (/I)  Ventral  view, 
slightly  compressed:  e,  eye;  m,  mouth;  vi,  yolk 
gland;  ov,  ovary;  go,  genital  pore;  co.  male 
copulatory  organ;  le,  testes.  X  115.  (B)  .Ad- 
hesive disk  of  posterior  end.  (C)  Male  copula- 
tory organ  enlarged:  c/i,  chitinous  tube;  ks,  vesi- 
cula  granulorum;  vs  vesicula  seminalis.  X  300. 
(After  von  Graff.) 


36  (35)     Provided  with  true  chitinous  organ 37 


37  (38)     Chitinous  portion  of  cirrus  consists  of  a  single  chitinous  spine. 

Dalyellia  rochesteriana  von  Graff  191 1. 


Scarcely  i  mm.  long.  Closely  resembles  Z).  rheesi.  Colorless,  transparent 
with  very  small  dermal  rhabdites.  Brownish  mesenchymatous  pigment  not 
so  abundant  as  in  D.  rheesi.  Intestine  reddish-ocher-yellow.  Sexual  ix>re 
lies  just  posterior  to  the  intestine  in  the  beginning  of  the  last  third  of  the 
body.     Rochester,  N.  Y. 


Fig.  605.     Dalyellia  rochesteriana.     Male  copulatory  organ  enlarged:  ch,  chitinous 
spine;    vs,  vesicula  seminalis;  ks,  vesicula  granulorum.     (After  von  Graff.) 


38  (37)     Chitinous  portion  of  cirrus  consists  of  more  than  one  piece.    . 


30 


39  (44)     Chitinous  portion  of  cirrus  consists  of  a  number  of  transverse  spines 
arranged  in  a  row 4° 


342 


FRESH-WATER    BIOLOGY 


40  (41)     Spines  of  unequal  size  and  shape  set  in  a  basal  piece. 

Dalyellia  dodgei  von  Graff  191 1. 

Length  rarely  more  than  i  mm  Integument  colorless.  Intestine  greenish  from  contained 
algae.  Mesenchyma  mottled  with  sepia-brown  pigment.  Eyes  black.  Found  very  commonly. 
Rochester,  N.  Y. 


Fig.  606.  Dalyellia  dodgei.  (.1)  Ventral  view  slightly  compressed.  X  65.  (B)  Male  copulatory  organ 
strongly  compressed.  Explanation  of  figures:  be,  bursa  copulatrix;  cli.  chitmous  organ;  cp.  adhesive 
papillae;  i  intestine;  e,  egg;  6,  brain;  ois  ovary;  go  genital  pore;  g/»,  graspmg  papillae  of  pharynx;  vg, 
vesicula  granulorum;  vi,  mouth;  mgc,  male  genital  canal;  ph,  phary^nx;  pe,  cirrus:  pi,  mesenchyma  pig- 
ment; rs,  receptaculum  seminalis;  sp,  sperm  masses;  te,  testes;  vi,  yolk  gland,  vs,  vesicula  seminalis.  Much 
enlarged.     (After  von  Graff.) 

41  (40)     Spines  of  same  size  and  shape,  arranged  loosely  in  a  ring  without  a 

basal  piece 42 

42  (43)     With  a  crown  of  about  16  spines,  tapering  from  base  to  the  point. 

Dalyellia  eastmani  von  Graff  191 1. 


Length  0.3  to  0.5  mm.  Color  of  me- 
senchymatous  fluid  pale  yellow  with 
spherical  bodies  which  contain  cinnamon- 
brown  granules  in  a  clear  brown  fluid. 
Rhabdites  short  and  relatively  thick  and 
rounded  at  both  ends.     Rochester,  N.  Y. 


Fig.  607.  Dalyellia  eastmani.  {A)  Ventral 
view  uncompressed.  X  loo.  (B)  Malecopula- 
tory  apparatus.  X  600.  Explanation  of  figures: 
he,  bursa  copulatrix;  be,,  blind  sack  of  burs.i; 
be,,,  opening  of  blind  sac;  e,  egg;  g,  brain;  m, 
mouth;  ge,  ovary;  go,  genital  pore;  rs,  recepta- 
culum seminis;  vs,  vesicula  seminalis;  te,  testes; 
vi,  yolk  gland;  ag,  common  atrium;  0,  opening 
of  the  male  copulatory  organs  into  genital  canal; 
vg,  vesicula  granulorum;  sp,  sperm  mass;  eh, 
chitinous  crown  of  spines;  da,  intestine;  pit, 
pharynx;  sb,  granules  of  secretion.  (After  von 
Graff.) 


THE   FREE-LIVING   FLATWORMS    (TURBELLARIA)  343 

43  (42)     With  a  crown  of  8  spines,  thickened  near  the  middle  and  tapering 
to  fine  points  at  both  ends. 

Dalyellia  blodgetti  (Silliman)  1885. 


OV 


Length  0.6  mm.  Color  light  brown. 
A  number  of  sensory  hairs  on  anterior 
end.  Basal  piece  of  the  tube  which 
encloses  the  spines  is  not  chitinous  but 
membranous  and  placed  in  the  male 
genital  canal  which  opens  into  the 
atrium.  Erie  canal,  Rochester,  and 
Monroe  Co.,  N.  Y. 


_  Fig.  608.  Dalyellia  blodgetti.  {A )  En- 
tire: b,  brain;  vi,  yolk  gland;  g,  cirrus;  e, 
eye;  ov,  ovary;  be,  bursa  copulatrix;  ph 
pharynx;  s,  salivary  gland.  X  90  (After 
billiman.)  {B)  Crown  of  spines  from  chitin- 
ous portion  of  male  copulatory  organ  with 
opening  {0)  into  the  genital  canal.  From 
a  strongly  compressed  preparation.  Very 
much  enlarged.      (After  von  Graff.) 


A  B 

U  (39)  Chitinous  portion  of  cirrus  bears  two  longitudinally  placed  stalks 
on  one  end  of  which  either  one  or  two  longitudinal  terminal 
branches  are  set.  The  terminal  branches  may  be  set  with 
spines 4- 

45  (46)  Each  chitinous  stalk  bears  two  terminal  branches,  one  set  with 
spines  and  one  with  no  spines. 

ds  Dalyellia  fairchildi  von  Graff  1 9 1 1 . 


eae' 


Similar  in  size  and  color  to  D.  rheesi  but  more 
slender,  with  a  longer  tail  and  the  uterus  lies  pos- 
terior to  the  sexual  pore.  The  egg  is  round  to  oval 
in  shape  and  measures  loS  to  140 /i.  Yolk  glands 
open  as  in  D.  rheesi  through  a  common  yolk  duct 
but  are  not  lobed,  barely  notched. 


Fig.  609.  Dalyellia  fairchildi.  (.4)  Male  copulatory 
apparatus.  X  430.  (fi)  Chitinous  piece  enlarged.  X 
850.  ds,  ductus  seminaiis;  eae,  outer  branch  with  spines 
folded;  eai,  inner  branch  with  no  spines;  mv,  median 
projection;  pd,  opening  of  cirrus  sheath;  pp,  cirrus  pa- 
pillae; .v,  double  row  of  spines;  st,  stalk;  vg,  vesicula  gran- 
ulorum;  vs,  vesicula  seminaiis;  q,  transverse  bar;  qs, 
transverse  spines.     (After  von  Graff.) 


344 


FRESH-WATER   BIOLOGY 


46  (45)     Each    chitinous    stalk    bears    a    single    terminal    branch    set    with 
spines 47 


47  (so)     The  spines  on  the  terminal  branch  are  jointed 48 


(49)     Each  spine  consists  of  three  joints.     Stalk  long,  somewhat  variable 
in  shape Dalyellia  rheesi  von  Graff  191 1. 


Length  i  mm.  When  swim- 
ming freely  the  anterior  end  is 
broadly  rounded,  in  crawling, 
truncated  as  shown  in  figure. 
Integument  colorless  with  nu- 
m  e  r  o  u  s  delicate  rhabdites. 
Mesenchyma  colored  by  sepia- 
brown  to  cinnamon-red  gran- 
ules in  a  clear  yellow  fluid.  In 
the  living  animal  the  brain 
region  appears  clear  white  and 
the  ventral  surface  lighter  in 
color  than  the  dorsal,  eyes 
black.  In  pools  along  Erie 
canal. 


Fig.  610.  Dalyellia  rheesi.  {A) 
slightly  compressed:  te,  testes;  vi, 
yolk  gland;  vs,  vesicula  seminalis; 
ch,  chitinous  portion  of  cirrus;  dg, 
duct  of  yolk  gland;  be,  bursa  copu- 
latrix;  go,  genital  pore;  e,  egg;  ov, 
ovary.  X  60.  {B)  Male  copula- 
tor>'  apparatus:  pr,  cirrus  tube; 
meg,  male  genital  canal;  0,  open- 
ing of  genital  canal  into  common 
atrium;  st,  short  stalk  of  chitinous 
piece.  X  600.  (C)  Median  ventral 
grooved  piece  (mv)  turned  back; 
si,  variation  in  stalk.  X600.  (After  | 
von  Graff.) 


THE  FREE-LIVING   FLATWORMS    (TURBELLARIA) 


345 


49  (48)     Each  spine  consists  of  two  joints.     Stalk  much  reduced  and  variable 
in  shape Dalyellia  articidata  von  Grafi  igii. 

Similar  to  D.  rheesi  in  color  and  general  structure.     Sexual  organs  differ  as  shown  by  a  com- 
parison of  Figs.  610  and  611.     Same  localities  as  D.  rheesi. 

St 


Fig.  611.  Dalyellia  articulata.  [A)  Posterior  end  with  sex  organs  from  a  strongly  compressed  specimen: 
be,  bursa  copulatrix;  ch,  chitinous  part  of  male  organs;  ge,  ovary;  gii,  genital  pore;  rs,  receptaculura 
seminis;  «,  uterus  with  egg;  vii  yolk  gland;  vs,  vesicula  seminalis.  {B)  Chitinous  organ  with  the  reduced 
stalk  (5/).     (C)  Chitinous  portion  of  cirrus  showing  variation  from  (5).   Much  enlarged.    (After  von  Graff.) 

50  (47)     The  reduced  spines  on  the  terminal  branch  are  unjointed  and  consist 

of  but  one  piece 51 

51  (52)     The  dorsal  transverse  bar  bears  a  row  of  fine  spines. 

Dalyellia  mohicana  von  Graff  191 1. 


Free  swimming,  of  extremely  slender  form,  similar  to  D. 
rossi.  Anterior  end  of  the  chitinous  portion  of  cirrus  not 
sharply  defined.  Differs  from  D.  rossi  chiefly  in  structure 
of  the  chitinous  organ,  the  stalk  of  which  is  not  so  broad 
or  flat  as  in  that  form.  One  terminal  branch  of  this  organ 
bears  eleven  curved  teeth,  the  other  seven  of  the  same 
type  and  one  which  is  larger  and  three  sided.  The  trans- 
verse bar  bears  a  row  of  straight,  sharply  pointed  spines. 
Brackish  water,  Falmouth,  Mass. 


Fig.  612.  Dalyellia  mohicana.  (/I)  The  animal  swimmmg. 
X  60.  (B)  Chitinous  part  of  cirrus.  Much  enlarged,  ca,  end 
branch  with  a  row  of  spines;  si,  stalk;  qd,  dorsal  transverse 
connecting  bar,  with  a  row  of  spines,  as;  qv,  ventral  transverse 
bar;  mv,  median  projecting  piece.     (After  von  Graff.) 


346 


FRESH-WATER  BIOLOGY 


52  (48)     The  dorsal  transverse  piece  between  the  longitudinal  stalks  has  a 
single  median  chitinous  spine 53 


53  (54)     The  median  point  is  rudimentary;    much  shorter  than  the  terminal 
branches Dalyellia  viridis  (G.  Shaw)  1791. 


Length  5  mm.  Unpigmented  except  during  the  maturing  of  the  eggs 
when  there  is  a  brownish  pigment,  but  with  a  continuous  layer  of  zoo- 
chlorellae  under  the  integument  giving  the  characteristic  green  color. 
Rochester,  N.  Y. 

Fig.  613.  Dalyellia  viridis.  Chitinous  portion  of  cirrus:  si,  two-parted  stalk; 
ea,  terminal  branch.     Much  enlarged.     (After  von  Graff.) 


54  (53)     The  median  point  is  as  long  as  the  terminal  branches 55 


55  (56)     One  terminal  branch  is  not  jointed  but  consists  of  a  single  piece 
shaped  Uke  a  plow-share,  and  does  not  have  spines. 

Dalyellia  armigera  (O.  Schmidt)  1861. 


I 


Length  0.6  to  1.5  mm.  Color  yellowish,  reddish,  or 
brownish-gray.  Pharj^nx  very  large,  almost  one-fourth 
of  entire  length  of  body.  Anterior  end  blunt,  tail  with 
adhesive  papillae.  Swims  actively  at  the  surface  of  stand- 
ing and  running  water.  Brooks,  Monroe  Co.,  N,  Y.; 
Lake  St.  Clair,  Mich. 


Fig.  614.  Dalyellia  armigera.  ^  (A )  living,  uncompressed.  X  5°- 
(B)  chitinous  portion  of  cirrus'  m,  median  point;  ea,  terminal 
branch  with  3  to  g  (mostly  7  or  8)  spines;  ea2.  terminal  branch 
shaped  like  a  plow-share;  g,  dorsal  and  ventral  cross  pieces; 
St,  stalk.     X  500.     (After  von  Graff.) 


56  (55)     Both  terminal  branches  bear  a  row  of  plates  or  spines. 


57' 


THE   FREE-LIVING   FLATVVORiMS    (TURBELLARIA) 


347 


57  (58)     Terminal    spine   of  only  one  cerminal  branch  unlike  the  others  in 
shape Daly ellia  rossi  von  Grsiii  igi I. 


Length  a  little  over  i  mm.  Similar  in  form  to  D.  rheesi.  Color  of 
mesenchyma  bright  or  dark  reddish-yellow  to  cinnamon-brown.  Eyes 
brown  or  black.  Intestine  brownish-yellow.  Adhesive  cells  on  short 
tail.  Common  at  Rochester,  N.  Y.  In  brackish  water,  Falmouth,  Mass. 
See  Fig.  589  for  view  of  entire  animal. 


Fig.  615.  Dalyellia  rossi.  Chitinous  part  of  male  copulatory  organs,  st,  chitin- 
ous  stalk;  eai  and  ea2,  terminal  branches  with  spines;  mv  and  md,  median  ventral  and 
dorsal  projections.     X  285.     (After  von  Graff.) 


58  (57)     Terminal  spines  on  both  terminal  branches  unlike  the  others  in  shape. 

Dalyellia  sillimani  von  Graff  191 1. 

Length  i  mm.  Integument  colorless  with  small  rhabdites.  In  heavily  pigmented  speci- 
mens the  mesenchyma  appears  dark  brown;  those  with  less  pigment  show  cells  hlled  with  yellow 
fluid  and  containing  brown  pigment  granules.  Intestine  ocher-yellow.  Eyes  black.  Roches- 
ter, N.  Y.,  in  brooks  and  pools. 


Fig.  616.  Dalyellia  sillimani.  (A)  slightly  compressed:  bs,  bursa  seminalis;  e,  egg;  ov,  ovar>';  go. 
sexual  pore;  vs,  vesicula  seminalis.  X  70.  (B)  Male  copulatory  organ:  ea,  and  eaj,  terminal  branches  of 
chitinous  organ;  kdr,  granular  glands  of  one  side;  ks,  granular  secretion;  nui,  median  dorsal  chitinous 
point;  mp,  retractor  muscles;  mv,  median  ventral  grooved  chitinous  piece;  />",  cirrus  opening;  vd,  vas  de- 
ferens; vs,  vesicula  seminalis;  Sy  last  chitinous  plate  of  right  terminal  branch;  sp,  last  chitinous  plate  of 
left  terminal  branch;   st,  stalk.     X  330.     (After  von  Graff.) 


348 


FRESH-WATER   BIOLOGY 


59  (34)     Sexual  pore  anterior  to  the  middle  of  the  body.     Yolk  glands  branched 
and  either  separate  or  united  to  form  a  network. 

Phaenocora  Ehrenberg  1836. 
This  is  the  genus  formerly  known  as  Derostomum  Oersted  1843. 

Only  one  species  known  in  this  country. 

Phaenocora  agassizi  von  Graff  191 1. 

Length  i  to  2  mm.  Milk-white.  Intestine 
greenish-yellow.  Eyes  reddish-yellow.  Between 
the  eyes  and  the  pharynx  or  extending  over  the  an- 
terior end  of  it  there  is  a  zone  of  so-called  crystal- 
loids which  appear  clear  or  grayish-brown  in 
transmitted  light.  This  species  is  an  exception  for 
the  genus  in  that  it  possesses  rhabdites.  Pharynx 
cask-shaped,  intestine  more  or  less  deeply  lobed. 
In  pool,  Rochester,  N.  Y. 

Fig.  617.  Phaenocora  agassizi.  (^)  slightly  compressed: 
te,  testes;  da.  intestine;  ph,  pharyn.x.  X  22.  (B)  An- 
terior part,  enlarged:  ^r,  crj'stalloids;  6c,  bursa  copulatrix; 
mm,  muscles  of  bursa;  de-^,  proximal,  and  den,  distal  part 
of  ductus  ejaculatorius;  dg,  duct  of  yolk  gland;  ge,  ovary; 
go,  genital  pore;  rs,  receptaculum  seminis;  au,  eye.  X  70. 
(After  von  Graff.) 


60  (33)     With  a  separate  pocket  for  the  chitinous  portion  of  male  copulatory 
organ.     Sexual  pore  lies  in  last  third  of  body  .    .  Jensenia. 
Only  one  species  known  in  this  country. 

Jensenia  pinguis  (Silliman)  1885. 


Length  about  1.5  mm.  Color 
brown  to  reddish,  darkest  in  middle 
of  body.  Male  genital  canal  divided 
at  its  connection  with  the  common 
atrium,  one  branch  forming  the 
pocket  for  the  chitinous  organ  while 
the  other  leads  to  the  seminal  ves- 
icle.    Rochester,  N.  Y. 


Fig.  618.  Jensenia  pinguis.  {A)  Entire:  m,  mouth;  vi,  yolk  glands;  /,  testes; 
e,  eye;  ph,  pharynx;  s,  glands;  i,  intestine.  X  30.  (After  Silliman.)  {B)  Sexual 
organs  from  animal  compressed  from  side:  hs,  bursa  seminalis;  bsm,  retractor  mus- 
cles of  same;  ch,  pocket  which  contains  chitinous  organ;  chm,  one  of  four  muscles 
for  same;  e,  egg;  gd,  oviduct;  ge,  ovar>';  go,  genital  pore;  sd,  shell  glands;  te,  testes; 
udi,  uterus  diverticulum  of  atrium;  list,  duct  of  uterus;  vd,  vasa  deferentia;  lis,  vesi- 
cula  seminalis;  vst,  duct  from  same;  wgc,  female  genital  canal.  X  60.  (After  von 
Graff.) 


61  (32)     Pharynx   rosette-shaped,   standing    perpendicular    to    the    ventral 
surface Family  Typhloplanidae  .    .     62 

The  genital  pore  Hes  back  of  the  mouth.  Ovary  one,  testes  paired.  Other  parts  of  sexual 
organs  variable.  Protonephridium  with  two  main  branches  which  may  have  either  one  or  two 
openings  on  the  ventral  surface  or  may  lead  to  the  surface  through  the  mouth  or  sexual  pore. 
Eyes,  non -pigmented  light-refracting  organs;  cihated  pits  may  be  present.  Rhabdoids  play 
an  important  part  in  classification.     Both  summer  and  winter  eggs  produced  in  some  species. 


THE  FREE-LIVING   FLATWORMS    (TURBELLARIA) 


349 


62  (63)     Genital  pore  in  posterior  third  of  body. 


Tribe  Olisthanellini 


Excretory  system  opens  on  ^dorsal  surface  with  one  asymmetrical  or  two  symmetrically 
placed  openings.     Testes  dorsal  to  the  yolk  glands.    Without  atrial  copulatory  organ. 

Single  genus  thus  far  reported  in  America Olisthatiella. 

Only  one  species  in  this  country.   .    Olisthanella  caeca  (Silliman)  1885. 


Length  1.3  mm.  Without  eyes.  Without  long  sensory  hairs.  Color 
grayish-white.  Sometimes  apparently  colored,  due  to  food  in  intes- 
tine. Pharynx  rosette-shaped  and  nearly  central  in  position.  Intes- 
tine large.  Rhabdites  and  tracts  prominent.  Female  organs  only  are 
known.  Sluggish  and  found  only  in  mud  under  stones.  Monroe  Co., 
N.  Y. 


Fig.  619.     Olisthanella  caeca,    ph,  pharynx;  t,  intestine;  b,  brain;    vi,  yolk 
pland;  oz),  ovary;  ^o,  genital  pore;  /j,  rhabdite  tracts.  X  35.     (After  Sillinaan.) 


63  (62)     Genital  pore  in  anterior  two-thirds 64 


64  (71)     Testes  ventral  to  the  yolk  glands.     Rhabdites  only  in  mesenchyma 
tracts Tribe  Typhloplanini    .    .     65 

Protonephridia  with  two  main  branches  which  communicate  with  the  exterior  through  a 
transverse  branch  which  leads  either  to  the  mouth  or  to  the  genital  atrium.  With  or  without 
atrial  copulatory  organs. 


65  (66)     Anterior  end  of  body  a  retractile  proboscis.     .    .    Rhynchomesostoma. 
Only  one  species.  .    .    .     Rhynchomesostoma  rostratum,  (Miiller)  1773. 


Length  2  mm.  European  specimens 
reach  a  length  of  5  mm.  when  extended. 
Very  transparent.  Body  t1uid  rose  or 
yellowish-red  in  color.  Intestine  contains 
yellowish-red  oil  droplets.    \'cntral  surface 

flat,  dorsal  convex.     Anterior  end  of  body  like  a  telescopic  tube. 

Pharynx  small,  lying  somewhat  before  the   middle  of  the   body. 

Rochester,  N.  Y. 

Fig.  620.    Rhynchomesostoma  rpstratum.    {A)  Proboscis  partly  extended. 
(5)  Fully  contracted.     X  40-     (After  von  Graff.) 


66  (65)     Anterior  end  of  body  without  retractile  proboscis 67 


67  (70)     Without  atrial  copulatory  apparatus 68 


3  so 


FRESH-WATER   BIOLOGY 


68  (69)     With  a  separate  receptaculum  seminis,  whose  short  duct  is  closed  by  a 
muscular  ring.    Dermal  rh^-bdites  present.    .    .  Strongylostoma. 

Only  one  species  known  in  this  country. 

Strongylostoma  gonocephalum  (Silliman)  1885. 


Length  1.2  mm.  Mesenchyma  yellowish,  intestine 
with  yellowish  oil  droplets.  Eyes  carmine  red.  Small 
rhabdites  are  present.  This  form  differs  from  the 
widely  distributed  European  form,  Strongylostoma 
radiatum  Miiller  chiefly  in  the  possession  of  two 
shallow  oval  pits  which  lie  close  behind  the  eyes  at 
the  side.  The  integument  is  slightly  raised  around 
them  and  each  bears  vacuoles  and  rhabdoids. 
Excretory  pore  opens  into  mouth.  Erie  Canal, 
Monroe  Co.,  N.  Y. 


Fig.    621.      Strongylostoma    gonocephalum.      [A)  Entire 

animal:    tr,  tracts  of  rhabdites;    ph,  pharynx;    ov,  ovary; 

bs,  bursa  seminalis;    vi,  yolk  glands;    p,  cirrus;   go,  genital 

pore;    ec,  egg  capsule.     X  40.      (After  Silliman.)      (B)  Out-  line  of  anterior 

end  with  eye  (ou)  and  shallow  pit  (g/)  of  one  side.     Enlarged.    (After  von 

Graff.) 


69  (68)    Without  a  separate  receptaculum  seminis Typhloplana. 

Only  one  species  known  in  this  country. 

Typhloplana  viridata  (Abildgaard)  1790. 


Length  0.5  to  i  mm.  Transparent.  Zoochlorellae  in  the  mesenchyma  give 
it  a  grass-green  color.  Tapering  at  both  ends.  Without  eyes.  Anterior 
end  bluntly  pointed,  posterior  end  pointed.  Pharynx  just  anterior  to 
center.  Sexual  pore  close  behind  pharynx.  Viviparous.  The  summer 
eggs  develop  within  the  body  of  the  parent.  Winter  eggs  are  as  many  as 
ten  in  number  and  yellowish-brown  in  color. 

The  pear-shaped  bulbous  cirrus  contains  a  straight  chitinous  tube,  the 
ductus  ejaculatorius.  The  male  genital  canal  is  set  with  small  spines;  the 
small  egg-shaped  or  somewhat  elongated  testes  he  near  or  back  of  the  pharynx. 

Luther  and  von  Graff  regard  the  form  collected  from  Monroe  Co.,  N.  Y., 
and  described  by  SiUiman  under  the  name  of  Mesostoma  viviparum,  also 
those  collected  from  West  Twin  Lakes  and  Old  Channel  Round  Lake, 
Charlevoix,  Mich.,  and  described  by  Woodworth  under  the  names  M. 
viviparum  and  M .  vividatum,  as  identical  with  the  European  species.  There 
seems  to  be  no  doubt  that  this  is  the  case,  Typhloplana  viridata  was  col- 
kcted  by  von  Graff  at  Rochester,  N.  Y. 


Fig.  6; 


Typhloplana  viridata.     />t,  Zoochlorellae;  /»A,  pharynx;  (5  ,  9,  male  and 
female  genital  pore;  pe,  cirrus.     X  70.     (After  von  GraS.) 


THE   FREE-LIVING   FLATWORMS    (TURBELLARIA) 


351 


70  (67)     With  atrial  copulatory  apparatus. 

Castrada  hofmanni  (M.  Braun)  1885. 

Length  1.5  mm.  Unpigmented.  Colored  green  from  zoochlo- 
rellae  in  mesenchyma.  Cylindrical.  Anterior  end  rounded,  pos- 
terior end  running  out  to  a  blunt  point.  Without  eyes.  Large 
rhabdoids  in  tracts.  Pharynx  somewhat  before  the  middle  of 
the  body  with  genital  pore  shortly  back  of  it.  Testes  are  elon- 
gated oval  to  pear-shaped.  Yolk  glands  are  deeply  lobed.  The 
male  copulatory  organ  and  bursa  copulatrix  are  entirely  enclosed 
by  the  muscular  mantle  of  the  atrium  copulatorium.  Rochester. 
N.  Y. 

Fig.  623.  Castrada  hofmanni.  Cirrus,  bursa  copulatrix,  and  atrium 
copulatorium.  Diagram  from  preparations  subjected  to  pressure:  vs, 
vesicula  seminalis;  ks,  granular  secretions;  sp,  spermatophore;  rm,  cir- 
cular muscles;  t,  teeth-like  spines;  ac,  atrium  copulatorium;  de,  ductus 
ejaculatorius.     Much  enlarged.     (After  Luther.) 


71  (64)     Testes   dorsal   or   lateral  to   the  yolk  glands.     Mesenchyma  with 

rhabdoids  outside  of  tracts.  .   Tribe  Mesostomatini  .    .   72 

Sexual  pore  lies  in  anterior  two-thirds  of  body.  Protonephridial  ducts  open  through  mouth 
to  exterior  as  in  most  Typhloplanini  and  in  some  cases,  mouth,  protonephridia,  and  genital 
organs  have  a  common  external  opening.  Rhabdites  play  a  very  important  part  in  classi- 
fication.    The  larger  rhabdocoels  belong  to  this  group. 

72  (73)     With  a  ventral  epidermal  pouch  and  a  ductus  spermaticus  which 

connects  the  bursa  copulatrix  with  the  female  genital  canal. 

BothromesostofUd. 
Only  one  species  known  in  this  country. 

Bothromesostoma  personatum  (O.  Schmidt)  1848. 

Length  7  mm.  Color  on  anterior  and  posterior  ends  and  on  lateral  margins  and  ventral 
side  a  clear  brown.  In  mature  specimens  the  pigment  is  so  massed  that  together  with  the  dark 
color  of  the  intestine  it  gives  a  dark  brown  to  bluish-black  color  to  the  dorsal  surface  above  the 
intestine.  Some  specimens  show  a  mixture  of  brown  and  black.  The  oval  eyes  are  about  as 
far  distant  from  the  lateral  margins  as  from  each  other.  They  are  i>erceptible  only  in  the 
lighter  pigmented  specimens.  The  ventral  epidermal  pouch  occurs  somewhat  posterior  to 
the  eyes.  The  common  opening  for  mouth,  protonephridial  ducts,  and  genital  pore  is  located 
about  the  middle  of  the  ventral  surface.  Both  summer  and  winter  eggs  are  produced.  The 
former  produce  the  viviparous  young.    Ann  Arbor,  Mich. 


A  B 

Fig.  624.     Bothromesostoma  personatum.     U)  entire  animal.  X  5-     (After  Schmidt.)    (B)  Diagram  of 

sexual  organs:   he,  bursa  copulatrix;    dsp,  ductus  spermaticus;  pm,  opening  of  cirrus;   rs,  receptaculum 

seminis;  pg,  genital  pore;  dg,  duct  of  yolk  gland;  ph,  phar>'nx;  no,  opening  of  protonephridium.     Much 
enlarged.     (After  Luther.) 


352 


FRESH-WATER   BIOLOGY 


73  (72)     Without  a  ventral  epidermal  pouch  and  ductus  spermaticus. 

Mesostoma. 
Only  one  species  known  in  America. 

Mesostoma  ekrenhergii  (Focke)  1836. 

This  species  attains  a  length  of  12  to  15  mm.  in  Europe.  Greatest  length  recorded  for  Amer- 
ican specimens  is  6  mm.  Verj^  transparent.  Color  pale  yellowish  to  brownish.  Intestine 
yellowish-brown.  Thin,  flat,  and  leaf-like  in  outline.  Anterior  end  tapering,  conical.  Poste- 
rior end  tapering  sharply  and  terminating  in  an  acute  caudal  process.  Conspicuous  tracts  of 
rhabdites  lead  to  the  anterior  end.  Eyes  black.  Two  shallow  pits  occur  on  the  dorsal  surface 
of  the  anterior  end,  one  on  either  side.  Both  summer  and  winter  eggs  are  produced  but 
rarely  at  the  same  time.  The  summer  eggs  develop  and  the  young  embryos  may  be  seen 
within  the  body  of  the  parent.  From  IlUnois  River;  Lake  St.  Clair,  Mich.;  Ohio;  and  Elk- 
horn  River,  Neb. 


)  ^y. 


B 


1 


Fig.  625.  Mesostoma  ehrenbergii.  (A)  Diagram  from  ventral  side  showing  nervous,  digestive,  and 
reproductive  systems.  Left  side  shows  summer  ©ggs,  the  light,  winter  eggs:  be,  bursa  copulatrix;  da, 
anterior  branch  of  intestine;  dai,  posterior  branch  of  intestine;  go,  genital  pore;  ^,  ovary;  pe,  cirrus; 
pit,  pharynx;  ts,  receptaculum  seminis;  le,  testes;  u,  uterus;  vd,  vas  deferens;  vi,  yolk  gland;  vs, 
vesicula  seminalis;  wgc,  female  genital  canal;  co,  subesophageal  commissure  of  ventral  nerves;  din, 
dorsal  longitudinal  nerve;  dn,  dorsal  nerve  of  brain;  g.  brain;  Inv,  ventral  longitudinal  nerve;  nr,  pharyn- 
geal nerve  ring;  us,  duct  of  uterus;  ven,  ventral  nerve  of  brain;  i^d,  duct  of  yolk  gland;  vtii  and  dm2,  the 
two  pairs  of  anterior  nerves  of  brain;  x,  chiasma  of  anterior  nerves.  X  6.  (After  von  Graff,  Vogt, 
Fuhrmann,  and  Luther.)     (B)  From  life,  showing  young  worms  in  left  uterus.     X  Q.     (After  Woodworth.) 


74  (31)  With  a  genuine  proboscis  which  lies  within  a  sheath  and  communi- 
cates with  the  exterior  through  an  opening  at  the  anterior 
end.     Pharynx  rosette-shaped. 

Subsection  Calyptorhynchia  .    .     75 

A  small  group  easily  recognized  by  the  genuine  proboscis.  A  bursa  copulatrix  is  present. 
The  cirrus  is  divided  into  vesicula  seminalis  and  vesicula  granulorum.  The  rosette-shaped 
pharynx  lies  on  the  ventral  surface. 


THE   FREE-LIVING   FLATWORMS   (TURBELLARIA) 


353 


75  (76)     With  a  single  sexual  pore Family  Polycystididae. 

Two  ovaries,  two  yolk  glands  with  finger-like  lobes,  -and  two  compact  testes.  Bursa  copu- 
latrix  small  and  without  a  separate  external  opening. 

Single  genus  thus  far  found  in  America Polycyslis. 

Only  one  species  known  in  America.  .  Polycystis  roosevclti  von  Graff  19 1 1 ! 

Length  2  mm.  Anterior  end  of  body  transparent,  the  rest  of  the  body  faintly 
reddish.  A  subcutaneous  brown  pigment  between  the  longitudinal  muscle  fibers 
gives  a  more  or  less  striated  appearance.  The  extremely  flexible  proboscis  lies 
withm  Its  sheath  just  in  front  of  the  brain  at  the  anterior  end.  The  mouth 
and  pharynx  lie  in  the  beginning  of  the  second  third  of  the  body  and  the  genital 
pore  lies  between  the  second  and  last  third  of  the  body.  Posterior  end  very 
bluntly  rounded,  anterior  end  somewhat  narrower.  Closely  resembles  the 
European  species  P.  gaciti  Bresslau  except  in  the  structure  of  the  chitinous 
portion  of  male  copulatory  organ. 
Fig.  626.  Polycystis  roosevelli.  Chitinous  cirrus  tube  with  bulb  (b),  ductus  seminal] 
(ds),  and  the  ducts  leading  from  the  granular  glands  (kd).     X  400.     (After  von  Graflf.) 

With  two  sexual  pores,  the  male  posterior  to  the  female. 

Family  Gyratricidae. 
One  or  two  ovaries,  with  yolk  glands  and  one  compact  testes  which  lies  on  the  left  side. 

Only  one  genus  known Gyratrix. 

Single  species  known  in  America. 

Gyratrix  hermaphroditus  Ehrcnbcrg  1831. 
Length  2  mm.  White  in  reflected  light.  Eyes  black.  Without  rhabdoids  or  pigment. 
Capable  of  contracting  into  a  ball,  or  extending  to  almost  double  its  length  as  long  as  it  remains 
actively  swimming.  Stiletto-sheath  of  male  copulatory  organ  a  short  wide  tube.  The 
very  large  bursa  copulatrix  has  a  separate  dorsal  opening  to  the  exterior.  Egg  capsule  oval. 
From  peat  bog,  Rochester,  Monroe  Co.,  N.  Y. 

One  subspecies  Gyratrix  hermaphroditus  hermaphroditus  Ehrenberg.  Stiletto-sheath  with  a 
hook  on  the  end.  The  egg  capsule  is  gradually  reduced  to  its  stalk  and  is  much  elongated. 
Rhabdoids  occur  in  the  terminal  cone  of  the  proboscis. 

-po 


76  (75) 


Fig.  627.  Gyratrix' hermaphroditus.  {A)  Ventral  view  of  compressed  specimen,  do,  dorsal  opening 
of;  be,  bursa  copulatrix;  ch,  chitinous  tube;  chst,  stalk  of  chitinous  tube;  chg,  chitinous  stiletto  IcidinK 
from  vesicula  granulorum;  ec,  egg  capsule  in  uterus;  ov,  ovary;  ,i;(/,  granular  secretor>'  glands;  ko,  external 
opening  of  kidney;  ph,  pharynx;  rltn,  attachment  of  the  long  prolx)scis  retractor  muscles;  ec,  end  cone 
of  proboscis;  rm,  muscular  portion  of  proboscis;  po,  external  opening  of  proboscis  sheath;  If,  tester; 
vd,  yas  deferens;  vg,  vesicula  granulorum;  vi,  yolk  glands;  vs,  vesicula  seminalis;  cf ,  male  and  9  .  female 
genital  pores.  X  30.  (After  von  Graff.)  (/?)  Stiletto-sheath  with  straight  tube.  0,  oiK-nin^  of  sliJctta 
sheath;  ch,  chitinous  stiletto  of  cirrus.  Much  enlarged.  (.After  Hallez.)  (C)  Gyratrix  hermaphroditus 
hermaphroditus.      Stiletto -sheath  with  curved  point.     Much  enlarged,     (.\fter  von  Graff.) 


354  FRESH-WATER   BIOLOGY 

77  (2)     Pharynx  either  variable  or  cyUndrical  and  lying  within  a  pharyngeal 

pocket.     Connective  tissue  well  developed. 

Suborder  AUoeocoela. 

The  intestine  is  an  irregular  sac  mostly  with  side  lobes  and  an  anterior  and  posterior  branch 
It  divides  to  form  a  ring  in  the  median  ventral  region,  thus  enclosmg  the  slender  cyhndrical 
pharynx  which  is  similar  in  position  and  appearance  to  that  of  the  plananans 

No  fresh-water  representative  of  this  Suborder  has  been  definitely  estabhshed  for  this 
country.  It  seems  clear  that  some  must  exist  in  this  region  and  be  found  on  further  study  ot 
the  American  favma. 

78  (i)     Intestine  consists  of  three  main  branches,  one  an  anterior  branch 

median  in  position,  and  two  running  to  the  posterior  end  of 
the  body,  one  on  either  side  of  the  pharyngeal  region. 

Order  Tricladida   .    .     79 

Mostly  larger  than  in  the  preceding  order.  Pharynx  usually  median  ventral  in  position,  elon- 
gated cyhndrical,  and  lying  within  a  pharyngeal  pocket  with  the  free  end  directed  posteriorly. 
Compare  figures  of  a  typical  Triclad  (Fig.  590)  and  Rhabdocoel  given  on  page  333- 

79  (104)     Found  in  fresh-water  ponds  or  streams.     .    .      Suborder  Paludicola. 

Only  one  family Planariidae  .    .     80 

Body  elongated,  flattened,  often  with  conspicuous  cephalic  appendages.  Inconspicuously 
colored. 


80  (103)     Pharynx  one • °^ 

81  (82)     With  an  adhesive  disk  on  anterior  end Dendrocoelum. 

Only  one  species  known  in  this  country. 

Dendrocoelum  lacleum  Oersted  1844. 

Greatest  length  22  mm.,  breadth  2  to  3  mm. 
Color  milk-white,  creamy,  yellowish,  or  in 
larger  older  specimens  sometimes  roseate.  No 
pigment  except  in  eye  spots.  Very  translu- 
cent. Intestine  colored  by  contained  food.  A 
shght  constriction  just  behind  the  plane  of  the 
eyes  sets  off  the  head  and  produces  the  rounded, 
cephaUc  appendages.  Posterior  end  rounded. 
Lateral  margins  nearly  parallel  when  at  rest 
or  contracted.  Median  adhesive  disk  extremely 
variable.  Usually  about  one-third  of  the  broad- 
est diameter  of  the  head.  Inconspicuous  in 
small  specimens.  It  is  not  a  true  sucker  but 
consists  of  a  depression  into  which  the  glands 
open  and  with  the  margin  somewhat  raised. 
Two  eyes  normally  but  from  one  to  six  accessory 
eyes  are  common.  Mass.,  Mich.,  Penn.,  Wis. 
'■  What  is  probably  a  variety  of  this  species  is 

described  as  a  non-pigmented  eyeless  Dendro- 
coelum collected  from  Mammoth  Cave  and  ad- 
joining caves  in  Kentucky. 


^-^ 


va.df. 


gl.sh:-::} 


Fig.  628.  Dendrocoelum  lacleum.  U)  From  life.  X4- 
(B)  Sex  organs,  dorsal  view:  brs,  copulatory  bursa; 
dt  ej,  ductus  ejaculatorius;  gl  sli,  shell  gland;  gl  prst, 
prostate  gland;  go  po,  genital  pore;  ov  dt,  oviduct; 
pe,  cirrus;  ut,  uterus;  va  df,  vas  deferens;  vag,  va- 
gina.    X  14.     (After  Woodworth.) 


82  (81)     Without  an  adhesive  disk  on  anterior  end 83 


J 


THE   FREE-LIVING    FLATWORMS    (TURBELLARIA)  355 

83  (102)     Normal  eyes  two  or  none Planaria   .    .     84 


84  (loi)     With  two  normal  eyes  (sometimes  with  one  or  more  irregularly 
placed  accessory  eyes) 85 


)5  (94)     Anterior  end  more  or  less  pointed  with  angular  cephalic  append- 
ages  86 


86  (91)  Anterior  end  bluntly  pointed,  angle  formed  by  lateral  margins  of 
head  not  less  than  60°.  Cephalic  appendages  blunt.  Body 
about  as  wide  just  back  of  appendages  as  immediately  in 
front  of  them 87 


87  (88)  Angle  formed  by  lateral  margins  of  head  much  greater  than  60^". 
Cephalic  appendages  very  inconspicuous,  almost  entirely 
wanting  in  young  specimens. 

Planaria  joremanii  (Girard)  1852. 

Length  of  mature  specimens  7  to  15  mm.,  breadth 
2  to  4  mm.  Color  nearly  uniform  seal-brown  or  dark 
gray  to  slate-black,  with  an  inconspicuous  gray  area 
on  each  cephalic  appendage.  Eyes  gray  with  a  cres- 
cent of  black  pigment  on  the  median  side.  Body 
comparatively  thick.  Ovaries  two,  ventral,  somewhat 
lobed  and  situated  about  halfway  from  anterior  end 
to  phar>'nx.  Testes  four  or  five  on  each  side,  un- 
paired, dorsal  and  irregularly  distributed  from  region 
of  ovaries  to  posterior  end  of  pharynx.  Does  not 
multiply  by  fission.  Found  in  small  streams  in 
Mass.,  Penn.,  Md.,  Va.,  and  near  Washington,  D.  C. 

The  species  described  by  Curtis  (1900)  under  the 
name  Planaria  simplicissima  and  later  by  Stevens  un- 
der the  same  name  clearly  must  be  regarded  as  syn- 
onymous with  the  species  establishetl  by  Girard  in 
1852  under  the  name  P.  foremannii.  This  species 
also  appears  under  the  name  P.  lugubris  in  various 
papers  dealing  with  the  physiology  of  planarians. 


ph\ 


tP 


Fig.  62Q.  Planaria  foremanii.  {A)  Outline  sketch  of  large  mature  specimen:  gp,  genital  pore;  pk. 
pharynx;  5,  sensory  area  on  cephalic  appendages.  X4  (.After  Stevens.)  (B)  Sexual  organs,  longitu- 
dinal section,  dorsal  view:  c,  cirrus;  d,  oviduct;  ph,  pharyn.x;  sv,  seminal  vesicles;  /,  testes;  ut,  uterus; 
V,  ovary;  vi,  yolk  glands;  vl,  vas  deferens.     X  20.     (After  Curtis.) 


88  (87)  Angle  formed  by  lateral  margins  of  head  about  60°.  CcphaHc  ap- 
pendages distinct.  Anterior  margin  of  cephalic  appendages 
of  about  same  length  as  posterior  margin 89 


356 


FRESH-WATER   BIOLOGY 


89  (90)  Color  blackish  to  purplish  or  brownish  by  reflected  light,  blackish 
or  gray  by  transmitted  light.  With  many  irregular  spots 
entirely  free  from  pigment.   .    Planaria  maculata  Leidy  1848. 

Length  15  mm.  Immature  specimens  average  about  8  to 
II  mm.  In  small  specimens  the  pigment  occurs  in  isolated 
patches  and  spots.  In  larger  specimens  the  pigment  patches 
are  confluent  chiefly  in  the  median  region  leaving  the  clear 
irregular  areas  which  give  a  ver>'  spotted  appearance  to  the 
animal.  Smaller  spots  of  deep  brown  or  black  scattered 
among  the  larger  patches.  Frequently  with  a  light  median 
streak.  Posterior  half  of  cephalic  appendages  with  non- 
pigmented  spots.  Ventral  surface  much  lighter  than  dorsal, 
almost  entirely  free  from  pigment.  Reproduces  freely  by 
transverse  fission  posterior  to  pharynx.  Sexually  mature 
specimens  not  common  in  most  localities.  Sluggish.  Much 
less  active  than  those  nearly  related  species  which  might 
be  confused  with  it.  Found  commonly  among  algae  and 
water  plants  or  under  stones  where  water  is  comparatively 
quiet.     Mass.,  Penn.,  111.,  Mich.,  Neb. 


Fig.  630.  Planaria  maculata.  U)  From  life.  X  6.  (After  Wood  worth.)  (5)  Sexual  organs,  dorsal 
view:  u,  uterus;  co,  common  oviduct;  od,  oviduct;  a,  atrium;  gp,  genital  pore;  p,  cirrus;  vd,  vas  de- 
ferens;  m,  mouth.     X  about  35-     (After  Curtis.) 


90  (89)     Color  dark  reddish-brown  to  grayish-brown.     Uniformly  pigmented. 

Planaria  gonocephala  Duges  1830. 


im 


Greatest  length  25  mm. 
Usually  not  over  15  mm. 
Girard  describes  the  color 
of  this  species  as  often  of 
a  blackish -brown.  Pos- 
terior margins  of  auricular  appendages  free  from 
pigment.  Much  lighter  on  ventral  than  on  dorsal 
side.  Eyes  in  a  plane  joining  the  apices  of  the 
auricles.  Clear  areas  around  eyes  sometimes 
elongated  in  an  antero-posterior  direction.  Re- 
production asexually  common.     Mich.,  111. 

Fig.  631.  Planaria  gonocephala.  (^)  From  life.  X  S. 
(After  Woodworth.)  {B)  Sexual  organs,  longitudinal 
section  side  view:  ui,  uterus;  od,  oviduct;  de,  ductus 
ejaculatorius;  ^a/),  papilla;  i'(/,  vas  deferens;  ag,  genital 
atrium;  vs,  vesicula  seminalis;  m,  mouth;  utd,  duct  of 
uterus;  pdr,  cirrus  glands;  pdr^,  ducts  of  cirrus  glands; 
gP,  genitfvl  pore.    Much  enlarged.     (After  Bohmig.) 


91  (86)  Anterior  end  rather  sharply  pointed.  Angle  formed  by  lateral  mar- 
gins of  head  not  more  than  60°.  Cephalic  appendages  long, 
slender,  sharply  pointed,  with  anterior  margin  shorter  than 
posterior  margin.  Body  distinctly  narrower  back  of  ceph- 
alic appendages  than  just  in  front 92 


THE   FREE-LIVING    FLATWORMS    (TURBELLARIA) 


357 


92  (93)     Angle  of  head  50°  to  60°.     Color  a  very  dark  sepia-brown  almost 
black  by  reflected  light.      .    .  Planaria  agilis  Stringer  1909. 

Length  of  immature  worms  usually  not  over  18  mm.  Mature  specimens  collected  have  meas- 
ured 30  mm.  Well  fed  specimens  in  aquaria  have  attained  a  length  of  55  mm.  Color  usually 
very  uniform.  Ventral  surface  but  little  lighter  than  dorsal.  One  variety  found  only  in  one 
locality  and  with  uniformly  colored  specimens,  shows  sharply  defined  non-pigmented  spots. 
Under  lens  a  clear  light-brown  ground  with  fine  dark  brown,  almost  black  pigment  granules, 
either  quite  uniformly  distributed  or  arranged  so  as  to  give  the  appearance  of  a  very  close  net 
work.  Circum-ocular  spaces  either  oval  or  slightly  pointed  at  outer  anterior  region  and  placed 
just  in  front  of  or  in  line  with  the  anterior  margins  of  cephalic  appendages.  Some  with  light 
areas  on  posterior  margins  of  cephalic  appendages,  others  with  auricles  uniformly  pigmented. 
A  light  median  streak  sometimes  present.     Lateral  margin  of  head  with  a  (Hstinct  inward  curve 


just  back  of  tip,  also  at  junction  of  head  with  cephalic 
appendages.  Wider  just  in  front  of  appendages  than 
at  any  point  posterior  to  them  except  in  large  specimens 
which  are  of  about  same  width  through  pharyngeal  region. 
Mature  specimens  much  broader  proportionally  than 
immature.  Asexual  reproduction  the  usual  method  of 
propagation  in  most  localities.  Very  restless  and  active. 
Collected  from  small  ponds  and  spring-fed  brooks  either 
among  algae  or  on  sandy  bottom  and  often  where  water 
flows  swiftly.     Neb.,  Mo.,  S.  Dak.,  Wis.,  and  Cal. 

Fig.  632.  Planaria  agilis.  (A)  Immature  specimen  from  life. 
X8.  (B)  Sexual  organs,  dorsal  view:  m,  uterus;  «/,  uterus  tube; 
0,  oviduct;  gp,  genital  pore;  a,  atrium;  sv,  seminal  vesicle;  vd, 
vas  deferens;  pi,  cirrus  lumen;  la,  limit  of  atrium.  Much  en- 
larged.    (After  Stringer.) 


93  (92)     Angle  of  head  about  45°. 


Color  reddish  to  yellowish-brown. 
Planaria  dorotocephala  Woodworth  1897. 

Length  of  immature  specimens  13  mm.  Head  about  one-sixth  of  total  length  of  body.  Uni- 
formly colored.  Posterior  margins  of  auricular  appendages  free  from  pigment.  Sometimes  a 
narrow  light  median  streak.  Pigment  in  spots  or  patches,  not  a  network  or  evenly  distributed 
as  in  P.  agilis;  ventral  side  much  lighter  than  dorsal.  Eyes  just  anterior  to  plane  joining 
auricles.  Intestine  usually  with  accessory  posterior  intestinal  trunks  which  arise  either  at  the 
root  of  the  pharynx  like  the  two  normal  posterior  trunks  or  exist  as  parallel  branches  of  the 
latter.  Those  of  a  side  usually  unite  with  each  other  near  their  posterior  terminations.  Very 
active  and  restless.     Sexual  organs  have  not  been  described.     III.,  Mich. 


Fig.  633.    Planaria  dorotocephala  from  life.     X  7-     (After  Woodworth.) 

94  (85)     Anterior  end  clearly  not  pointed 05 

95  (loo)  Anterior  end  truncated 06 

96  (99)     Margin  of  anterior  end  with   a   median   anterior  and   two  lateral 

rounded  projections  giving  a  sinuous  outline 97 


358 


FRESH-WATER   BIOLOGY 


97  (98)     Color  gray Planaria  velata  Stringer  1909. 

Length  of  mature  specimens  15  mm.  Color  of  dorsal  side  to  unaided  eye  varies  from  almost 
white  to  a  very  dark  gray  almost  black.  Under  lens,  a  colorless  groundwork  with  black  pig- 
ment granules  extremely  variable  in  number.  Much  lighter  in  front  of  eyes  and  over  cephalic 
appendages.  Lighter  on  ventral  surface,  over  pharynx,  and  near  lateral  margins.  Preserved 
material  often  appears  colorless  and  oval  in  shape.  Encystment  of  the  entire  animal  or  divi- 
sion into  a  variable  number  of  pieces  followed  by  encystment  of  the  pieces  occurs  in  response 
to  unfavorable  conditions.  The  cysts  resemble  egg  cocoons  in  appearance  and  are  provided 
with  a  shell.    Cilia  conspicuous.     Crete  and  Omaha,  Neb. 


3 


Fig.  634.    Planaria  velata  from  life.     X  12.     (After  Stringer.) 


98  (97)     Color  brownish-red  mottled  with  purpHsh  dots  except  at  margins. 

Planaria  unionicola  Woodworth  1897. 

Length  of  the  one  specimen  (preserved)  from  which  the  description  was  made  2.8  mm., 
breadth  1.8  mm.  Probably  8  to  10  mm.  long  when  alive  and  extended.  Purple  dots  occur 
in  masses.  Red  color  absent  over  an  elongated  posterior  median  area  extending  nearly  to  the 
p)osterior  axis  of  the  animal.  Appearance  of  posterior  end  suggests  an 
injury  or  transverse  division.  Color  of  alcoholic  material  a  deep  rusty 
red.     Found  creeping  on  the  mantle  of  Unio  alatiis  in  Illinois  River. 

Fig.  635.    Planaria  unionicola  from  life.    About  X  3-     (After  Woodworth.) 


99  (96)     Margin  of  anterior  end  uniformly  curved,  not  sinuous.     Color  white. 

Planaria  truncata  Leidy  185 1. 

Length  10  to  12  mm.    Thickness  slight.     Translucent.     Digestive   tract  variously  colored 
by  food.     Two  crescent-shaped  eyes  situated  far  back  and  near  together.     Phar>'nx  much 
elongated  and  central  in  position  in  sexuallj'  mature  specimens.     Intestine  with  Httle  anas- 
>— V  tomosis    of    branches.      Ovaries  two,  sometimes 

\,, /  lobed.    Testes  many.     Uterus  large  with  stalk 

ICVi  running  to  left  side,  dorsal  to  vasa  deferentia  and 

//   \\  oviducts  and  entering  atrium  laterally.     Asexual 

reproduction  by  fission.     Small  stream  Bryn  Mawr 
campus;   rivulet  at  Newark,  Delaware. 

A  comparison  of  descriptions  of  P.  truncata 
Leidy  and  P.  morgani  Stevens  and  Boring  leaves 
but  little  doubt  that  they  are  identical.  The 
blackish-white  color  mentioned  by  Leidy  evidently 
was  due  to  food  contained  in  the  digestive  tract 
and  not  to  body  pigment  since  the  margin  is  de- 
scribed as  translucent. 


Fig.  636.  Planaria  truncata.  (^)  From  life.  X  4-  (5) 
Dorsal  view  of  sexual  organs:  a,  atrium;  c,  cirrus;  gp, 
genital  pore;  oi,  oviduct;  ph,  pharynx;  /,  testes;  «, 
uterus;  vs,  vas  deferens.    X  7.     (After  Stevens.) 


100  (95)     Anterior  end  rounded  in  preserved  condition  (living  condition  not 
known) Planaria  simplex  Woodworth  1897. 

Length  4  mm.,  greatest  diameter  1.8  mm.  Color  of  alcoholic  specimen  ocher-yellow.  Pig- 
ment located  in  spots  of  nearly  uniform  size,  distributed  uniformly  over  all  parts  of  the  body; 
no  clear  areas  surrounding  eyes  or  at  sides  of  head.  General  shape  ovate.  Broadest  at  one- 
fifth  the  total  length  from  the  anterior  end,  tapering  from  here  to  rounded  posterior  extremity. 
Anterior  end  rounded,  set  off  from  the  rest  of  the  body  by  slight  lateral  indentions  at  the levelof 
the  eyes.    No  evidence  of  cephalic  appendages.    Mouth  one-third  of  total  length  from  posterior 


THE   FREE-LIVING   FLATWORMS   (TURBELLARIA) 


359 


end.     Eye  spots  elongated,  crescentic,  facing  outward  and  forward  at  an  angle  of  45°  to  the 

chief  axis  of  the  worm.    Intestine  of  the  simple  triclad 
type;  no  fusion  or  anastomoses  of  posterior  stems. 

This  description  is  from  a  single  immature  alcoholic 
specimen.    (It  is  quite  possible  that  the  apparent  lack 
*  :  of  cephalic  appendages  is  due  to  the  eflfect  of  the  killing 

'J  fluid.)     Collected  off  N.  Y.  Point,  Lake  Mich. 

Fig.  637.     Planaria  simplex.     From  preserved  material. 
X  10.     (After  Woodworth.) 

101(84)     Withouleyes Planaria  fidiginosus  Leidy  iS si- 

Length  about  5  mm.,  breadth  4  mm.  Body  oval,  dilated;  inferiorly  flat,  superiorly  mo<l- 
crately  convex,  fuliginous.  Eyes  none;  in  their  ordinary  position  a  slightly  greater  accu- 
mulation of  black  pigment  upon  the  upper  surface.  Mouth  a  little  posterior  to  the  center- 
I'.sophagus  simple.     Rancocas  Creek  near  Pemberton,  New  Jersey. 

102  (83)     Normal   eyes   many,  arranged   so   as   to   suggest   a   coronet   near 

the  margin  of  truncated  head  and  extending  back   near 
the  lateral  margins  to  a  somewhat  variable  distance. 

^  ,  .      ,         ■  Polycelis. 

Only  one  species  known  in  this  country. 

,  Polycelis  coronata  (Girard)  1891. 

Length  8  mm.,  breadth  2  mm.     Color  fuliginous  or  sooty,  uniform,  somewhat  darker  on  the 

median  dorsal  region  than  on  margins.     Elongated  lanceolate.     Anterior  margin  truncated 

weakly  bilobed  or  undulating.     The  numerous  eyes  are  arranged  as  a  coronet  or  as  an  arc  of 

a  circle,  the  arrangement  being  dependent  to  some  extent 

on  size.     Pharynx  elongated,  central.     Collected  near  Fort 

Bridger,  Wyoming.     It  is  quite  possible,  as  Haflcz  notes,  that 

this  is  a  synonym  of  the  European  Polycelis  nigra. 

Fig.  638.    Polycelis  coronata.    From  life.     X  5.     (After  Girard.) 

103  (80)     Pharynges  numerous Phagocata. 

Only  one  species  known  in  this  country. 

Phagocata  gracilis  (Haldeman)  1840. 
yThis  species  was  found  and  recorded  by  Haldeman;  it  was  first  adequately  described  by 
Leidy  to  whom  it  is  ordinarily  attributed. 

Largest  specimens  35  mm.  long,  4.5  mm.  wide.  Color  shiny  black  by  reflected  light,  green- 
ish-gray by  transmitted  light.  Varies  from  black  to  a  reddish-brown  on  one  hand  or  to  a  light 
gray  on  the  other.  Small  specimens  at  times  almost  milky-white.  Ventral  side  lighter  than 
dorsal.  Lateral  margins  nearly  parallel.  Widest  through  pharyngeal  region.  Anteriorly 
sides  converge  slightly  up  to  about  the  region  of  eyes  where  the  diameter  increases  to  form  the 
head  with  its  rounded  cephalic  appendages.  Posteriorly  sides  converge  to  a  {wint.  Eyes 
two  with  elongated  circum-ocular  areas.  The  numerous  pharyngeal  tubes  lie  in  a  common 
chamber  and  open  separately  into  the  intestinal  tract.  When  extruded  they  reach  the  exterior 
through  a  single  orifice.     Pools  and  rivulets,  Mass.,  Penn.,  Ohio,  Wis. 


Fig.  639,    Phagocata  gracilis.     {A)  Living  animal  extended.    X  4.    (B)  Partial  reconstruction  to  show 
pharynges  and  their  relation  to  the  intestinal  tract.     X  about  8.      (After  Woodworth.) 

104  (79)     Found  in  moist  places  on  land.     .    .   Suborder  Terricola  .    .       105 

The  so-called  land  planarians  are  forms  which  in  a  biological  sense  stand  verv  near  the 
water-hving  species.  They  occur  only  in  very  moist  localities  and  under  circumstances  may 
^e  taken  for  fresh-water  forms.     In  general  appearance  they  resemble  minute,  delicate  sIurs. 

vf^  ^^^.mined  under  the  microscope  the  structure  appears  clearly  to  be  that  of  a  flat  worm 
rather  than  of  a  mollusk.     The  few  known  species  are  widely  and  sparsely  distributed.     They 


360  FRESH-WATER   BIOLOGY 

are  likely  to  be  transported  in  tropical  or  subtropical  vegetation  and  to  make  their  appearance 
suddenly  and  in  considerable  numbers  in  greenhouses  or  in  moist  shady  nooks  that  have  been 
planted  with  exotic  species.  Of  one  form  indeed  the  proper  habitat  is  not  known.  Walton 
has  worked  out  a  key  and  synopsis  of  the  few  species  reported  from  North  America  and  ad- 
jacent islands.  In  modified  form  this  is  followed  here.  Almost  no  records  of  the  occurrence 
of  these  forms  on  this  continent  have  been  published,  and  their  numbers  as  well  as  their  range 
are  sure  to  be  considerably  extended  when  attention  is  directed  to  them. 

105(110)     Eyes  either  absent  or  numerous;  length  more  than  40  mm.   .    .     106 

106  (109)     Head  anteriorly  not  broader  than  remainder  of  body. 

Family  Geoplanidae  .    .     107 

107  (108)     Posterior  part  of  head  with  eyes  in  two  rows;  sides  margined  with 

orange Geoplana  nigrofusca  (Darwin)  1844. 

Length  50  mm.     Found  in  Mexico;   reported  also  from  South  America. 

108  (107)     Posterior  part  of  head  with  eyes  in  one  row;   sides  margined  with 

Hght  brown Geoplana  stolli  (von  Graff)  1899. 

Length  60  mm.     Thus  far  known  only  from  a  single  specimen  collected  in  Guatemala. 

109  (106)     Head  anteriorly  broader  than  the  body.    .    .    .  Family  Bipalidae. 

Only  one  species Placocephalus  kewense  (Moseley)  1878. 

Color  dorsally  yellow  or  greenish-yellow 
with    five    dark    violet    longitudinal    lines. 
Length    80    to    250    mm.    An    introduced 
species  found   in  hot  houses.     Its  original 
Fig.  640.     Placocephalus  Kewense.     Anterior  end.         home  is  unknown 
X  I.     (After  von  Graff.) 

110(105)     Eyes  two  in  number;    ventral  suckers  absent;    length  less  than 

30  mm. Ill 

Rarely  the  eyes  are  apparently  absent  but  even  here  they  may  be  demonstrated  in  sections. 
Ventral"  suckers  do  occur  in  the  related  family  Cotyplanidae .  Known  from  Africa  and  New 
Zealand. 

111  (114)     Eyes  small,  marginal  sense  organs  present. 

Family  Rhynchodemidae  .    .     112 

112  (113)     Color  dorsally  light  brown  with  two  darker  longitudinal  stripes 

and  transverse  area  at  posterior  two-thirds  of  body. 

Rfiynchodemus  syhaticus  (Leidy)  1851. 
Length  not  over  10  mm.     Common  in  places  de- 
scribed by  Leidy  (1851)  in  Pennsylvania  and  redis- 
covered in  Ohio  by  Walton  (1904).     Frequents  under 
^                                      side  of  slightly  decayed  boards,  sticks,  etc.,  in  com- 
pany with  snails,  the  young 
forms  of  which  it  closely  re- 
sembles.    Range,  Eastern 
United  States. 

B 
Fig.  641.     Rhvnchodemus  syhaticus.     {A)  Dorsal  view  of  individual  from  Philadelphia,  Pa.    X J-    (5) 
Individual  from  Newport,  R.'l.,  showing  arrangement  of  esophagus  and  structure  of  mtestme.     X  about 
5.     (After  Girard.) 

113  (112)     Color  dorsally  uniformly  dark  blue. 

Rhynchodemus  atrocyaneus  Walton  191 2. 
Length  20  mm.     Only  two  specimens  of  this  form  have  been  reported.     Found  at  Gambler, 
Ohio,  under  decayed  boards. 
114(111)     Eyes  well  developed;  marginal  sense  organs  absent. 

Amhly plana  cocker elli  von  Graff  1899. 
Color  dorsally  bluish-black  with  light  yellow  median  stripe  longitudinally  and  yellow  "neck 
band."     Length  17  mm.     Represented  only  by  two  known  specimens  found  in  Jamaica. 


THE   FREE-LIVING   FLATWORMS    ^TURBELLARTA)  361 

The  following  is  a  list  of  those  forms  which  are  not  sufficiently  well  known 
to  be  given  their  proper  place  in  the  key. 

Order  Rhabdocoelida 
Section  I  Hysterophora 
Family  Catenulidae 

Microstomiim  philadelphicum  Leidy  185 1 
Microstomum  varlahile  Leidy  185 1 
Section  II  Lecithophora 
Subsection  Liporhynchia 
Family  Typhloplaxidae 

Typhloplanid  from  Canandaigua  Lake,  N.  Y.,  von  Graff  igii 
Typhloplanid  from  Irondequoit,  N.  Y.,  von  Graff  1911 
Mesostoma  patter soni  SiUiman  1885 
Family  Dalyellidae 

Dalyellia  hilineata  (Wood worth)  1896 
Dalyellia  marginatum  (Leidy)  1847 
Derostoma  elongatiun  Schmarda  1859 
Subsection  Calyptorhynchia 

Rhynchoproholus  papillosus  Schmarda  1859 

The  following  Rhabdocoels  are  of  very  doubtful  position  and  relationships 

Vortex  (?)  cavicolens  Packard  1883 

Plagiostoma  (?)  planum  Silliman  1885 

Acmostomum  crenulatum  Schmarda  1859 
Order  Tricladida 

Dendrocoelum  sp.  Pearl  1903 

A  brief  description  of  these  doubtful  species  will  serve  to  promote  their  re- 
discovery and  further  study.  Each  description  is  taken  from  the  original 
account  of  the  species  which  is  also  the  only  record  of  it  yet  published. 

Microstomum  philadelphicum  Leidy  185 1. 

Body  linear,  slightly  attenuated  posteriorly;  head  conoida!  with  the  apex  surmounted  by 
a  small  oval  papilla;  tail  obtusely  rounded.  Respiratory  fovea  subhemispherical.  placed  at 
the  base  of  the  cone  of  the  head.  Mouth  oval,  projectile;  esophagus  keg-shaped,  intestine 
narrowed,  cyUndroid,  dilated  at  the  commencement.  Colorless,  translucent,  ciliated,  in- 
creasing by  transverse  segmentation,  always  observed  in  the  process  of  forming  two  segments. 
Length  0.9  mm.     Found  in  water  of  marshes  and  ditches  near  Philadelphia. 

Microstomum  variable  Leidy  185 1. 

Body  broad,  linear;  anteriorly  and  posteriorly  obtusely  rounded.  Respiratorj-  fovea 
longitudinally  oval,  lateral.  Intestine  very  broad.  Colorless,  increasing  by  twos.  Length 
from  0.3  to  I  mm.  No  nematocysts  or  rhabdites.  Found  with  Microstomum  philadelphicum. 
Also  a  chain  of  4  individuals  was  collected  in  algae  culture  from  shore,  Charlevi)ix,  Mich.,  by 
Dr.  H.  B.  Ward. 

Typhloplanid  from  Lake  Canandaigua,  N.  Y.,  von  GrafT  191 1. 

Length  i  mm.  Anterior  end  set  off  from  the  rest  of  the  body  by  depressions  at  the  sides,  prob- 
ably sensory  pits.  Broadest  through  middle  of  body  which  measures  about  one-fourth  the 
length.  Spindle-shaped  rhabdites  in  glands  and  tracts  of  anterior  end.  Pigment  is  present  in 
the  form  of  large  reddish-brown  granules  which  mostly  lie  lengthwise  of  the  body,  stimctimes 
branched,  and  enlarged  at  posterior  end.  The  pigment  forms  a  reticulation  between  and  passes 
over  the  irregularly  shaped  eyes.  Eyes  twice  as  far  apart  as  they  are  distant  from  the  margin  of 
the  body.  Pigment  of  eyes  the  same  as  that  of  the  body,  only  much  closer  compacted  so  that 
they  are  deeper  in  color. 

The  mouth  lies  in  the  anterior  third  of  the  body.     In  the  uncompressed  animal  the  pharynx 


362 


FRESH-WATER  BIOLOGY 


shows  as  a  typical  rosette-shaped  pharynx.  This  form  is 
unusual  in  that  the  rosette-shaped  pharynx  does  not  lead 
into  the  intestine  from  its  ventral  side,  but  opens  into  its 
anterior  end  so  that  when  compressed  its  axis  becomes 
directed  forward.  Intestine  yellowish  and  extending 
almost  to  the  posterior  end,  and  having  the  general  shape 
of  the  body. 


Fig.  642.  Typhloplanid  from  Lake  Canandaigua,  N.  Y.  (A) 
Swimming  freely,  showing  the  dorsal  pigmentation.  X  55-  (B) 
Slightlycompressed  with  pharynx  directed  forward.  X  4°-  a", 
eyes;  da,  intestine;  ehv,  anterior  branches  of  pro tonephridium;  g, 
brain;   ph,  pharynx;  stz,  rhabdite  glands.     (After  von  Graff.) 


Typhloplanid  from  Irondequoit,  N.  Y.,  von  Graff  191 1, 


Length  0.5  mm.  Without  pigment  and  color» 
less  apart  from  the  brownish-red  eyes  and  the 
oil  drops  of  the  intestine.  Eyes  irregular  in  shape 
and  almost  twice  as  far  from  the  side  of  the 
body  as  from  each  other.  The  mouth  lies  on  the 
boundary  between  the  first  and  second  thirds  of 
the  body.  The  anterior  end  shows  many  tracts 
of  rhabdites.     Collected  from  a  reedy  swamp. 

Fig.  643.  Typhloplanid  from  Irondequoit,  N.  Y.  (A > 
The  animal  slightly  compressed.  X  80.  (B)  Male 
copulatory  organ.  X  320.  au,  eye;  be,  bursa  copula- 
trix;  dr,  gland  cells;  ds,  ductus  seminalis;  /,  fat  drops; 
ge,  ovary;  go,  genital  pore;  kd,  granular  glands;  ks, 
granular  secretion;  m,  muscles;  />A,  pharynx;  j<,  tracts 
of  rhabdites;  te,  testes.     (After  von  Graff.) 


Mesostoma  pattersoni  Schmarda  1885. 


Length  3  to  3.5  mm.,  0.6  mm.  broad  through  middle.  Color  in 
reflected  light  brownish  except  anterior  to  the  eyes  which  appears 
grayish  from  the  rhabdites.  Intestine  yellowish.  Body  fluid  with 
many  cells  which  contain  granules.  Eyes  directly  above  the  brain. 
Pharynx  rosette-shaped,  not  far  from  middle  of  body. 


Fig.  644.  Mesostoma  pattersoni.  st,  tracts  of  rhabdites;  ph,  pharynx; 
vi,  yolk  gland;  ut,  uterus;  be,  bursa  copulatrix;  ov,  ovary;  P,  cirrus;  t, 
testes.    X  20.    (After  SilHman.) 


THE   FREE-LIVING   FLATWORMS    (TURBELLARIA) 


363 


Dalyellia  bilineata  (Wood worth)  1896. 


Length  0.96  mm.,  breadth  0.24-0.52  mm. 
Anterior  end  truncated,  posterior  end  fKjinted. 
Pharynx  dolioliform,  in  anterior  third  of  b(xiy, 
traversed  by  two  prominent,  lateral,  nearly  lon- 
gitudinal bands  of  light  chocolate-brown,  and 
numerous  other  pale  indistinct  longitudinal 
lines.  Zoochlorellae  in  central  part  of  the 
body,  posterior  fifth  free  from  them,  trans- 
parent-brown. Egg  dark  chocolate,  120  m  X 
80  M- 

The  figures  given  here  are  those  which 
were  in  possession  of  Woodworth  with  the 
material  when  the  description  was  written 
and  the  species  named. 

Fig.  645.  Dalyellia  bilineata.  i4,  compressed.  X 
about  50.  z)d,vas  deferens;  j)x,  vesiculaseminalis;  0, 
ovary;  c,chitinous  portion  of  cirrus;  e,  egg;  be,  bursa 
copulatrix;  yg,  yolk  gland.  B,  chitinous  piece.  X 
about  200.     (Unpublished  sketch  by  Ward.) 


Dalyellia  marginatum  (Leidy)  1847. 

Blackish,  narrow  lanceolate,  anteriorly  truncate;  marginate  margin  delicately  striate; 
mouth  large;  pharynx  large  and  oblong;  eyes  two,  anterior,  distant,  each  consisting  of  two 
round  masses  of  black  pigment  in  contact  with  each  other  and  of  which  one  is  larger  than  the 
other;  generative  orifice  one-fourth  the  length  of  the  body  from  the  posterior  extremity. 
Length  2  mm.  A  single  specimen  found  in  ditches  near  Philadelphia,  Pa.  Digestive  cavity 
consists  of  a  large  capacious  sac  extending  as  far  back  as  the  posterior  third  of  the  body  and 

having  a  cecum  upon  each  side  of  the  proboscis.  The 
cirrus  has  a  yellow  color  and  consists  of  a  round  granu- 
lar mass  with  a  moderately  long  and  bent  spiculum  pro- 
jecting from  its  posterior  part.  This  is  the  form  de- 
scribed by  Leidy  under  the  name  Prostoma  marginatum. 
Fig.  646.   Dalyellia  mar fiinatum.    X  about  20.    (.^fter  Girard.) 


Derostoma  elongatum  Schmarda  1859. 


Fig.  647.    Derostoma  elongatum.    X  about  25. 
(After  Schmarda.) 


The  body  is  long,  ribbon-shaped,  flattened. 

Posteriorly  uniformly  tapering.  Color  red- 
dish-gray. Length  2  mm.  Without  eyes. 
Mouth  opening  elliptical.  Pharynx  long,  cask- 
shaped.  From  brackish  water  in  swamp,  New 
Orleans,  La. 


Rhynchoproholus  papillosus  Schmarda  1859. 


n\Uil-lJill-LU.IJiUfUll.'.U.ujj^ 


tP^S^fei 


^^miifnjn'Tnmiwlmmmm^ 

Fig.  648.    Rhynchoprobolus  papillosus.    X  about 
9.     (After  Schmarda.) 


Body  somewhat  compressed,  anteriorly 
rounded,  posteriorly  gradually  tapering.  Color 
clear  yellow.  Length  5  mm.  Without  eyes. 
Proboscis  short,  round,  externally  set  with 
small  papillae.  Mouth  oF>cning  central.  Phar- 
ynx rosette-shaped.  From  brackish  water, 
Hoboken,  N.  J. 


Vortex  (?)  cavicolens  Packard  1883. 

Found  in  X  cave,  one  of  the  Carter  caves,  Kentucky.  Body  flat,  elongated,  narrow  lan- 
ceolate-oval, contracting  in  width  much  more  than  is  usual  in  Vortex  (Dalyellia).  Phar>-nx 
is  situated  much  farther  back  from  anterior  end  of  body  than  is  usual  in  Vortex,  being  placed 
a  little  in  front  of  the  middle  of  the  body;  it  is  moderately  long,  being  oval  in  outline.  The 
body  behind  suddenly  contracts  just  before  the  somewhat  pointed  end.     The  genital  outlet 


364 


FRESH-WATER   BIOLOGY 


is  about  one-half  as  wide  as  the  pharynx  and  orbicular   in  outline.     Apparently  eyeless. 
White.     Length  4  mm.,  breadth  1.5  mm.     Brooks,  Carter  Caves,  Kentucky. 


Plagiostoma  (?)  planum  Silliman  1885. 


Length  1.5  mm.,  breadth  0.7  mm.  Mouth  opening  in  anterior 
end.  Pharynx  lies  within  a  sheath  and  has  both  longitudinal 
and  transv^erse  muscle  layers.  Radial  muscle  fibers  pass  from  the 
base  of  the  pharj'nx  to  the  body  wall.  Without  eyes  or  other 
sense  organs.  The  poorly  developed  brain  hes  in  front  of  the  phar- 
ynx as  a  transverse  band.  The  intestine  is  capacious  and  has  short 
lateral  diverticula.  This  species  probably  belongs  to  the  genus 
Prorhynchus. 


Fig.  649. 


Plagiostoma  (?)  planum,     ph,  pharynx;  d,  intestine. 
30.     CAfter  Silliman.) 


X  about 


Acmostomum  crenulatum  Schmarda  1859. 


0^^^!^^'mmmLL^k 


The  body  is  cylindrical,  yellowish,  i  mm.  long.  Pharynx  cylindrical,  protractile  with  six 
deep  lobes  on  its  margin.  Otolith  large  and  spherical  contained  within  a  transparent  capsule 
which  is  located  at  the  end  of  the  first  third  of  the  body. 
The  ovaries  form  a  large  spherical  mass  in  the  posterior  part 
of  the  body.  The  cirrus  is  short  knife-shaped  and  has  a 
slight  double  curve.     Found  in  brackish  water,  Hoboken,  N.  J. 

Fig.  650.    Acmostomum  crenulatum.    From  life     X  about  30. 
(After  Schmarda.) 


Dendrocoelum  sp.  Pearl  1903. 

Agrees  with  description   of   Dendrocoelum  lacleum,  except  in  respect  to  the  color.     Color 
ranges  from  a  light  grey  to  nearly  black,  and  is  uniform.     Found  about  Ann  Arbor,  Mich. 


IMPORTANT    REFERENCES    ON    NORTH    AMERICAN    FRESH- 
WATER TURBELLARIA 


Graff,  L.  von.     1882.    Monographic  der  Turbellarien.     I  Rhabdocoelida. 

Leipzig. 
1904-1912.     Bronn's  Klassen  und  Ordnungen  des  Tierreichs.    IV.  Bd.,  Wiir- 

mer:   Vermes,  Turbellaria,  Acoela,  and  Rhabdocoela.     Leipzig. 
191 1.     Acoela,  Rhabdocoela  und  Alloeocoela  des  Ostens  der  Vereinigten 

Staaten  von  Amerika.     Zeitschr.  f.  wiss.  ZooL,  99  1321-428.     Taf.  I-VI. 
Silliman,   W.   A.     1885.     Beobachtungen  iiber  die    Siisswasser-Turbelarien 

Nordamerikas.    Zeitschr.  f.  wiss.  Zool.,  41  148-78;   Taf.  Ill,  IV. 
WooDWORTH,  W.   McM.     1897.     Contributions   to   the  IMorphology  of  the 

Turbellaria  II.     On  some  Turbellaria  from  Illinois.     Bulletin  Mus.  Comp. 

Zool.  Harvard  Coll.,  31  :  1-16;    i  plate. 


CHAPTER   XIII 
PARASITIC    FLATWORMS 

By  henry  B.   ward 

Professor  of  Zoology  in  the  University  of  Illinois 

The  parasitic  worms  do  not  all  belong  to  a  single  systematic 
division.  Coming  in  many  cases  from  widely  separated  groups, 
they  often  show  much  closer  relationship  to  certain  free-living 
forms  than  to  each  other.  But  because  of  a  likeness  in  manner 
of  Hfe  these  forms  were  grouped  together  by  early  students  of  ani- 
mal life  as  the  Helminthes  and  in  fact  were  long  regarded  as  related 
by  reason  of  similarities  in  appearance  and  habit.  There  are  five 
such  groups,  usually  ranked  as  classes;  they  are  Trematoda  or 
flukes,  Cestoda  or  tapeworms,  Nematoda  or  roundworms,  Acan- 
thocephala  or  proboscis-worms,  and  Gordiacea  or  hair-worms. 

In  any  given  host  only  a  few  parasitic  species  may  be  found  or 
again  the  number  of  individuals  and  species  of  parasitic  worms  in 
a  single  host  may  be  very  large.  I  have  taken  5000  flukes  from  a 
single  fish  (Amia),  and  even  larger  figures  are  recorded.  At  a 
given  time  the  variety  of  species  may  be  Hmited;  yet  as  the  kinds 
of  parasites  change  with  the  food,  the  season,  and  the  region,  the 
total  number  found  in  a  certain  host  may  be  very  large;  thus  over 
one  hundred  species  of  parasitic  worms  are  reported  from  man 
and  thirty  or  forty  from  some  well-known  and  widely-studied  fish 
or  aquatic  birds.  Some  parasites  are  found  in  more  than  a  single 
host  species,  a  few  infest  a  wide  range  of  animals,  and  others  occur 
in  one  host  only;  all  in  all,  parasites  are  far  more  numerous  than 
free-living  animals  both  in  number  of  individuals  and  of  species. 

The  abundance  of  parasites  varies  greatly  under  dilTerent  con- 
ditions of  existence.  Desert  animals  are  not  without  them,  but 
they  are  much  more  numerous  and  more  varied  in  water-living 
animals  than  in  hosts  from  any  other  habitat. 

Representatives  of  some  or  all  groups  of  parasites  occur  in  the 
various   aquatic   vertebrates   and    invertebrates,    and    while   in    a 

365 


366  FRESH-WATER   BIOLOGY 

certain  sense  they  are  not  inhabitants  of  fresh  water,  they  infest 
aquatic  animals  and  their  hfe  histories  form  a  part  of  aquatic 
biology.  To  be  sure  some  species  of  parasites  never  come  into 
contact  with  the  external  world  but  are  transferred  from  host  to 
host  with  the  material  in  which  they  are  Kving  and  others  are  en- 
tirely dependent  upon  terrestrial  animals  as  hosts.  Such  parasites 
have  no  direct  relation  to  fresh-water  life  and  will  be  entirely 
omitted  in  the  present  discussion.  However,  in  the  large  majority 
of  parasitic  forms  the  parasitic  stage  alternates  with  a  longer  or 
shorter  non-parasitic  period.  During  this  period  of  free  existence 
the  species  is  a  dweller  in  fresh  waters  alongside  of  their  normal 
inhabitants,  possessed  of  similar  organs  of  locomotion  and  other 
adaptations  to  a  free  existence,  often  unrecognized  in  their  true 
nature,  and  properly  regarded  as  members  of  the  shore  or  bottom 
fauna  or  plankton.  This  fact  alone  compels  their  consideration 
in  any  discussion  of  aquatic  life. 

Contrasted  with  this  stage  is  the  parasitic  period  which  is  more 
extended,  usually  embracing  almost  all  of  the  life  history.  In  it 
the  worm  remains  with  its  host,  dependent  upon  the  latter  for 
protection,  locomotion,  and  subsistence,  showing  structural  modi- 
fications which  aid  in  maintaining  this  dependence  and  indicating 
by  the  absence  of  organs  calculated  to  provide  for  successful  inde- 
pendent activity  the  changes  which  the  parasitic  habit  has  induced 
in  its  original  structure. 

As  already  indicated  most  parasites  show  distinct  adaptations 
to  the  conditions  under  which  they  Hve.  To  be  sure  some,  such 
as  certain  small  parasitic  nematodes,  are  indistinguishable  from 
their  free-living  relatives,  but  such  instances  are  rare.  The  large 
majority  have  lost  organs  usually  found  in  free  forms  and  have 
gained  structures  of  significance  only  for  a  parasitic  existence. 
Furthermore,  both  loss  and  gain  are  relative  and  graded,  rather 
than  absolute  and  unrelated.  Thus  in  some  flukes  the  ahmentary 
system  is  about  as  well  developed  as  in  the  free-living  Turbellaria, 
and  of  much  the  same  type  {cf.  Figs.  678  and  639^);  in  other 
flukes  the  system  is  greatly  reduced  {cf.  Microphallus,  Fig.  697); 
and  finally  in  the  cestodes  it  is  entirely  lacking.  The  same  condi- 
tions prevail  in  the  threadworms.     Most  of  the  true  Nematoda 


PARASITIC    FLATWORMS  367 

have  a  well-developed  and  functional  digestive  system;  in  Mermis 
the  system  is  active  during  early  life  and  becomes  inert  and  de- 
generate in  the  adult  stage.  Finally  in  the  Acanthocephala  there 
is  no  trace  of  an  alimentary  system  at  any  stage  in  the  life-history. 
The  gains  are  no  less  marked.  Hold-fast  organs,  like  suckers  and 
hooks,  enable  the  parasite  to  maintain  its  position  against  the  con- 
stant and  vigorous  movements  of  the  host.  Such  organs  of  simi- 
lar structure  appear  in  widely  separated  groups,  e.g.,  suckers  in 
flukes  and  threadworms. 

While  these  structural  likenesses  between  parasitic  worms  of 
different  groups  are  striking  and  important,  they  are  in  a  real 
sense  superficial  and  do  not  serve  to  conceal  more  than  tempo- 
rarily the  fundamental  differences  in  structure  between  the  various 
groups. 

The  flatworms  (Plathelminthes)  are  soft-bodied,  usually  elon- 
gate and  somewhat  flattened  forms.  In  the  phylum  are  included 
the  free-living  Turbellaria  (Ch.  XII)  and  Nemertina  (Ch.  XIV), 
as  well  as  two  classes  of  parasitic  worms :  the  Trematoda  or  flukes, 
and  the  Cestoda  or  tapeworms.  The  other  three  classes  of  para- 
sitic worms  named  previously  are  grouped  together  under  the 
phylum  Nemathelminthes  or  roundworms,  which  forms  the  topic 
of  a  separate  chapter.  The  structure  of  each  group  will  be  dis- 
cussed separately,  but  certain  biological  features  are  general  enough 
to  deserve  brief  mention  first. 

Aquatic  animals  possess  some  external  parasites;  among  them 
the  species  of  ectoparasitic  flatworms,  rare  in  fresh  water,  belong 
to  a  single  subdivision  of  the  flukes  or  Trematoda;  all  other  flukes 
and  the  Cestoda  which  are  all  parasitic  live  as  endoparasites  in 
some  part  of  the  host  organism  where  they  find  better  protection 
than  on  the  surface.  The  most  common  place  of  residence  is  the 
alimentary  canal  or  its  adnexa,  air-bladder,  lungs,  liver,  etc. 
Parasites  occur  regularly  in  the  body  cavity  and  other  serous 
spaces,  in  the  kidney  and  bladder,  in  the  sex  organs,  in  the  heart 
and  blood  vessels,  encysted  in  the  skin,  connective  tissue  and 
muscle,  and  finally  in  the  nervous  system,  even  entering  the  eye 
or  brain  and  its  cavities. 

Parasites  may  be  collected  by  opening  an  animal  in  a  dissecting 


368  FRESH-WATER   BIOLOGY 

dish  of  suitable  size  and  examining  the  contents  of  various  organs. 
The  parasites  usually  betray  their  presence  by  sluggish  move- 
ments of  the  body  which  make  even  minute  objects  conspicuous 
in  a  mass  of  debris.  A  watchmaker's  lens  held  in  place  at  the  eye 
by  a  spring  is  of  service  in  recognizing  and  sorting  out  the  smaller 
forms,  and  long  bristles  or  a  camel's  hair  pencil  are  useful  in  pick- 
ing out  the  forms  for  study  and  preservation.  Doubtful  objects 
should  be  examined  under  a  higher  magnification  whereupon  the 
firm,  definite  outline  of  a  parasite  enables  the  student  to  distinguish 
it  even  when  motionless  from  partly  digested  fragments  of  food, 
blood  clots,  or  other  foreign  bodies  of  similar  size  and  texture. 

Parasitic  flatworms  may  be  kept  some  hours  in  weak  normal  salt 
solution  for  examination  or  even  in  tap  water,  but  deteriorate  so 
that  for  careful  study  material  should  be  preserved  as  soon  as 
possible.  For  preservation  an  aqueous  solution  of  corrosive  sub- 
limate is  most  satisfactory,  and  the  precise  method  of  handhng 
suggested  by  Looss  gives  results  well  worth  the  extra  time  and 
trouble  because  of  the  greater  ease  with  which  future  work  may  be 
carried  on.  Because  of  the  great  similarity  in  external  form  be- 
tween different  types,  a  determination  can  be  safely  reached  only 
after  a  worm  has  been  stained  and  mounted  in  toto,  or  sectioned 
in  case  of  large  and  opaque  specimens. 

The  parasitic  flatworms  have  received  relatively  Httle  attention 
in  North  America;  it  is  consequently  a  difficult  matter  to  prepare 
a  synopsis  that  is  of  value  to  the  student,  for  from  our  knowledge 
of  the  group  in  other  parts  of  the  world  it  is  safe  to  assert  that 
the  known  forms  do  not  constitute  more  than  a  small  fraction 
of  those  that  actually  exist  on  this  continent.  Another  difficulty 
which  presents  itself  is  the  impossibihty  of  defining  clearly  the 
Hmits  of  the  topic.  I  have  endeavored  to  include  in  the  key  all 
North  American  parasitic  flatworms  thus  far  recorded  from  fresh- 
water animals  whenever  the  record  permits  of  any  reasonable 
interpretation.  I  have  omitted  a  few  records  so  brief  or  indefinite 
that  a  diagnosis  was  impossible.  There  is  included  also  a  consid- 
erable number  of  parasites  from  distinctly  land  animals,  the  life 
history  of  which  is  certainly  bound  up  with  stages  parasitic  in  the 
fresh-water  fauna.     On  the  other  hand  I  have  omitted  all  clearly 


PARASITIC    FLATWORMS  369 

marine  species  and  all  from  hosts  commonly  frequenting  the  sea 
and  most  likely  to  become  infected  there. 

The  parasitic  flatworms  fall  readily  into  two  great  classes,  the 
Trematoda  or  flukes  and  the  Cestoda  or  tapeworms.  Some  authors 
would  make  a  third  intermediate  group  out  of  the  few  forms  which 
are  known  as  Cestodaria  and  resemble  the  flukes  in  having  a  simple 
body  and  the  tapeworms  in  details  of  internal  anatomy.  In  this 
work  they  are  treated  with  the  tapeworms.  As  apart  from  these 
few  cases  flukes  and  tapeworms  can  be  fairly  readily  distinguished, 
it  is  advantageous  for  the  student  to  have  each  group  treated  sep- 
arately in  a  distinct  section  of  the  chapter;  and  to  this  treatment 
the  following  brief  synopsis  may  serve  as  an  introduction. 

Body  soft,  flattened,  shaped  more  or  less  like  a  simple  scale,  leaf,  band, 
or  ribbon Phylum  Plathelminthes. 

The  external  surface  may  have  hooks,  spines,  or  scales,  or  be 
provided  with  warts  or  rugosities,  but  it  does  not  possess  a  tough, 
shiny,  smooth,  resistant  cuticula.  In  a  few  cases  the  body  is  cyhn- 
drical,  conical,  or  spindle-shaped  and  does  not  display  the  charac- 
teristic flattening  mentioned  in  the  key. 

Intestine  present Class  Trematoda     .    .     page  369. 

Intestine  absent Class  Cestoda  ....     page  424. 

Sometimes  the  intestine  is  so  rudimentary  or  so  thoroughly  con- 
cealed by  other  organs  that  its  presence  is  difficult  to  determine. 
It  is,  however,  the  only  absolute  diagnostic  characteristic  which  in 
the  last  analysis  separates  a  fluke  from  a  tapeworm. 

Trematoda 

The  trematode  or  fluke  is  usually  flattened,  oval,  seed-shaped, 
or  rarely  rodlike,  attenuate,  or  globular  in  shape.  With  few  ex- 
ceptions one  finds  on  the  surface  one  or  more  cup-shaped  suckers. 
The  number  and  arrangement  of  these  constitute  a  means  of  sub- 
dividing the  group.  Careful  examination  under  magnification  dis- 
closes pores  or  openings  and  also  in  some  cases  hooks  or  spines  on 
the  surface.  Many  of  the  flukes  are  transparent  and  permit  the 
observer  to  identify  the  main  internal  organs. 

The  alimentary  system  which  usually  starts  at  the  forward  tip 


370 


FRESH-WATER   BIOLOGY 


of  the  body  or  close  to  it  and  in  the  anterior  or  oral  sucker  is  com- 
monly shaped  like  a  tuning  fork  (triclad).  More  rarely  it  is  rod- 
like (rhabdocoel),  or  branching  (dendritic).  A  sphincter,  the 
pharynx,  is  ordinarily  found  on  the  esophagus 
and  the  true  digestive  region  consists  of  the 
two  branches,  the  ceca  or  crura,  which  vary 
greatly  in  length. 

The  excretory  system  (Fig.  651)  usually 
opens  at  the  opposite  end  of  the  body,  and 
is  I-,  Y-,  or  U-shaped.  The  main  branches 
are  distinct,  containing  in  Hfe  a  clear  fluid 
with  a  shghtly  yellowish  or  bluish  tinge. 
The  finer  branches  can  be  traced  only  with 
difflculty.  They  terminate  in  the  essential 
Fig. 6^1. Microphallus opacus.  excretory  clemcnts  known  as  "flame  cells" 

Excretory  system,  dorsal  view.  -^  ^      ^  .11  ti  i        • 

Reconstructed  from  senes  of  which  mav  bc  distmguished  readily  only  m 

transverse  sections.    X  30.    (Af-     " -^  J  ^  .  . 

ter Wright.)  ^^iQ  Hviug  aulmals  under  high  magnification. 

In  the  larger  tubes  one  finds  commonly  highly  refractive  granules 
of  excretory  material. 

Of  the  nervous  system  one  can  usuafly  see  irregular  masses 
(ganglia)  right  and  left  of  the  aHmentary  canal,  near  its  anterior 
end.  They  are  joined  to  form  a  sort  of  collar  around  the  esopha- 
gus, and  from  them  nerves  pass  anteriad  and  posteriad  throughout 
the  body.  Further  details  of  structure  can  be  followed  only  by  j 
special  methods  and  in  well-preserved  specimens. 

Special  sense  organs  are  not  common.  A  few  of  the  ectopara- 
sitic  trematodes,  which  are  rare  in  fresh  water,  have  pigmented 
eye-spots  near  the  brain,  and  the  free-swimming  stages  of  endo- 
parasites  show  similar  structures  which  with  rare  exceptions  are 
wanting  in  the  adult  internal  parasites. 

The  reproductive  system  is  the  most  conspicuous  part  of  the 
worm  but  is  exceedingly  complicated  and  often  difficult  to  follow. 
Yet  it  is  the  most  important  feature  in  the  classification  of  the 
group.  Most  flukes  are  hermaphroditic,  and  contain  complete 
organs  of  both  sexes.  The  arrangement  of  these  organs  in  a  simple, 
typical  case  is  given  in  the  accompanying  diagram  (Fig.  652). 
In  many  species  an  enormous  accumulation  of  eggs  in  the  uterus 


PARASITIC    FLATWORMS 


371 


obscures  all  other  structures  in  the  body.  The  eggs  are  covered 
with  a  firm  chitinous  shell  which  is  often  opaque  but  in  other  cases 
is  transparent  enough  to  permit  one 
to  follow  the  gradual  development 
of  the  enclosed  embryo. 

The  development  of  most  ecto- 
parasitic  trematodes  is  simple  and 
not  different  from  that  of  free-living 
flatworms.  There  emerges  from  the 
egg-shell  in  due  time  a  ciliated  larva 
which  swims  about  in  the  water  until 
it  finds  a  new  host  to  which  it 
attaches  itself.  In  endoparasitic 
trematodes  the  life  cycle  is  more 
compHcated  in  all  cases  and  ex- 
tremely involved  in  some.  Only  a 
general  outline  of  conditions  can  be 
given  here. 

The  eggs  of  the  fluke  reach  the 
external  world  in  the  feces  or  dis- 
charges from  the  host.  Within  the 
egg-shell    is    developed    a    minute 


FiG.6s2.   Azygia  sebago.    Dorsal  view.  X  16. 
larva,       the       miracidium,       evidently   ^.^male  reproductive  system  in  dorsal  aspect. 
'  '  -'     Semi-diagrammatic  to  snow  relation  of  organs 

p  ovarian  complex,  ovarv'  drawn  in  outline  only. 

acetabulum;    exb,    e.x- 

intes- 


adapted  by  its  ciliated  covering  to  JJ«Jf;  ^^^^-^^^^ 

a  tree  existence.     Sooner  or  later  the  tin^;  u,  Laurer's  canai-  oo,  ootype-,  ot.  ovar>-; 

,  1  i-l-        T-    11    5g,  shell  gland;  to,  anterior  testis;  /p,  posterior 

egg  arrives  m  water  where  the  shell  testis;  «/,  uterus;  t/.vitciiaria;  w.yoikduct; 

,      ,        ,  .  .  yr,  yolk  reser\-oir.     (Original.) 

opens  and  the  larva  escaping  swims 

about  in  search  of  a  new  host.  The  latter  is  not  the  species  which 
shelters  the  adult  but  an  intermediate  host  which  for  almost  all  flukes 
is  a  mollusk,  in  the  tissues  of  which  the  miracidium  changes  to  an 
irregular  sac  (sporocyst);  this  produces  within  itself  a  new  gen- 
eration (redia)  which  also  in  this  host  produces  a  third  generation 
(cercaria).  The  miracidium  possesses  an  eye-spot  and  often  a 
boring  apparatus  at  the  anterior  end.  These  structures  are  lost 
in  the  metamorphosis  into  a  sporocyst,  a  stage  so  simply  con- 
structed that  the  young  rediae  escape  by  the  rupture  of  the  wall. 
A  redia  is  characterized  by  the  presence  of  a  rhabdocoel  intestine 


372  FRESH-WATER   BIOLOGY 

with  pharynx,  an  oral  sucker,  and  usually  a  birth  pore.  The 
redia  generation  may  be  repeated  and  either  this  or  the  sporocyst 
generation  be  eliminated,  so  that  the  cycle  may  become  modified 
in  either  direction. 

When  development  within  the  mollusk  is  completed  and  the 
transfer  to  the  adult  host  takes  place,  the  transfer  may  be  direct 
if  the  mollusk  is  eaten  by  a  suitable  host.  Yet  this  is  not  the 
usual  method  since  the  ordinary  cercaria  possesses  a  well-developed 
swimming  organ  in  the  tail  which  characterizes  this  stage  and  is 
cast  off  when  the  larva  reaches  a  new  host  or  a  place  of  encyst- 
ment.  This  swimming  tail  is  reduced  in  a  few  types  and  wanting 
only  very  infrequently.  In  other  cases  various  modifications,  such 
as  bristles,  folds,  branches,  lateral  membranes,  etc.,  increase  its 
functional  value. 

The  cercaria  usually  deserts  the  snail  and  actively  seeks  out  its 
primary  host,  but  after  reaching  the  outer  world  it  may  also  encyst 
on  vegetation  or  force  its  way  into  a  second  intermediate  host,  an 
aquatic  arthropod  or  small  fish,  and  encyst  there.  Here  it  rests, 
a  small  immature  encysted  distome,  until  the  tissue  is  consumed 
by  a  suitable  host,  whereupon  it  is  set  free  in  the  afimentary  canal 
and  seeks  its  final  location  to  attain  after  a  period  of  growth  the 
adult  form  and  full  maturity.  Life  histories  are  known  among 
trematodes  only  in  the  most  fragmentary  way  and  the  field  offers 
inviting  prospects  to  the  student. 

As  appears  from  the  account  just  given  two  free-living  stages 
recur  in  the  development  of  most  flukes.  The  miracidium  nor- 
mally depends  on  active  migration  through  the  water  to  reach 
and  infect  the  secondary  host.  In  spite  of  the  constant  and 
abundant  production  of  such  larvae  their  occurrence  in  plankton 
or  other  fresh-water  collections  is  not  recorded.  This  may  be  due 
to  the  extreme  deHcacy  of  the  larvae  which  go  to  pieces  almost  as 
soon  as  collected. 

When  infected  snails  are  kept  in  an  aquarium,  the  cercariae 
swarm  out  at  certain  times  in  great  numbers  and  can  be  seen 
swimming  actively  about  in  the  water.  They  conduct  themselves 
under  such  circumstances  like  true  plankton  organisms:  protozoa, 
rotifers,  and  entomostraca  in  the  same  aquarium.     Yet  although 


PARASITIC    FLATWORMS 


373 


such  larvae  are  produced  in  great  abundance  and  infected  mollusks 
are  also  abundant  and  widely  distributed,  there  are  few  records  of 
cercariae  in  reports  on  aquatic  life. 

Leidy  found  cercariae  free  in  the  Delaware  River  and  in  a  \V\'- 
oming  pool.  Wright  discovered  the  remarkable  anchor-tailed  cer- 
caria  among  weeds,  and  I  have  taken  several  forms  including  the 
striking  Cercaria  gorgonocephala  in  the  tow  with  a  plankton  net. 
None  the  less  among  the  fresh-water  organisms  that  are  least 
known  one  may  well  Hst  the  free-swimming  stages  of  parasitic 
worms. 

From  this  survey  of  the  life  history  it  is  evident  that  the  degree 
of  trematode  infection  depends:  first,  on  the  presence  of  water  at 
the  time  when  the  cercariae  or  miracidia  swarm  out;  and  second, 
on  the  occurrence  of  mollusks  in  the  region  to  act  as  intermediate 
hosts.  Hence  flukes  are  rare  in  arid  areas  and  also  in  regions 
lacking  in  lime  where  mollusks  are  all  but  wanting. 

In  general,  infection  is  seasonal  and  may  be  traced  to  the  climatic 
conditions  because  periods  of  excessive  moisture  permit  the  swarm- 
ing of  the  larvae,  whereas  during  dry  months  the  egg-shells  remain 
unbroken.  The  study  of  the  adult  parasites  has  shown  that  in 
most  cases  observed  the  flukes  produce  eggs  continually  and  seem 
to  display  equal  reproductive  activity  in  all  parts  of  the  year. 
The  number  of  flukes  found  in  a  given  host  does  not  appear  to  vary 
seasonally  although  it  does  vary  widely  in  individual  hosts. 

The  fishes,  amphibians,  reptiles,  birds,  and  mammals  that  occur 
in  and  around  various  fresh-water  bodies  shelter  a  multitude  of 
species  of  trematodes.  The  group  has  never  been  studied  care- 
fully on  this  continent  and  data  available  include  mostly  casual  or 
fragmentary  observations  on  a  few  of  its  members.  Pratt  made 
the  first  general  Hst  of  these  species.  Since  then  a  number  of 
students  of  individual  genera  or  groups  of  flukes  have  added  to 
the  count.  Even  this  has  only  made  a  start  at  recording  the 
North  American  species  in  the  region  which  has  been  studied  and 
one  can  hardly  venture  to  predict  the  number  of  species  in  parts 
of  the  country  where  no  collections  at  all  have  been  made.  The 
total  trematode  fauna  of  North  America  is  greatly  beyond  any 
present  records  and  cannot  be  estimated  from  the  data  at  hand. 


374  FRESH- WATER    BIOLOGY 

Even  concerning  the  forms  listed  it  must  be  confessed  that  our 
knowledge  is  very  imperfect. 

In  preparing  the  key  I  have  followed  the  plan  so  admirably 
formulated  by  Looss  and  worked  out  in  various  groups  by  Braun, 
Liihe,  and  Odhner.  The  data  on  larval  forms  (Cercariae)  are 
adapted  from  Cort  and  Faust. 

KEY  TO  NORTH   AMERICAN  FRESH-WATER  TREMATODA 

1  (169)     Adult  forms;  sex  organs  developed  and  functioning 2 

2  (28)     Posterior  organs  of  attachment  powerfully  developed;   those  at  ante- 

rior end  absent  or  if  present  poorly  developed  and  paired. 
Chitinous  hooks  and  anchors  almost  always  present. 

Subclass  Monogenea  .    .     3 

Excretory  pores  anterior,  double,  dorsal;  uterus  short  usually  containing  only  a  single  egg. 
Development  simple,  direct.  Most  forms  are  ectoparasitic  on  body  surface  or  gills.  In 
fresh-water  hosts  found  in  urinary  bladder  (Amphibia)  or  respiratory  passages  (turtles). 

3  (8)     Posterior  organ  single.     Vagina  unpaired.     No  genito-intestinal  canal. 

Order  Monopisthocotylea  Odhner  .    .     4 

4  (5)     Two  suckers  at  anterior  end,  entirely  independent  of  the  oral  cavity. 

A  single  large  posterior  sucker. 

Family  Tristomidae  van  Beneden  1858. 

Monogenetic,  ectoparasitic  trematodes  with  a  single  large  round  terminal  sucker,  often 
armed  with  hooks,  and  with  two  smaller  yet  conspicuous  lateral  suckers  at  the  anterior  end. 
Mouth  ventral  just  behind  anterior  suckers.  Many  forms  parasitic  on  gills  of  marine  fishes; 
a  few  reach  fresh  water  through  the  movements  of  migratory  fish. 

Only  species  reported  from  North  America. 

Nitzschia  sturionis  (Abildgaard)  1794. 

Reported  by  Linton  from  gills  of  sturgeon  (Acipenser  sturio)  at  Woods  Hole.  May  be 
carried  at  times  into  fresh  water. 

5  (4)     Anterior  end  expanded,  bearing  special  structures  of  some  sort  and  yet 

never  true  suckers  alone. 
Family  GYRODACXYLroAE  van  Beneden  and  Hesse  1863   .    .     6 

Small,  slender,  elongate  trematodes  with  anterior  end  variably  provided  with  specialized 
structures,  only  rarely  true  suckers  and  then  associated  with  other  special  organs.  Posterior 
disc  without  suckers,  usually  with  two  or  four  huge  hooks  in  the  center  and  a  considerable 
number  of  small  marginal  booklets. 

On  the  skin  and  gills  of  fishes. 

The  genera  reported  from  fresh  water  all  fall  in  the  section  of  the  family  in  which  the  an- 
terior end  is  provided  with  two  or  four  retractile  cephalic  tips  in  which  open  ducts  of  numer- 
ous dermal  glands. 

6  (7)     Posterior  disc  with  two  large  central  hooks.     No  eyes. 

Gyrodadylus  von  Nordmann  1832. 

Anterior  end  provided  with  two  lateral  contractile  lappets.  Large  central  hooks  of  pos- 
terior disc  turned  ventrad,  shaped  like  fish  hooks  and  bound  together  at  the  roots  by  a  special 
clamp  piece.     Marginal  hooks  sixteen,  simple.     Viviparous. 

On  skin  and  gills  of  many  fresh- water  fish,  especially  Cyprinidae.  At  times  nimierous  enough 
to  destroy  the  external  dermal  layer  and  leave  the  fin  rays  naked.     May  cause  death  of  host. 

Reported  only  twice  in  North  America;  from  young  lake  trout  in  Maine  and  small-mouthed 
black  bass,  Ontario,  Canada.  Species  uncertain.  Cause  of  serious  epidemic  among  young 
fish  at  hatchery  (Craig  Pond);  also  on  wild  fish  in  same  stream. 


PARASITIC   FLATWORMS 


375 


7  (6)     Posterior  disc  with  four  large  central  hooks.     Two  pairs  of  eyes. 

Ancyrocephalus  Creplin  1839. 

Anterior  end  bluntly  triangular  with  two  inconspicuous  lobes  on  each  side,  but  no  distinct 
cephalic  lappets.  Posterior  disc  bears  four  large,  heavy  hooks  and  clamp,  and  fourteen  or 
sixteen  small  marginal  hooks  of  which  two  lie  before  and  two  behind  the  large  hooks.  Ovi- 
parous. 

On  the  gills  of  many  fresh-water  fish. 

Two  species,  determination  doubtful,  reported  by  Cooper  from  Ontario,  Canada.  On  the 
gills  of  young  l3lack  bass.     Also  from  rock  bass  and  sunfish. 

8  (3)     Posterior   organs   multiple    (two    to    many   parted).     Vagina   double. 

Genito-intestinal  canal  present. 

Order  Polyopisthocotylea  Orlhner  .    .     9 

Suckers  at  anterior  end,  if  present,  open  into  oral  cavity.  Posterior  end  with  variable  but 
well-developed  organs  of  attachment  consisting  of  hooks  and  suckers  grouped  on  a  terminal 
field  or  disc. 

9(12)     With  two  oral  suckers  and  with  genital  hooks 10 

10  (11)     Posterior  disc  with  eight,  less  often  four  (five)  small  peculiar  sucking 

organs. 

Family  Octocotylidae  van  Beneden  and  Hesse  1863. 

Elongate,  flattened  ectoparasitic  trematodes.  The  posterior  organ  of  attachment  has  — 
usually  in  two  parallel  symmetrical  rows  —  eight,  more  rarely  four  or  six,  small  suckers  braced 
with  a  characteristic  chitinous  framework  or  armed  with  hooks.  Extra  hooks  occur  often  on 
the  disc.  Genital  pore  always  armed  with  hooks.  Eggs  supplied  with  one  or  two  long  fila- 
ments.    On  gills  of  marine  and  fresh-water  fishes. 

These  parasites  are  rare  in  fresh  water  yet  no  doubt  other  genera  than  the  two  cited  here 
do  occur.  The  American  representatives  are  not  well  known  and  only  the  first  is  more  than 
an  accidental  member  of  the  fresh- water  fauna.  For  this  reason  no  eflfort  has  been  made  to 
incorporate  them  in  the  key. 

Mazocraes  Hermann  1782. 

One  species,  formerly  known  as  Odobothrium  sagitlatum,  is  reported  by  Wright  from  the 
sucker  (Catostoniiis  teres). 

Plectanocotyle  Diesing  1850. 

Reported  from  the  gills  of  Roccus  americaniis  which  enters  fresh  water  to  spawn  so  that  this 
parasite  may  be  taken  at  times  in  that  habitat. 

11  (10)     Posterior  disc  with  a  large  number  of  small  suckers. 

Family  Microcotylidae  Taschcnberg  1879. 

Elongate  ectoparasitic  trematodes  with  two  small  anterior  suckers  connected  with  the  oral 
cavity  and  with  the  posterior  end  expanded  into  a  foot-like  region  bearing  a  multitude  of 

minute  suckers.     Eggs  with  large  filaments  at  both  poles. 
Body  and  posterior  organ  of  attachment  symmetrical. 

Microcotyle  van  Beneden  and  Hesse  1863. 

A  genus  parasitic  on  the  gills  of  marine  fishes.  G.  A.  and  \V.  G.  MacCalluni  report  three 
species  from  the  rock  bass  {Rocciis  Imeatiis)  which  ascends  rivers  along  the  Eastern  Coast 
for  spawning.  Hence  these  parasites  might  be  taken  in  fresh  water,  though  no  record  of  such 
an  occurrence  has  been  found. 

12  (9)     Anterior  end  pointed,  without  suckers  or  other  special  organs. 

Family  Polystomidae  van  Beneden  1858   .    .      13 

Elongate,  flattened  monogenetic  trematodes  with  simple  anterior  end.  and  with  prominent 
adhesive  disc  at  posterior  end.  Posterior  disc  with  hooks  and  either  two  or  six  large  ix.wertui 
suckers.  Mouth  subterminal,  intestine  triclad,  often  dc-ndntic,  with  anastomoses.  .M.iic 
genital  pore  and  uterine  orifice  median,  ventral,  postpharyngeal.  r,,^ 

,  On  body  surface,  gills,  and  in  urinary  bladder  of  amphibians;  in  pharynx  and  cloaca  oi  rep- 
tiles. 


376                                       FRESH-WATER   BIOLOGY 
13  (27)     Posterior  disc  with  six  suckers 


14 


[4  (26)     Posterior  disc  terminal;  suckers  large. 


Poly  stoma  Zeder  1800 


IS 


Six  suckers  in  a  circle  or  in  two  rows  somewhat  separated  in  the  median  Une.  In  the  center 
of  each  sucker  a  small  hook,  and  others  on  anterior  and  posterior  margins  of  shield;  between 
posterior  acetabula  two  large  hooks.  Vagina  double,  one  pore  on  each  side  near  the  ante- 
rior end.     Eggs  without  polar  filament.     Genital  atrium  with  circle  of  hooks. 

Several  species  in  reptiles  and  amphibians.  Not  common  but  widely  distributed.  P. 
integerrimum  Zeder,  type  of  the  genus,  is  not  reported  from  North  America.  American  species 
worked  out  by  Stunkard. 

All  North  American  forms  fall  in  the  section  of  the  genus  characterized  by  the  presence  of 
a  short  uterus  containing  a  single  egg;  to  these  forms  a  new  subgeneric  name  should  be  given. 

Polystoma  (Polystomoides)  Ward. 


15  (23)     Great  hooks  present  on  caudal  disc  and  well  developed 16 


16  (22)     Genital  hooks  of  equal  length 17 


17  (18,  21) 


Not  more  than  16  genital  hooks. 

P.  (Polystomoides)  hassalli  Goto  1899. 

Length  1.3  to  2  mm.;  width  0.4  to  0.65  mm. 
Caudal  suckers  0.12  to  0.16  mm.  in  diameter. 
Caudal  disc  with  18  hooks,  the  largest  0.125 
mm.  and  the  smallest  0.033  nun.  long.  Cir- 
rus hooks  0.028  mm.  long  with  a  winglike 
process  at  the  middle.  Uterus  contains  only 
a  single  large  egg  measuring  o. 11  by  0.25  mm. 
to  0.18  by  34  mm. 

Urinary  bladder  of  Cinosternum  pennsylvan- 
iciim,  Aromochelys  carinatus,  A.  odoratus,  Chel- 
ydra  serpentina;  Maryland,  North  Carolina, 
Texas,  Iowa. 


Fig.  653.    Polystoma  hassalli.     Ventral  view. 
(After  Stunkard.) 


X18. 


18  (17,  21)     Genital  hooks  32 19 


19  (20)    Acetabula  large,  adjacent,  not  contiguous;    pharynx  smaller  than 
oral  sucker.     .    .     P.  {Polystomoides)  coronatum  Leidy  1888. 

Body  3. 1 5  by  0.83  mm.  Caudal  suckers 
0.37  mm.  in  diameter.  Caudal  disc  with 
one  pair  of  great  hooks,  0.132  mm.  long, 
one  pair  of  intermediate  hooks,  0.051  nun. 
long,  and  small  hooks,  0.02  mm.  long. 

From  the  common  food  terrapin  (Leidy). 

Fig.  654.    Polystoma  coronatum.    Ventral  view. 
X  9.    (After  Stunkard.) 


PARASITIC   FLATWORMS 


377 


20  (19)     Acetabula  small,  widely  separated;    pharynx  equal  in  size  to  oral 
sucker.    ...  P.  {Polystomoidcs)  microcotyle  Stunkard  19 16. 

Body  3  by  0.78  mm.  Caudal  suckers 
0.28  mm.  in  diameter.  On  caudal  disc  one 
pair  of  great  hooks,  0.116  mm.  long,  one 
pair  of  intermediate  hooks,  0.061  mm. 
long,  and  small  hooks,  0.017  mm.  long, 
(ienital  coronet  of  32  equal  and  similar 
hooks. 

In  mouth  of  Chrysemys  marginata; 
Creston,  Iowa. 


Fig.  655.  Polystoma  microcotyle.    Ventral  view 
X  9.     (After  Stunkard.J 


21  (17,  18)     Genital  hooks  more  than  32  in  number. 

P.  {Polystomoides)  megacotyle  Stunkard  19 16. 

Body  2.5  to  2.7  by  0.71  to  0.78  mm. 
Genital  coronet  36  to  42  equal  hooks. 
Caudal  suckers  large,  crowded.  On  caudal 
disc  one  pair  of  great  hooks,  0.116  mm. 
long,  one  pair  of  intermediate  hooks, 
0.058  mm.  long,  and  small  hooks  0.017 
mm.  long. 

From  mouth  cavity  of  Chrysemys  mar- 
ginata;  Creston,  Iowa. 

Fig.  656.   Polystoma  megacotyle.   V'entral  view. 
X  12.     (After  Stunkard.) 


22  (16)     Genital  hooks  Unequal  in  length. 

P.  {Polystomoides)  ohlongiim  Wright  1870. 

Up  to  2.5  mm.  long  and  1.5  mm.  wide.  Caudal  suckers  0.2  mm.  in  diameter.  Large  hooks 
on  caudal  disc  0.15  mm.  and  small  hooks  0.015  mm.  long.  Genital  coronet  of  32  hooks,  alter- 
nately large  and  small,  with  free  end  sharply  curved. 

From  urinary  bladder  of  Aromochelys  odoratus;  Canada. 


23  (15)     Great  hooks  of  caudal  disc  reduced  in  size  or  absent 24 


I  24  (25)     Genital  hooks  16  in  number. 

P.  (Polystomoides)  orbicularc  Stunkard  iqi6. 

Length  2.7  to  3.7  mm.;  width  o.y  to 
T.2  mm.  Caudal  suckers  0.3  mm.  in 
diameter.  On  caudal  disc  only  a  single 
minute  booklet  0.016  mm.  long,  in  the 
base  of  each  sucker;  no  large  ht)oks. 
Genital  coronet  of  16  equal  and  similar 
hooks.  Fpg  spherical,  0.21  to  0.^4  mm. 
in  diameter. 
-^  In  urinary  bladder  of  Chrysemys  mar- 

FlG.  657.     Polystoma  orbiculare.     E.Uended.     Ventral         «'"'^/''.    and    /'.v;H(/rwy5    scripta;     North 
view.     X  10.     (After  Stunkard.)  Carolina,  Illinois,  Iowa. 


378 


FRESH-WATER   BIOLOGY 


15  (24)     Genital  hooks  32  in  number. 

P.  {Polystomoides)  opacum  Stunkard  1916. 

Length  3  to  4  mm.,  width  0.8  to  i  mm.  Caudal  suckers  0.4  mm.  in 
diameter.  On  caudal  disc  many  small  hooklets  7  to  9  /x  long,  and  one 
larger  pair,  75 /x  long;  no  great  hooks  present.  Genital  coronet  of  32 
i.3>c>l)  equal  hooks.     Egg  oval,  0.25  by  0.2  mm. 

Vitellaria  of  large  compact  follicles  under  dorsal  surface  from  pharynx 
to  caudal  disc  except  over  ovarian  complex;  so  extensively  developed  as 
to  obscure  internal  organs  and  render  body  opaque. 

In  esophagus  of  Trionyx  ferox  and  of  Malacoclemmys  lesueurii; 
Texas. 


Fig.  658.     Polystoma  opacum. 


Extended. 
Stunkard.) 


Ventral  view.      X  7-     (After 


26  (14)     Posterior  disc  overhung  by  a  flap  bearing  four  hooks. 

Diplobothrium  F.  S.  Leuckart  1842. 

Elongate,  ectoparasitic  trematodes  with  slender  posterior  end.  Six  short  stalked  suckers 
arranged  in  two  longitudinal  rows  and  armed  with  chitinous  hooks,  stand  just  anterior  to 
slender  caudal  tip  which  carries  two  hooks  on  each  side. 

One  species  {D.  annatum)  reported  on  the  gills  of  the  lake  sturgeon  (Acipenser  rubicundus) 
from  St.  Lawrence  River. 


27(13)     Posterior  disc  with  two  suckers Sphyranura  Wright  18 jg. 


Caudal  lamina  considerably  wider  than  slender  body,  with  two  im- 
mersed suckers,  two  large  hooks  behind  them,  and  sixteen  small  hooks 
arranged  seven  along  each  side  of  the  lamina  and  one  in  each  sucker. 
Two  contractile  bladders  anteriorly,  each  with  a  dorsal  pore.  No  lateral 
vaginae.     Oviparous. 

Only  species  known. 

Sphyranura  osleri  R.  R.  Wright  1879. 

On  the  skin  of  Nedurus  lateralis  in  the  Great  Lakes  region.  Corre- 
sponds to  larval  stage  of  Polystoma  in  having  only  two  terminal 
suckers. 


Fig.  659.     Sphyranura  osleri. 


Ventral  surface. 
MacCallum.) 


X  20.     (After  Wright  and 


PARASITIC   FLATWORMS 


379 


28  (2)  Organs  of  attachment  one  or  two  suckers  of  which  the  anterior  is 
always  single  and  median;  without  chitinous  hooks  or 
anchors;  accessory  suckers  rare.   Subclass  Digenea    .    .     29 

Excretory  organs  empty  by  a  single  pore  at  or  near  posterior  end.  Uterus  usually  long 
containing  masses  of  eggs,  rarely  only  a  few.  Development  complex,  with  alternation  of 
hosts  and  most  often  also  of  generations. 

With  rare  exceptions  adults  endoparasitic  in  visceral  organs,  usually  alimentary  system  of  ver- 
tebrates. Isolated  adults  occur  in  moUusks  and  insects  which  are  the  normal  hosts  for  young 
stages. 

For  key  to  free  living  larval  stages  see  section  on  Cercaria,  171  (170)  in  this  key. 


29  (30)     Anterior  sucker  not  perforate;    mouth  on  mid-ventral  surface;    no 
oral  or  ventral  suckers.  .    .  Order  Gasterostomata  Odhner. 

Pharynx  and  esophagus  present.  Intestine  sacculate,  simple.  Vitellaria  lateral  in  anterior 
region  of  body.  Germ  glands  behind  intestine,  in  posterior  region.  Testes  two;  cirrus  elon- 
c:ate;   pore  ventral  near  posterior  end.     Ovary  simple,  opposite  or  in  front  of  anterior  testis. 

Single  family Bucephalidae  Poche  1907. 

Only  genus  known Bucephalus  von  Baer  1826. 

Anterior  end  bears  large  sucker  with  ventral  orifice  and  small  muscular 
papillae  at  lateral  angles. 

The  adult,  better  known  as  Gasterostomum,  has  been  reported  only  from 
Canada  though  to  judge  from  the  abundance  of  the  characteristic  two-tailed 
cercaria  it  must  occur  frequently  in  other  regions. 

Stomach,  intestine,  and  ceca  of  black  bass  and  Boleosoma  nigrum.  Early 
stages  encysted  in  young  black  bass,  rock  bass,  perch,  and  minnow. 

Cercariae  parasitic  in  Unionidae,  especially  in  sex  organs.  Pennsylvania, 
Illinois,  Iowa,  Canada.  Not  common;  occurring  in  fifteen  species  of  Unionidae 
out  of  forty-four  examined;  in  susceptible  hosts  only  4  per  cent  of  individuals 
affected  (Kelly). 

Representative  North  American  species. 

Bucephalus  pusillus  Cooper  191 5. 

Fig.  660.     Bucephalus  pusillus.    Ventral  view.     X  75-     (After  Cooper.) 


30  (29)  Mouth  at  or  near  anterior  tip  of  body  ordinarily  surrounded  by  oral 
sucker;  another  sucker  if  present  median,  behind  mouth 
on  ventral  surface  or  at  posterior  end. 

Order  Prosostomata  Odhner  .    .     31 


31  (36)  Intestine  simple,  rhabdocoel;  oral  sucker  ver>^  poorly  developed; 
ventral  sucking  organ  a  powerful,  conspicuous,  adhesive 
disc  or  a  series  of  smaller  suckers. 

Suborder  Aspidocotylea  Monticelli. 

Terminal  or  subterminal  mouth  surrounded  by  funnel-shaped  expansion  of  skin,  but  not  by 
true  sucker.  Holdfast  organs  ventral,  usually  in  form  of  large  sucking  disc  distinctly  set 
off  from  body  and  subdivided  into  numerous  sucking  alveoli,  hut  never  carrying  chitinous 
hooks  or  anchors;  or  in  place  of  disc  single  series  of  small  disconnected  suckers.  .\limentar>- 
canal  simple,  rhabdocoel.  Sexual  organs  simple.  Development  with  or  without  alternation 
of  hosts  and  generations.  Endoparasitic,  or  rarely  ectoparasitic,  in  mollusks  and  cold-blooded 
vertebrates. 

Forms  not  numerous,  little  known,  grouped  together  at  present  into 
a  single  family.   .    .    Aspedogastridae  Poche  1907   .    .     32 


380  FRESH-WATER   BIOLOGY 

$2  (ss)     Adhesive  organ  oval,  composed  of  four  rows  of  alveoli. 

Aspidogaster  von  Baer  1826. 

Ventral  sucking  disc  large,  equal  in  breadth  and  nearly  so  in  length 
to  entire  body;  oval  in  outline  with  four  convergent  longitudinal 
rows  of  quadrangular  sucking  grooves.  Margin  notched,  with  sense 
organs.  Mouth  terminal;  intestine  extending  into  posterior  end. 
Sexual  pore  median;  in  depression  between  ventral  shield  and  fore- 
body.  Ovary  small;  testis  single,  same  size  as  ovary.  Uterus 
moderately  long;  ova  large.     In  fishes  and  moUusks. 


Representative  American  species. 

Aspidogaster  conchicola  von  Baer  1826. 

The  common  North  American  species  in  fresh  water,  Aspidogaster 
conchicola  v.  Baer,  is  also  the  most  common  parasite  of  the  Union- 
idae.  From  pericardial  and  renal  cavities  of  various  species  of  the 
group;  St.  Lawrence  River;  Havana,  Illinois;  North  Judson,  In- 
diana; Iowa;  Pennsylvania.  Kelly  reported  thirty-seven  cut  of 
forty-four  species  of  Unionidae  and  41  per  cent  of  the  1577  individuals 
examined  were  parasitized  by  this  species.  Occasionally  found  in 
the  intestine  of  various  fishes  into  which  it  has  been  introduced 
when  its  proper  host,  the  mussel,  was  taken  as  food. 


Fig.  661.  Aspidogaster  conchicola.  Anterior  end  of  ventral  sucker  as  seen 
from  below  combined  with  genital  system,  partly  diagrammatic.  Uterus 
and  yolk  follicles  left  out.     Est.      X  35-     (After  Stafford.) 


3i 


(32)     Adhesive  disc  oval,  composed  of  three  rows  of  alveoH 34 


34  (35)     Mouth  subterminal,  not  surrounded  by  buccal  disc. 

Cotylaspis  Leidy  1857. 


( 


Ventral  shield  much  as  in  Aspidogaster,  save  that  the  alveoU 
are  in  three  longitudinal  rows,  the  central  alveoli  being  elongated 
transversely.  Marginal  sense  organs  present,  also  two  eyes. 
Ovary  dextral,  smaller  than  single  testis  in  posterior  end.  Ova 
not  numerous,  large. 

Of  several  species  known,  Cotylaspis  insignis  Leidy  1857,  is 
most  frequent.  It  is  adherent  to  surface  of  host  in  angle  between 
inner  gill  and  visceral  mass  (Kelly) ;  or  branchial  cavity  (Leidy) 
of  many  species  of  Unionidae:  Havana,  111.;  Grand  Rapids, 
Mich.;  Lake  Chatauqua,  N.  Y.;  Cedar  River,  la.;  SchuylkiU 
River,  Penn.  Kelly  examined  over  1600  individuals  of  44  species 
which  belong  in  24  separate  host  species  and  found  18  per  cent 
infected.     The  number  in  a  single  host  is  small. 

Representative  American  species. 

Cotylaspis  cokeri  Barker  and  Parsons  1914- 

C.  cokeri  Barker  and  Parsons  occurs  in  the  intestine  of 
Malacoclemmys  lesueurii. 


Fig.  662.     Cotylaspis  cokeri.     Ventral  view.     X  30.     a,  X  IS* 
(Original.) 


PARASITIC    FLATWORMS 


381 


35  (34)     Mouth  terminal,  surrounded  by  expanded  buccal  disc. 

C ot yl ogasier 'MoniicdVi  1892. 


Ventral  disc  composed  of  single  median  row  of 
grooves  greatly  elongated  transversely  and  sur- 
rounded by  marginal  row  of  small,  circular  alveoli. 
Mouth  in  center  of  discoidal  expansion  of  anterior 
tip  of  forebody.  Long  prephar>'nx  and  esophagus. 
Ovary  and  two  testes  just  behind  it  form  linear 
series  posterior  to  center  of  body.  Laurcr's  can^l 
present.  Embryo  with  large  posterior  sucker; 
development  unknown. 

Parasitic  in  intestine  of  fishes. 


Single  North  American  species. 
Cotylogaster  occidentalis  Nickerson  1 900. 


In  intestine  of  sheepshead  (Aplodinolus  Rrun- 
niens),  Minnesota.     Rare. 


Fig.  663.  Cotylogaiter  occidentalis.  A.  Lateral 
view  of  an  entire  alcoholic  specimen  in  which  the  an- 
terior portion  is  retracted.  X  8.  B.  Diapram  show- 
ing relation  of  organs  as  seen  from  the  dorsal  side,  the 
animal  being  represented  as  straightened  horizontally 
with  the  dorsal  cone  projected  backward.  Magnified. 
(After  Nickerson.) 


36  (31)     Intestine  forked;  oral  sucker  distinctly  developed;  ventral  sucker  if 
present  simple 37 


In  one  genus  (Cryptogonimiis)  the  ventral  sucker  consists  of  two  small  acetabula  close 
together;  in  a  few  genera  it  is  more  or  less  intimately  connected  with  a  genital  sucker  sur- 
rounding the  sexual  pore,  but  in  no  case  does  it  consist  of  a  series  of  small  sucking  organs  or 
have  a  complex,  many-parted  structure. 

The  forms  embraced  under  this  heading  in  the  four  suborders  which  follow,  stand  in  sharp 
contrast  with  those  of  the  suborder  Aspidocotylea  just  preceding.  In  fact  the  latter  are  so  dis- 
tinct in  general  appearance,  in  structure,  and  in  development,  that  they  have  regularly  been 
grouped  heretofore  apart  from  the  orders  which  follow.  They  were  generally  included  under 
the  Monogenea  (p.  374)  until  Monticelli  revived  the  original  view  that  they  should  be  regarded 
as  an  independent  subdivision  of  equal  rank  intermediate  between  the  Monogenea  and  the 
Digenea  (p.  379).  Their  very  recent  inclusion  in  the  latter  group  has  been  well  justified;  yet 
even  with  that  the  striking  differences  noted  above  must  be  kept  clearly  in  mind. 

The  forms  which  follow  fall  naturally  into  four  groups  ranked  here  as  suborders;  they  are 
easily  distinguished  by  a  single  external  feature,  the  adhesive  apparatus,  consisting  of  suckers 
which  in  number  and  arrangement  are  characteristic  of  each  group.  Thus  the  holostomes  h.ive 
in  addition  to  the  oral  and  ventral  suckers  a  special  adhesive  organ  behind  the  latter  ins 
special  organ  is  variable  in  form  and  character.  In  the  amphistomcs  one  finds  an  oral  and  a 
terminal  sucker,  but  no  other  adhesive  organs.  The  distomes  p<issess  an  oral  and  a  ventral 
sucker  but  none  further  back,  while  finally  the  monostomes  have  only  one  sucker  and  that  is 
circumoral  in  location.  .       .     •  n 

These  long  recognized  groups  are  already  beginning  to  break  up  under  the  influence  of  more 
careful  study,  and  as  noted  in  the  next  section  steps  have  been  taken  to  eliminate  the  monostomes 
as  an  independent  subdivision,  distributing  its  members  among  other  groups. 


382 


FRESH-WATER    BIOLOGY 


37  (48)     No  ventral  sucker  present;   oral  sucker  only  adhesive  organ  present. 

Suborder  Monostomata  Zeder   .    .     38 

Endoparasitic  trematodes  with  flattened  body  and  single  sucker  which  surrounds  mouth 
at  anterior  end.  Intestinal  crura  often  unite  in  posterior  end  of  body.  Genital  pore  usually 
ventral  or  marginal  in  anterior  region,  or  rarely  rnedian  posterior.  Life  history  relatively  un- 
known.    For  developmental  stages  see  174  (183)  in  this  key. 

Forms  not  well  known,  though  frequent  especially  in  reptiles  (turtles)  and  birds;  rarely  also 
mammals.     North  American  records  scanty. 

Most  of  the  forms  described  from  this  continent  as  "  :Monostomum "  cannot  be  located 
except  generally  in  this  section  since  the  data  are  lacking  on  which  a  more  exact  determina- 
tion depends.  It  is  indeed  likely  that  some  of  them  were  wrongly  placed  in  this  group  and 
more  complete  knowledge  of  their  structure  will  result  in  their  transfer  to  some  other  section. 
Until  the  specimens  are  restudied  they  must  all  be  regarded  as  uncertain.  Such  doubtful 
forms  are  those  hsted  as  Monostoma  sp.  in  Stiles  and  Hassall's  Catalog  (1904)  and  the  following: 

Monostoma  affine  Leidy  from  muskrat,  M.  aminri  Stafford  from  bullhead,  M.  aspersnm 
Vaill  of  Pratt  from  salamander,  M.  incommodum  Leidy  from  alligator  (which  later  the  author 
conjectured  to  be  in  fact  a  distome),  M.  ornatum  Leidy  from  frog,  M.  spatulatum  Leidy  from 
"fish." 

Odhner  contends  that  the  monostomes  are  isolated  members  of  other  groups  that  have 
lost  all  suckers  save  the  oral  and  that  they  should  be  classed  in  the  various  families  from  which 
they  have  sprung.  For  practical  reasons  it  will  be  necessary  to  retain  the  group  at  least  until 
its  forms  are  much  better  known. 


38  (45)     With  two  compact  testes,  and  follicular  vitellaria 39 

39  (44)     Body  elongated.     Not  parasitic  in  dermal  cysts 40 

40  (41)     Intestinal  crura  connected  at  posterior  end.     Testes  near  posterior 

end,   within  crura,   asymmetrical.     Ovary  between  testes, 
and  intercecal  but  opposite  to  them. 

Family  Cyclocoelidae  Kossack  1911. 

Large  monostomes  with  thick,  muscular  body,  somewhat  flattened.  Esophagus  short,  no 
pharynx.  (Kossack  designates  the  structure  which  lies  near  the  mouth  as  the  pharynx;  I  have 
called  it  the  oral  sucker.  He  says  these  forms  do  not  possess  an  oral  sucker.)  Intestinal 
branches  simple  or  with  small  ceca  on  the  inner  side  connected  at  posterior 
end  by  continuous  arch.  Genital  pore  median,  ventral  to  and  near  oral 
sucker.  Receptaculum  seminis  and  Laurer's  canal  wanting.  Vitellaria  well 
developed,  lateral  and  sometimes  dorsal  to  intestine;  transverse  duct  just  in 
front  of  posterior  testis.  Uterine  coils  numerous,  regular,  transverse,  occu- 
pying space  between  posterior  testis  and  fork  of  intestine.  Eggs  numerous, 
without  polar  filaments. 

Air  passages  of  water  birds;   frequently  reported  as  in  body  cavity. 

Only  American  genus.      .    .    .    Cyclocoelum  Brandes  1892. 

Intestinal  crura  simple,  genital  pore  near  sucker,  or  at  anterior  margin. 
Cirrus  sac  small,  rarely  extending  beyond  fork  of  intestine.  Vitellaria 
extracecal  from  fork  of  intestine  to  posterior  end,  not  continuous  with 
opposite  side.  Reproductive  glands  in  posterior  region  in  arch  of  intestine 
at  corners  of  triangle.  Ovary  smaller  than  testes,  on  side  opposite  them. 
Uterine  coils  do  not  extend  laterad  beyond  the  intestinal  branches.  Eggs 
thick-shelled,  large. 

The  species  designated  by  Leidy  as  "probably  Monostoma  mutabile 
Zeder"  belongs  here  if  his  determination  be  accepted.  It  was  collected 
from  the  gray  snipe  {Gallinago  wilscni). 

Fig.  664.     Cyclocoelum  mutabile.     X  3-     (After  Kossack.) 

41  (40)  Intestinal  crura  end  blindly  at  posterior  end.  Testes  symmetrical,  in 
posterior  region,  outside  of  crura.  Ovary  intercecal,  between 
testes.      .    .    .     Family  Notocotylidae  Liihe  1909   .    .     42 

Small  monostomes  with  elongated  flattened  body  tapering  and  rounded  at  both  ends.  On 
ventral  surface  several  (3  to  5)  rows  of  small  excrescences  or  papillae  with  unicellular  dermal 
glands      Esophagus  short,  no  pharynx;    intestinal  ceca  simple,  long,  not  united  in  posterior 


PARASITIC   FLATWORMS 


383 


region.  Genital  pore  median,  not  far  from  oral  sucker.  Cirrus  sac  elongate  enclosing  only  part 
of  the  convoluted  seminal  vesicle.  Testes  symmetrical,  near  posterior  end,  outside  intestinal 
crura.  Ovary  between  te.stes.  V'itellaria  lateral,  anterior  to  testes.  Uterine  coils  behind 
cirrus  sac,  transverse,  regular,  not  extending  outside  intestinal  crura.  Eggs  with  long  fila- 
ments at  both  poles. 

42  (43)     With  conspicuous  longitudinal  rows  of  papillae  on  ventral  surface. 
Metraterm  barely  half  as  long  as  cirrus  sac. 

Notocotylus  Diesing  1839. 


Body  attenuated  in  front,  broadly  rounded  behind.  V^entral  surface 
with  three  rows  (in  A'^.  quinquesenalis  with  five  rows)  of  glandular 
masses  which  open  into  protrusible  grooves. 

European  species  reported  from  cecum  of  water  birds. 

Representative  American  species. 

Notocotylus  quinqueserialis  Barker  and  Laughlin  igii. 

In  North  America  one  species;  in  the  cecum  of  the  muskrat. 
Nebraska,  Michigan. 

Fig.  665.     Notocotylus  quinqueserialis.     Ventral  view.     Magnified.     (After 
Barker  and  Laughlin.) 


43  (42)     \>ntral  rows  of  papillae  poorly  developed.     Metraterm  about  equal 

in  length  to  cirrus  sac Catatropis  Odhner  1905. 

Body  tapering  only  slightly,  about  equally  rounded  at  both  ends.  \'en- 
tral  surface  with  three  rows  of  poorly  developed  gland  masses;  the  middle 
row  opens  on  a  low  keel  or  ridge;  the  lateral  rows  contain  each  eight  to 
twelve  small  wart-like,  non-retractile  prominences.  Metraterm  well  de- 
veloped, as  long  as  cirrus  sac. 

European  species  in  cecum  and  rectum  of  water  birds. 

Representative  American  species. 

Catatropis  filamentis  Barker  191 5. 
Only  North  American  species;  in  the  duodenum  of  the  muskrat. 

Fig.  666.     Catatropis  filamentis.     \'cntral  view.     Magnified,     (.\fter  Barker.) 

Nudocolylc  novicia,  very  recently  described  by  Barker  from  the  muskrat,  is 
placed  in  this  family  despite  some  striking  mori)hological  dilTerences.  The 
form  is  small  (0.7  to  0.9  mm.  long  by  0.5  to  0.65  mm.  wide),  thick-bodied, 
and  without  ventral  glands.  The  genital  pore  is  lateral  and  well  behind  the 
middle  of  the  body,  being  thus  far  removed  from  the  intestinal  bifurcation. 
The  heavy  pyriform  cirrus  pouch  encloses  part  of  the  convolutnl  seminal 
vesicle.  Vitellaria  in  compact  masses  lie  e.xtracecal  and  just  behind  the 
middle  of  the  body.  Transverse  uterine  coils  extend  over  the  intestinal 
crura  nearly  to  the  lateral  margins  of  the  body;  they  fill  the  anterior  half 
and  are  limited  posteriorly  by  the  cirrus  pouch  and  vitelJaria.  The  eggs 
measure  20  to  24^  by  10  to  13/i  and  have  long  heavy  polar  filaments. 

Parasitic  in  intestine  of  muskrat;  Minnesota. 

44  (39)     Body  compressed,  broader  than  long.     Parasitic  in  pairs  in  dermal 

cysts Family  Collyriclidae  Ward. 

Small  to  moderate  sized  monostomes  with  thick  but  not  muscular  body,  smooth  skin;  oral 
sucker  and  phaiynx  present;  ceca  long,  capacious,  not  united.  C.enital  pore  ventral  near 
center  of  body;  vitellaria  follicular,  scanty,  antero  lateral.  Ovary  much  lobed.  asymmetrical. 
Testes  oval,  symmetrical  behind  ovary.  Uterus  in  irregular  coils  showing  a  tendency  to  antero- 
posterior direction.     Terminal  region  of  uterus  enlarged. 

Parasitic  in  dermal  cysts  on  abdominal  surface.     Usually  two  in  each  cyst.     In  birds. 

Only  American  genus 0>//ynV/Mm  Kossack  loi  i. 

Submoderate  sized  trematodes  with  dorsally  arched  and  ventrally  flattened  Ixxly.  Oral 
sucker  weak,  pharynx  small,  intestinal  crura  simple,  very  broad.     Oenital  ixjre  median,  just 


3B4 


FRESH-WATER   BIOLOGY 


anterior  to  center.  Vitellaria  in  seven  symmetrical  groups,  marginal  in  anterior  region. 
Testes  symmetrical.  Ovary  in  front,  strong] v  lobed.  Coils  of  uterus  irregular,  mostly  lateral 
in  posterior  half  of  body.     Eggs  very  small. 

Representative  American  species Collyriclum  colei  Ward. 

The  single  European  species,  formerly  known  as  Monostoma 
faba,  was  reported  for  North  America  as  the  cause  of  an 
epidemic  among  sparrows  at  Madison,  Wisconsin.  The  life 
history  is  unknown;  the  supposition  that  avian  insect  para- 
sites act  as  the  intermediate  host  is  extremely  improbable. 
It  attacks  only  young  sparrows  and  infected  birds  are  found 
only  during  or  just  after  a  wet  period  (Cole). 

The  parasite  has  been  found  again  in  Boston,  Mass.  These 
specimens  differ  clearly  from  the  European  form  in  numerous 
minor  details,  such  as  ovary,  yolk  glands,  dermal  spines,  etc., 
and  demand  recognition  as  a  distinct  species  under  the  name 
given  here. 


Fig.  667.     Collyriclum  colei.     X  9-     Detail  of  surface. 
(Original.) 


Xios. 


45  (38)     With  elongate  tubular  testes  and  vitellaria. 

Family  Heronimidae  W'ard 


46 


Moderate  sized  monostomes  with  thick,  elongate,  soft  body  somewhat  flattened,  tapering 
both  towards  pointed  anterior  and  bluntly  rounded  posterior  end.  Skin  smooth.  Oral  sucker 
weak,  pharynx  large,  esophagus  short,  ceca  simple,  extending  to  but  not  united  at  posterior 
end.  Vitellaria  compact,  tubular,  shaped  like  inverted  V.  Uterus  in  four  longitudinal  re- 
gions. Genital  pore  ventral  to  oral  sucker  near  anterior  tip.  Testes  tubular,  lobed  or  with 
short  branches,  vmited  into  V-shaped  organ  with  apex  anteriad.  Copulatory  apparatus  poorly 
developed. 

Limgs  of  reptiles.     Northern  North  America. 

Two  genera  imperfectly  known  which  may  prove  to  belong  in  a  single  genus. 


46  (47)     Vitellaria    extend   only  half    way 
Seminal  receptacle  present . 


from    ovary,    to    posterior    end. 
.    .    Heronimus  MacCallum  1902. 


Oral  sucker  small,  pharynx  large,  no  esophagus,  simple  intestinal 
crura  which  reach  the  posterior  end  but  do  not  unite.  Ovary  oval 
or  bean-shaped,  lateral  in  anterior  third  of  body;  receptaculum 
present  but  no  Laurer's  canal.  Uterine  loops  intracecal;  terminal 
section  of  uterus  sacculate.  Vitellaria  small,  elongate,  not  follicular, 
tubular  (?).  Genital  pore  ventral  to  oral  sucker.  Testes  Y-shaped 
with  coarse  lobes,  in  median  third  of  body,  with  median  stem 
directed  anteriad. 


Only  species  known. 

Heronimus  chelydrae  MacCallum  1902. 

In  lungs  and  air  passages  of  river  snapping  turtle  {Chelydra  ser- 
pentina), Ontario,  Canada. 


Fig.  668.  Heronimus  chelydrae.  From  above,  combined  with  dorsal  view 
showing  male  genital  apparatus.  (Excretory  vesicle  not  shown.)  Magnified. 
(After  MacCallum.) 


PARASITIC   FLATWORMS 


385 


47  (46)     Vitellaria  extend  from  ovary  to  posterior   end  of  body.     Seminal 
receptacle  absent.    .    .    .    Aorchis  Barker  and  Parsons  iqi4. 

Oral  sucker  small,  weak,  pharynx  large,  esophagus  short, 
intestinal  ceca  long,  not  united  at  posterior  end.  Ovary  entire, 
just  behind  fork  of  intestine.  \'itellaria  compact,  tubular^ 
coarsely  lobed  or  with  short  irregular  branches  extending  almost 
entire  length  of  body.  Two  divisions  of  uterus  looped  or  coiled 
around  intestinal  ceca.  Other  two  divisions  straight  longitudi- 
nal tubes.  Terminal  division  conspicuous,  heavy,  dark  band 
through  length  of  the  body  in  the  median  plane.  Testes 
elongate,  tubular,  irregularly  lobed.  Genital  pore  ventral, 
near  anterior  tip  of  body.  Eggs  with  short  polar  stalk  at  one 
end. 


Type  species. 

Aorchis  extensus  Barker  and  Parsons  19 14. 

Lungs  oi  Chrysemys  marginata,  Mississippi  River  (Minnesota) 
and  also,  in  various  turtles  from  Michigan,  Indiana,  Illinois, 
Nebraska. 

Fig.  669.  Aorchis  extensus.  Only  anterior  portion  of  testes  shown 
in  drawing.  X  8.  a.  Embryos  in  uterus;  note  conspicuous  eye  spots. 
X  22.     (Original.) 


48  (37)     Ventral   sucker  present,  usually  single  though  varied    in  form  and 

position;  never  represented  by  numerous  small  organs  in 
series 4g 

The  acetabulum  or  ventral  sucker  proper  is  a  closed  organ,  not  possessing  any  inner  opening 
or  connecting  with  any  special  organ  or  system.  It  may  be  so  insignificant  in  size  as  to  be 
difficult  to  distinguish,  in  which  case  the  form  is  erroneously  diagnosed  as  a  monostome  as  has 
often  occurred.  On  the  other  hand  it  may  be  as  wide  as  the  body  or  wider  and  so  powerful 
as  to  distort  the  form  of  the  animal.     It  may  be  sessile  or  be  borne  on  a  stalk  or  peduncle. 

In  some  species  a  special  secondary  sucking  organ  is  developed  around  the  genital  orifice 
and  this  may  even  become  so  highly  differentiated  as  to  exceed  in  size  or  include  the  true  ven- 
tral sucker.  Those  forms  which  possess  this  highly  developed  adhesive  organ  ordinarily  have 
the  body  divided  into  two  distinct  regions. 

In  location  the  acetabulum  is  near  the  posterior  end  in  the  group  of  amphistomes  and  at  or 
anterior  to  the  center  of  the  body  in  the  distomes  and  holostomes.  The  latter  are  readily 
recognized  by  the  peculiar  adhesive  organ  and  the  separate  regions  of  the  body  even  though 
the  details  of  form  are  very  variable  in  different  genera. 

49  (62)     Acetabulum  terminal  or  subterminal  and  posterior   to   the   repro- 

ductive glands Suborder  Amphistomata  Nitzsch. 

Endoparasitic  trematodes  with  oral  opening  anterior  and  terminal.  Oral  sucker  powerful, 
oval  or  more  elongate,  often  with  two  dorso-lateral  muscular  pockets.  Acetabulum  conspicu- 
ous, much  larger  than  oral  sucker,  at  or  very  near  posterior  end.  Body  muscular,  thick,  little 
flattened  and  often  conical,  tapering  anteriad.  Skin  without  spines  but  regularly  provided 
with  sensory  or  glandular  papillae.  Excretory  bladder  sacculate,  with  median  ventral  pore 
near  posterior  end.  Genital  pore  ventral,  median,  in  anterior  region.  Testes  large  anterior 
to  small  ovary.  Vitellaria  follicular,  lateral,  paired.  Uterus  simple,  with  few  coils.  Eggs 
numerous,  small,  plain.     Development  complex  with  alternation  of  generations  and  hosts. 

Only  family  recognized. 

Paramphistomidae  Fischoeder  iqoi  .    .     50 

50(61)     Oral  sucker  terminal;  acetabulum  simple,  not  divided 51 

51  (52)     No  postero-lateral  pockets  on  pharynx. 

Subfamily  Paramphistominae  Fischoeder  iqoi. 
None  of  these  forms  is  parasitic  as  adults  in  aquatic  animals.     One  species  occurs  in  domes- 
tic ruminants  in  North  America.     The  redia  and  cercaria  develop  in  some  fresh,  water  snails  as 
is  known  of  the  related  European  forms.     Compare  185  in  this  key. 


386  FRESH-WATER   BIOLOGY 

52  (51)     Postero-lateral  pockets  present  on  pharynx. 


53 


53  (56)     Testes  two,  more  or  less  deeply  lobed. 

Subfamily  Cladorchiinae  Fischoeder  1901 


54 


Amphistomes  with  more  or  less  strongly  flattened  body,  and  with  acetabulum  usually  con- 
spicuously ventral,  rarely  only  terminal.  Testes  branching  or  lobed.  Cirrus  sac  incom- 
plete or  nearly  wanting. 

In  this  subfamily  belongs  possibly  the  "Amphistoma  grande  Diesing"  of  Leidy  from  the  terra- 
pin which  does  not  seem  to  conform  to  the  species  designated.  The  description  is  inadequate 
for  a  final  diagnosis. 


54  (55)     Pharyngeal  pockets  small,  not  affecting  external  boundary  of  oral 
sucker Stichorchis  Fischoeder  1901. 

Body  noticeably  attenuated  anteriorly,  broadly  rounded  posteri- 
orly. Margins  rounded,  dorsal  surface  high,  arched,  ventral  flattened. 
Acetabulum  ventral.  Pharynx  lacking;  crura  not  much  separated 
from  lateral  margins.  Cirrus  sac  small,  genital  sucker  not  conspicu- 
ous. Vitellaria  well  developed,  mostly  behind  testes  and  median 
to  crura,  as  well  as  partly  dorsal  and  ventral  to  same. 

North  American  species. 

Stichorchis  siihtriquetrus  (Rudolphi)  1814. 

One  species,  St.  suhtriquetriis,  the  true  A  mphistoma  subtriquetrum 
Rud.     In  intestine  of  the  beaver;  Quebec,  Ontario. 


Fig.  670.     Stichorchis  subtriquetrus.     Dorsal  view  to  show  arrangement  of 
parts.     Magnified.     (After  Duff.) 


55  (54)     Pharyngeal  pockets  large,  conspicuous,  modifying  greatly  outline  of 
oral  sucker Wardiiis  Barker  and  East  191 5. 


Moderate  sized  amphistomes  with  prominent  pharyngeal  pockets,  and 
large  subterminal  sucker.  Esophagus  well  developed,  without  differ- 
entiated regions;  crura  long  and  wavy.  Testes  shghtly  lobed,  tandem, 
in  center  of  body.  Ovary  median,  behind  testes  near  posterior  sucker. 
Genital  pore  posterior  to  bifurcation  of  intestine.  Vitellaria  extend  out- 
side crura  from  oral  to  posterior  sucker. 


Only  one  species. 

Wardius  zihethicus  Barker  and  East  k 


'15. 


In  cecum  of  muskrat.     Regarded  by  these  authors  as  the  "^;w- 
phistomiim  subtriquetrum  Diesing"  of  Leidy  (1888). 


Fig.  671.    Wardius  zibethicus. 


Ventral  view,  specimen  compressed. 
(After  Barker.) 


Magnified. 


56  (53)     One  or  two  testes,  spherical 57 


PARASITIC   FLATWORMS 


387 


57  (58)     Vitellaria  consist  of  few  large  follicles  or  form  i)aired  compact  organ. 
No  cirrus  sac.    .    .      Subfamily  Diplodisci.vae  Cohn  1904. 

Moderate  sized  amphistomes  with  conical  body,    round  in   transsection,  attenuated   ante- 
riorly.    Terminal  sucker  very  large.     Intestinal  crura  extend   to  terminal   sucker,  relatively 
broad.      Vitellaria  a  few  large  follicles  on  each  side  which  may  be 
condensed  into  a  more  or  less  compact  but  lobed  organ. 
In  alimentary  canal  of  Amphibia  and  Reptilia. 

Only  North  American  genus. 

Diplodiscus  Diesing  1836. 

Two  testes  confluent  in  older  specimens.  Genital  pore  near  oral 
opening.  Esophagus  long,  pharynx-like  enlargement  at  bifurcation 
of  intestine,  not  sharply  marked  ofT.  Excretory  vessels  looped  into 
coils,  some  above  and  some  below  intestine. 

Only  North  American  species. 

Diplodiscus  temperatus  Stafiford  1905. 


Rectum  of  various  frogs, 
braska,  Minnesota. 


Canada,  Pennsylvania,  Indiana,  Ne- 


FiG.  672.  Diplodiscus  temperatus.  Adult  worm  somewhat  contracted, 
drawn  from  the  ventral  side  as  a  transparent  object.  Magnified.  (,.\fter 
Gary.) 


58  (57)     Vitellaria   consist   of   small   scattered   lateral   foUicles.     Cirrus   sac 

present.    .   .   .   Subfamily  Schizamphistominae  Looss  191 2. 
Representative  North  American  genus. 

Allassostoma  Stunkard  1916  .  .  59 
Large  oral  invaginations  open  independently  into  oral  sucker;  no  preoral  sphincter;  esoph- 
ageal bulb  composed  of  concentric  muscle  lamellae.  Hermaphroditic  duct  present,  (ierm 
glands  median,  near  center  of  body.  Both  testes  anterior  to  ovary.  Vitellaria  consist  of  small 
scattered  lateral  follicles,  in  posterior  region  with  median  follicles  also.  Laurer's  canal  opens  in 
mid-dorsal  line  anterior  to  excretory  pore. 

59  (60) .  Large  worm  (over  10  mm.  long)  with  small  suckers. 

Allassostoma  magnum  Stunkard  1916. 


Length  10  to  12  mm.,  breadth  3  to  s  mm.,  thickness  1.5  to  2  mm. 
Living  worm  clear,  slow-moving,  capable  of  great  extension.  Acetabu- 
lum sub-terminal,  ovoid,  wider  anteriad,  2  to  2.5  mm.  long  by  2  mm.  wide. 
Oral  sucker  terminal,  0.9  to  1.35  mm.  long  by  0.6  to  0.9  mm.  wide;  oral 
pockets  arise  at  posterior  end  of  oral  sucker  by  separate  lateral  openings 
and  extend  dorsad  and  caudad. 

Testes  oval,  0.27  to  0.35  by  0.45  to  0.9  mm.,  long  axis  transverse, 
located  near  center  of  body  and  slightly  oblique.  Ovary  median,  spheri- 
cal or  oval,  0.28  to  0.35  by  0.33  to  0.57  mm.  in  diameter.  \'ilelline 
foUicles  small,  sparse,  anteriorly  extracecal,  but  posteriorly  also  intracccal. 
No  receptaculum  seminis  and  nc  vitelline  reservoir.  Eggs  0.1  by  o.ii 
mm. 

In  intestine  of  Pseiidemys;    Illinois,  Missouri. 


Fig.   673.      Allassostoma  magnum.      W-ntral  view.     X  a.     (After  Stunkard.) 


60  (59)     Small  worm  (length  about  3  mm.  or  less)  with  large  .suckers. 

Allassostoma  parvum  Stunkard  191 6. 
From  Chetydra  serpentina;  Urbana,  111. 


388 


FRESH-WATER   BIOLOGY 


6i  (50)     Oral  sucker,  subterminal ;    acetabulum  divided  by  transverse  ridge 
into  two  pockets.  ,    .    .      Subfamily  Zygocotylinae  Ward. 


Differs  from  all  other  subfamilies  in  position  of  oral  sucker  and 
ofY-yy.  peculiar  character  of  acetabulum.     Testis  lobed;  ^cirrus  sac  lack- 

"'""'  ing. 

Representative  American  genus. 

Zygocotyle  Stunkard  19 16. 

Acetabulum  consists  of  anterior  part  extending  dorsad  and 
anteriad  into  body,  and  posterior  overhanging  lip  bearing  on  each 
side  conical  projection.  Posterior  end  of  esophagus  surrounded 
by  muscular  bulb  in  which  fibers  are  not  arranged  in  concentric 
lamellae  as  in  other  amphistomes.  Vitellaria  well  developed,  with 
large  follicles,  in  extracecal  region  from  oral  sucker  to  acetabulum. 
Uterus  and  germ  glands  intracecal.  Eggs  numerous,  0.14  by 
0.083  min- 

Type  species.     .     .    Zygocotyle  cerafosa  Stunkard  19 16. 

From  intestine  of  Anas  platyrhynchos;  Nebraska. 

Fig.  674.     Zygocotyle  ceratosa.     Ventral  view.     X  5-      (After  Stunkard.) 


62  (49)     Acetabulum  conspicuously  ventral  and  usually  anterior  to  center  of 

body.     Reproductive  organs  completely  or  largely  posterior 
to  acetabulum 63 

63  (160)     No  holdfast  organs  present  except  oral  and  ventral  suckers.     No 

sharp    separation    between    anterior   region   with    holdfast 
organs  and  posterior  region  with  genital  organs. 

Suborder  Distomata    .    .      64 

64  (159)     Hermaphroditic  distomes 65 

65  (148)     Ovary  anterior  to  testes 66 

66  (107)     Coils  of  uterus  do  not  extend  posterior  beyond  testes,  or  at  most  not 

beyond  the  posterior  testis 67 

Bunodera  (see  103  in  this  key)  forms  the  single  exception. 

67  (106)     Acetabulum  a  single  typical  sucker  which  may  be  stalked  or  united 

with  special  genital  sucker  but  is  not  divided 68 

68  (105)     Not  more  than  two  testes  present 69 

69  (74)     Both  ovary  and  testes   dendritic;    uterus  limited  to  a  restricted 

area 70 


PARASITIC    FLATWORMS 


389 


70  (73)     Large  flattened  distomes;    ovary  and  testes  both  highly  branched; 
uterus  median,  a  short  series  of  transverse  coils. 

Family  Fasciolldae  Railliet  1895. 

Large  distomes  with  muscular,  more  or  less  broad  and  flattened  leaf-shaped  body.  Ventral 
sucker  powerful,  close  to  anterior  end.  Intestinal  crura  extend  to  posteror  end.  Excretory 
bladder  tubular,  extends  anteriad  beyond  testes.  Genital  pore  median,  at  anterior  margin 
of  acetabulum.  Cirrus  and  cirrus  sac  well  developed.  Ovary  lateral,  in  front  of  acetabulum. 
testes  symmetrical,  postacetabular.  Vitellaria  extensive,  reaching  posterior  end.  Uterus 
short,  in  condensed  coil,  entirely  preovarian.  Eggs  very  large,  thin  shelled,  in  moderate  num- 
bers.    Development  with  alternation  of  hosts  and  generations. 

Parasites  in  intestine  and  gall  ducts  of  Mammalia. 

Reported  in  North  America. 

Subfamily  Fasciolinae  Stiles  and  Hassall  1898   .    .     71 


71  (72)     Anterior  tip  distinctly  set  off  from  main  body;   vitellaria  both  dorsal 
>     and  ventral  of  intestinal  branches.     F(Z.yc/o/(Z  Linnaeus  1758. 


Very  large  distomes  with  leaf-shaped  body  having  so-called  "cephalic 
cone"  set  off  at  anterior  end,  and  pointed  posterior  end.  Skin  spinous. 
Acetabulum  large,  at  junction  of  cephahc  cone  and  main  body.  Esophagus 
short,  with  pharynx  and  prepharynx.  Intestinal  crura  near  median  line, 
extend  to  posterior  end,  provided  on  mesial  aspect  with  short  branches 
and  on  outer  side  with  long  branches  which  again  may  be  branched. 
Uterus  in  front  of  acetabulum,  forming  a  rosette.  Vitellaria  richly  de- 
veloped in  lateral  area,  and  in  posterior  region  also  on  both  surfaces  of  body. 

In  the  gall  passages  of  herbivores,  very  rarely  in  man. 


Type  species. 


Fasciola  hepatica  Linnaeus  175S. 


An  introduced  species  {F.  hepatica)  common  in  sheep  and  cattle  in 
limited  regions;  Long  Island,  N.  Y.,  introduced  from  Texas,  Gulf  States, 
California.  The  North  American  intermediate  host  is  not  known.  Stiles 
suspects  Limnaea  humilis  Say. 


Fig.  675.     Fasciola  hepatica.     X  3-     (Original.) 


72  (71)     No  distinct  anterior  conical  portion.     X'itellaria  ventral  to  intestinal 
branches Fascioloides  Ward. 

Body  very  large,  broad,  thick,  without  separate  anterior  portion  or  cephalic  cone,  iwsterior 
end  bluntly  rounded.     Vitellaria  confined  to  region  ventral  to  intestinal  branches. 

Type  species Fascioloides  magna  (Bassi)  1875, 

In  liver  and  lungs  of  Xorth  .\merican  herbivores  both  do- 
mestic and  wild;  usually  included  in  former  genus.  On  the 
advice  of  Odhner  anew  genus  is  made  for  the  Xorth  .Vmcrioin 
form.  First  discovered  in  a  European  zoological  garden  para- 
sitic in  the  wapiti,  it  is  known  to  occur  in  many  hosts  and  to 
be  widely  distributed  from  Maine  to  California.  It  is  espe- 
cially abundant  in  parts  of  the  South.  Egg  and  embr>'o  are 
said  by  Stiles  to  agree  with  those  of  the  last  species. 

Fig.  676.     Fascioloides  magna.     Intestinal  crura  and  branches 
drawn  as  solid  black  lines.     Natural  size.     (Original.) 

Another  genus,  Fasciolopsis,  common  as  a  parasite  of  man 
in  some  parts  of  the  East,  has  been  reported  in  \orth  .\nu-rica 
a  few  times  as  a  human  parasite.  Apparently  all  these  rases 
have  been  imported  and  the  parasite  has  not  so  far  as  known 
gained  a  foothold  on   this  continent. 


390 


FRESH-WATER   BIOLOGY 


73  (70)  Distomes  moderate  in  size,  thick  bodied;  ovary  and  testes  lobed 
or  coarsely  branched;  uterine  coil  chiefly  lateral  to  acetab- 
ulum  Family  Trogloteematidae  Odhner  19 14. 

Distomes  of  small  to  moderate  size  with  compressed  body.  Skin  with  spines  in  groups. 
Ventral  surface  flat,  dorsal  arched.  Musculature  and  suckers  poorly  developed.  Intestinal 
crura  do  not  reach  posterior  end.  Excretory  bladder  Y-shaped,  or  tubular.  Genital  pore 
close  to  acetabulum.  Cirrus  sac  lacking.  Testes  symmetrical,  postacetabular.  Ovary 
dextral,  immediately  in  front  of  testes,  lobed  or  branched.  Laurer's  canal  present.  Vitel- 
laria  very  extensive,  covering  dorsal  surface  save  for  narrow  median  strip.  Uterus  long,  in 
open  loops,  or  shorter  in  tight  coil;  eggs  in  first  case  small,  in  second  moderately  large. 

Parasites  of  birds  and  carnivores,  living  usually  by  pairs  in  cyst-Nke  cavities. 

The  monostome,  CoUyriclum  colei\{p.  384).  is  regarded  by  Odhner  as  properly  a  member  of- 
this  family. 

Only  American  genus Paragonimus  M.  Braun  1899. 

Body  opaque,  thick,  nearly  rounded  in  cross  section.  Skin 
with  spines.  Pharynx  ahnost  spherical,  crura  wavy  with  irregular 
walls.  Testes  lobed,  symmetrical,  in  hindbody.  Ovary  lobed, 
lateral,  pretesticular,  and  postacetabular.  Vitellaria  extend  en- 
tire length  of  body,  lateral  and  dorsal.  Laurer's  canal  and 
rudimentary  receptaculum  present.  Uterus  in  coil,  postacetabu- 
lar, opposite  ovary.  Eggs  large,  thin-shelled,  laid  before  cleav- 
age begins. 

Encysted,  in  pairs  usually,  in  lungs  of  mammals. 

Single  American  species. 

Paragmiimus  kellicotti  Ward  1908. 

Parasitic  in  dog,  cat,  and  pig.  Ohio,  Illinois,  Wisconsin, 
Minnesota,  Kentucky.  Confused  in  records  with  the  human 
lung  fluke  (P.  westermanii  Kerbert)  which  has  been  positively 
determined  in  North  America  only  in  a  few  human  cases,  all  of 
which  are  probably  imported  from  Asia. 

Fig.  677.  Paragonimus  kellicotti.  Total  preparation,  ventral  surface. 
The  vitellaria  are  represented  on  the  left  side  and  omitted  on  the  other 
side  in  order  to  show  ovary,  testis,  vitelline  ducts  and  intestine  normally 
obscured  by  them.  X  38.  a,  egg  from  same  specimen.  X  150- 
(After  Ward  and  Hirsch.) 


74  (69)     Ovary  and  testes  entire  or  lobed  but  not  dendritic 75 

75  (82)     Oral  sucker  surrounded  by  a  reniform  collar   open  ventrally  and 

bearing  a  series  of  strong  spines. 

Family  Echinostomidae  Looss  1902   .    .     76 

Elongate  distomes,  very  variable  in  size.  Acetabulum  powerful,  close  to  anterior  end. 
Oral  sucker  small,  weak  or  degenerate;  anterior  end  surrounded  laterally  and  dorsally  by 
skin  fold  or  "collar"  which  carries  large  spines  ("spikes")  definite  in  number  and  arrange- 
ment. "Corner  spines"  on  ventro-median  lobe  usually  difi'er  from  others,  i.e.,  "marginal 
spines."  Skin  in  anterior  region  at  least  richly  provided  with  fine  dermal  spines.  Pharynx 
and  esophagus  present;  intestinal  crura  extend  almost  to  posterior  tip.  Excretory  bladder 
Y-shaped  with  numerous  lateral  branches.  Genital  pore  median,  near  acetabulum  or  between 
it  and  fork  of  intestine.  Cirrus  and  cirrus  sac  well  developed.  Germ  glands  postacetabular, 
usually  median;  ovary  pretesticular,  sometimes  lateral.  ViteUaria  lateral,  well  developed, 
reaching  posterior  end.  Uterus  between  ovary  and  acetabulum,  with  scanty^  lateral  loops, 
or  none.  Laurer's  canal  present,  receptaculum  seminis  absent.  Eggs  large,  thin  shelled,  not 
numerous.  Development  with  alternation  of  hosts  and  generations.  For  characteristic 
cercariae  see  224  (220)  in  this  key. 

Parasites  of  intestine,  rarely  of  gall  ducts,  in  mammals  and  birds. 


76  (81)     With  well-developed  oral  sucker.     Parasitic  in  intestine.      ...     77 

77  (80)     Anterior  region  not  enlarged.     Spines  in  a  double  row 78 


PARASITIC   FLATWORMS 


391 


78  (79)  '  Uterus  long  and  much  coiled Echinostoma  Rudolphi  1S09. 

Echinostomes  of  moderate  size  with  elongate  body.  Collar  with  double  unbroken  row  of 
spines.  Oral  and  ventral  suckers  close  together.  Cirrus  sac  reaches  ordinarily  center  of 
acetabulum.  Cirrus  long,  not  spinous,  when  contracted  it  lies  in  coil.  Vesicula  seminalis 
twisted,  not  bipartite.  Pars  prostatica  present.  Vitellaria  lateral,  posttesticular  extendiuL' 
in  places  towards  median  line.     Uterus  long,  much  coiled.     Eggs  large.  ' 

A  mixed  group  of  unplaced  and  unrelated  species,  many  of  which  are' not  well  enough  known 
to  determine  their,  true  place  in  the  family.  Several  uncertain  North  American  species  are 
reported  under  this  generic  name  from  chickens  (Hassall),  and  muskrat  (Leidy)  Some  forms 
from  the  muskrat  are  more  perfectly  described  by  Barker  et  alii. 

79  (78)     Uterus  short,  coils  few,  open.    .    .    .    Echinopharyphium  Dietz  1909. 
Small  echinostomes,  slender.     Much  Uke  last  genus  except  in  absence  of  pars  prostatica 

Cirrus  sac  long,  often  extending  dorsad,  or  posteriad  to  center  of  acetabulum.     Uterus  short- 
eggs  not  numerous,  large.  ' 

The  placing  of  Distomum  flcxnm  Linton  from  the  black  scoter  (Yellowstone  Lake)  in  this 
genus  is  probably  correct.  Another  species  has  been  reported  by  Barker  and  Bastion  from  the 
muskrat. 

80  (77)     Spines  in  a  single  row.      Subfamily  Echinochasminae  Odhner  1910. 

Spines  in  a  single  row  interrupted  at  the  mid-dorsal  line,  with  20  to  26 
spines  only.  Cirrus  sac  when  present  pyriform.  not  projecting  behind 
the  center  of  the  acetabulum.  Vesicula  seminalis  not  coiled,  distinctly 
bipartite. 

Several  genera  common  in  Europe. 

Only  genus  yet  recorded  from  North  America. 

Stephanoprora  Odhner  1902. 

Small,  elongate  echinostomes.  Cirrus  sac  well  developed,  cirrus  short 
but  muscular,  often  apparently  entirely  preacetaljular.  Testes  median, 
close  together,  in  posterior  half  of  body.  Vitellaria  lateral,  never  prc- 
acetabular,  often  nearly  confluent  along  median  line.  Uterus  not  long; 
eggs  of  moderate  size. 

Representative  American  species. 

Stephanoprora  gilhcrti  Ward. 

The  species  reported  by  Gilbert  from  the  loon  iGavia  imhrr)  and  from 
Bonaparte's  gull  {Lams  Philadelphia)  near  Ann  .\rbor,  iMichigan,  probably 
belongs  to  this  genus.  It  cannot  be  Echinostoma  spinulosum  Rud.,  as 
designated. 

Fig.  678.     Stephanoprora  gilberti.     X  7a     (Original.) 

Parasitic  in  gall  ducts. 

Pcgosomum  Ratz  1903. 

Echinostomes  of  moderate^  size  with  lance-shaped  muscular  body.  Collar  poorly  developed, 
with  single  row  of  blunt  spines.  Skin  spinous.  Oral  sucker  entirely  degenerate.  Pharyn.x 
present.  Fork  of  intestine  not  near  acetabulum  which  is  powerful  and  near  center  of  body. 
Cirrus  sac  large,  mostly  preacetabular.  Testes  median,  in  posterior  half  of  body.  Ovary 
dextral,  postacetabular  and  pretesticular.  Vitellaria  from  pharynx  to  posterior  end,  confluent 
in  median  line,  only  in  front  of  genital  pxire.     Uterus  short.     Eggs  large,  not  numerous. 

In  gall  ducts  of  Ardeidae.  Only  one  species  reported  from  North  America  as  Distomum 
asperum  Wright  from  Ardea  minor. 

82  (75)     Oral  sucker  without  collar  and  spines ^;^ 

A  condition  not  represented  in  the  key  is  found  in  the  AcANTHOcMiASMroAE  where  the  large 
funnel-shaped  oral  sucker  opens  at  the  anterior  tip  and  is  surrounded  by  a  crown  of  promi- 
nent spines.  Acanthochasmus  coronarium  (Cobbold)  was  taken  from  the  alimentary  canal  of 
an  Alligator  mississipicnsis  that  died  in  England.  According  to  Odhner  Crypto^^onimus  and 
Caecincola  are  meml^crs  of  this  family  which  have  lost  the  crown  of  spines.  Drropristis  may  also 
be  related  to  it. 

83  (94)     Genital  glands  median  in  linear  series  in  posterior  region  of  body.     84 


81  (76)     Oral  sucker  degenerate. 


392 


FRESH-WATER  BIOLOGY 


84  (91)     Uterus  between  ovary   and   acetabulum,   possessing  an   ascending 

ramus  only.     Testes  ordinarily  behind  ovary  and  close  to 
it,  or  rarely  {Leiiceruthrus)  near  acetabulum  and  separated 

from  ovary  by  coils  of  uterus 85 

In  Deropristis  hispida,  a  peculiar  distome  found  in  Acipenser  in  Europe  and  reported  once 
by  Stafford  in  the  lake  sturgeon  from  Canada  the  arrangement  of  the  germ  glands  differs  from 
either  plan  noted  in  the  key  line  above.  Two  oval  testes  are  median  in  posterior  end;  median 
ovary  lies  near  large  receptaculum,  separated  from  acetabulum  and  testes  by  about  equal 
distances  which  are  filled  by  uterine  coils.  Uterus  has  short  descending  ramus  which  extends 
posteriad  from  ovarian  complex  to  anterior  testis,  and  long  ascending  ramus  from  this  pomt_  to 
genital  pore  on  median  anterior  margin  of  acetabulum.  Vitellaria  are  extracecal,  in  uterine 
region.  Cirrus  sac  and  seminal  vesicle,  nearly  median  and  postacetabular,  are  both  well  de- 
veloped, but  rather  distinctly  separated.  The  relationship  of  the  genus  is  not  clear  and  the 
American  record  needs  confirmation,  hence  this  form  is  not  included  in  the  key. 

85  (88)     Body  muscular;  cirrus  sac  present. 

Family  Azygiidae  Odhner  191 1    .    .     86 

Infra-medium  to  large  distomes.  More  or  less  elongate,  flattened,  with  thick,  muscular 
body.  Suckers  powerfully  developed.  Skin  smooth,  on  contraction  drawn  into  irregular 
transverse  folds.  No  prepharynx.  Pharynx  powerful,  esophagus  very  short,  intestinal  crura 
reach  posterior  end.  Excretory  bladder  Y-shaped  with  very  long  branches  reaching  even  to 
anterior  end.  Genital  pore  median,  in  front  of  and  above  acetabulum;  genital  sinus  spacious. 
Uterus  with  ascending  limb  alone,  extending  direct  from  ovary  to  genital  pore  in  closely  laid 
transverse  loops.  Laurer's  canal  present;  receptaculum  seminis  wanting.  Vitellaria  follic- 
ular, lateral,  extracecal,  not  reaching  to  posterior  end.  Eggs  45  to  85  n  long,  with  cap;  when 
deposited  they  contain  each  a  ripe  embryo,  regularly  nonciUated. 

Stomach  parasites  of  fishes. 

86  (87)     Germ  glands  form  series  in  posterior  region;   ovary  anterior,  not  far 

separated  from  testes Azygia  Looss  1899. 

Distomes  of  moderate  size  or  larger,  with  slightly  flattened,  much  elongate,  nearly  cyhndri- 
cal  muscular  body,  rounded  at  both  ends  (Fig.  652).  Genital  pore  close  to  acetabulum.  Cirrus 
sac  present.  Seminal  vesicle  long  and  coiled.  Uterus  intercecal,  in  center  third  of  body. 
Vitellaria  extend  at  least  between  acetabulum  and  posterior  testes.  Ovary  and  testes  behind 
middle  of  body.  Main  stem  of  excretory  bladder  splits  behind  testes;  lateral  branches  do  not 
unite  in  anterior  region.     Eggs  45  by  21  ^  with  thin  shell  and  albumen  covering. 

Azygia  is  a  powerfully  muscular  type  and  is  usually  much  distorted  in  the  process  of  preser- 
vation so  that  a  lot  of  specimens  taken  from  the  same  host  at  the  same  time  present  marked 
external  differences  in  the  preserved  condition.  Such  extreme  specimens  have  been  the  basis 
for  various  new  genera,  e.g.,  Megadlstomum  of  Leidy  and  Stafford,  Mimodistomum  of  Leidy 
and  Hassalliiis  of  Goldberger.     The  same  factor  has  led  to  the  separation  of  too  many  as  species. 

Despite  many  records  of  its  occurrence  the  common  European  A .  lucii  {=  A.  tereticolle)  has 
not  been  found  in  North  America.  Several  species  pecuHar  to  this  continent  occur  in  Amia  calva, 
Micro pter us  salmoides  and  dolomieu,  Esox  lucius  and  reticulatus,  Ambloplites  rupestris,  Salve- 
linus  namaycush,  Lucioperca,  Lota  lota,  Salmo  sebago.  Maine,  St.  Lawrence,  Great  Lakes, 
Wisconsin. 

87  (86)     Testes  just  behind  acetabulum,  separated  from  ovary  by  coils  of 

uterus Leuceruthrus  Marshall  and  Gilbert  1905. 

Anterior  end  rounded,  posterior  end  pointed.  Oral  sucker  ventral,  promi- 
nent, acetabulum  one-half  as  large.  Intestinal  crura  slender,  straight,  ex- 
tending nearly  to  posterior  end.  Excretory  vesicle  forking  at  ovary.  Testes 
small,  postacetabular,  oblique  to  each  other.  Uterus  at  first  confined  to  area 
between  intestinal  crura,  ovary  and  testes,  later  filUng  posterior  three-fourths 
of  body.     Vitellaria  lateral,  in  posterior  half  of  body.     Laurer's  canal  present. 

One  species  known  (L.  micro  pter  i)  from  mouth  and  stomach  of  black  bass 
and  bowfin  in  Wisconsin  and  Indiana. 

Odhner  advocates  the  association  of  this  genus  with  Azygia  from  which 
it  differs  primarily  only  in  the  fact  that  the  testes  have  moved  from  their 
original  place  behind  the  ovary  and  have  been  drawn  anteriad  by  the 
shortening  of  the  sperm  ducts  to  a  location  a  Httle  posterior  to  the  acetabu- 
lum. This  is  the  relation  they  hold  in  Hemiurus,  marine  distomes  descended 
from  the  Azygiidae. 

Fig.  679.  Leuceruthrus  micropteri.  Ventral  view  showing  internal  topography. 
After  a  press  preparation.  Very  slightly  diagrammatic.  Magnified.  (After  Gold- 
berger.) 


PARASITIC    FLATWORMS 


393 


88  (85)     Body  flat,  thin,  transparent;   no  cirrus  sac  present. 

Family  Opisthorchiidae  Luhc  1901  .  .  89 
Elongate  flattened  transparent  distomcs  with  weak  musculature.  Suckers  close  toRcthcr 
and  very  weak  Intestinal  crura  reach  fully  or  nearly  to  posterior  end.  Excretory  bladder 
Y-shaped  with  short  branches  and  long  stem.  Genital  pore  close  in  front  of  acetabulum  No 
cirrus  or  cirrus  sac.  Coiled  seminal  vesicle.  Germ  glands  in  series  in  posterior  region  ovary 
in  front  of  testes.  Vitellaria  outside  intestinal  crura,  moderately  developed,  not  reaching 
posterior  end.  Uterus  long,  preovarian,  in  transverse  loops,  mostly  postacetabular  Ercs 
very  numerous,  small,  light  yellowish  brown  in  color. 

Parasites  of  gall  passages  of  Amniota. 
_    An  important  parasite  of  man,  Clonorchis  sinensis,  which  belongs  to  this  family  has  been 
introduced  several  times  into  this  continent  but  apparently  has  not  gained  a  footing. 

89  (90)     Neither     uterine     coils     nor    vitellaria     extend     anteriad     beyond 

acetabulum Opisthorchis  R.  Blanchard  i'8o5. 

Anterior  end  conical,  posterior  end  broader.  Main  stem  of  excretory  bladder  S-shaped, 
passing  between  testes,  anterior  forks  of  Y  short.     Vitellaria  in  groups. 

In  gall  ducts  of  mammals,  birds,  and  (?)  fishes.  Young  distomes  encysted  in  skin  and  con- 
nective tissues,  especially  subdermal  tissue  of  fishes. 

Several  species  in  North  America;  best  known  O.  pscudojelineus  Ward  190 1  in  the  cat. 


Fig.  680.     Opisthorchis  pseudofelincus.     From  liver  of  cat 


((  rii,'inal.) 


90  (89)     Uterine  coils  and  vitellaria  both  in  part  anterior  to  acetabulum. 

Metorchis  Looss  1899. 

Small  to  moderate  sized  distomes  with  short,  compressed  body  tapering  anteriad.  Skin 
spinous.  Testes  slightly  lobed,  nearly  symmetrical.  Coils  of  uterus  compact,  extending  clearly 
over  crura  to  margins.     Vitellaria  compact,  extending  anterior  to  acetabulum. 

A  single  American  species  M.  complexus  (Stiles  and  Hassall)  from  the  liver  of  cat.  New 
York,  Maryland,  District  of  Columbia.  Peculiar  in  extent  and  arrangement  of  vitellaria  and  in 
position  of  testes.  May  need  to  be  transferred  to  a  new  genus  when  its  structure  has  been 
worked  out. 


Fig.  681.     Metorchis  complexus.     Magnified,     (.\fter  Stiles  and  Hassall.) 


91  (84)     Ovary  anterior,  near  acetabulum,  separated  from  one  or  both  testes 
by  coils  of  ascending  and  descending  rami  of  uterus. 

Subfamily  Telorchiinwe  Looss  1899.    .     92 

Small  to  middle  sized  distomes  with  slender,  elongate,  spinous,  somewhat  flattened  body. 
Anterior  region  very  mobile;  posterior  region  stable,  .\cctabulum  small,  in  anterior  region. 
Pharynx  present,  esophagus  variable,  crura  long.  Testes  tandem,  both  in  i^)sterior  end  or 
one  there  and  the  other  not  far  behind  ovary.  Laurer's  canal  and  receptaculum  seminis  pres- 
ent. Vitellaria  lateral,  elongate,  outside  intestinal  crura.  Uterus  in  coils  or  loops  between 
ovary  and  testes  or  when  one  testis  is  near  ovary,  between  ovary  and  posterior  testis.  Eggs 
numerous,  small. 

In  the  intestine  of  reptiles. 


394  FRESH-WATER   BIOLOGY 

92  (93)     Genital  pore  anterior  to  and  near  acetabulum;   cirrus  sac  very  long 
extending  far  behind  acetabulum  to  round  ovary. 

Telorchis  Liihe  1899. 

Small  to  middle  sized  distomes.  Musculature  light;  hence  worms  translucent.  _  Testes 
close  together,  near  posterior  end,  separated  from  ovary  which  lies  at  the  end  of  the  cirrus  sac 
and  near  the  center  of  the  body,  by  a  mass  of  uterine  coils.  Excretory  vesicle  long,  median, 
extends  anteriad  about  to  ovary  where  it  forms  two  lateral  branches. 

Species  distinguished  by  length  of  esophagus  and  direction  and  extension  of  uterine  coils. 
Cercorchis  Liihe  with  esophagus  and  having  uterine  coils  entirely  intercecal,  grades  into  Telorchis 
s..§tr.  Liihe  (without  esophagus  and  with  uterus  coiled  beyond  ceca),  and  cannot  be  accepted 
as  a  valid  subgenus. 

Apparently  confined  to  reptiles;  six  or  more  species  in  North  America".  Revision  of  genus 
by  Stunkard. 


(After  Stunkard.) 


93  (92)     Genital  pore  dorso-lateral,  separated  by  marked  interval  from  ace- 

tabulum.    Cirrus  sac  entirely  preacetabular. 

Protenes  Barker  and  Covey  191 1. 
Two  species,  P.  leptus  Barker  and  Covey  and  P.  angnstiis  (Stafford)  in  North  America. 
From  Chrysemys  marginata  and  C.  picta. 

94  (83)     Ovary  lateral;   testes  either  median  or  slightly  lateral 95 

95  (96)     Ovary  separated  from  acetabulum  by  coils  of  uterus. 

Plagioporus  Stafford  1904. 

Small,  fusiform  distomes  with  acetabulum  larger  than  oral  sucker  and  anterior  to  middle 
of  length.  Skin  smooth.  Pharynx  and  esophagus  present;  crura  extend  to  posterior  end. 
Testes  median,  close  together  in  center  of  postacetabular  region.  Ovary  small,  lateral,  just 
in  front  of  anterior  testis.  Uterus  from  ovary  to  acetabulum.  Genital  pore  lateral,  on  level 
of  intestinal  bifurcation.  Cirrus  sac  large,  preacetabular,  obliquely  transverse.  Vitellaria 
lateral,  from  esophagus  to  posterior  end. 

Only  species  known Plagioporus  serotinus  Stafford  1904. 

Intestine  of  large-scaled  sucker  {Moxosionia  macrolepidotum)  in  Canada. 

96  (95)     Ovary  close  to  acetabulum,  at  least  not  separated  from  it  by  coils  of 

uterus 97 

97  (104)     Testes  large,  in  posterior  region  of  body,  separated  from  ovary  by 

small  uterus  with  few  eggs;    or  when  eggs  are  numerous, 

they  extend   beyond   testes  into   posterior   end  {Bunodera 

only).  .    .     Family  Allocreadiidae  Odhner  1910   .    .     98 

Distomes  of  small  to  moderate  size;    body  attenuated  and  mobile  'anteriorly.     Suckers 

well  developed.     Pharynx  and  esophagus  present;   crura  long,  but  not  reaching  posterior  end. 

Genital  pore  near  acetabulum  or  not  more  than  halfway  to  oral  sucker,  median  or  sHghtly 

lateral.     Ovary  lateral,  behind  but  not  far  from  acetabulum.     Testes  large,  proximate,  in 

posterior  region  halfway  or  more  from  acetabulum  to  posterior  end.     Vitellaria  lateral.     Eggs 

large. 

Parasites  of  fishes;  rarely  of  higher  vertebrates. 

98  (103)     Uterus  short  with  few  coils,  between  anterior  testis  and  acetab- 

ulum. 

Subfamily  Allocreadiinae  Odhner  1905  .  .  99 
Acetabulum  at  end  of  first  third  or  fourth  of  total  length.  Excretory  bladder  single,  un- 
divided, sac-shaped,  rarely  pyriform.  Genital  pore  preacetabular,  median  or  slightly  lateral. 
Cirrus  and  sac  large,  well  developed.  Testes  large,  proximate,  median  or  oblique  in  posterior 
region.  Ovary  spherical  or  lobed,  close  between  acetabulum  and  testes,  not  median.  Vitel- 
laria lateral,  well  developed,  partly  covering  crura,  often  confluent  behind  testis. 
Eggs  not  numerous,  usually  large. 


PARASITIC    FLATWORMS 


395 


99  (loo)     Oral  sucker  smooth;    not  provided  with  muscular  papillae  around 
anterior  end •  .    .    .        Allocrcadium  Looss  1900. 


Esophagus  long,  not  dividing,  until  just  before  the  acetabulum.  Ex- 
cretory bladder  very  short,  ending  at  posterior  margin  of  posterior  testes. 
Ovary  spherical,  lateral;  vitellaria  e.xclusively  ventral.  Cirrus  and  sac 
rather  short;  prostate  well  developed.  Genital  pore  median.  Eggs 
without  filament,  large  (60  to  90  n)  with  light  yellow  shell. 

Intestine  of  fresh-water  fishes. 

Several  species  from  stomach  and  intestine  of  sheepshead,  pum[>lcin- 
seed,  sturgeon,  sucker,  dace,  minnow,  and  gall-bladder  of  red-finned  min- 
now. Collected  in  (ireat  Lakes  region.  Lake  Erie,  Ontario;  Lake 
Sebago,  Maine.     Synopsis  of  genus  by  Wallin. 

Young  forms  of  A.  commune  Olsson  encysted  in  Mayfly  nymph 
(Blasturus  ciipidus  Say)  with  eggs  and  living  miracidia  in  body  cavity 
of  nymph  (Cooper). 

Representative  American  species. 

Allocreadium  lohatiim  Wallin  1909. 

Length  4  to  7  mm.,  breadth  i  to  1.5  mm.  Suckers  equal,  0.46  to  0.5 
mm.  in  diameter.  No  prepharynx;  pharynx  0.24  to  0.3  mm.  long  by 
0.22  mm.  broad. 

Testes  lobed;  cirrus  sac  extends  to  center  of  acetabulum.  Ovary 
spherical;  vitellaria  postovarial,  profuse,  confluent  behind  posterit)r 
testis.  Receptaculum  large,  pyriform,  between  ovary  and  anterior  testis. 
Uterus  compact,  between  anterior  testis  and  acetabulum.  Eggs  very 
numerous,  67  to  85  m  long  by  46  to  57  ^  broad. 

Fig.  683.     Allocreadium  lohatum.     Uterus  indicated  by  dotted  area, 
added  from  slide.     X  19.        (After  Wallin.) 


100  (99)     Six  oral  papillae  surround  anterior  end loi 


loi  (102)     Genital  pore  anterior  to  fork  of  intestine. 

Crepidostomum  Braun  1900. 


Bifurcation  of  intestine  just  anterior  to  acetabulum.  Excretorj'  bladder 
elongate.  Cirrus  sac  muscular;  pore  anterior  to  fork  of  intestine;  testes 
large,  round,  median,  halfway  from  acetabulum  to  posterior  end.  Vitel- 
laria confluent  behind  testes.  Uterus  short,  with  few  eggs,  between  ace- 
tabulum, ovary,  and  anterior  testis.     In  intestine  of  fresh-water  fishes. 

Several  species  not  adequately  described. 

Representative  American  species. 

Crepidostomum  conmtum  (Osborn)  1903. 

Probably  the  best  known  species  in  the  North  American  fauna  is  C. 
cornutum  (Osborn)  from  the  stomach  and  pyloric  ceca  of  black  buss,  rock 
bass,  channel  cat,  perch,  sunfish,  darter,  etc.  Immature  forms  encysted  in 
viscera  of  various  crayfish,  Ontario,  Canada.  The  worm  manifests  pre- 
cocious sexual  maturity  as  the  larger  cysts  contain  many  eggs  already  ex- 
truded. Very  young  forms  have  been  taken  from  Mayfly  nymphs  {Hexa^cma) 
by  Cooper. 

Fig.  684.     Crepidostomum  cornutum.      Ventral  view;   compressed.      X  20.     (.After 
Osborn.) 


396 


FRESH-WATER   BIOLOGY 


[02  (loi)  Genital  pore  posterior  to  fork  of  intestine.     .      Acrolichanus  Ward. 

(Syn.  Acrodactyla  Stafford  1904  preocc.) 

Body  uniform  in  width  or  slightly  constricted  behind  oral  sucker  which  is 
noticeably  larger  (0.325  mm.)  than  the  acetabulum  (0.275  mm.)  located 
about  at  center  of  body.  Ovary  posterior  and  close  to  acetabulum,  slightly 
lateral.  Vitellaria  from  pharynx  to  posterior  end.  Uterus  tubular,  short, 
with  few  eggs.  Genital  pore  midway  from  acetabulum  to  oral  sucker. 
Cirrus  large,  with  broad  lumen  at  anterior  end.  Cirrus  sac  reaching  to 
posterior  border  of  acetabulum  or  even  a  little  beyond.  Testes  spherical, 
close  together,  median,  or  slightly  obUque,  halfway  from  acetabuliom  to  pos- 
terior end. 

Representative  American  species. 

Acrolichanus  petalosa  (Lander)  1902. 

One  species,  A .  petalosa  (Lander),  is  common  in  intestine  of  Lake  sturgeon 
{Acipenser  rubicundus)  in  the  Great  Lakes  and  St.  Lawrence  River. 

"This  is  the  Z>.  auriadatum  Wedl  of  Linton  and  it  is  upon  the  authority  of 
Looss  that  I  use  the  above  specific  demonstration  "  (Stafford) .  The  comment 
of  Odhner  that  Acr.  petalosa  is  a  synonym  of  Acr.  lintoni  appears  to  be  in- 
correct. 

Fig.  6S5.     Acrolichanus  petalosa;  type  specimen.     X  39-     (Unpublished  drawing 
by  C.  H.  Lander.) 


103  (q8)     Uterus  ventral  to  both  testes,  extending  nearly  to  extreme  posterior 
end Subfamily  Bunoderinae  Looss  1902. 

Small  distomes,  with  elongate  body,  and  smooth  skin.  Anterior 
region  small,  muscles  moderately  developed.  Oral  sucker  with  circle 
of  six  muscular  mammiform  processes,  often  a  collar-like  expansion. 
Acetabulum  equal  to  or  larger  than  oral  sucker.  Pharynx  and 
esophagus  present,  crura  long.  Genital  pore  between  ventral  and 
oral  suckers.  Ovary  close  behind  acetabulum  and  lateral.  Testes 
oblique,  in  posterior  half  of  body.  Uterus  with  descending  and 
ascending  rami  in  sacculate  form,  ventral  to  testes  in  posterior 
region.  Laurer's  canal  and  receptaculum  seminis  present.  Vitellaria 
lateral,  well  developed,  extending  from  pharynx  to  caudal  end.  Eggs 
large. 


Type  genus Bunodera  Railliet  1896. 

Esophagus  long,  forebody  narrow.  ^  Fork  of  intestine  somewhat 
anterior  to  acetabulum.  Cirrus  sac  without  muscular  tissue  in  wall. 
Testes  obUque,  far  back  in  body.  Vitellaria  not  confluent,  not 
reaching  posterior  end.  Uterus  with  descending  and  ascending 
rami,  greatly  enlarged,  not  coiled,  extending  to  posterior  end  and 
covering  testes  on  ventral  side  of  body. 


Recorded  in  North  America. 

Bunodera  luciopercae  (O.  F.  Miiller)  1776. 

One  species  B.  luciopercae   (O.  F.  Miiller)  {=  Dist.  nodulosum 
Zeder)  reported  by  Stafford  from  perch. 


Fig.  686.     Bunodera  luciopercae.     Dorsal  view.     X  47-     (After  Looss.) 


I04  (97) 


PARASITIC   FLATWORMS  3^^ 

Testes  small,  in  center  of  body,  separated  from  ovary  by  dense 

uterine  coils  with  masses  of  eggs;   no  eggs  posterior  to 

^^ ^Kfidislomum^Vdaord  ic)os. 

uuLi,   wail  tmck.     Vitellana  continuous  from  r  L'ht  to  left  Ixjth  -ilx.v.-   mH  \J 

Only  species  known.  .  Aundistomum  chelydrae  StaffoTcl  rgoo. 
Intestine  of  Chelydra  serpentina. 

Fig.  687.     "^""'i^J^f^^^l^^/^ydrae      yitellaria  changed  to  correspond  with  later  account 
of  author.    Ventral  view.    Magnified.     (After  Stafford.)  **ccouni 


105  (68)     Testes  numerous,  in  two  longitudinal  series. 


Pleorchis  Railliet  1896. 


Inframedium  sized  distomes  with  oval,  somewhat  flattened  bodv  Skin 
spinous  Suckers  small  equal,  separated  by  only  one-fourth  bodv 'lenrth 
Oral  sucker  subterminal.  Prepharynx  prominent,  pharynx  small,  esophaRu^ 
extended,  crura  with  single  branch  directed  anteriad.      Excretory  system 

,  Genital  pore  preacetabular.  Cirrus  sac  absent  (?).  Testes  numerous 
in  two  rows  near  niedian  plane  in  posterior  half  of  body,  \-itellaria  in  two 
broad  lateral  bands  from  acetabulum  to  posterior  end.  Other  organs  con- 
hned  to  small  area  between  anterior  testes  and  fork  of  intestine  mostly  be- 
hind acetabulum.     Uterus  short;   ova  scanty,  48  ^  long. 

Reported  by  Leidy  from  lungs  of  musk  turtle  (Aronwchdys  odorata 
Latr.)  as  Monostoma  tnplle.  Shown  by  Stiles  and  Hassall  to  be  distome 
somewhat  like  Distoma  polyorchis  Stossich.  Position  and  relationship  de^ 
pendent  finally  on  more  perfect  knowledge  of  structure  which  awaits  dis- 
covery of  new  material. 

Fig.  688.    Pleorchis  mollis.     Magnified,     (.\fter  Stiles.) 


loO  (67)  Acetabulum  represented  by  two  small  suckers  set  close  together  in 
depression  on  mid-ventral  surface  near  center  of  bod)-; 
genital  cloaca  opens  between  the  two  suckers. 

Subfamily  Cryptogoniminae  Ward. 

Very  small,  spinous  distomes  of  uniform  width  throughout,  with  bluntly  rounded  ends 
Oral  sucker  ver>^  large  and  prominent.  Ventral  sucker  doul)!e.  minute,  withdrawn  into  pocket; 
gemtal  pore  between  the  two.  Prepharynx,  jiharynx,  and  short  est)phagus  present;  crura 
extend  to  anterior  margin  of  testes.     E.xcretory  vesicle  V-shaix-d,  fork  at  oviduct,  anterior 


398 


FRESH-WATER   BIOLOGY 


branches  reach  to  posterior  margin  of  pharj'nx.  Testes  elongate,  parallel, 
dorsal,  in  posterior  third  of  body;  seminal  vesicle  convoluted,  large;  no 
cirrus  or  sac.  Ovary  ventral,  proximate  to  testes,  slightly  lobed;  Laurer's 
canal  (?);  vitellaria  lateral,  in  central  region.  Uterus  with  descending 
ramus  on  right,  shghtly  coiled,  extending  to  posterior  end,  ascending 
ramus  returning  on  left,  crossing  anterior  to  ovary  and  passing  on  right 
to  genital  atrium.     Eggs  small,  dark,  about  20  by  10  ^i. 


Type  genus. 


Cryptogonimus  H.  L.  Osborn  19 10. 


The  genus  has  been  placed  in  the  Acanthochasmidae;  see  note  under 
82  (75).  Even  if  that  action  be  justified  it  occupies  a  position  suffici- 
ently isolated  to  demand  rank  in  a  separate  subfamily  as  indicated 
here. 

Only  species  known  in  North  America. 

Cryptogonimus  chyli  Osborn  1903. 

In  stomach  and  intestine  of  Micro ptencs  dolomieu  and  AmblopHtes 
rupestris;  Lake  Chautauqua,  New  York;  St.  Mary's  River,  Michigan; 
Canada.  Young  distomes  encysted  in  small  black  bass,  rock  bass,  and 
minnows  (Cooper). 


Fig.  689.     Cryptogonimus  chyli.     Ventral  view  with  spines  omitted  and  coils 
of  uterus  simplified.     X  9.     (After  Osborn.) 


107  (66)     Coils  of  uterus  extend  well  beyond  testes  into  posterior  portion 

of  body 108 

108  (109)     Mouth  surrounded  by  a  crown  of  six  muscular  papillae  which 

are  outgrowths  of  oral  sucker Bimodera. 

See  note  under  66  in  this  key  and  description  with  figure  under  103. 

109(108)     Mouth  without  crown  of  papillae no 

no  (115)     Vitellaria  represented  by  small  solid  more  or  less  lobed  organ  on 
each  side  of  body  just  anterior  to  ovary. 

Family  Gorgoderidae  Looss  1901. 

Muscular  distomes  with  slender  mobile  anterior  region  and  flattened  posterior  region. 
Suckers  muscular;  acetabulum  especially  projects  noticeably  beyond  surface  of  body.  Skin 
without  spines  but  often  with  fine  papillae.  Esophagus  long  without,  or  short  with  pharynx. 
Crura  simple,  extend  to  posterior  end.  Excretory  bladder  simple  tubular,  extending  from 
dorsal  pore  near  posterior  end  to  region  of  ovarian  complex.  Genital  pore  median,  between 
acetabulum  and  fork  of  intestine;  without  male  copulatory  organs.  Ovary  lateral,  post-' 
acetabular;  Laurer's  canal  or  receptaculum  seminis  present.  Testes  lateral,  obhque  or  sym- 
metrical. Uterus  in  numerous  open  loops  chiefly  postovarian.  Eggs  relatively  large  with 
thin,  faintly  colored  shell. 


Only  one  subfamily  reported  in  North  America. 

GORGODERINAE   LoOSS  1 899 


III 


Small  to  submedium  in  size,  sometimes  slender,  sometimes  broad  in  posterior  region. 
Esophagus  relatively  long,  without  muscular  pharynx.  Testes  more  or  less  oblique  and  within 
intestinal  crura.  Laurer's  canal  present  but  no  receptaculum  seminis.  Vitellaria  not  far 
apart. 

In  urinary  bladder  and  ducts  of  fishes  and  amphibians. 


i 


PARASITIC   FLATWORMS 


399 


Body  elongate,  lanceolate  without  conspicuous  well  marked  anterior 
and  posterior  regions j  j  ^ 

Testes  subdivided,  forming  on  one  side  a  series  of  four  and  on  the 
other  five  parts;  in  all  nine  separate  lobes. 

Gorgodera  Looss  1899. 

Testis  on  ovarian  side  has  five  parts;  the  opposite  testis  lies  further  an- 
teriad  and  is  divided  into  four  parts  only.  In  well-developed  adults  these 
organs  are  completely  concealed  by  the  coils  of  the  uterus  filled  with  dark 
brown,  almost  black  eggs. 

Found  in  the  bladder  of  various  Amphibia:  Rana  and  Salamandra  (?). 
At  least  two  species  in  North  .Axnerica. 

Representative  American  species. 

Gorgodera  minima  Cort  191 2. 


Fig.    690.      Gorgodera   minima.      \'entral   view.      Young  specimen   with   but   few 
eggs.     X  72.     (After  Cort.) 


113  (112)     Two  simple  testes,  elongate-oval,  not  divided. 

Gorgodcrina  Looss  1902. 

Testes  are  elongate  and  have  irregular  notched  margins  but  do  not  divide  into  sections. 
Vitellaria  have  only  few  lobes.  Much  like  the  former  genus.  Adults  are  difficult  to  distinguish 
'  after  the  uterine  coils  cover  the  testes. 

Found  in  the  bladder  of  Amphibia:  Bufo,  Rana  and  Sala?nandra  (?).  Three  species  known 
from  North  America. 

Representative  American  species. 

Gargoderina  attenuata  Stafford  1902. 


Fig.  691.     Gogoderina  attenuata.     Ventral  view.     X  24.     (After  Cort.) 

114  (ill)     Body  elongate;   slender  anterior  region  distinct  from  broad  poste- 
rior region Phyllodistomum  M.  Braun  1899. 

No  sharp  line  of  division  marks  the  transition  between  the  two  regions 
of  the  iDody.  The  vitellaria  are  soHd  masses  only  slightly  indented 
marginally.  The  testes  are  oblique,  well  separated  from  each  other, 
and  only  weakly  lobed  if  at  all. 

In  urinary  bladder  of  fishes  and  amphibians. 

Representative  American  species. 

Phyllodistomum  americanum  Osborn  1003. 

One  species  {P.  americifmim  Osborn)  reported  from  North  .\meric.i 
in  Amblystoma;  two  others  doubtful  from  pike  (Esox  liuius),  bullhead 
(Ameiurus  ncbidosiis),  and  perch  (Perca  jhivrurns)  in  Canada. 


Fig.  692.     Phyllodistomum  americanum.     Ventral  view.     X  i6.     (.\ftcr 
Osborn.) 


115  (no)     V'itellaria  composed  of  distinctly  separated  follicles. 


116 


400 


FRESH-WATER   BIOLOGY 


ii6  (119)     Vitellaria  confined  to  extreme  anterior  region  of  body,  not  ex- 
tending posteriad  further  than  acetabulum 117 

117  (118)     Vitellaria  extend  across  entire  body  in  anterior  region,  reaching 

nearly  to  acetabulum. 
Genital  pore  on  ventral  surface. 

Subfamily  BRACHYCOELnNAE  Looss  1899. 
Intestinal  crura  short,  not  extending  posteriad  to  acetabulum.     Genital  pore  median,  between 
suckers.     Testes  lateral,   near   acetabulum.     Ovary   lateral,   pretesticular.     Uterine   coils  fill 
entire  posterior  region.     Eggs  numerous,  small. 

A  single  species  Brachycoelium  hospitale  Stafford  1903  is  recorded  from  North  America. 

Genital  pore  marginal. 

Subfamily  Pleurogenetinae  Looss  1899. 
Intestinal  crura  of  variable  length.     Genital  pore  sinistral,^  often  marginal.     Cirrus  sac 
large,  pyriform,  with  coiled  vesicula  seminaUs  and  muscular  cirrus.     Eggs  23  to  40 /x  long. 
Intestines  of  Anura;   a  single  species  in  Chamelion. 

The  family  description  as  written  by  Odhner  will  not  take  in  the  American  genus  which 
Looss  and  he  think  should  certainly  be  included  here.  Until  more  data  are  available  it  is 
unwise  to  make  a  new  place  for  this  single  genus. 

Only  North  American  genus  yet  described. 

Loxogenes  Stafford  1905. 
Small  distomes,  with  broad,  thick,  heart-shaped  body  in- 
dented at  posterior  end.  Skin  spinous.  Suckers  small,  poorly 
developed,  nearly  equal;  acetabulum  near  center  of  body. 
Pharynx  present;  esophagus  very  short;  crura  short,  some- 
what inflated,  not  reaching  even  to  center  of  body.  Excretory 
vesicle  divides  near  pore,  lateral  branches  inflated,  terminat- 
ing behind  testes.  Ovary  pyramidal,  lobed,  preacetabular, 
between  testes,  slightly  dextral.  Vitellaria  ventral,  extend 
across  entire  body  from  pharynx  nearly  to  acetabulum. 
Laurer's  canal  and  small  receptaculum  present.  Uterus 
chiefly  postacetabular,  with  longitudinal  folds  in  two  groups 
one  on  each  side  of  body.  Testes  oval,  small,  lateral  at  ends 
of  crura,  in  line  with  acetabulum  or  shghtly  posterior.  Cir- 
rus sac  long  and  narrow,  preacetabular,  sinistral,  with  coiled 
cirrus.  Sexual  pore  dorsal,  sinistral,  midway  between  center 
and  margin  at  level  of  fork  in  intestine.  Ova  small,  24  by 
14  /x,  numerous. 

In  thick-walled  closed  cysts  on  pylorus,  liver,  and  bladder 
of  various  frogs.  The  single  species  L.  arcanum  (Nickerson)  is  encysted  in  pairs.  Massachu- 
setts, Minnesota,  Ontario. 

118  (117)     Vitellaria  consist  of  small  groups  of  follicles  lateral  to  pharynx  in 
extreme  anterior  region. 

Caecincola  Marshall  and  Gilbert  1905. 
Very  small  distomes;  anterior  end  truncate,  posterior  end  bluntly 
rounded.  Entire  body  spinous.  Oral  sucker  very  large,  acetabulum 
much  smaller.  Mouth  terminal,  prepharynx  and  esophagus  equal,  rather 
long,  pharynx  prominent,  ceca  short  but  wide.  Excretory  vesicle  Y- 
shaped,  extending  anteriad  beyond  pharynx.  Testes  very  large,  ovoid, 
in  posterior  half;  no  copulatory  organs;  seminal  vesicle  large,  bipartite. 
Ovary  lobed,  anterior  to  right  testis;  vitellaria  scanty,  far  anterior,  lateral 
to  pharynx.  Uterus  poorly  developed,  a  few  open  loops,  above  and  be- 
hind testes,  extending  nearly  to  posterior  end  of  body.  Receptaculum 
seminis  dorsal  to  ovary.  Assigned  by  some  to  the  family  Acanthochas- 
midae;   see  note  under  82  (75)  in  this  key. 

Type  species. 

Caecincola  parvulus  Marshall  and  Gilbert  1905. 
One  species  known  (C.  parvulus)  in  ceca  and  stomach  of  large-mouthed 
black  bass  in  Wisconsin. 

Fig.  694.     Caecincola  parvulus.     Ventral  view;    ovary  drawn  somewhat  to  one 
side  to  show  underlying  parts.     X  95-     (After  Marshall  and  Gilbert.) 

119(116)     Vitellaria  not  confined  to  extreme  anterior  region 12c 


Fig.  69,3.     Loxogenes  arcanum 
Dorsal  view.      X  lo.      (After  Os- 
born.) 


40I 


121 


PARASITIC   FLATWORMS 

1 20  (123)     Intestinal  crura  short,  diverging,  not  passing  acetabulum. 

121  (122)     Testes  symmetrical,  lateral,  postacetabular. 

Subfamily  Microphallinae  Ward  1901. 

Small  distomcs  having  pear-shaped  body  with  mobile  anterior  rcRion 
contammg  ahmentary  system.  Suckers  small,  prepharynx.  pharynx 
and  long  esophagus  present;  crura  short,  not  surpassing  acetabulum 
Excretory  system  V-shaped.  (Jenital  pore  sinistral,  rarely  pcjst- 
acetabular.  No  cirrus-sac.  Seminal  vesicle  immediately  preacetabu- 
lar.  Testes  symmetrical,  behind  acetabulum.  Ovary  dextral  along- 
side of  acetabulum.  Vitellaria  symmetrical,  behind  testes  in  form 
of  a  lobcd  mass  of  follicles.  Uterus  coiled  in  posterior  region  ex- 
tending anteriad  about  as  far  as  posterior  margin  of  acetabulum 
Eggs  small,  very  numerous. 

In  intestine  of  water  birds  and  fishes. 

Representative  American  genus. 

MicrophaUus  Ward  igoi. 
One  species  (M.  opacus)  in  Amia  calva,  Micropterns  dolomieu,  An- 
gialla  chrysypa,  Ictalurus  pundatus,  Percaflavescens;  the  young  dis- 
lome  encysted  in  crayfish. 

Fig    695.     Microphallus  opacus.     Ventral  view;   dotted  line  represents 
hnuts  of  coils  of  uterus,  filled  with  eggs.     X  37.     (After  Ward.) 

122  (121)     Testes  oblique,  in  center  of  body,  posterior  to  acetabulum. 

Protenteron  Stafford  1904. 
Small  distomes.  Broadest  at  center,  narrowed  behind.  Skin  spinous.  Oral  sucker  termi- 
nal, 0.186  mm.,  acetabulum  0.62  mm.  in  diameter.  Prepharynx  longer  than  pharj-nx  or 
esophagus.  Crura  short,  diverging,  not  passing  acetabulum.  Black  eye  spots  lateral  to 
pharynx.  Testes  obhque  in  center  of  body  behind  acetabulum.  Ovary  in  front  of  left  testis 
Uterus  reaching  posterior  end.  Vitellaria  lateral,  short,  from  fork  of  intestine  to  near  ovary. 
Cirrus  (and  sac  ?)  extending  posteriad  to  ovary.     Eggs  22  by  11  n. 

Type  species Protenteron  diaphanum  Stafford  1904. 

Intestine  of  Amhloplites  rupestris;  Montreal,  Canada. 

123(120)     Intestinal  crura  extend  beyond  acetabulum 124 

124  (125)     Uterus  forms  rosette  in  center  of  body. 

Centr ovarium  Stafford  1904. 

Small  distomes,  tapering  somewhat  towards  both  rounded 
ends.  Ventral  sucker  larger  than  oral,  at  end  of  anterior  third  of 
body.  Crura  terminate  opposite  center  of  ovary.  Testes  behind 
ends  of  crura,  not  conspicuous.  Uterus  rosette-shaped,  in  center 
of  body.  Vitellaria  lateral,  from  esophagus  to  anterior  margin  of 
testes. 


Only  species  known. 

Centrovarium  lohotcs  (MacCallum)  1S95. 


DeHcate  worms,  i  to  ,s  mm.  long.  Suckers  relatively  small  and 
weak.  Ovary  deeply  iobed.  Acini  of  vitellaria  more  or  less  con- 
fluent imparting  a  tubular  appearance  to  the  organ.  Eggs  very 
numerous,  small,  pyriform,  32.5  by  15  /f.  with  thick  brown  shell. 

Intestine  of  Esox  lucius,  Stizostrdion  vitrcum,  Ambloplitrs 
rupestris,   Ani^uilla  rlirysvpa  :  Ontario.  Canada. 


Fig.  696.     Centrovarium  lobotcs.     Dorsal  view.     Magnified.     (After 
MacCallum.) 


402 


FRESH-WATER   BIOLOGY 


125  (124)     Uterus  more  or  less  elongated  or  in  coils  but  not  in  form  of  a  cen- 

tral rosette 126 

126  (129)     Genital  pore  near  oral  sucker  on  left  margin  of  body. 

Subfamily  Prosthogoniminae  Liihe  1909.   .    .     127 

Small  to  medium  sized  distomes  with  body  somewhat  flattened  and  elongate.  Skin  spinous. 
Pharynx  present,  esophagus  variable,  crura  half  or  three-quarters  length  of  body.  Excretory 
bladder  Y-shaped,  sometimes  with  caudal  vesicle.  Genital  pore  marginal,  dorsal  or  anterior 
to  oral  sucker.  Cirrus  sac  long,  slender,  cylindrical,  extending  to  or  beyond  intestinal  bifur- 
cation. Testes  behind  acetabulum  and  ovary.  Ovary  close  to  acetabulum,  vitellaria  extra- 
cecal  in  central  portion  of  body.  Receptaculum  seminis  and  Laurer's  canal  present.  Uterus 
in  coils  in  posterior  region,  chiefly  behind  testes. 

127  (128)     Testes  symmetrical;  ovary  lobed;  uterine  coils  pass  between  testes. 

Prosthogonimus  Liihe  1899. 

From  the  bursa  Fabricii  of  various  water  birds  in  Europe.  Reported  from  North  America 
in  a  hen's  egg  and  also  from  two  birds. 


128  (127)     Testes  oblique  or  tandem;   ovary  entire;   uterine  coils  do  not  pass 
between  testes Cephalogonimus  Poirier  1886. 


Genital  pore  dorsal  or  anterior  to  oral  sucker. 
Uterus  passes  from  ovarian  complex  directly 
posteriad  between  crura  and  testes,  on  right 
side  of  body,  forms  mass  of  coils  behind  testes 
and  passes  anteriad  on  left  to  genital  pore. 
Vitellaria  not  always  entirely  extracecal. 
Testes  round  or  irregular.  Eggs  numerous, 
moderate  in  size,  development  unknown. 

Two  species  in  intestine  of  frogs,  Toronto 
and  Montreal;  and  of  soft-shelled  turtles 
(Aspidonedes  and  Amyda),  Minnesota. 


Fig.  697.  Cephalogonimus  americanus.  Living 
animal,  from  ventral  surface.  Magnified.  (After 
Stafford.) 

Fig.  698.  Cephalogonimus  vescaudus.  Entire 
worm  from  dorsal  surface,  somewhat  flattened. 
Magnified.     (After  Nickerson.) 


Fig.  697. 

129  (126)     Genital   pore   anterior   to   acetabulum,    from   nearly   median   to 
marginal  in  position. 

Family  Plagiorchiidae  Liihe  char,  emend.   .    .      130 
(Syn.  Lepodermafidae  Odhner  1910.) 

More  or  less  elongate  distomes  with  moderately  flattened  to  cylindrical  body;  rarely  {Oche- 
tosoma)  strongly  flattened.  Skin  usually  spinous  over  entire  body.  Prepharynx,  pharynx, 
and  esophagus  present;  crura  very  variable  in  length.  Excretory  bladder  typically  Y-shaped 
with  median  stem  dividing  into  two  short  branches  behind  complex  of  Mehlis'  gland.  Genital 
pore  usually  just  in  front  of  acetabulum,  slightly  left  of  median  line.  Cirrus  sac  crescentic, 
powerful,  with  prominent  longitudinal  fibers,  containing  cirrus,  vesicle,  and  prostate;  rarely 
(Astiotrema)  reduced.  Ovary  on  posterior  margin  of  acetabulum,  dextral,  rarely  sinistral 
Testes  usually  oblique,  rarely  symmetrical  or  median,  close  behind  ovary.  Laurer's  canal 
present,  except  in  Pneumonoeces;  receptaculum  seminis  variable.  Vitellaria  lateral,  variable 
in  extent.  Uterus  extends  posteriad  to  end  of  body  and  then  anteriad  to  pore,  simple  or  com- 
plicated by  coils  filling  posterior  region.  Eggs  very  numerous,  small,  thin-shelled,  measvure 
20  to  50  fz. 


PARASITIC    FLATWORMS 


403 


130(139)     Receptaculum  seminis    present  (except  Plagiorchis);    crura  reach 
posterior  end  (except  Styphlodora) j^i 

131  (138)     VesicuJa  seminalis  fills  greater  part  of  cirrus  sac;    pars  prostalica 
follows  after  it  and  is  very  short. 

Subfamily  Plagiokchiinae  Liihe  1909.   .    .      132 


132  (135)     Genital  pore  near  oral  sucker. 


133 


133  (134)     Testes  median  or  nearly  so Pneumonocccs  Looss  1902. 

Medium  sized  distomes,  with  body  elongate,  thick,  and  only  slightly  flattened,  tapering  an- 
teriorly. Acetabulum  small.  Oral  sucker  large,  pharynx  well  developed,  esophagus  short,  in- 
testinal crura  long,  extending  to  posterior  end.  GenitaJ  pore  just  behind  oral  sucker,  median, 
ventral.  _  Cirrus  sac  greatly  elongate,  reaching  acetabulum.  Ovary  near  acetabulum.  Testes 
postovarian,  slightly  oblique.  Large  seminal  receptacle  between  testes  and  ovary.  No  Laurer's 
canal.  Vitellaria  lateral  in  middle  region  of  body.  Uterus  much  coiled,  extending  to  extreme 
posterior  end.     Eggs  numerous,  small,  dark  shelled. 

In  lungs  of  Anura;  widely  distributed  and  abundant.  Develop  p)erhaps  from  Xiphidiocer- 
cariae.     North  American  species  well  worked  out  and  described  with  key  by  Cort. 

Representative  American  species. 

Pueumonoeces  colonidensis  Cort  191 5. 


Fig.  699.     Pneumonoeces  color adensis.     Fully  developed  specimen,  ventral  view, 
receptacle.      X  27.     (After  Cort.) 


ovary;   sr,  seminal 


134  {^2>^)     Testes  lateral  and  symmetrical  or  nearly  so.       Pnciimobitis  Ward. 

Much  like  Pneumonoeces  but  body  larger,  thicker,  with  testes  lobed,  elongate,  lateral  and 
symmetrical  or. only  slightly  oblique.  Extracecal  longitudinal  folds  of  uterus  pronouncedly 
longer  than  in  Pneumonoeces.  Ovary  lobed.  Vitellaria  with  many  very  small  acini  in  each 
group.     Eggs  small. 

In  lungs  of  Anura.  Two  species  in  North  America:  P.  longiplexus,  P.  brrciplcxus.  Cort. 
who  grouped  these  in  Pneumonoeces,  called  attention  to  their  close  relationship.  The  i^)ints 
of  resemblance  constitute  also  characteristic  differences  from  other  species  in  Pneumonoeces 
sufficient  to  justify  their  being  made  an  independent  genus. 

Type  species Pncumobiks  longiplexus  (Stafford)  1902. 


Fig.  700. 


Pneutnobitcs  longiplexus.     Dorsal  view. 
(After  Cort.) 


ovary;  sr,  seminal  reccptacl 


404 


FRESH-WATER   BIOLOGY 


135  (132)     Genital  pore  near  acetabulum 136 


136  (137)    No  conspicuous  pharyngeal  glands. 


Plagiorchis  Liihe  1899. 


Body  elongate  oval,  somewhat  attenuated  at  both  ends,  covered 
with  minute  spines.  Pharynx  and  esophagus  of  approximately  equal 
length,  crura  reach  posterior  end,  or  near  it.  Genital  pore  just  an- 
terior to  acetabulum,  median  or  slightly  sinistral.  Cirrus  sac  curved 
around  and  reaching  posterior  margin  of  acetabulum,  with  large 
vesicula  seminalis.  Testes  round  to  oval,  oblique,  separated  by 
uterine  branches.  No  receptaculum  seminis.  Ovary  spherical,  at 
inner  end  of  cirrus  sac.  V'itellaria  with  many  closely  crowded  foUi- 
cles  usually  reaching  posterior  end.  Uterine  coils  partly  pretesticu- 
lar,  chiefly  posttesticular.     Eggs  numerous. 

In  intestine  of  insectivorous  vertebrates,  chiefly  birds,  but  also 
amphibians,  reptiles  and  mammals,  infection  probably  through  in- 
sects. 

Little  specialized  forms  that  constitute  the  type  of  the  family  and 
from  which  other  genera  have  diverged  in  several  directions. 

North  American  species. 

Plagiorchis  proximus  Barker  191 5. 

Reported  from  the  muskrat  in  North  America. 
Fig.  701.    Plagiorchis  proximus.    Ventral  view.     X  25.     (After  Barker.) 


137  (136)     Conspicuous  pharyngeal  glands  present 


Glypthelmins  Stafford  1905. 


Small,  oval  distomes  with  rounded  ends  and  cyHndrical  body.  Skm 
spinous.  Acetabulum  smaller  than  oral  sucker,  anterior  to  middle  of  body. 
Pharynx  and  esophagus  present,  pharyngeal  glands  conspicuous;  crura 
nearly  reach  posterior  end.  Testes  small,  spherical,  at  center  of  body,  post- 
acetabular,  nearly  symmetrical.  Genital  pore  median  between  acetabulum 
and  fork  of  intestine.  Cirrus  sac  overlaps  acetabulum  in  part.  ^  Ovary  small 
at  left  of  acetabulum,  receptaculum  seminis  present.  Uterus  with  numerous 
short  transverse  coils  within  crura  between  testes  and  posterior  end,  spread- 
ing somewhat  beyond  ends  of  intestine.  Vitellaria  lateral  from  fork  of  in- 
testine nearly  to  end  of  crura.     Eggs  small,  numerous. 

Single  North  American  species  known. 

Glypthelmins  quieta  Stafford  1900. 

In  intestine  of  Canadian  frogs. 

Fig.  702.    Glypthelmins  quieta.     Magnified.     (After  Stafford.) 


PARASITIC   FLATWORMS 


405 


138  (131)     Vesicula  seminalis  at  inner  end  of  cirrus  sac,  continued  to  outer 
end  by  long,  tubular  pars  prostatica. 

Styphlodora  Looss  1899. 

Body  somewhat  attenuated  antcriad,  but  broadened 
posteriorly,  with  rounded  ends.  Skin  covered  with  fine 
spines.  Pharynx  and  esophagus  present;  crura  do  not 
reach  posterior  end.  (Jenital  pore  median,  preacetabular. 
Cirrus  sac  encloses  coiled  vesicula  seminalis.  Cirrus  pcjw- 
erful.  Testes  oblique,  close  together  in  center  of  body. 
Vitellaria  poorly  developed.  Receptaculum  seminis  pres- 
ent, but  small.  Uterus  intercecal,  but  spreading  to  margin 
beyond  ends  of  crura.     Eggs  numerous. 

In  intestine  of  reptiles. 

One  North  American  form  described  by  Goldberger  as 
Styphlodora  bascaniensis  from  the  liver  (?)  of  Bascanion 
constrictor,  Virginia,  is  a  doubtful  member  of  this  genus. 


Fig.  703.     Styphlodora  bascaniensis.     Ventral  view. 
(After  Goldberger.) 


Magnified. 


139  (130)     No  receptaculum  seminis,  intestinal  crura  half  to  three-fourths 

body  length,  at  least  never  reaching  posterior  end. 

Subfamily  Reniferinae  Pratt  1902   .    .      140 

Crura  of  medium  length,  reaching  beyond  center  of  body  but  not  into  posterior  tip.  In 
every  case  an  open  space  or  uterine  coils  intervene  between  the  crura  and  posterior  end  of 
body. 

No  receptaculum  seminis. 

Testes  at  ends  of  crura,  more  or  less  symmetrical. 

In  mouth,  air  passages,  lungs,  esophagus  and  stomach  of  snakes. 

A  group  clearly  worked  out  and  defined  by  Odhncr,  richly  represented  in  North  America 
where  occur  five  out  of  the  seven  genera  already  described. 

140  (141)     Genital  pore  marginal  or  nearly  so Rcnijcr  Pratt  1902. 

Small  distomes  with  elliptical,  ventrally  flattened  body  covered  with 
fine  spines.  Suckers  moderately  developed;  acetabulum  larger,  anterior, 
to  middle.  Mouth  subterminal;  pharyn.x  present;  esophagus  short;  in- 
testinal ceca  reach  beyond  acetabulum,  about  to  center  of  body.  Ex- 
cretory vessel  Y-shaped.  Genital  pore  marginal,  about  level  of  fork  of 
intestine.  Testes  both  symmetrical  just  behind  center  of  body  near 
ovary  which  is  lateral  at  right  posterior  margin  of  acetabulum.  Cirrus 
sac  large,  reaching  to  or  beyond  acetabulum  with  convoluted  seminal 
vesicle.  Vitellaria  submoderate  in  size,  lateral,  in  central  third  of  lK)dy. 
Uterus  with  descending  and  ascending  limb,  jiassing  between  testes  nearly 
to  posterior  tip;  capacitj'  provided  by  increase  in  breadth  of  tube  and  not 
by  extension  in  length  and  formation  of  coils. 

Representative  American  species. 

Renifcr  clliptkus  Pratt  1003. 

Mouth  and  air  passages  of  Heterodon  platyrhinus.  Only  one  certain 
North  American  species,  R.  ellipliciis  Pratt  190.^,  type  of  the  genus. 

Fig.  704.    Renijer  ellipticus.    Ventral  view.     X  iS-     (.\ftcr  Pratt.) 

141(140)     Genital  pore  median  or  nearly  so M- 


4o6 


FRESH-WATER   BIOLOGY 


142  (143)     Testes  oblique,  separated  by  greatly  enlarged  branch  of  uterus. 

Dasymetra  Nicoll  191 1. 

Body  moderately  flattened,  spinous.  Pharynx  large,  crura  wide,  not 
reaching  posterior  end.  Excretory  vesicle  Y-shaped,  with  many  side 
branches.  Genital  pore  median,  slightly  preacetabular.  Cirrus  sac  short, 
plump;  cirrus  long.  No  receptaculum  seminis;  Laurer's  canal  present. 
Vitellaria  branching,  lateral.  Uterus  coiled  in  posterior  end,  ascending 
ramus  wide,  nearly  straight,  metraterm  long,  muscular.     Ova  35  ix  long. 

Type  and  only  species. 

Dasymetra  conferta  Nicoll  191 1. 

Length  3.5  to  4.6  mm.,  maximum  width  i  to  1.4  mm.,  near  center 
Spines  long,  straight.  Oral  sucker  0.56  mm.  in  diameter.  Acetabulum 
same  size  or  httle  less,  about  1.7  mm.  from  anterior  end.  Pharynx  0.28 
mm.  in  diameter;  esophagus  short;  crura  wide,  enlarged  at  ends.  Ex- 
cretory tubules  pigmented.  Testes  oblique,  separated  by  uterus.  Ovary 
at  right  posterior  margin  of  acetabulum.  Vitellaria  lateral,  extend  from 
genital  pore  to  posterior  border  of  right  testis;  follicles  large.  Uterus 
spacious;  descending  ramus  dorsal,  small;  posterior  coil  behind  ends  of 
intestinal  crura;  ascending  ramus  irregular,  broad,  extending  to  acetabu- 
lum. Metraterm  with  thick  muscular  walls.  Ova  dark  brown,  Z2>  to 
37  by  16  to  19  IX. 

In  mouth  (?)  of  diamond  water-snake  (Tropidonotus  rhombifer);  North 
America,  locality  unknown. 


Fig.  705.     Dasymetra  conferta.     Ventral  view.     X  i5-     (After  Nicoll.) 


143  (142)     Testes  lateral,  symmetrical 144 


144  (145)     Topography  inverted,   i.e.,  genital  pore  right  and  ovary  left  of 
median  line Pneumatophilus  Odhner  19 10. 

Broad,  flat  distomes  of  submedian  size  with  moderately  de- 
veloped suckers.  Greatest  wadth  behind  center,  tapering  to 
anterior  end,  rounded  posteriorly.  Skin  spinous.  Suckers  in 
anterior  third  of  body,  acetabulum  sUghtly  larger.  Genital  pore 
dextral,  near  fork  of  intestine,  half  way  between  suckers.  Oral 
sucker  slightly  subterminal,  pharynx  present,  esophagus  very 
short.  Crura  extend  to  or  just  beyond  testes,  with  numerous 
short  lateral  projections  on  outer  margin.  Excretory  vesicle  Y- 
shaped,  slender.  Stem  reaches  to  anterior  margin  of  testes. 
Testes  opposite,  just  behind  center  of  body,  lobed.  Cirrus  sac 
and  cirrus  moderate  in  size.  Ovary  at  left  posterior  margin  of 
acetabulum.  Laurer's  canal,  but  no  receptaculum  seminis.  Vi- 
tellaria extracecal,  extend  from  level  of  genital  pore  to  anterior 
part  of  testes.  Uterus  with  descending  and  ascending  limb  pass- 
ing between  testes;  thrown  into  transverse  loops  that  fill  post- 
testicular  region. 

In  the  lung  and  trachea  of  Heterodon  platyrhinus  and  Tropi- 
donotus sipedon. 

One  species  in  North  America,  originally  described  by  Leidy 
as  Distoma  variahile  var.  b.,  and  Usted  later  by  Pratt  as  Rejtifer 
variabilis  taken  by  Odhner  as  type  of  the  new  genus. 

Fig.  706.  Pneumatophilus  variabilis.     Dorsal  view.   X  12.  (After  Pratt.) 


145  (144) 


Topography  direct, 
line.    .    .    . 


i.e.,  genital  pore  left  and  ovary  right  of  median 
146 


PARASITIC    FLATWORMS  407 

146  (147)     Cirrus  sac  does  not  extend  posteriad  beyond  acetabulum. 

Lechriorchis  Stafford  1905. 

Distomes  of  submoderate  size  oval,  narrower  behind,  ventral  sucker 
much  larger  than  oral  (?),  one-third  body  length  from  anterior  end.  Skin 
spinous.  Pharyn.x  and  esophagus  present;  crura  extend  to  [rxjsterior 
margin  of  ?]  testes,  two-thirds  length  of  body.  Testes  large,  nearly 
symmetrical,  almost  in  contact.  Cirrus  sac  large,  dorsal  and  anterior  to 
acetabulum  on  right  side,  (ienital  pore  at  fork  of  intestine.  Ovary 
small,  spherical,  at  the  end  of  cirrus  sac,  on  right  posterior  margin  of 
acetabulum.  Uterus  extends  directly  posteriad  to  end  of  body  and  then 
anteriad,  ascending  limb  greatly  expanded.  Vitellaria  [lateral  ?],  nearly 
entire  length  of  ceca.     Eggs  dark  brown. 

Two  species  from  North  .\merica;  type  L.  primus  in  lung  of  garter 
snake.  The  only  well-described  species  is  one  which  Stafford  says  be- 
longs here;  it  is  L.  clongalus  (  =  Renifer  elonf^atus  Pratt)  in  mouth  of 
Heterodon  platyrhinus.  Renijcr  megasorchis  Crow  19 13  from  the  uterus 
of  Matrix  rhombifera  may  belong  here. 


Fig.  707.     Lechriorchis  clongatus.     Dorsal  view.     X  15.     (.\fter  Pratt.) 

147  (146)     Cirrus  sac  extends  posteriad  beyond  posterior  margin  of  acetab- 

ulum  Zeugorchis  Stafford  1905. 

Small,  elongate  elliptical  distomes  with  subterminal  oral  sucker  and  spinous  skin.  Ace- 
tabulum near  center  of  body.  Pharynx  and  esophagus  present,  crura  extend  to  testes  only. 
Testes  oval,  lateral,  separated.  Cirrus  sac  large,  dorsal,  extending  posterior  to  acetabulum. 
Genital  pore  in  fork  of  intestine.  Ovary  small,  spherical,  at  end  of  cirrus  sac.  Uterus  with 
descending  and  ascending  limbs,  reaches  to  posterior  end;  eggs  very  numerous.  Vitellaria 
lateral  along  crura,  but  also  covering  same  and  approaching  median  line  dorsally.  Excretory 
bladder  median,  large,  with  evident  lateral  branches. 

Single  North  American  form,  type  species. 

Zeugorchis  aequatus  Stafford  1905. 
In  esophagus  and  stomach  of  garter  snake;    Canada.     This  form  is  very  inadequately  de- 
scribed and  its  position  is  somewhat  a  matter  of  conjecture.     Odhner  believes  it  should  be 
placed  in  this  subfamily. 

148  (65)     Ovary  posterior  to  one  or  both  testes 149 

149(152)     Ovary  posterior  to  both  testes 150 

150  (151)     Uterine  coils  anterior  to  ovary,  between  it  and  acetabulum;  testes 

small,  oblique,  nearly  symmetrical,  widely  separated  from 
each  other,  lateral  near  acetabulum.       .    .    .     Lciiccruthrus. 
For  description  and  figure  consult  87  (86)  in  this  key. 

151  (150)     Uterine  coils  posterior  to  ovary,  between  it  and  posterior  end; 

testes  large,  oblique  or  nearly  median,  forming  with  acetabu- 
lum and  ovary  almost  a  continuous  median  series. 

Family  Dicrocoi:liid.\i-:  Braun  191 5. 

Elongate,  flattened,  transparent  distomes  of  moderate  size  with  weak  suckers  and  ptxjrly 
developed  musculature.  Acetabulum  near  anterior  end.  Intestinal  crura  do  not  reach  jxjs- 
terior  end.  Excretory  bladder  tubular,  reaching  anteriad  to  center  of  body.  Ccnital  pore 
median,  between  suckers,  near  fork  of  intestine.  Cirrus  sac  small,  cirrus  conspicuous,  derm 
glands  postacetabular  with  testes  symmetrical,  oblique,  in  median  series  in  front  of  ovary. 
Vitellaria  occupy  central  region  of  body  mostly  outside  of  intestinal  crura.  Uterus  long  with 
descending  and  ascending  branches  in  transverse  coils,  mostly  filling  area  behind  t)var>-.  Eggs 
moderate  in  size,  very  abundant,  thick  shelled,  dark  brown. 

Parasitic  chiefly  in  gall  ducts  of  Amniota. 

Type  genus Dlcrococlium  Dujardin  1845. 

Body  tapering  towards  both  ends,  more  anteriad.  Testes  oblique,  close  together.  Vitel- 
laria lateral,  symmetrical,  small.  Genital  pore  with  cirrus  sac  between  ventral  sucker  and 
fork  of  intestine.  Uterus  prominent,  filling  entire  body  behind  germ  glands  which  he  between 
acetabulum  and  center  of  body. 


4o8 


FRESH-WATER    BIOLOGY 


The  common  European  species  (D.  dendriticum,  the  old  Distoma  lanceolahim)  is  said  by 
Leidy  to  be  frequent  in  sheep  in  several  western  states,  but  Stiles  and  Hassall  report  it  as  ap- 
parently not  in  North  America.  I  have  never  seen  a  specimen  collected  here.  Confusion 
with  Opisthorchis  and  similar  forms  is  common  in  earlier  records. 

North  American  genus HaUpegus  Looss  1899. 

Moderate  sized  distomes  with  muscular  body,  round  in  cross-section,  and  powerful  suckers. 
Pharynx  large,  esophagus  short,  crura  extending  to  posterior  end.  Genital  pore  close  to 
pharynx.  No  cirrus.  Testes  lateral,  near  posterior  end,  symmetrical.  Ovary  close  behind 
right  testis;  vitellaria  just  behind  ovary  and  composed  of  group  of  4  to  5  large  follicles  on  each 
side.  Uterus  in  crowded  transverse  coils,  filling  almost  entire  body.  Eggs  extremely  numer- 
ous, small,  with  long  polar  filament.     In  mouth  and  pharynx  of  amphibia. 

North  American  species.    .    .    .   HaUpegus  occidtmlis  Stafford  1905. 
In  mouth  and  eustachean  tube  of  Rana  catesbiana;  Canada,  Massachusetts. 

152  (149)     Ovary  between  testes 153 

153  (156)     Ovary  median  or  nearly  so,  hence  directly  behind  anterior  tes- 


tis. 


154 

154  (155)     Genital  pore  between  acetabulum  and  pharynx. 

Sphaerostoma  Stiles  and  Hassall  1898. 

Small  distomes  with  actively  mobile,  powerful  anterior  region  and  broad  posterior  region. 
Suckers  powerful.  Pharynx  present,  esophagus  long,  crura  reach  into  caudal^  end.  Cirrus 
sac  large,  cirrus  muscular.  Testes  separate,  anterior  one  near  acetabulum  on  right,  posterior 
one  near  caudal  tip,  median.  Ovary  intermediate  but  slightly  to  left  of  median  line.  Vitel- 
laria extensive,  lateral,  from  pharynx  to  posterior  end.  Uterus  in  few  coils  between  posterior 
testis  and  acetabulum.     With  few,  large  eggs. 

This  genus  has  not  yet  been  reported  from  fresh-water  fishes  in  North  America.^  Linton 
has  found  it  in  marine  fishes  in  the  Woods  Hole  region  and  it  is  common  in  Europe  in  Cypri- 
nidae  and  many  other  fresh-water  fishes  so  that  it  is  very  likely  to  be  found  on  this  continent 
in  similar  fresh-water  hosts. 

155  (154)     Genital  pore  some  distance  behind  acetabulum,  just  anterior  to 

anterior  testis Clinostomum  Leidy  1856. 


Middle  sized  distomes  with  flattened  body. 
Oral  sucker  small  and  retracted  at  times  so  that 
the  body  wall  rises  around  it  like  a  collar.  Ace- 
tabulum near  oral  sucker,  larger,  very  muscular, 
with  triangular  orifice.  No  phar>'nx,  short  eso- 
phagus and  long  crura  provided  with  lateral 
pockets.  Cirrus  sac  present.  Vitellaria  lateral, 
strongly  developed,  confluent  behind  testes.  Uter- 
us inverted  U-shaped,  reaching  forward  nearly  to 
acetabulum,  with  expansion  on  distal  branch  of  U. 
Several  species  in  North  America.  Not  clearly 
distinguished  in  records.  Adults  are  parasitic  in 
the  pharynx  and  esophagus  of  fish-eating  birds 
such  as  herring  gull,  various  herons,  bittern,  eagle, 
stork.  Young  forms  encysted  in  frogs  and  fish 
(minnows,  perch,  bluegill,  bullhead,  rock  bass, 
pike,  black  bass,  trout,  etc.) .  Cort  has  shown  that 
the  young  encj'sted  in  amphibia  are  a  different 
species  from  those  in  fish.  Widely  distributed  in 
eastern  North  America  at  least.  The  larval  stages 
are  so  abundant  in  some  regions  that  food  fish  are 
rendered  unfit  for  use  by  the  middle  of  June.  The 
cysts  are  deserted  by  late  fall  and  the  fish  are  free 
from  infection  in  winter. 

Distoma  oricola  Leidy  from  the  mouth  of  Alli- 
gator mississippiensis  is  undoubtedly  a  related 
form  as  Pratt  surmised.     It  falls  in  this  family 
Fig.   708.      Clinostomum  but  too  little  is  known  of  its  structure  to  justify  tomum    marginatum.    I 
marginatum.     Larval  stage  assigning  it  to  a  definite  genus.  Young    adult     from    : 

from  perch.     X  i9-     (After  heron.    X  i9-   (After    j 

Cort.)  Cort.)  •' 


#^  J 


Fig.  709.     C linos- 


PARASITIC    FLATWORMS  409 

156  (153)     Ovary  lateral  and  slightly  posterior  to  anterior  testis    but   not 

directly  behind  it ^ 

157  (158)     Genital  pore  at  posterior  end.       .    .     Uucochloridium  Carus  1835. 

Small  distomes  with  compressed  muscular  body.  Both  suckers  and  pharynx  large  and  p«jw- 
erful.  Esophagus  short  crura  very  slender,  reaching  nearly  to  posterior  end  Excretory 
pore  dorsal  near  caudal  tip.  Cirrus  sac  present.  Laurer's  canal  present;  rcccptaculum 
wanting.  Vitellana  lateral,  conspicuous,  extracecal.  Uterus  in  loops  ascends  on  one  side  of 
acetabulum,  crosses  body,  and  descends  on  the  other  side.     Eggs  small    thick  shelled 

In  the  cloaca  of  birds,  not  reported  in  North  America.  The  larval'  stage  "in  Sucdnva  is  a 
si^orocyst  which  sends  into  the  tentacles  of  the  snail  branches  that  are  banded  in  <ol<,r  and 
are  bitten  off  by  birds  Reported  in  a  personal  letter  by  Mr.  Bryant  Walker  who  found  it  in 
Succmea  ovalis  in  Michigan. 

158  (157)     Genital  pore  ventral,  median,  just  anterior  to  posterior  testis. 

Hasstilesia  Hall  1916. 

Very  small  oval  distomes,  nearly  round  in  cross  section.  Skin 
with  minute  spines  in  anterior  region.  Suckers  .small,  nearly 
equal  Pharynx  and  esophagus  present,  equal  in  length;  crura 
irregular,  reach  to  posterior  end  of  body.  Excretory  bladder 
minute  with  two  delicate  lateral  branches,  (ienital  pore  ventral, 
slightly  dextral,  midway  from  acetabulum  to  posterior  end.  Cir- 
rus sac  flask-shaped,  large;  cirrus  long.  Testes  large,  one  in 
extreme  posterior  region,  nearly  median,  the  other  near  center  of 
body  on  left.  Ovary  small,  round,  ventral  to  right  intestinal 
cecum,  near  anterior  margin  of  posterior  testis.  \'itellaria  lateral 
in  anterior  half.  Uterus  in  anterior  region  of  body,  moderately 
developed,  mostly  pretesticular  but  with  a  single  loop  between 
the  testes. 

Eggs  13  by  20  ^£. 

Single  American  species. 

Fig.  710.    Hasstilesia  tricolor.  HasstUesia  tricolor  (Stiles  and  Hassall)  1804. 

'     ^^    ^^  ^''■'  ^  In  small  intestine  of  'Lepiis;  abundant,  Maryland.  District  of 

Columbia,  Virginia. 

159  (64)     Distomes  of  separate  sexes. 

Family  Schistosomatidae  Looss  iSqq. 

Adults  parasitic  in  blood  vessels  of  man,  cattle,  and  birds;    not  yet  found  in  North  \merica 
Cercariae  very  similar  to  those  of  this  family  occur  in  North  .American  snails. 
Compare  furcocercous  cercariae  241  (246)  in  this  key. 

160  (63)     Special  adhesive  organ  behind  acetabulum,     .\nterior  region  with 

holdfast  organs  usually  distinctly  separated  from  posterior 
region  with  genitalia Suborder  Holostomata  Luhe. 

The  genus  Cyathocotylc  without  diflerentiated  regions  has  not  been  nvordid  in  X.irih 
America. 

Only  family  represented. 

Family  HEiUSTOMiDAE  Brandes  1888   .    .     i6r 

Distomes  with  body  more  or  less  distinctly  divided  into  two  regions.  Anterior  rcRion  sp»K)n 
or  cup-shaped,  serving  as  adhesive  organ.  Suckers  poorly  dcvelo|x-d.  but  with  pi-culiar  |>.)st- 
acetabular  sucking  organ.  Posterior  region  cylindrical  t)r  ovoid.  Intestinal  crura  extend 
to  posterior  end.  Excretory  bladder  in  form  of  subcutaneous  network,  (ienifal  jxirc  at 
posterior  end.  Neither  cirrus  sac  nor  cirrus.  Ovary  and  testes  in  series  in  |>osterior  region. 
Vitellana  conspicuously  developed.  Uterus  short  with  few,  very  large,  thin-shelKil  eggs.  .\o 
alternation  of  generations.  Develop  with  intermediate  host  but  without  alternation  of 
generations. 

Parasitic  in  intestine  of  .Vmniota. 


4IO  FRESH-WATER   BIOLOGY 

i6i  (i66)     Adult  forms  with  developed  sex  organs. 


162 


162  (165)     Dorsal  surface  without  special  suckers 163 


163  (164)     Anterior  region  flat,  with  foliate  margins    sharply  set  off  from 
posterior  region Hemistomum  Diesing  1850. 

Anterior  region  more  or  less  in  the  form  of  a  cone  opening  an- 
teriorly and  ventrally.  Acetabulum  often  covered  by  special  ven- 
tral holdfast  organ,  not  larger  than  oral  sucker,  in  one  case  entirely 
lacking.     Sexual  pore  dorsal. 

North  American  species. 

Hemistomum  craterum  Barker  and  Noll  191 5. 

Length  0.75  to  1.89  mm.  Cephalic  region  0.62  to  0.79  mm.  long 
by  0.41  to  0.49  mm.  wide.  Caudal  region  0.28  to  0.47  by  0.20  to 
0.36  mm.  Adhesive  disk  large,  flattened  cone  with  crateriform 
top,  without  papillae. 

An  unnamed  species  is  recorded  from  Didelphis  virginiatia  by  C. 
Curtice. 


Fig.  711.     Hemistomum  craterum.     Ventral  view. 
Barker.) 


Magnified.     (After 


164  (163)     Anterior  region  cup  shaped,  with  anterior  circular  entrance. 

Strigea  Abildgaard  1 790. 

Frequently  called  Holosfomum,  a  name  of  later  date. 

Anterior  region  sharply  set  off  from  posterior  by  circular  groove.  Flattened  lateral  region 
united  ventrally  to  a  cup,  with  mouth  at  anterior  end.  Concealed  in  this  cup  small  acetab- 
ulum and  posterior  adhesive  organ  in  form  of  a  papilla  extending  to'  mouth  of  cup.  In  genital 
pore  a  well  developed  genital  cone;   opening  terminal. 

North  American  species Strigea  cornu  (Rudolphi)  1819. 

Recorded  from  Ardea  herodias  in  Alaryland  by  Stiles  and  Hassall. 

Another  species  described  by  Leidy  as  Holostomum  nitidutn  from  the  small  intestine  of  Rana 
pipiens  is  according  to  Stafford  a  distome,  and  if  so  could  not  be  placed  here. 


165  (162)     With  row  of  suckers  on  dorsal  surface. 

Polycotyle  WiUemoes-Suhm  1871. 

Type  species Polycotyle  ornata  Willemoes-Suhm  1871. 

Length  4.5  mm.     Posterior  region  growing  larger  posteriorly,  longer  than  anterior.     In 
mid-dorsal  line  14  or  15  suckers. 

In  intestine  of  Alligator  lucius;  Charleston,  S.  C. 


Fig.  712.     Polycotyle  ornata.     X  25.     (After  Willemoes-Suhm.) 


166  (161)     Larval  forms;  sex  organs  wanting  or  only  partly  developed.  .      167' 

Sometimes  diflficult  to  separate  from  adults  and  hence  noted  here  as  well  as  later,  I 

Compare  under  Holostome  Cercariae,  250  (184)  in  this  key.  .'  I 


PARASITIC   FLATWORMS 


411 


167  (168)     Larval  forms  with  an  oval  sucker-like  depression  on  each  side  of 

the  oral  sucker ZV/rt/ro/v/e  Filippi  1854. 

Body  pyriform  or  oval.  On  each  side  of  oral  sucker  an  oval  groove,  not  muscular,  with 
pores  of  special  (cystogenous  ?)  glands.  ' 

Encysted  in  mollusks  and  vertebrates.  European  forms  belong  to  various  species  of  Strigea. 
Ruttger  found  these  larvae  in  Limnaca  stai^nalis  and  fed  them  to  ducks;  ten  days  later  he 
obtained  mature  holostomids  (species  not  given).  Leidy  recorded  T.  typica  from  Limnae'a 
catascopium  and  Physa  heterostropha  (cf.  251  in  this  key).  Other  undescribed  spedes  encysted 
in  North  American  frogs. 

168  (167)     Larval  forms  without  sucker-like  depressions  at  the  side  of  the 

oral  sucker Diplostomulum  Brandes  1892. 

Body  flattened  with  lateral  margins  turned  ventrad  in  anterior  region;  short  tip  represents 
posterior  region.     On  anterior  margin  near  oral  sucker  group  of  gland  pores  on  each  side. 

Several  species  encysted  in  body  of  fishes,  or  free  in  optic  bulb  of  similar  hosts.  Belong  to 
various  Hemistomuni  species  (cf.  252  in  this  key). 

A  form  is  frequent  which  has  been  identified  as  D.  cuticola  (v.  Nordmann),  the  larva  of 
Ilemistomum  denticidatum  (Rud.)  common  in  Europe.  It  has  been  reported  from  sunfish, 
perch,  bluegill,  pumpkin-seed,  minnows,  horned  dace,  rock  bass,  small-mouthed  black  bass, 
pike,  and  other  fish  from  Canada  to  Iowa.  Not  a  few  of  the  larger  cysts  contain  two  worms, 
one  usually  much  smaller  than  the  other. 

Cooper  found  a  form  in  the  optic  lens  in  young  Micropterus  dolomieu  which  he  identified  as 
Diplostomulum  volvens  (von  Nordmann). 

169  (i)     Larval  forms;   sexual  organs  entirely  wanting  or  at  most  only  partly 

developed 170 

A  few  encysted  forms  are  described  that  contain  eggs  and  are  apparently  se.xually  mature. 

170  (171)     Young  flukes,  encysted  or  free,  always  without  caudal  appendage. 

Aganwdistomum.  Stossich  1892. 

Many  immature  forms  whose  relationship  to  adult  types  has  not  yet  been  determined. 
The  group  is  artificial,  temporary,  and  collective,  including  all  agamic  flukes  with  two  suckers. 
Agamic  forms  in  other  groups  have  been  given  special  names  as  noted  in  connection  with  the 
description  of  the  adults. 

Forms  of  this  sort  are  mentioned  frequently  without  specific  names.  Named  forms  are  also 
on  record,  e.g.  A.  apodis  (Packard  1882)  from  the  ovisac  of  A  pus  from  Kansas,  a  unique  record 
of  a  distome  in  a  phyllopod  crustacean,  but  without  data  adequate  to  fix  the  species. 

All  forms  described  as  encysted  cercariae  belong  in  this  subdivision  rather  than  in  the  next 
since  the  two  marks  of  distinction  between  the  two  are  the  tail,  which  is  cast  otT  when  the  larva 
encysts,  and  the  cystogenous  glands,  pure  larval  organs,  that  are  emptied  in  this  process  and 
disappear. 

Various  species  which  belong  here  have  been  recorded  without  description  under  other 
names  as  " Heterostomum  echinatum  Diesing"  of  Leidy  from  the  oviduct  of  Paludina  "quite 
common,"  and  Distomum  centra ppendiculatum  of  the  same  author  from  Helix  arborea. 

171  (170)     Caudal  appendage  present,  usually  simple,  sometimes  modified. 

even  greatly  reduced,  rarely  absent.     .     Ccrcaria    .    .     172 

No  hard  and  fast  line  can  be  drawn  between  this  group  and  the  last  since  a  few  tailless  cer- 
cariae are  known.  Furthermore  the  transition  in  any  case  will  be  instantaneous  when  the 
cercaria  under  stimulation  casts  off  its  tail,  which  happens  normally  as  well  as  in  cultures. 

Small,  barely  visible,  microscopic,  free-living  forms  of  simple  trematode  structure,  having 
a  triclad  alimentary  canal.  A  tail,  single,  double,  branched,  setose,  or  otherwise  modified  is 
nearly  always  present,  and  is  the  efficient  organ  of  locomotion.  Rarely  the  tail  is  rudimentary 
or  entirely  lacking  and  the  form  can  be  classified  here  only  by  its  strong  resemblance  in  other 
features  to  the  tailed  larvae.  The  reproductive  organs  are  always  rudimentary,  and  sometimes 
entirely  wanting.  At  most  one  can  distinguish  masses  or  cords  of  cells  that  indicate  the  loca- 
tion of  future  organs.  Faust  has  found  that  these  agree  fully  with  adult  conditions.  Promi- 
nent larval  organs  are  the  stylet,  a  boring  spine  in  the  anterior  tip  al)ove  the  oral  sucker,  simple 
eyes  appearing  as  pigment  spots  on  the  anterior  dorsal  region  usually  near  the  brain.  con.-;piru- 
ous  dermal  glands  that  in  one  group  are  designated  stylet  glands  and  in  another  are  assigned  a 
cystogenous  function  and  are  perhaps  always  digestive  in  character;  they  present  varied  features 
in  different  species.     All  of  these  constitute  useful  specific  characters. 

Very  few  North  American  species  have  been  described  and  the  brief  records  that  exist  are 
in  most  cases  adequate  only  for  the  definition  of  groups  rather  than  species  in  the  true  sense. 
Most  of  the  following  subdivisions  of  the  key  are*  to  be  regarded  in  thai  light. 

Some  names  in  use  like  Cercaria  bilineata  Hald.  can  have  even  no  general  signiQcancc  since 
the  original  reference  contains  no  data  that  will  fix  the  species. 


412 


FRESH-WATER   BIOLOGY 


172  (173)     Mouth  opening  some  distance  from  anterior  end,  near  center  of 

ventral  surface.     Intestine  rhabdocoel. 

Gasterostomous  or  rhabdocoelous  cercariae. 

Alimentary  canal  short,  simple,  rod-shaped.  Swimming  organ  in  the  form  of  two  long 
narrow  appendages  directed  obliquely  right  and  left  from  posterior  end  of  body  in  the  only 
known  type.  Larval  stages  of  Bucephalidae,  such  as  the  well-known  Bucephalus  polymorphus 
von  Baer  of  Europe. 

Not  yet  reported  on  this  continent  though  the  adult  (see  29  in  this  key)  is  known  here. 

173  (172)     Mouth  opening  at  or  very  near  anterior  end  of  body.     Intestine 

triclad Prostomatous  cercariae   .    .     174 

174  (183)     Only  one  sucker,  and  that  around  mouth  opening. 

Monostome  cercariae   .    .      175 
All  yet  studied  have  a  pair  of  lateral  pigment  spots  on  the  dorsal  surface,  the  simple  eyes. 
Some  have  also  a  medium  pigment  area  between  the  lateral  eyes  or  slightly  anterior  to  them. 

175  (178)     Cercariae  without  median  eye  in  cephalic  region 176 

Under  the  designation  "median  eye"  is  included  always  an  optic  cup  with  pigment  lining 

and  an  optic  cell;    part  of  these  are  found  in  certain  developmental  stages  but  in  species  in- 
cluded under  this  heading  disappear  so  that  the  structure  never  becomes  complete. 


176  (177)     Six  pairs  of  large  gland  cells  in  tail. 


Cercaria  urbariensis  Cort  19 14. 


Length  0.27  to  0.54  mm.,  width  o.ii  to  0.2  mm.,  tail  0.2  to  1.2  mm.  long  and 
0.05  mm.  at  base.  Develops  in  rediae.  An  active  swimmer.  Encysts  on  soHd 
objects.  Cysts  shaped  like  thick  discs.  Moves  over  surface  by  aid  of  two  pro- 
jections one  at  each  postero-lateral  angle  of  body  and  with  cuticular  knob  in 
tip.  Heavily  pigmented,  especially  near  anterior  end.  A  pair  of  lateral  eyes; 
intermediate  pigment  nucleus  present  in  later  stages,  but  no  optic  cup  or  cell  at 
any  time.  Cystogenous  glands  abundant.  From  Physa  gyrina  at  Urbana. 
lUinois. 


Fig. 


713.     Cercaria  urbanensis,  mature,  ventral  view.     Cystogenous  glands  not  shown. 
X  70.      a,  posterior  locomotor  projection.     X  216.     (After  Cort.) 


177  (176)     Six  groups  of  paired  gland  cells  in  tail,  each  pair  dove-taiUng  into 

the  one  next  anterior Cercaria  konadensis  Faust. 

Cercaria  0.4  to  0.46  mm.  in  length,  o.i  to  0.16  mm.  in  width.  Tail  0.4  to  0.45  mm.  long  by 
0.03  to  0.04  mm.  diameter  at  base.  This  species  possesses  no  median  pigment  area  in  cephalic 
region.  Glands  of  posterior  locomotor  organ  large  and  prominent.  Cercariae  and  rediae 
aspinose.     Germ  balls  arise  from  central  germinal  rachis  in  subdistal  region  of  redia. 

From  liver  of  Lymnaea  proxima  Lea,  Bitter  Root  River,  CorvaUis,  Montana. 

178  (175)     Cercariae  with  median  eye  or  median  pigment  area  in  cephahc 

region.     Larger  species  than  preceding 179 

179  (180)     Distinct  mobile,  evertible  spinose  pharynx. 

Cercaria  pellucida  Faust. 
Length  0.4  to  0.7  mm.,  width  0.18  to  0.2  mm.  Tail  0.5  mm.  in  length,  0.07  mm.  in  diam- 
eter at  base.  No  large  gland  cells  in  tail.  Rediae  provided  with  multispinose  evertible 
piercing  organ  in  prepharynx  region.  Germ  balls  arise  from  central  germ  cells  in  distal 
region  of  redia.  From  liver  interstices  of  Physa  gyrina  Say,  Bitter  Root  River,  Fort  Missoula 
and  CorvaUis,  Montana. 

180  (179)     No   evertible    spinose    pharynx    mentioned    (imperfectly   known 

species) 181 


PARASITIC   FLATWORMS  413 

181  (182)     Body  dark  brown,  or  blackish. 

Cercaria  hyalocauda  Haldcman  1842. 

Very  imperfectly  known.  The  form  described  under  this  name  by  Evarts  (1880)  has  a  body 
0.47  mm.  long  and  0.24  mm.  wide  with  a  tail  0.55  mm.  long  and  o.i  mm.  wide  in  ma.ximum 
Cyst  0.32  mm.  m  diameter.  Body  dark  brown  or  blackish.  Two  eye  spots  and  smaller  less 
distinct  pigment  mass  between.  Tail  semitransparent,  corrugated  when  contracted,  active 
long  after  detachment  from  body. 

Evarts'  description  of  the  living  organism  shows  it  is  much  like  C.  iirbanensis  though  easily 
distinguishable  by  greater  size  of  larva  and  cyst.  Haldeman's  account  is  entirely  inadequate 
to  differentiate  the  form  and  suffices  only  to  place  it  in  this  group.  Taken  in  numbers  from 
Physa  hetcrostropha  Say  by  Evarts. 

182  (181)     Body  white.     Doubtful  form. 

Cercaria  {Glenocer carta)  lucania  Leidy  1877. 
Length  0.5  mm.  WTiite,  ovoid,  with  conical  tail  equal  to  or  longer  than  body  and  frequently 
monihform.  Two  eyes  with  intermediate  black  pigment  spot  and  smaller  scattered  pigment 
spots  near  them.  Produced  in  bright  orange-colored  sporocysts  which  are  cylindrical  and 
bluntly  rounded  at  the  ends.  Leidy  calls  this  a  Monostoma,  and  all  data  given  agree  with 
that  conclusion  except  that  his  description  lists  an  acetabulum  which  would  make  it  a  dis- 
tome  cercaria.     Abundant  in  Planorbis  parvus  found  near  Philadelphia,  Pa. 

183  (174)     JMore  than  one  sucker 1S4 

184  (250)     Oral  sucker  well  developed;   genital  atrium  not  modified.      .      185 

185  (190)     Second  sucker  ventral  and  at  posterior  end  of  body. 

xAmphistome  cercariae.   .    .      186 

According  to  studies  on  European  species  the  cercaria  of  Paramphistoma  cervis  lacks  pockets 
in  the  oral  sucker  and  has  a  connection  between  the  longitudinal  e.xcretory  vessels.  It  belongs 
to  one  subfamily.  All  other  known  cercariae  in  this  group  belong  to  another  subfamily. 
They  have  the  pockets  in  the  oral  sucker  and  a  muscular  enlargement  of  the  esophagus  at 
the  bifurcation  of  the  intestinal  crura. 


186  (189)     Cercariae  separate,  not  attached  in  bunches 187 

Very  likely  one  of  the  species  described  below  is  the  larval  form  of  Diplodiscus  tempcraius 
Stafford,  see  57  (58)  in  this  key. 

187  (188)     Anterior  half  of  body  pigmented.   .    .  Cercaria  inhabilis  Cort  1914. 


Large,  pigmented  form,  sluggish  in  movement.  Swims  slowly  in  or)cn 
water,  does  not  progress  on  substratum.  Two  large  eye  spots  with  lenses. 
Cystogenous  glands  thickly  developed  both  dorsally  and  ventrally.  Tail 
lightly  attached  above  acetabulum  and  easily  lost.  Location  of  genital  or- 
gans distinctly  indicated  by  four  dense  masses  of  nuclei  connected  by  tine 
lines. 

From  Planorbis  Irivohis,  Lawrence.  Kan.,  and  Urbana.  III. 


Fig.  714.     Cercaria  inhabilis,  mature,  ventral  view.    Cystogenous  glands  not  shown, 
X  44-     (After  tort.) 


414  FRESH-WATER    BIOLOGY 

i88  (187)     Pigment  in  limited  area  near  eyes. 


Cer carta  diastropha  Cort  19 14. 


Smaller  than  last,  eye  spots  larger  in  proportion.  Pigment  confined  to 
limited  area  near  eyes.  Tail  always  shorter  than  body.  Genital  organs  dis- 
tinctly marked  out. 

Fig.  715.     Cercaria  diastropha,  mature,  dorsal  view.    Cystogenous  glands  not  shown. 
X  60.     (After  Cort.) 


189  (186)     Cercariae  grouped  in  bunches  with  individuals  united  by  tips  of 
tails,  which  are  very  long  and  slender. 

Such  forms,  designated  Rattenkonig- 
cercarien  by  their  discoverer,  Leuckart, 
are  as  rare  as  they  are  striking.  C. 
daitsii  frorn  the  marine  fauna,  the  only 
form  of  this  type  known  previously, 
was  determined  by  Odhner  to  belong 
to  Phyllodistomiim  folium.  The  strik- 
ing pecuharity  in  that  the  cercariae 
are  joined  in  groups  is  evidently  not  of 
fundamental  importance  as  the  marine 
form  (C.  ddusii)  and  the  species  noted 
here  belong  to  different  orders  of  trema- 
todes. 

North  American  species. 
Cercaria  gorgonocephala 

Ward  1916. 

Fifty  or  more  cercariae  in  a  single 
bunch.  Tail,  i.e.,  stalk,  enlarged  at 
base  with  thick  wall.  Yellow  pigment 
in  body.  Stalk  marked  by  two  longi- 
tudinal lines  of  dark  pigment,  attached 
to  postero-dorsal  aspect  of  worm. 

Fig.  716.     Cercaria  gorgonocephala.     Free- 
hand sketch  from  life.    X  40.   (Original.) 


190  (185) 


Second  sucker  ventral,  not  at  or  near  posterior  end  of  body. 

Distome  cercariae  .    . 


191 


Some  distome  cercariae  are  readily  recognizable  by  characteristic  features  of  adult  struc- 
ture like  the  collar  and  spines  of  the  Echinostomidae  which  are  as  prominent  in  the  cercaria 
as  in  the  adult,  and  apparently  identical  in  form  and  arrangement.  In  the  majority  of  cases, 
however,  the  various  groups  of  distome  cercariae  at  present  recognized  are  purely  arbitrary 
as  they  are  based  on  superficial  characters.  But  the  system  cannot  be  rewritten  until  much 
more  is  known  of  the  origin  of  all  of  these  larval  organs  and  until  a  large  number  of  species 
has  been  studied. 

191  (247)     Tail  present  in  larva 192 

The  name  Cercaria  is  applied  strictly  only  to  such  larvae  as  possess  a  tail,  though  the  tail 
may  be  thrown  off  at  an  early  period. 


[92  (234)     Tail  not  conspicuously  modified  in  form  or  divided  into  regions.     193 


PARASITIC    FLATWOKMS 


415 


193  (233)     Tail  slender,  never  as  broad  as  body  of  cercaria. . 

Cercariae  leptocercac   .    .      194 

The  long,  slender,  unbranched  tail,  which  even  in  maximum  contraction  does  not  reach  the 
width  of  the  body,  and  in  extension  is  twice  the  body  length  or  more,  is  found  in  the  majority  of 
distome  cercariae.  The  anterior  end  of  the  body  furnishes  data  for  the  subdivision  oi  these 
forms. 

194  (199)     Anterior  end  rounded,  entirely  devoid  of  spines. 

Gymnocephalous  cercariae  .  .  195 
So  far  as  known  these  forms  develop  in  rediae.  Many  exist  on  this  continent  which  have 
not  been  reported,  for  many  adults  are  listed  in  the  earlier  sections  of  this  key  which  must 
possess  such  larvae  as  one  may  infer  from  European  studies  on  related  species.  These  ceitariat 
are  conveniently  subdivided  on  the  structure  of  the  tail  which  in  all  is  a  prominent  oigan  but 
which  in  some  does  not  function  as  a  swimming  organ. 

195  (196)     Tail  simple,  not  provided  with  fin-folds  or  terminal  sucking  organ. 
Three  different  forms  may  be  noted  without  attempting  to  analyze  them  in  the  key 

Cercaria  {Gymnoccphala)  ascoidca  (Leidy)  1877. 

Length  0.25  to  0.4  mm.  Body,  white  clavate;  tail  long,  narrow,  cylindrical  pointed 
Cephahc  end  triangular  and  slightly  constricted  from  rest  of  body.  Acetabulum  at  or  behind 
center  of  body  often  protruded  into  a  cone  or  expanded  into  a  cup.  Xo  eyes.  In  movement 
excessively  elongated.  Rediae  white;  head  distinct  from  cylindrical  body,  with  birth  pore 
and  caudal  prolongation. 

Abundant  in  Planorbis  parvus  and  found  free  in  water  containing  that  species.  Leidy  is  in 
error  in  identifying  this  form  as  Cercaria  minuta  Nitzsch  of  Europe. 

Cercaria  agilis  Leidy  1858. 

Body  pyriform,  oral  sucker  large,  acetabulum  slightly  larger,  near  middle  of  body.     Tail  as 
long  as  body,  clavate,  transversely  pHcate.     White.     Very  active. 
Found  in  Delaware  River;   ordinarily  with  snails.     Common. 

Cercaria  fasciolae  hepaiicae. 

Larva  of  the  well-known  sheep  liver  fluke,  not  yet  reported  but  undoubtedly  frecjuent  in 
certain  regions  and  years  as  the  adult  is  known  to  be  abundant  at  certain  ix)ints  in  North 
America. 


196  (195)     Tail  modified,  having  fin-folds  or  terminal  organ. 


197 


197  (198)     Tail  provided  with  dorsal  and  ventral  fin-folds. 

Cercaria  rcflexa  Cort  19 14. 


Develops  in  rediae.  Encysts  in  same  snail  as  redia  inhabits  or  other 
snail  of  the  same  species.  Tail  as  long  as  body  or  longer,  provided 
with  dorsal  and  ventral  fins.  Cystogenous  glancls  abundant.  Es<^)ph- 
agus  long,  fine;  alst)  crura;  bifurcation  at  anterior  level  of  acetabu- 
lum. Genital  organs  marked  out  by  four  masses  of  nuclei.  Cort 
believes  this  form  is  undoubtedly  related  to  the  Echinostomcs,  but 
the  spines  are  not  yet  developed.  .Ml  other  characters  accord  with 
this  view.     From  Lymnaea  rcjlcxa,  Chicago,  Illinois. 


Compare  232  (231)  in  this  key 


Fig.  717.     Cercaria  rcjlexa,  ventral  view.     Cvstogcnous  glands  not  showi 
X  60.     (.\ftcr  Cort.) 


4i6 


FRESH-WATER   BIOLOGY 


198  (197)     Tail  long  with  terminal  organ  for  attachment. 

Megalurous  cercariae. 
Single  American  species  known. 

Cercaria  megalura  Cort  19 14. 

Develops  in  rediae.  Cystogenous  glands  abundant.  Does  not  swim  in  open  water  or  use 
tail  as  swimming  organ,  but  as  a  stalk,  becoming  attached  by  the  adhesive  organ,  a  group  of 
unicellular  glands  at  the  tip.  The  tail  has  the  power  of  elongating  very  greatly.  In  this 
position  the  worm  waves  or  wriggles  about  in  a  serpentine  fashion.  When  taken  up  in  a  pi- 
pette it  encysts  quickly  and  this  seems  to  be  normal  on  contact  with  fresh  water. 

From  Pleurocera  elevatum,  Sangamon  River,  111.,  and  Goniobasis  virginica,  Princeton,  N.  J. 
Adult  unknown.     Reproductive  organs  indicated  by  two  masses  of  nuclei  joined  by  line. 

199  (195)     One  or  more  spines  present  at  anterior  end 200 

200  (224)     xA.nterior  end  provided  with  single  median  boring  spine. 

Stylet  cercariae   .    .     201 

These  forms  called  Acanthocephala  by  Diesing  and  Xiphidiocercariae  by  Liihe  are  numer- 
ous and  perhaps  not  closely  related;  even  if  the  stylet  cercariae  do  belong  to  different  adults, 
their  assemblage  in  a  single  group  is  convenient. 

Small,  slender-tailed  cercariae  with  rounded  anterior  margin,  bearing  a  dagger-shaped 
boring  spine  or  stylet,  usually  in  the  upper  lip  of  the  oral  sucker.  The  form  of  this  organ 
is  very  definite  in  each  species  and  varies  between  different  species  distinctly  enough  to  form 
in  many  cases  a  valuable  mark  for  diagnosis.  Eye  spots  are  usually  wanting.  Development 
in  sporocysts  is  most  frequent  and  encystment  in  a  second  intermediate  host  usual  in  species 
of  which  the  development  is  known. 

201  (217)     Tail  slender,  not  provided  with  special  organs  (bristles,  fin-fold) 

or  regions 202 

202  (203)  Stylet  glands  few  in  number,  not  more  than  four  on  each  side. 
Tail  attached  to  median  posterior  extremity,  not  arising 
from  distinct  caudal  pocket.      .    .      Cercariae  microcotylae. 

Very  small.  Body  less  than  0.2  mm.  long.  Stylet  glands  3  to  4  only, 
near  acetabulum.  Excretory  bladder  small,  forking  more  or  less  acutely 
at  anterior  end.  These  forms  are  all  minute  and  further  study  may  dis- 
close the  presence  of  a  caudal  pocket  with  minute  spines  in  some  or  all 
species.     Two  species;  not  analyzed  in  key. 

Median  stem  of  excretory  bladder  elongate,  club-shaped. 

Cercaria  leptacantha  Cort  1914. 

Body  oval;  circular  in  cross  section,  0.12  mm.  long  by  0.063  mni-  wide. 
Tail  slender,  shorter  than  body.  Stylet  small.  Not  fully  developed.  Sur- 
face in  living  specimen  with  highly  refractive  prominent  globules  of  differ- 
ent size. 

Produced  in  oval  thin-walled  sporocysts  from  Campeloma  decioum 
Hartford,  Conn. 


Fig.  718.     Cercaria  leptacantha,  immature,  ventral  view,     a,  stylet,  ventral  view. 
X  320.     (After  Cort.) 

Median  stem  of  excretory  bladder  short. 

Cercaria  caryi  Cort  19 14. 

Very  small;  stylet  glands  present,  few  in  number.    Acetabulum  small; 
develops  in  sporocysts.     From  Goniobasis  virginica,  Princeton,  N.  J. 

Fig.  719.     Cercaria  caryi,  ventral  view.     From  Gary's  material.     X  140.    (After 
Cort.) 

203  (202)  Stylet  glands  more  numerous,  six  or  more  on  each  side.  Tail  aris- 
ing from  posterior  caudal  pocket,  ventral  to  excretory 
bladder Polyadenous  cercariae   .    .      204 


PARASITIC   FLATWORMS  417 

204(210)     Caudal  pocket  present,  distinct,  devoid  of  hooks  or  spines.    .     205 

205  (206,  207)     Ceca  short,  lateral  trunks  of  excretory  bladder  circumscribe 
acetabulum C.  brcvicaeca  Cort  1914. 


Body  elongate  oval,  0.3  mm.  long,  0.14  mm.  wide.  Tail  caducous, 
slender  in  length  about  equal  to  body.  Oral  sucker  0.0.S2  mm.,  ace- 
tabulum 0.087  mm.  in  diameter.  Stylet  glands  10  to  12  on  each  side. 
Intestinal  ceca  short.  Anterior  half  of  body  spinous.  A  poor  swim- 
mer. 

Found  in  sausage-shaped  sporocysts  in  liver  of  Physa  anatina 
from  Manhattan,   Kansas. 


Fig.  720.  Cercaria  brevicaeca;  a,  free  hand  drawing,  ventral  view.  Cys- 
togenous  glands  not  shown.  X  about  100.  b,  stylet,  ventral  view.  X  290, 
(.\fter  Cort.) 


206  (205,  207)     Ceca  arise  directly  from  pharynx  region,  excretory  bladder 

muscular,  crenate,  capable  of  great  distension. 

Cercaria  crenata  Faust. 

Body  length  0.25  mm.,  width  0.13  mm.  Tail  weak,  0.15  to  0.16  mm.  in  length,  0.02  to  0.03 
mm.  wide  at  base.  Body  oblong-ovate,  with  deep  pocket  at  posterior  extremity  for  reception 
of  tail.  Stylet  glands  13,  8  in  outer  series  and  5  in  inner  series,  minute,  extending  tu  mid- 
acetabular  region.  Esophagus  lacking.  Sporocysts  small  oblong-ovate.  In  hver  tissue  of 
Lymnaea  proxima  Lea  from  springs  at  Fort  Missoula,  Montana. 

207  (205,  2c6)     Ceca  undeveloped,,  excretory  bladder  bicornuate.     .    .    .      20S 

Cort  regards  these  forms  as  a  natural  group  characterized  by  development  in  elongate  sac- 
shaped  sporocysts  in  Gastropoda,  with  a  slender  tail,  not  usually  shorter  than  the  body,  with 
a  small  post-central  acetabulum,  a  stylet  30  fx  long,  with  six  or  more  stylet  glands  on  each 
side  in  front  of  acetabulum,  and  a  bicornuate  excretory  bladder.  He  considers  that  they  prob- 
ably belong  to  the  Plagiorchiinae.  Nothing  is  known  regarding  the  development  of  the 
American  species. 


208  (209)     Six  stylet  glands  on  each  side 


Cercaria  isocotylca  Cort  i()i4. 


Develops  in  sporocysts.  Tail  small,  vcr>'  extensile.  Suckers  rela- 
tively large.  Stylet  glands  just  in  front  of  ventral  sucker.  Excretor\' 
pore  dorsal,  at  base  of  tail.  Cenital  glands  indicated  by  nuclear  ma.ss 
dorsal  and  anterior  to  acetabulum,  and  a  larger  mass  dorsal  and  jx>s- 
terior,  but  connected  with  the  former  by  a  band  on  left  margin  of  ace- 
tabulum. 

From  Planorbis  Irivolvis  at  Urliana,  llliiu)is. 


Fig.  721.     Cercaria  isocotylca;   a 
side  view 


ventral 
X  -'yo. 


C.Vfl, 


X  20T.     b,  slylct,  vtiilraJ  oud 
r  Cort.) 


4l8  FRESH-WATER   BIOLOGY 

209  (208)     Twelve  stylet  glands  on  each  side.      Cercaria  polyadena  Cort  1914. 


Encysts  readily.  Tail  active,  easily  detached,  somewhat  larger  than 
in  last  species.  Oral  sucker  smaller,  stylet  glands  more  numerous.  Body 
also  larger  than  former  species.  Genital  system  marked  out  by  S-shaped 
nuclear  mass,  elongate  and  dorsal  to  acetabulum. 


Fig.  722.     Cercaria  polyadena;  a,  ventral  view.     Cystogenous  glands  not  shown. 
X  207.     b,  stylet,  ventral  view.     X  290.     (After  Cort.) 


210  (204)     Caudal  pocket  distinct,  provided  with  hooks  or  spines  that  are 

mostly  situated  in  posterolateral  sacs 211 

211  (212)     Digestive  tract  naked,  ceca  rudimentary. 

Cercaria  dendritica  Faust. 

Body  length  0.38  to  0.40  mm.,  width  0.16  to  0.17  mm.  Tail  small,  0.16  mm.  in  length, 
0.04  mm.  wide  at  base.  Body  obovate,  muscular;  cuticula  thick.  Caudal  pocket  lined  with 
spines.  Excretory  bladder  large,  muscular,  bicornuate;  tubules  dendritic.  In  long  oval  sporo- 
cysts  in  liver  of  Lymnaea  proxima  Lea,  sloughs  of  Bitter  Root  River,  Fort  Missoula,  Montana. 

212  (211)     Digestive  tract  provided  with  special  glands,  in  addition  to  stylet 

glands.     Ceca  developed 213 

213  (214)     Glands   along   entire   course   of   digestive   tract.     Three   median 

spines  on  lip  of  caudal  pocket.    .   Cercaria  glandulosa  Faust. 

Body  length  0.45  mm.,  width  0.2  mm.  Tail  length  0.3s  mm.  by  0.05  to  0.06  mm.  at  base. 
Body  oblong-ovate,  acetabulum  shghtly  behind  center  of  body,  smaller  than  oral  sucker. 
Esophagus  long,  ceca  short,  unicellular  glands  along  entire  digestive  system.  Cuticula  delicate. 
Eight  cephalic  glands.  Body  filled  with  cystogenous  glands.  In  sporocysts,  in  liver  of  Physa 
gyrina  Say,  Bitter  Root  River,  Corvallis,  Montana. 

214  (213)     Glands  in  pharynx   region   only,   spines   confined   to  pockets  of 

caudal  pocket 215 

215  (216)     Ceca  attenuate,  excretory  bladder  with  long  median  shank. 

Cercaria  diaphana  Faust. 

Body  oblong-ovate  to  ovate.  Acetabulum  median,  about  half  size  of  oral  sucker.  Pharynx 
small,  surrounded  by  great  mass  of  unicellular  glands.  CephaUc  glands  8,  anterior  to  cecal 
bifurcation.  Stylet  set  with  an  internal  spine  at  anterior  end.  Body  length  0.2  to  0.2b  mm., 
width  o.io  to  0.12  mm.  Tail  0.15  mm.  in  length  by  0.04  mm.  wide  at  base.  In  oblong 
sporocysts  in  liver  tissue  of  Lymnaea  proxima  Lea,  Bitter  Root  River,  CorvaUis,  Montana. 

216  (215)     Ceca  inflated,  excretory  bladder  bicornuate,  inflated. 

Cercaria  micropharynx  Faust. 

Body  minute,  ovate,  covered  with  fine  spines.  Acetabulum  mid-ventral,  smaller  than  oral 
sucker.  Pharynx  extremely  small,  esophagus  short,  ceca  inflated  Digestive  glands  in  pre- 
pharynx  region  only.  Body  length  0.18  mm.,  width  0.09  mm.  Tail  0.14  mm.  in  length  Dy 
0.03  mm.  at  base.  In  oval  sporocysts  with  well-developed  excretory  tracts.  Liver  of  Lymnaea 
proxima  Lea,  Rattle  Snake  Creek,  Missoula,  Montana. 

217  (201)     Tail  modified,  not  of  simple  form 218 


PARASITIC   FLATWORMS 


419 


218  (223)     Tail  provided  with  fin-like  fold,  but  of  normal  length. 

Cercariae  ornatae 


219 


219(220)     Eye  spots  present Cenaria  raconosa  FausL 

Body  length  0.29  mm.,  width  o.ii  mm.  Tail  0.22  mm.  in  length  by  0.04  mm.  wide  at  base. 
Body  ovate,  oral  sucker  small,  acetabulum  somewhat  smaller.  Esophagus  long,  ceca  short, 
e.xtending  around  acetabulum.  Excretory  tubules  multi-dendritic.  Tail  with  lateral  rulUcd 
fin-folds.  Stylet  delicate,  attenuate.  In  polygonal  sporocysts  in  liver  of  Lymnaca  proxima 
Lea,  sloughs  of  Bitter  Root  River,  Fort  Missoula,  Montana. 

220(219)     Eye  spots  lacking 221 

221  (222)     Stylet  small,  without  thickened  region. 

Cercaria  hemiloplmra  Cort  19 14. 


Body  oval,  0.38  mm.  long,  0.14  mm.  wide,  densely  covered  with 
small  spines.  Tail  about  length  of  body,  extensile  to  double  body 
length,  with  fin  half  as  wide  along  ventral  surface  of  distal  half.  (Jral 
sucker  0.065  mm.,  acetabulum  0.049  mm.  in  diameter.  Stylet  small, 
without  thickened  region. 

Produced  in  orange-colored,  elongate  and  non-branching  sporocysts, 
much  twisted  together.     In  Physa  gyrina  from  Rockford,  Illinois. 


Fig.  723.     Cercaria  hemilophura;  a,  ventral  view.      C  ystoRenous  f^lands  not 
shown.     X  80.     b,  stylet,  side  view.     X  2yo.     (.\fter  Cort.) 


222  (221)     Stylet  heavy Cercaria  platyura  Lcidy  1S90. 

Length  0.8  mm.,  body  0.4  by  0.12  mm.,  tail  0.36  by  0.06  mm.  at  base,  width  with  mem- 
branous alae  0.14  mm.  Body  ovoid,  head  rounded,  oral  sucker  large  (0.08  mm.)  with  heav-y 
stylet.  Acetabulum  0.06  mm.  Tail  nearly  as  long  as  body,  stout,  tapering,  corrugated, 
with  broad,  costate,  lateral  membrane. 

Taken  free  in  a  pool  with  Lymnaea,  at  Fort  Bridger,  Wyo. 

223  (218)     Tail  short  and  peculiarly  modified.  .    .    .     ^Microcercous  cercariae. 

Tail  short,  stumpy,  with  F>owerfulIy  developed  muscles. 
Not  a  swimming  organ,  but  used  as  a  prop  or  lever.  In 
the  Cotylocercous  cercariae  of  Dollfus  the  organ  is  still 
further  modified  into  a  type  of  sucker.  This  latter  group 
develops  in  sporocysts  and  is  mostly  marine. 

Only  species  thus  far  recorded  in  Xorth 
America. 

Cercaria  trigouura  Cort  191 4. 

Body  0.24  mm.  long,  0.06  mm.  wide.  Tail  0.05  mm. 
long  by  0.024  mm.  wide.  Oral  sucker  0.049  mm.  long  by 
0.039  Tirn-  wide.  Acetabulum  just  back  of  center  of 
body,  0.04  mm.  in  diameter.  Cuticula  covered  with  tine 
spines.  Tail  sht)rt,  blunt,  easily  detached,  triangular, 
folded  into  groove.  Just  anterior  i)n)minent  gland  ojx'n- 
jng  into  the  head  of  this  groove.  Stylet  dorsid  to  oral 
sucker.  Stylet  glands  small  but  numerous.  Elxcretory 
system    bicornuate,    thick    walled.      Free   in    tissues   of 

■    Tf,^  n        ■   .  ■  1^1  snails;    rediae   in   s;ime   host.      No  tcndenc>'  to  encyst 

Fig.  724.     Cercarta  trtqonura.la.teTa.1  =""•". 

and  ventral  views.    X  170.    Each  with  noted.  .  i,      rj#- 

stylet.     X  400.     (After  Cort.)  Found  in  Campdoma  dcctsum  from  Ilartford.  C  uon. 


420 


FRESH-WATER   BIOLOGY 


224  (200)     Anterior  end  with  fleshy  collar  and  crown  of  spines. 

Echinostome  cercariae 


225 


These  cercariae  develop  in  rediae  which  have  collar,  birth  pore,  arid  posterior  locomotor 
appendages.  They  are  characterized  by  the  conspicuous  collar  and  spines,  also  found  in  the 
adult  distome.  The  esophagus  is  long  and  the  ceca  reach  to  the  posterior  end  of  the  body. 
The  tail  is  long  and  powerful. 


225  (228)     Collar  spines  in  a  single,  if  sometimes  slightly  irregular  row. 


226 


226  (227)     Collar  spines  42,  rounded  at  both  ends;    excretory  trunks  doubly 

reflexed  in  cephahc  region Cercaria  biflexa  Faust. 

Acetabulum  in  posterior  third  of  body.  Great  number  of  cephahc  glands  in  2  series,  50  to 
60  in  each  series,  lateral  to  digestive  ceca.  Excretory  tubes  reflexed  twice  in  cephahc  region 
prehminary  to  entering  lateral  trunks.  Bladder  long,  with  median  swelling;  scaleriform  anas- 
tomosis of  excretory  tubules  in  tail.  Body  length  0.45  to  0.5  mm.,  width  0.13  to  0.15  mm.  Tail 
about  same  length  as  body,  powerful.  Encysts  within  redia.  Redia  with  "feet"  in  posterior 
third  of  body.  In  liver  tissue  of  Physa  gyrina  Say,  near  Buckhouse  Bridge,  Bitter  Root  River, 
Montana. 

227  (226)     Collar  spines  36,  acute  at  distal  end;    excretory  trunks  arising 

from  triangular  anastomosis  in  cephalic  region. 

Cercaria  trisolenata  Faust. 

Deltoid  anastomosis  of  tubules  from  3  flame  cells  in  cephalic  region,  preliminary  to  entering 
lateral  trunks.  Excretory  bladder  obtruncate.  Acetabulum  spinose  in  posterior  third  of 
body.  Readily  encysts  in  free  state,  easily  drops  tail.  Body  length  0.45  mm.,  width  o.i  mp. 
Tail  short,  about  0.2  mm.  Rediae  with  lateral  "feet"  about  one-third  distance  from  anterior 
end.  In  Hver  of  Physa  gyrina  Say  and  Planorbis  Irivolvis  Say.  Entire  length  of  Bitter  Root 
River,  Montana. 

228  (225)     Collar  spines  in  mature  cercariae  in  two  alternating  rows;    excre- 

tory trunks  reflexed  once 229 


229  (230)     Excretory  bladder  long,  attenuate;  43  equal  spines. 

Cercaria  rubra  Cort  1914' 


Cysts  large,  spherical,  thick- walled,  transparent.  Collar  has  forty-three 
equal  spines  in  two  alternating  rows;  four  spines  on  each  side  of  mid- 
ventral  line  point  in.  Encysted  above  gills  in  Canipeloma  decisum,  Hart- 
ford, Conn.  No  redia  found.  Known  only  in  encysted  stage  which  is 
really  an  Agamodistomum  and  not  a  Cercaria. 


Fig.  725. 


Cercaria  rubra  in  Agamodistomum  stage  freed  from  cyst,  ventra 
view.     X  130.     (After  Cort.) 


230  (229)     Excretory  bladder  ovoid   to  depressed  spheroid,  excretory  trunk 
reflexed  almost  entire  length 231 


PARASITIC    FLATWORMS  42 1 

231  (232)     Tail  simple,  unmodified Cercaria  trivolvis  Cort  19 14. 


Both  rediae  and  cercariae  in  Planorbis  trivolvis,  Urbana,  Illinois. 
Moves  actively  in  free  water  and  on  solid  bodies;  found  encysted  in 
same  host  with  rediae  and  cercariae.  Nuclei  of  se.x  organs  in  two 
masses,  connected  l)y  slender  thread.  Collar  carries  thirty-seven  equal 
spines  in  two  alternating  rows;  two  or  three  spines  near  mid-ventral  line 
point  inward. 


Fig.  726.      Cercaria  trivolvis,  mature,  ventral  view.      Cystogenous  glands  not 
shown.     X  65.     (After  Cort.) 


232(231)     Tail  with  lateral  fin-folds Cercaria  rejlcxa  Cori. 

Though  without  oral  spines  in  the  stage  originally  discovered  and  described  this  species 
probably  belongs  here  among  Echinostomid  cercariae. 
For  description  see  197  (198)  in  this  key. 

233  (194)     Tail  simple  but  heavy,  when  contracted  exceeding  in  breadth  the 

body Rhopalocercous  cercariae. 

Listed  from  North  America. 

Cercaria  {Rhopalocerca)  tardigrada  Leidy  1858. 

Reported  by  Leidy  from  Anodonta  species.  The  true  R.  tardigrada  is  Dist.  diiplicatum  v. 
Baer  renamed  and  is  the  larva  of  Phyllodistomum  folium  according  to  Liihe.  Perhaps  Leidy's 
form  is  the  larva  of  some  American  species  in  that  genus. 

No  North  American  cercariae  have  yet  been  well  described  which  fall  into  this  subdivision 
though  both  of  the  species  listed  by  Luhe  for  Central  Europe  belong  to  genera,  AUocrcadium 
and  Phyllodistomum,  which  are  reported  here.  These  are  not  closely  related  genera  and  the 
group  of  cercariae  does  not  appear  to  be  a  natural  one  as  at  present  constituted. 

Note  that  Odhner  believes  that  the  larva  of  Phyllodistomum  folium  occurs  in  bunches,  as 
stated  in  189  (186)  of  this  key. 

234  (192)     Tail  well  developed  and  highly  modified 235 

235  (240)     Base  of  tail  envelops  body  of  young  distome. 

Cystocercous  cercariae  .    .     236 

The  anterior  end  of  the  tail  is  expanded  in  the  form  of  a  bladder  into  which  is  folded  the 
body  of  the  young  distome  that  lies  thus  in  a  sac  or  chamber. 

236  (237)     Chamber  globular,  small.     Tail  simple,  slender.     Europciin  type. 

Cercaria  macroccrca  Filippi  1S54. 

These  forms  of  which  several  have  been  described  in  Europe  are  the  young  forms  of  (Tor.co- 
derinae  (no  in  this  key).  The  adults  have  been  reported  from  this  country,  but  this  l.irval 
form  is  yet  to  be  identified  here. 

237  (236)     Chamber   large;     round.     Tail    fiat,   forked,    anchor-shaped   with 

broad  terminal  flukes;  powerful  swmimmg  organ      .    .      j^*^ 

These  move  by  rapid  alternate  lateral  jerks  of  the  anchor  tlukes.     .\s  the  distome  is  thus 

pulled  along  by  the  tail,  the  usual  orientation  of  a  cercaria  is  r.-versed.     The  adults  arc  unknown. 


422 


FRESH-WATER   BIOLOGY 


238  (239)     Distome  fills  three-fifths  of  stem  of  anchor. 

Cercaria  wrightii  Ward  1916. 

Length  0.75  mm.,  width  0.133  mm.  Flukes  measure  0.53  by  o.i  mm.  Young  distome 
0.4s  by  0.1  mm.  Genital  rudiment  forms  rod-like  mass  partly  preacetabular  and  partly 
postacetabular. 

Originally  described  as  a  free-swimming  sporocyst  by  R.  R.  Wright,  it  was  shown  by  obser- 
vations of  Braun  on  the  European  C.  miriabilis  to  be  a  highly  modified  cercaria.  Found 
in  an  aquarium  at  Toronto. 

239  (238)     Distome  fills  less  than  half  of  stem  of  anchor, 

Cercaria  anchor oides  Ward  1916. 


Length  2  mm.,  width  0.24  to  0.34  mm.;  flukes 
curved,  tips  0.84  mm.  apart.  Young  distome  0.64 
by  0.288  mm.  Germ  glands  already  laid  down  in 
middle  third  of  body.  Ovary  postacetabular,  pre- 
testicular;  testes  obHque.  Genital  pore  preacetabu- 
lar.    Adult  unknown. 


Fig.  727.     Cercaria  anchoroides.     Young  distome  just  set 
free.     X  73'    o,  Cercaria  complete.     X  27.     (Original.)^ 


240  (235)     Tail  of  cercaria  does  not  envelop  young  distome,  but  is  modified 

in  form 241 

241  (246)     Modification  consists  in  forked  end. 

Furcocercous  cercariae  .    .     242 

The  long  slender  tail  is  split  in  its  distal  region  and  terminates  in  two  slender  branches, 
one-third  to  one-half  the  length  of  the  entire  structure.  An  unnatural  group  as  this  modi- 
fication has  apparently  arisen  more  than  once  in  different  types. 

242  (243)     Cephalic  glands  with  short  ducts,  never  reaching  acetabulum. 

Cercaria  douthitti  Cort  1914. 


\ 


Develops  in  sporocysts.  Tail  bifid;  nearly  twice  as  long  as  body.  Oral 
sucker  very  large.  Two  pigment  eye-spots  with  lenses.  Eight  large  cephalic 
glands  in  posterior  region  with  ducts  opening  into  or  through  oral  suckers; 
no  stylet  found.  Single  genital  nuclear  mass  at  posterior  extremity  of  body. 
Found  in  Lymnaea  reflexa  from  Chicago,  111. 


Fig.  728.     Cercaria  douthitti,  ventral  view.     X  98.     (After  Cort.) 


t 


PARASITIC    FLATWORMS 


423 


243  (242)     Cephalic  glands  open  into  ducts  posterior  to  acetabulum.  .    .     244 

244  (245)     Cephalic  region  crowned  with  spines;   two  eye-spots  present. 

Cercaria  gracillima  Faust. 

Body  length  0.13  to  0.16  mm.,  width  0.02  to  0.03  mm.  CcphaUc  glands  in  ixjstfrior  third 
of  body.  A  pair  of  flame  cells  (in  pockets)  in  posterior  third  of  excretory  trunks.  Eyc-sp«jls 
lying  directly  lateral  to  cephalic  ganglia,  unpigmented.  (Jcnital  rudiment  extends  anterior 
to  acetabulum.  Tail  about  twice  body  length,  furcae  of  same  length  as  undivided  ix^rtion.  In 
long  attenuated  sporocysts  in  Hver  of  Physa  gyrina  Say,  near  Buckhouse  Bridge,  Bitter  Root 
River,  Montana. 

245  (244)     Cephalic   region  crowned   with  two   small   tubercules;   eye-spots 

lacking Cercaria  tuberistoma  Faust. 

Body  length  0.2  mm.,  width  0.05  to  0.06  mm.  Tail  about  0.32  mm.,  furcae  equal  in  length  to 
undivided  portion.  Cephalic  glands  small;  excretory  system  simple,  most  anterior  tubules  of 
tail  refiexed,  bladder  muscular.  In  sporocysts,  either  dumbbell  shaped  or  attached  at  one 
end.  No  birth  pore.  Cercariae  escape  by  splitting  wall  of  sporocysts.  In  liver  tissue  of 
Physa  gyrina  Say,  Bitter  Root  River,  Corvallis,  Montana. 

246  (241)     Modification  consists  of  lateral  spines  in  rows. 

Setiferous  cercariae. 
None  yet  recorded  from  North  America.     A  small  group,  mostly  marine. 

247  (191)     Tail  apparently  entirely  wanting 24S 

The  tail  may  be  small  and  easily  lost  or  actually  not  developed. 


248  (249)     Develop  in  rediae  or  unbranched  sporocysts. 


Cercariacum. 


The  young  distomes  possess  no  cyst  or  protective  mem- 
brane. Found  not  infrequently  in  our  fresh-water  mussels. 
Species  not  described.  Adults  unknown.  One  of  the  Euro- 
pean species  is  thought  to  be  the  larva  of  Asymphylodora. 

Cercariacum  hclicis  (Leidy)  1847. 

Total  length  0.85  mm.;  breadth  0.6  mm.,  active  and  vcr>' 
extensive.  Body  white,  oval,  with  oval  tail.  Oral  sucker 
marked  by  radial  Hues;  acetabulum  central,  equal  in  size  to 
oral  sucker,  0.15  mm.  in  diameter.  Pharynx  oval.  Intestine 
large,  sinuous,  extending  to  end  of  body.  Excretory  bladder 
small;   lateral  vessels  double.     Oenital  pore  ix)stacetal)ular. 

In  pericardial  cavity  of  Helix  allcrtiala  and  //.  albolabris. 
The  "first"  and  "third"  stages  of  Leidy's  later  account  arc 
clearly  not  the  same  species  as  the  "second  stage"  to  which 
the  name  Disloma  hclicis  was  originally  given. 

Called  later  D.  vagans  al.st)  by  Leidy.  Die.sing  makes  it 
Cercariacum  vagans.  Possibly  a  cercaria  which  has  thrown 
off  its  tail  but  has  not  encysted. 


Fig.  729.      Cercariaeum  Ittlicis.     Second  stage;   hiRhly  magnific<I. 
(.\fter  Lciiiy.) 


249  (248)     Develop  in  branching  sporocysts Lcucochloriiiium 

The  remarkable  species  is  known  in  Europe  in  the  adult  ft)rm  as  a  fxirasite  of  sin^ng  birds 
and  in  the  sporocyst  stage  in  certain  snails,  Succinea.  Sec  157  in  this  key.  It  has  no  free- 
living  period. 

250  (184)     Oral  sucker  rudimentary,  much  smaller  than  acetal)ulum.     Geni- 

tal atrium  modified  into  sucking  organ. 

I loJostome  cercariae   .    .    251 

Genital  opening  posterior,  ventral  to  excretory  pore. 


424  FRESH-WATER    BIOLOGY 

251  (252)     Anterior  part  of  body  hemispherical  to  cup-shaped;   two  lateral 

sucking  discs  also  present.   .    .   Cercaria  flabelliformis  Faust. 

Typical  tetracotyle  form.  Body  length  0.48  to  0.56  mm.,  width  o.44_mm.  Animal  slipper- 
shaped,  with  two  posterior  and  two  lateral  lappets  around  sucking  discs.  Anterior  part  of 
excretory  system  fan-shaped.  In  rediae  or  encysted  in  tissues  in  liver  of  Physa  gyrina  Say, 
Bitter  Root  River,  Corvallis,  Montana. 

Compare  167  (168)  in  this  key. 

252  (251)     Anterior  part  of  body  lamellate  or  only  sUghtly  patelliform. 

Cercaria  ptychocheilus  Faust. 

Hemistomum  larva.  Body  length  0.48  to  0.63  mm.,  width  0.17  to  0.37  mm.  Posterior 
portion  abbreviated.  Atrial  chamber  posteriad,  well-developed.  Varying  number  of  mu- 
cous glands,  situated  in  posterior  part  lateral  to  genital  atrium,  empty  into  the  latter.  En- 
cysted within  semitransparent  ovoid  membrane,  with  discoid  attachment  to  mesentery  of 
Ptychocheilus  oregonensis  Richardson,  Bitter  Root  River,  Stevensville  and  Carlton,  Montana. 

The  encysted  form  described  by  Faust  is  really  a  Diplostomulum,  i.  e.,  the  stage  succeeding 
the  true  Cercaria.     Compare  168  (167)  in  this  key. 


Cestoda 

The  cestode  or  tapeworm  is  as  the  name  suggests  more  or  less 
like  a  band  or  ribbon,  and  in  the  majority  of  cases  the  band  is 
subdivided  by  cross-markings  into  a  series  of  Hnks  or  proglottids. 
In  a  few  primitive  tapeworms  the  body  consists  of  but  a  single 
link  and  the  general  appearance  is  so  similar  to  that  of  the  fluke 
as  to  make  distinction  difficult.  In  some  other  cases,  especially  of 
fish  tapeworms,  the  ribbon-like  body  is  not  subdivided  by  ex- 
ternal cross-markings,  but  the  internal  structure  shows  the  poten- 
tial presence  of  proglottids,  for  the  organs  are  multiplied  suc- 
cessively in  the  undivided  body  as  they  are  in  the  segmented  body 
of  the  ordinary  tapeworm.  Most  tapeworms  are  distinctly  flat- 
tened so  that  one  may  speak  of  surfaces  and  margins.  A  few 
species  are,  however,  so  nearly  circular  in  cross  section  that  it  is 
difficult  to  use  such  terms.  Abnormal  individuals  of  the  flat- 
tened species  have  been  described  which  are  three-cornered  or 
prismatic  in  cross  section;  these  represent  partially  fused  or  par- 
tially spHt  chains. 

One  can  usually  recognize  two  or  three  fairly  distinct  regions  in 
the  ordinary  tapeworm:  the  head  or  scolex,  the  neck,  and  the  chain 
or  strobila.  The  head  is  more  or  less  enlarged,  globular  or  oval, 
and  not  infrequently  provided  with  an  apical  extension  designated 
a  rostellum,  which  in  some  forms  is  held  withdrawn  in  a  pocket 
under  most  circumstances.  The  head  is  commonly  suppHed  with 
suckers  and  sometimes  hooks  also  by  which  it  attaches  itself  to  the 


PARASITIC    FLATWORMS 


425 


tissue  of  the  host.  In  some  tapeworms  the  head  carries  long  suck- 
ing grooves  or  bothria,  and  in  others  round  cup-shaped  suckers  or 
acetabula.  More  compUcated  hold-fast  organs  are  developed  on 
the  scolex  in  certain  groups  of  cestodes  parasitic  in  marine  hosts. 
A  slight  constriction  behind  the  head  has  been  given  the  name  of 
^^neck";  many  cestodes  have  no  neck.  The  body  usually  in- 
creases in  caliber  from  the  head  toward  the  opposite  end.  The 
partition  lines  of  proglottids  are  at  first  very  indistinct,  and  be- 
come more  marked  as  one  goes  backward  along  the  chain.  The 
form  of  the  proglottids  also  changes  from  the  scolex  toward  the 
other  end  of  the  worm.  Much  has  been  made  of  these  and  other 
minor   details    of    external 

appearance  in  the  descrip-  Hi  exv  9J  <^ef  tt  \\  ^{\^ 
tions  of  cestodes.  They 
are  not  adequate  for  the 
determination  of  many 
species  and  moreover  are 
not  of  fundamental  signifi- 
cance. Unfortunately  very 
few  cestodes  are  transpar- 
ent and  it  is  not  easy  to 
study  the  internal  struct- 
ure, since  the  specimen 
must  first  be  subjected  to 
a  time-consuming  technic. 
Methods  for  the  prepara- 
tion of  cestode  material 
were  outhned  briefly  in  the 
general  section  of  this  chap- 
ter (page  368).  .  Specimens 
must  be  kept  flat  and  ex- 
tended or  they  are  difficult 
to  study  and  interpret  cor- 
rectly. 

Each  proglottid  may  be 
considered  a.^  a  unit  of  structure  as  it  contains  a  complete  set  of 
reproductive  organs  (Fig.  730).     With  rare  exceptions  tapeworms 


Fig.  730.  Ophiotaenia  filaroidcs.  Mature  provluttid,  un- 
flattened,  showing  relationships  of  orRans.  Abbreviations 
used  in  thi^  and  following  figures:  ci,  cirrus;  cip,  cirrus-pouch; 
dej,  vas  deferens;  dj.  ductus  ejaculatorius;  r/,  vasa  cffcrentia; 
ei!>,  excretory  vi-ssel.  ventral;  n/,  lateral  ncr\c;  <><)<■,  (HKapt; 
OT,  ovary;  m/,  uterus;  ij,  vagina;  ri,  vitellaria.  X  5^-  (Af- 
ter La  Ruf.) 


426  FRESH-WATER   BIOLOGY 

exhibit  the  same  condition  of  hermaphroditism  that  was  de- 
scribed for  the  flukes,  since  all  organs  of  both  sexes  are  repre- 
sented in  a  single  proglottid.  The  reproductive  organs  of  one 
proglottid  have  usually  no  connection  with  those  preceding  or  fol- 
lowing; other  organs  are  continuous  throughout  the  chain.  One 
may  readily  observe  at  the  side  of  the  proglottid  the  main  longi- 
tudinal nerve  trunks  which  connect  with  a  complicated  series  of 
enlargements  or  ganglia  in  the  scolex.  These  main  nerve  trunks 
are  joined  by  cross-connectives  in  each  proglottid.  Near  them  and 
parallel  to  them  are  the  main  canals  of  the  excretory  system,  and 
these  also  are  joined  by  transverse  vessels.  A  network  of  finer 
tubes  terminating  in  flame  cells  is  present  in  each  proglottid  and 
empties  into  the  main  vessels  just  described.  The  longitudinal 
muscles  of  the  body  are  sometimes  continuous  throughout  the 
chain  and  sometimes  divided  at  the  partitions. 

No  trace  of  an  aHmentary  system  has  been  found  at  any  time 
in  the  entire  life  history  of  the  cestode. 

As  one  proceeds  backward  along  the  chain  one  can  observe  the 
gradual  development  of  the  reproductive  organs.  These  appear 
first  as  faint  lines  or  bands  in  the  tissue,  outlining  the  positions  of 
the  main  organs;  they  grow  more  definite  until  at  sexual  maturity 
a  complete  set  of  organs  of  both  sexes  can  be  demonstrated  (Fig. 
730).  The  organs  are  very  similar  in  character  and  interrelation 
to  those  of  the  trematodes.  As  one  passes  further  along  the  chain 
other  changes  take  place,  primarily  the  gradual  accumulation  of 
eggs  in  the  uterus  and  the  coincident  gradual  shrinkage  of  other 
reproductive  organs  until  the  latter  may  ultimately  disappear  save 
for  insignificant  vestiges.  Two  different  plans  are  observable 
with  regard  to  the  production  of  eggs.  The  latter  may  be  held  for 
a  time  in  a  uterine  cavity  and  then  discharged  through  a  pore,  or 
they  may  accumulate  indefinitely  in  a  blind  uterine  sac  until  they 
come  to  occupy  nearly  the  entire  volume  of  the  proglottid.  Where 
the  latter  condition  prevails,  the  last  proglottids  of  the  chain  have 
been  reduced  to  mere  egg  cases  that  are  cut  off  periodically,  either 
singly  or  in  groups,  and  carry  to  the  outer  world  masses  of  ova  for 
the  dissemination  of  the  species. 

Some  cestodes  have  a  free-Hving  stage  which  hatches  from  the 


PARASITIC   FLATWORMS 


427 


egg  in  the  form  of  a  spherical  cihated  larva  (Fig.  731)  that  for  a 
short  time  carries  on  an  existence  in  the  outer  world.  This  larva 
occurs  among  the  fish  tapeworms.  The  ex- 
ternal layer  of  large  ciliated  cells  may  be 
regarded  as  an  embryonic  membrane  within 
which  is  a  narrow  fluid  filled  chamber  contain- 
ing a  smaller  spherica  mass  that  in  fact  is  the 
true  cestode  larva,  known  as  an  onchosphere. 


^■ 


%. 


w 


This  larva  derives  its  name  from  the  presence  '^^^////jiil&v. 


of  three  pairs  of  long  slender  hooks  arranged      fig.  731.    mphyiiohoihri. 

,   .  ,  ,  1^1,  ""*  latum.     Free  swimming 

at  equal  intervals  around  one  pole  of  the  sphere   embryo.  MagniSed.  (After 

■*  ,  ,  ^  ^  Schauinsland.) 

and  provided  with  special  muscles  that  serve 

to  push  the  hooks  out  and  then  away  from  the  center  so  as  to 

open  up  tissue  and  force  the  larva  through  it. 

In  most  cestodes  the  onchosphere,  surrounded  by  two  or  more 
membranes  characteristic  in  form  in  particular  groups,  is  retained 
within  the  egg-shell  until  the  mass  is  brought  passively  into  the 
alimentary  canal  of  a  suitable  host.  Here  the  onchosphere  is  set 
free  by  digestion  and  bores  its  way  out  of  the  alimentary  canal 
into  the  body  cavity  or  vascular  spaces.  It  may  remain  there 
free  and  undergo  further  development,  or  by  active  or  passive 
migration  reach  a  point  where  it  encysts  and  remains  fixed  during 
the  period  of  growth.  During  this  period  it  develops  to  one  of 
the  larval  forms  of  the  group.  These  forms  difi'er  in  different 
subdivisions  of  the  class  Cestoda.  Among  the  lower  forms  they 
are  small,  oval  or  elongated,  spindle-shaped,  solid-bodied  larvae 
known  as  plerocercoids,  and  in  the  highest  groups  of  cestodes 
they  become  large  fluid-filled  vesicles  known  as  cysticerci  or  blad- 
der-worms.    Other  types  occur  among  other  kinds  of  cestodes. 

These  larval  forms  almost  without  exception  develop  in  an  inter- 
mediate host.  In  some  cases  the  larva  wanders  out  later  and 
achieves  actively  the  infection  of  the  adult  or  final  host,  but  in 
most  instances  it  is  held  in  the  body  of  the  intermediate  host 
until  the  latter  is  eaten.  Thereupon  it  is  set  free  by  digestion, 
migrates  to  the  organ  which  is  its  normal  seat,  and  enters  upon 
a  period  of  growth  that  brings  it  to  the  fully  matured  adult 
form. 


428  FRESH-WATER   BIOLOGY 

Certain  important  changes  have  occurred  during  this  larval 
growth  period.  These  are  most  marked  in  the  bladder- worm  ces- 
todes.  The  fully  developed  cysticercus  shows  a  completely  formed 
scolex  that  corresponds  in  detail  with  the  scolex  of  the  adult  ces- 
tode  save  that  it  is  reversed  and  lies  turned  into  the  internal  cavity 
of  the  bladder.  When  the  bladder- worm  reaches  its  final  location 
the  head  is  everted  and  appears  with  the  armament  of  suckers  and 
hooks  that  characterizes  the  adult.  This  scolex  attaches  itself  in 
the  region  appropriate  for  the  adult  and  the  bladder  remnant  is 
lost  by  digestion  while  the  neck  continues  to  grow  in  length  until 
it  has  produced  a  full-sized  adult  worm.  The  formation  of  pro- 
glottids  and  the  growth  within  them  of  the  reproductive  organs 
proceeds  slowly  as  the  worm  lengthens,  the  oldest  proglottids 
being  found  regularly  at  the  end  furthest  from  the  scolex. 

The  Kfe  histories  of  North  American  cestodes  are  entirely  un- 
known and  can  only  be  inferred  to  be  similar  to  related  species 
that  have  been  studied  in  the  Old  World.  The  evidence  fur- 
nished by  the  latter  indicates  clearly  that  tapeworms  are  not 
bound  up  with  an  aquatic  existence  in  some  stage  as  are  the  flukes. 
Certain  cestodes  have  aquatic  larvae  and  others  bladder-worm 
stages  in  aquatic  invertebrates,  or  vertebrates,  but  many  of  the 
species  parasitic  in  birds  and  mammals  pass  the  larval  period  in 
terrestrial  hosts  (insects,  land  snails,  birds,  mammals)  and  have 
no  relation  to  the  aquatic  fauna  at  any  time.  Such  forms  do  not 
belong  rightly  in  such  a  synopsis  as  this;  but  the  data  available 
are  insufficient  to  mark  out  clearly  which  forms  belong  to  the  fresh- 
water fauna  during  some  phase  of  their  existence  and  which  are 
entirely  unconnected  with  it. 

Cestodes  are  found  as  parasites  in  all  types  of  fresh- water  verte- 
brates. The  adults  occur  most  frequently  in  the  alimentary  canal 
or  pyloric  ceca.  Certain  kinds,  chiefly  larval  forms,  are  found  in 
the  body  cavity  and  the  encysted  stages,  the  bladder-worms,  may 
be  encountered  in  almost  any  tissue,  even  in  the  brain;  yet  they 
are  most  frequent  in  connective  tissue  and  seem  to  find  the  liver  a 
preferential  location.  Usually  only  a  few  cestodes  are  found  in 
an  individual  host,  but  they  may  occur  in  such  numbers  that  the 
cavity  of  the  ahmentary  canal  is  stuffed  full  and  the  wall  of  the  body 


PARASITIC    FLATWORMS  429 

is  markedly  distended.  The  distribution  of  various  species  is  prob- 
ably nearly  concurrent  with  that  of  the  particular  hosts. 

North  American  cestodes  are  very  imperfectly  known  and  the 
large  part  of  the  data  available  concerns  species  parasitic  in  ])ir(ls 
and  mammals.  Because  of  the  lack  of  defmite  knowledge  it  has 
been  necessary  to  decide  upon  somewhat  artificial  limits,  and  the 
synopsis  has  been  made  to  include  all  cestodes  reported  in  North 
America  from  fresh-water  hosts  and  all  likely  to  have  develop- 
mental stages  in  fresh-water  hosts  even  though  such  stages  have 
not  yet  been  identified  on  this  continent.  Among  the  various 
hosts  from  which  tapeworms  are  reported  the  water  birds  are  most 
difficult  to  group  correctly.  Many  of  them  visit  both  fresh  and 
salt-water  bodies,  and  most  of  them  feed  at  times  and  places  on 
terrestrial  plants  and  insects  either  intentionally  or  incidentally. 
Consequently,  the  source  of  a  given  infection  is  difficult  to  deter- 
mine and  some  errors  have  no  doubt  been  made  in  these  cases; 
yet,  thanks  to  Ransom's  careful  and  extensive  work,  avian  ces- 
todes are  better  known  than  those  from  any  other  host  group  in 
North  America. 

The  data  on  North  American  cestodes  are  not  only  scanty  but 
also  so  indefinite  as  to  be  of  Httle  value  in  the  attempt  to  prepare 
a  systematic  outline  of  the  group.  Early  references  are  to  "ces- 
todes" or  ''Taenia,"  and  even  in  later  years  the  same  habit  has 
prevailed.  Most  existing  records  of  the  occurrence  of  tapeworms 
in  aquatic  hosts  cannot  be  referred  to  known  genera.  For  these 
reasons  the  appended  synopsis  must  be  presented  with  an  apology. 
Among  the  Proteocephalidae  I  have  been  able  to  depend  on  the 
work  of  La  Rue  and  for  bird  cestodes  I  have  made  free  use  of  Ran- 
som's monograph.  Outside  of  these  groups  there  is  little  definite 
knowledge  of  the  North  American  forms. 

KEY  TO   NORTH   AMERICAN    FRESH-WATER   CESTODA 

1  (122)     Adult  worms;  sex  organs  developed 2 

2  (7)     Body  simple,  not  divided  into  joints  or  proglottids.     A  single  set  of 

genital  organs Subclass  Cestodaria   .    .     3 

The  few  forms  included  here  are  often  designated  the  monozootii-  cestodes.  and  sometimes 
are  regarded  as  a  separate  class  intermediate  in  position  between  Trematoiles  and  Cestinlcs. 
In  external  appearance  they  resemble  the  flukes  but  are  readily  distinguished  from  them  by 
the  entire  absence  of  an  alimentary  canal.  The  internal  structure  is  much  like  that  of  tape- 
worms but  the  sexual  organs  are  never  duplicated. 


430  FRESH-WATER    BIOLOGY 

3  (4)     Anterior  end  not  peculiarly  modified.     No  suckers,  hooks,  or  special- 

ized scolex  region Amphilina  Wagner  1858. 

Large,  oval,  flattened  forms,  parasitic  in  body  cavity  of  fishes.  Anterior  end  usually  notched, 
but  occasionally  extended  in  the  form  of  a  small  papilla  bearing  the  pores  of  a  group  of  uni- 
cellular glands.  Male  genital  pore  at  posterior  end.  No  cirrus  sac  present.  Female  pore 
slightly  anterior  to  male  pore,  separate  from  it.  Uterus  long,  uterine  pore  at  anterior  end. 
Embryo  with  circle  of  ien  hooks  at  one  pole. 

Not  yet  reported  from  North  America  but  present. 

4  (3)     Anterior  end  with  unarmed,  poorly  developed  adhesive  organ,  imper- 

fectly set  off  as  scolex  from  rest  of  body. 

Family  Caryophyllaeidae  Claus  1885   .    .     5 
Body  elongate,  flattened,  with  nearly  parallel  sides  and  primitive  scolex.     Neck  may  be 
present  or  wanting,  as  also  a  caudal  appendix.     All  genital  pores  ventral,  median,  near  poste- 
rior end;  cirrus  anterior;  uterus  and  vagina  open  together  into  a  genital  atrium. 

5  (6)     Caudal  appendix  present  in  adult.     Two  distinct  sucking  grooves  on 

rudimentary  scolex Archigetes  Leuckart  1878. 

Sexually  mature  in  oligochaetes.  A  form  which  undoubtedly  belongs  here  has  been  described 
to  me  as  found  in  native  earthworms.  It  has  not  been  recorded  in  the  literature.  The  species 
known  are  2  to  6  mm.  long  and  parasitic  in  the  body  cavity  of  Tubificidae. 

6  (5)     No  sucking  grooves  present.     Caudal  appendix  lacking  in  adult  though 

present  in  larval  form.  .     Caryophyllaeus  0.  F.  Miiller  1787. 

Expanded  anterior  end  very  mobile,  irregularly  folded  but  without  definite  sucking  grooves. 
Intestinal  parasites  of  Cyprinid  fishes.     Larvae  parasitic  in  body  cavity  of  Tubificidae. 

7  (2)     Body  multiplex,  usually  divided  externally  into  joints  or  proglottids; 

always  containing  successive  sets  of  reproductive  organs 
generally  corresponding  to  such  subdivisions  even  in  cases 
where  external  proglottid  markings  are  lacking. 

Subclass  Cestoda  s.  str.    .    .     8 

Elongate,  ribbon-like  forms  in  which  the  reproductive  organs  are  serially  duplicated,  each 

set  constituting  a  reproductive  unit,  usually  though  not  always  set  off  from  adjacent  units  by 

internal  septa  and  external  boundaries.     These  forms  are  often  spoken  of  as  the  true  tapeworms, 

or  polyzootic  cestodes. 

8  (29,  30)     Scolex  with  a  single  terminal  or  with  two  opposite  sucking  organs, 

never  with  four  suckers  or  accessory  proboscides. 

Order  Pseudophyllidea  .  .     9 

Scolex  rarely  armed  with  hooks,  never  provided  with  rostellum,  or  extrusile  proboscides. 
The  two  sucking  grooves  sometimes  combined  by  complicated  growth  of  their  margins  into  a. 
funnel-shaped  or  tubular  organ  which  may  be  united  with  that  of  the  opposite  side  to  a  termi- 
nal sucker  of  peculiar  form.  External  jointing  is  rarely  lacking,  but  often  indistinct  in  certain 
regions  at  least.  Uterine  pore  present,  on  the  surface  of  the  proglottid.  Uterus  in  the  form  of 
rosette-shaped  coils  or  of  a  large  sacculate  uterine  cavity. 

Characteritic  fish  parasites  in  one  or  more  stages  of  the  life  history. 

Liihe  places  the  Caryophyllaeidae  (see  above),  as  the  first  family  under  this  order,  grouping 
them  as  monozootic  Pseudophyllidea  in  contrast  with  all  other  famiUes  as  polyzootic.  For 
practical  reasons  they  are  treated  here  under  the  Cestodaria. 

9  (28)     Adult  forms  with  developed  reproductive  organs 10 

The  larval  forms  are  sometimes  hard  to  distinguish  from  adults.    Consult  also  28(9). 

10  (13)     Eggs  thin-shelled,  without  Hd.     Uterine  pore  ventral;    cirrus  and 

vagina  open  dorsal  and  posterior  to  uterine  pore,  or  margi- 
nal. .  .  .  Family  Ptychobothriidae  Liihe  1902  .  .  11 
Scolex  with  two  separate  bothria,  rarely  replaced  by  a  pseudoscolex.  No  neck;  external 
segmentation  always  present  but  incomplete  or  obscured  by  secondary  folds  in  many  cases. 
Reproductive  organs  single  in  each  proglottid.  Cirrus  and  vaginal  pores  posterior  to  uterine 
pore,  marginal  or  median  and  then  on  opposite  surface  from  uterine  pore.  Ovary  and  shell 
gland  median;   testes  in  two  lateral  fields.     Uterus  in  form  of  a  single  spacious  cavity,  never 


PARASITIC    FLATWORMS 


431 


of  a  rosette.     Eggs  tliin-shelled,  without  lid.     Embryonal  development  in  uterus;    all  eggs  of 
an  entire  worm  may  be  in  many  cases  at  the  same  stage  of  development,  at  a  given  season. 
Liihe  makes  two  subfamilies,  Ptychobothriinae  and  Amphicotylinae. 

11  (12)     Genital  pore  on  surface  of  proglottid. 

Bothriocephalus  Rudolphi  1808. 

Scolex  distinctly  elongated,  bothria  not  well  developed.  External  segmentation  inc(<mplete 
between  successive  proglottids;  serrate  marginal  incisions  distinct  but  markings  on  surface  of 
proglottids  often  imperfect  or  wanting.  VitcUaria  in  cortical  layer,  continuous  from  pro- 
glottid to  proglottid,  as  are  also  testes.  No  seminal  receptacle.  Beginning  of  uterus  a  con- 
voluted canal  (uterine  duct)  which  opens  into  spherical  uterine  cavity.  Uterine  pore  median, 
ventral;  orifice  of  cirrus  and  vagina  median,  dorsal. 

Many  entries  under  this  name  really  belong  in  other  genera  of  the  family.  A  revision  of 
the  group  is  necessary  before  one  can  say  which  are  true  species  of  this  genus. 

12  (11)     Genital  pore  at  margin  of  proglottid. 

Ahothrium  van  Beneden  187 1. 

Scolex  not  elongate,  with  two  bothria  powerful  but  not  deep.  Segmentation  uncertain 
among  older  proglottids  because  of  surface  wrinkles;  even  oldest  proglottids  much  broader 
than  long.  Nerve  trunks  near  margin,  dorsal  to  cirrus  and  vagina.  Testes  exclusively  be- 
tween nerve  cords  in  two  lateral  fields.  Vitellaria  irregular,  also  in  two  broad  lateral  fields, 
mostly  between  longitudinal  muscle  bundles,  "separated  at  proglottid  limits.  Ovary 
reniform,  ventral,  median.  Shell  gland  dorsal  to  ovarj'.  Uterine  sac  in  ripe  proglottids 
filling  almost  entire  medullary  region.  Uterine  pores  ventral,  in  median  longitudinal  furrow 
on  strobila. 

Representative  North  American  species. 

Ahothrium  crassiim  (Bloch)  1779. 

Reported  from  salmon  in  Lake  Sebago,  Maine;   not  uncommon  in  the  Great  Lakes  trout. 

13  (10)     Orifice  of  cirrus  and  vagina  on  same  surface  as  uterine  pore  and  an- 

terior to  latter  or  marginal.     Eggs  thick-shelled,  with  hd. 

Family  Diphyllobothriidae  Luhc  1910  .    .     14 

Scolex  and  sucking  organs  variable  in  form,  or  replaced  by  pseudoscolex.  Segmentation 
usually  distinct.  Receptaculum  seminis  sharply  set  oflE  from  vagina  near  inner  end.  Uterus 
long,  convoluted  tube,  in  form  of  central  rosette;  without  uterine  sac  except  in  Uaploboth- 

riuni.     Eggs  thick-shelled  with  lid. 

14  (27)     Genital  pore  on  surface  of  proglottid 15 

15  (24)     All  genital  pores  exclusively  on  one  and  the  same  surface  of  the 

strobila 16 

16  (19)     Scolex  very  short,  not  set  off  from  the  rest  of  the  worm. 

Subfamily  Ligulinae  Monticelli  and  Crety  1891     .    .     17 

Scolex  roughly  triangular,  more  or  less  drawn  out  to  a  point  with  contraction  of  worm. 
Bothria  median,  small,  weak.  Genital  organs  in  adult  fully  develojx^d  just  behind  scolex 
Testes  form  dorsal  layer  in  lateral  fields  of  medullary  ixin luhyme.  Volk  follicles  in  lateral 
part  of  cortical  area.     Ovary  median,  ventral;    shell  gland  median.  dt)rsal.        .       ,  ,,     . 

Adult  in  intestine  of  water  birds;  larva  in  body  cavity  of  tcleosts,  attammg  full  size  and 
forming  advanced  rudiments  of  sexual  organs,  found  occasionally  in  water,  having  been  set 
free  by  rupture  of  abdominal  wall  of  intermediate  host. 

17  (18)     External  evidences  of  proglottid  formation  Hmitcd  to  anterior  end  or 

entirely  lacking I/i,w</ci  Bloch  1782. 

When  fully  grown  jointed  only  at  anterior  end,  but  the  divisions  do  not  agrcx;  with  the  in- 
ternal segmentation  of  reproductive  organs.  Bothria  poorly  developed.  Lan-ae  without 
segmentation  and  without  bothria,  five  chiefiy  in  Cyprinids.  Adults  in  water  birds;  stay  m 
definitive  host  only  brief.  ,  „         .    .  n     .  •» 

Several  species  have  been  reported  and  described  by  various  authors,  all  too  bncfly  to  ponnit 
of  posidve  identification.  The  parasites  come  from  chub,  sucker,  and  trout;  .New  \ork, 
Pennsylvania,  Maryland,  Yellowstone  Park,  Arizona. 


432 


FRESH-WATER   BIOLOGY 


i8  (17)     Proglottid  formation   evident   externally   throughout   entire   worm, 
even  in  larval  condition.  .    .      Schistocephalus  Creplin  1829. 

Apex-  of  scolex  pitted,  retractile.  Bothria  poorly  developed.  Segmentation  complete. 
Suckers  and  proglottids  visible  in  larva.  Adults  in  water  birds;  larvae  in  abdomen  of  Gaste- 
rosteus. 

At  least  one  adult  and  one  larva  are  found  in  North  America.  No  records  have  been 
published. 

19  (16)     Scolex    more    or    less    elongate,    distinctly    set    off    from    rest    of 

worm 20 

20  (21)     Scolex  similar  in  form  to  first  proglottids,  separated  by  sharp  boun- 

daries; no  unjointed  region    (neck). 

Subfamily  Haplobothriinae  Cooper. 

Proglottid  formation  evident  externally  only  in  anterior  part  of  strobila.  Large  median 
dorsal  and  two  smaller  ventro-lateral  excretory  vessels.  Both  vitellaria  and  testes  medullary. 
Cirrus  covered  with  minute  spines.  Uterus  sharply  divided  into  uterine  duct  and  large  uterine 
sac. 

Type  and  only  genus Haplohothrium  Cooper  19 14. 

Scolex  small,  simple;  rectangular,  excavated  dorso-ventrally 
to  form  simple  bothria,  and  also  slightly  laterally.  Apex  slightly 
extended  to  form  low  pyramidal  disc;  posterior  end  of  scolex 
modified  as  auricular  appendages  which  with  edges  of  apical  disc 
bear  minute  spines.  No  neck.  Proglottids  elongate  and  auricu- 
lae decrease  posteriad  until  segmentation  near  end  is  indicated 
only  by  successive  sets  of  reproductive  organs.  Large  median 
dorsal  and  two  small  ventro-lateral  excretory  trunks.  Testes 
small,  numerous  (80)  in  2  lateral  fields.  No  genital  sinus.  Cir- 
rus and  vagina  open  close  together  well  anterior  on  ventral  sur- 
face. Uterine  pore  ventral  also,  anterior  to  posterior  end  of 
uterine  sac.  Ovary  horse-shoe  shaped,  ventral,  posterior.  Large 
yolk-reservoir. 

Uterus  in  2  regions  formed  very  early,  viz. :  coiled  thin- walled 
uterine  canal  and  capacious  uterine  sac  which  when  filled  occupies 
almost  entire  central  field  of  proglottid.  Eggs  with  opercula, 
carrying  cihated  larva. 

Type  species. 

Haplohothrium  glohidiforme  Cooper  1914. 

Intestine  of  Amia  calva.  The  uterine  sac  and  the  armed  cirrus 
exclude  this  genus  from  the  family  in  which  it  was  placed  formerly. 
It  certainly  shows  some  points  of  resemblance  to  the  Triaenopho- 
rinae  and  has  been  included  in  a  new  subfamily  which  at  present 
stands  isolated  in  a  position  intermediate  between  that  and  the 
following  family. 


Fig.  732.  Haplohothrium 
globuliforme.  a,  scolex  and  first 
three  proglottids;  X  20;  b, 
twenty  -  third ,  twenty- fourth, 
and  twenty-fifth  proglottids, 
lateral  view,  showing  disappear- 
ance of  auricular  appendages; 
X  6;  c,  young  scolex  showing 
beginning  of  proglottid  forma- 
tion; X  11;  d,  smallest  plero- 
cercoid observed;  Xn-  (After 
Cooper.) 


21  (20)     Scolex  separated  from  first  proglottids  by  unjointed  region  (neck). 
Subfamily  Diphyllobothriinae  Liihe  1910   .    .    22 

Proglottid  formation  always  evident  externally.  Genital  organs  single  or  double  in  each 
proglottid.  Vitellaria  cortical;  testes  medullary  in  position.  Vas  deferens  with  muscular 
bulb  before  entrance  to  cirrus  sac.     No  spines  on  cirrus. 

Adults  in  intestine  of  Amniota;  larvae  so  far  as  known  in  fishes,  reproductive  organs  want- 
ing at  time  of  transfer  to  definitive  host. 

2  2  (23)     One  set  of  reproductive  organs  in  each  proglottid. 

Diphyllohothrium  Cobbold  1858. 

The  most  famous  member  of  this  genus  is  the  broad  fish  tapeworm  of  man,  D.  latum,  commonly 
referred  to  as  Bothriocephalus  latus,  though  it  is  very  distinct  from  that  genus  as  reference  to 
the  section  will  show.  This  species  has  become  established  on  the  North  American  continent, 
having  been  introduced  no  doubt  by  immigrants  from  infected  territory  in  Europe. 

Possibly  related  species [Dibothrium]  cordiceps  Leidy  187 1. 

Length  of  adult  2  m.;  scolex  cordiform  2  by  0.6  to  0.8  mm.,  neck  short.  Widest  about 
IS  to  25  cm.  from  head,  where  proglottids  are  7.5  mm.  long,  4.5  mm.  broad,  0.5  mm.  thick. 


PARASITIC    FLATW'ORMS  433 

Genital  pores  median,  ventral,  approximated  but  distinct;  cirrus  pore  most  anterior.  Cirrus 
large,  oval.  Testes  in  lateral  fields,  dorsal.  Vagina  with  vesicle  near  distal  end.  Ovary  pos- 
terior, ventral,  transverse  to  main  axis.  Shell-gland  d(jrsal,  near  ovary  and  posterior  to  it. 
Uterus  in  lateral  coils,  approaching  form  of  rosette.     Ova  70  by  35  /x. 

Adult  in  white  pelican;  larvae  in  muscles  and  body  cavity  of  trout;  Yellowstone  Lake, 
Wyoming. 

The  name  of  this  form  cannot  be  accepted  as  Dibolhriiim  is  only  a  synonym  of  Bothrio- 
phalus  and  the  location  of  the  genital  pores  rules  this  species  .out  of  that  genus  as  at  present 
dcfmed.  Furthermore  its  exact  position  and  true  relationship  must  remain  uncertain  until 
its  structure  is  better  known. 

23  (22)     Two  sets  of  reproductive  organs  in  each  proglottid. 

Diplogonoporiis  Lonnbcrg  1892. 

Very  large  cestodes  parasitic  in  whales,  seals,  and  occasionally  in  man. 

The  human  parasite,  D.  grandis,  is  reported  by  Ashford  and  King  from  Porto  Rico  so  it  may 
easily  reach  the  southeastern  coast  of  North  America  (see  also  Spargantim  mansoni). 

24  (15)     Genital  pores  of   different   proglottids   found  on   both   surfaces  of 

strobila,  alternating  irregularly  from  proglottid  to  proglot- 
tid.     .    Subfamily  Cyathocephalinae  Luhe  1899   .    .     25 

Scolcx  unarmed,  variable  in  form,  not  longer  than  wide,  with  two  median  or  one  apical 
sucking  organ  in  form  of  acetabula.  External  proglottid  limits  not  marked,  or  absent.  Geni- 
tal organs  single  in  each  proglottid;  all  pores  median.  Vagina  and  uterus  open  in  common 
female  genital  atrium  provided  with  sphincter  and  located  posterior  to  male  pore.  Adults  in 
fishes. 

25  (26)     Apical  sucking  organ  single,  undivided  by  transverse  fold. 

Cyatlwccphalus  Kessler  1868. 

Scolex  with  single  apical  sucking  organ  in  form  of  a  cup,  and  without  evidence  in  shape  or 
structure  of  its  origin  from  fusion  of  two  bothria  located  on  surface.  Proglottid  limits  distinct 
externally.     Sphincter  of  female  genital  atrium  poorly  developed. 

Adults  in  fishes. 

Type  species C yatJiocephal us  I runcal us  (PaWas)  1781. 

Reported  by  Linton  from  pyloric  ceca  of  common  whitefish.  Lake  Superior. 

26  (25)     Apical  sucking-organ  single  but  divided  by  transverse  fold  indicating 

its  double  origin Bothriomonus  Duvernoy  1842. 

Scolex  large,  approximately  spherical,  with  single  apical  sucking  organ  like  acetabulum, 
yet  divided  transversely  by  a  fold  which  indicates  its  origin  from  two  bothria  typical  of  family. 
No  external  proglottid  boundaries.     Sphincter  of  female  genital  atrium  well  developed. 

In  Acipenser  oxyrhynchus;  Wabash  River,  Indiana. 

Type  species Bothriomonus  slur  ion  is  Duvernoy  1842. 

27  (14)     Genital  pore  at  margin  of  proglottid. 

Subfamily  Thiaexofiiokinae  Liihe  1890. 

Scolex  always  with  typical  bothria,  not  very  deep;  flattened  apex  of  scolex  projects  above 
bothria  as  a  more  or  less  distinct  annular  cap.  Marginal  genital  jx)res  alternating  irregu- 
larly; uterine  pore,  median  on  ventral  surface,  anterior  to  marginal  genital  |x)re.  Repro- 
ductive organs  single  in  each  proglottid.  No  muscular  l)ulb  at  inner  end  «if  cirrus  sac.  Re- 
ceptaculum  seminis  small.  Uterus  in  coils,  Init  never  in  rosette  form,  somewhat  enlarged  nc;ir 
its  terminus. 

Adults  in  intestine  of  fishes  and  marine  turtles;    larvae  in  hshes.  mostly  unknown. 

Type  genus Triacnophorus  Rudolph!  1793- 

Scolex  with  4  three-pointed  hooks.  No  external  iiroglottid  markings.  Testes  occupy  all 
medullary  layer  not  taken  by  other  organs.  Vitellaria  continuous  \\\  cortical  layer,  interrupted 
only  at  genital  pores.  Ovary  and  shell  gland  adjacent  to  margin  bearing  genital  i>ore.  I  ter- 
ine  pore  usually  not  median  but  on  surface  at  right  of  median  line  when  marginal  ix)re  is  sinis- 
tral and  vice  versa.  .     ».t      •    » 

Adults  in  intestine  of  fishes;  larva  encysted  in  fishes.  Present  m  North  Amcnca;  no  siJC- 
cies  definitely  recorded  as  yet. 


434  FRESH-WATER   BIOLOGY 

28  (9)     Immature  forms;  sexual  organs  wanting  or  at  least  as  yet  only  partly 

developed Sparganum  Diesing  1855. 

Larval  stages,  without  sex  organs;  not  yet  at  a  period  in  which  specific  determination  is 
possible.  Many  undescribed  forms  in  various  hosts;  three  known  forms  are  hsted  below.  The 
first  named  is  not  yet  reported  for  this  continent;  the  second  and  third  are  definitely  recorded 
for  United  States  of  America. 

Sparganum  mansoni  (Cobbold)  1882. 

Large  forms,  8  to  36  cm.  long;  o.i  to  12  mm.  broad.  Two  longitudinal  grooves  on  dorsal 
surface;  one  median  longitudinal  groove  on  ventral  surface.  In  connective  tissue  and  body 
cavity  of  man.  Japan.  The  probable  adult,  Diplogonoporus  grandis  has  been  reported  from 
Porto  Rico. 

Sparganum  proliferum  (Ijima)  1905. 

Small  form,  i  to  12  mm.  long,  2.5  mm.  broad.  Body  usually  irregular  in  form.  Multipli- 
cation in  cysts  by  formation  of  supernumerary  heads  and  transverse  division.  Encysted  in 
subdermal  connective  tissue  and  elsewhere;  in  man,  Florida,  U.  S.  A.,  and  Japan. 

Sparganum  sebago  Ward  1910. 
Length  25  to  36  mm.,  breadth  1.8  to  0.36  mm.     Head  with  keyhole-shaped  bothria.     Body 
elliptical  in  cross-section  with  sUghtly  thickened  margins.     No  segmentation  developed  and 
no  sex  organs.     In  spleen  and  body  cavity  of  Salmo  sebago;  Maine. 

29  (8,  30)     Scolex  with  two  or  four  sucking  grooves,  and  also  at  apex  four 

protrusile  proboscides  armed  with  many  hooks. 

Order  Trypanorhyncha. 

The  four  long  slender  cylindrical  proboscides  are  conspicuous  enough  to  render  the  deter- 
mination of  adult  or  larva  easy.  The  adults  are  found  in  the  spiral  valve  of  sharks  and  rays; 
the  larval  forms  occur  encysted  in  migratory  fish.  They  are  among  the  rarest  of  finds  in 
fresh-water  collecting  and  are  present  in  North  America  though  no  species  are  recorded  as 
yet. 

30  (8,  29)     Scolex   with   four   sucking  organs   (exceptionally   replaced  by  a 

pseudoscolex)     but     without    extensile    proboscides.       No 
uterine  pore 31 

31  (54)     Vitellaria  with  very  numerous  follicles,  distributed  on  each  side  in 

longitudinal  marginal  zone,  rarely  in  the  entire  surface  zone 
of  the  proglottid Order  Tetraphyllidea. 

Sucking  organs  4,  cup-shaped,  small,  or  very  mobile  stalked  or  unstalked  modified  bothridia. 
Small  apical  sucking  organ  frequent.  Pseudo-scolex  exceptionally  present.  External  seg- 
mentation evident,  but  less  conspicuous  at  end  of  chain.  Genital  organs  single  in  each  pro- 
glottid. No  uterine  pore,  but  uterus  opens  in  median  ventral  line  by  rupture  of  wall.  Testes 
numerous.  Ovary  posterior,  median,  usually  with  two  wings.  Eggs  thin-shelled,  without 
lid;   embryonal  development  in  uterus. 

Adults  in  intestine  of  cold-blooded  vertebrates. 

Only  family  in  North  America  in  fresh-water  hosts. 

Family  Proteocephalidae  La  Rue  1911   .    .     32 

Heads  small.  Suckers  sessile  and  without  accessory  areola.  Fifth  sucker  functional,  ves- 
tigial, or  lacking.  No  rostellum.  Genital  organs  in  general  as  in  other  TetraphyUidea. 
Genital  pores  marginal,  irregularly  alternating.  Vitellaria  lateral,  follicular,  follicles  closely 
grouped  about  a  central  conducting  tubule.  Ovary  bilobed,  posterior.  Oocapt,  ootype,  shell 
gland,  and  uterine  passage  present.  Uterus  with  lateral  outpocketings  and  one  or  more  pre-  1 
formed  ventral  uterine  openings.  Vitellaria,  testes,  ovary  and  uterus  within  the  inner  longi-  i 
tudinal  muscle-sheath. 

Habitat:  In  fresh-water  fish,  amphibians,  and  aquatic  reptiles. 

32  (53)     Head  without  lappets  or  folds  of  tissue  around  suckers ^t,    \ 

2,2>  (46)     Testes  in  one  broad  mass  between  vitellaria;    parasitic  in  fresh-    ' 
water  fish Proteocephalus  Weinland  1858   .    .     34    i 

Head  globose  or  conical,  flattened  dorsoventrally.  No  rostellum.  No  spines  or  hooks.  , 
Suckers  circular  or  oval.  Fifth  sucker  functional  or  vestigial,  rarely  lacking.  Musculature  ' 
well  developed.     Eggs  with  three  membranes.  ' 


PARASITIC    FLATWORMS 


435 


34  (41)     Functional  fifth  or  apical  sucker,  absent  or  vestigial 35 

35  (t,8)     Testes  number  100  or  more 36 

36  (37)     Genital  pore  on  lateral  margin  near  center  of  proglottid. 

Proteoccphalus  macrocephaliis  (Creplin)  1825. 

As  much  as  40  cm.  lonR  by  i  to 
1.8  mm.  broad,  or  perhaps  more. 
Proglottids  very  numerous;  first 
much  l)r(>ader  than  lonj,';  maturi.*, 
broader  than  lonj,'  or  nearly  cjuad- 
rate;  ripe,  longer  than  broad. 
Suckers  0.095  to  0.106  mm.  in 
diameter.  Fifth  sucker  vestigial. 
Testes  100  to  120,  irregularly 
scattered  between  vitellaria,  ly- 
ing in  one  or  two  layers,  usually 
one.  Cirrus-pouch  short,  about 
0.16  mm.  long;  ratio  to  proglot- 
tid breadth  i  :  6  to  i  :  8.  Uterine 
pouches  7  to  14  on  either  side. 

Habitat:  In  intestine  of  An- 
gxiilla  vulgaris  and  A.  chrysyPa 
Raf. 


^  Fig.  733.  Proleocephalus  macrocephalus.  a,  Head.  X  70;  b, 
ripe  proglottid  showing  female  reproductive  organs.  X  40.  (After 
La  Rue.) 


37  (36)     Genital  pore  on  lateral  margin  anterior  to  center  of  proglottid. 

Proleocephalus  per  plexus  La  Rue  191 1. 

Length  as  much  as  155  mm.;  maximum  breadth  1.7  mm.  First  proglottids  much  broader 
than  long;  mature  proglottids  1.70  mm.  broad  by  0.595  mm.  long;  ripe  proglottids  quadrate 
or  longer  than  broad.  Suckers,  0.340  to  0.459  "im.  long  by  0.255  to  0.272  mm.  broad.  \o 
vestige  of  fifth  sucker. 

Genital  pore  at  end  of 
first  fourth  or  half  of 
proglottid.  Cirrus-fM)uch 
0.30  to  0.344  mni.  long, 
extending  to  one-third  or 
one-fifth  width  of  proglot- 
tid. Testes  135  to  155  in 
number,  in  one  layer  an- 
terior to  ovar>'.  \'agina 
anterior  to  cirrus-pouch, 
never  crossing  same.  Vi- 
tellaria extend  to  posterior 
margin  of  proglottid  and 
parallel  to  it.  L'teruswith 
20  to  25  lateral  pouches 
on  each  side. 

Hal)itat:  In  intestine  of 
Fig.  734.  Proleocephalus  perplexus.  a.  Head.  X  36;  b,  ripe  proglottid,  -^'"i^  ^^^^'^  and  Le  pi  so  stats 
reconstruction  showing  male  reproductive  organs  (U,  testes),  and  ovary.  Piatosiomus.  llunois,.^orin 
Note  also  position  of  sphincter  vaginae  (I'aj).     X  36.     (.\fter  La  Rue.)  Carohna. 


38  (35)     Testes  number  less  than  loo 30 


39  (40)     Suckers  with  pointed  apex  and  shallow  cavity. 

Proleocephalus  singular  is  La  Rue  191 1. 

Strobila  long,  slender,  up  to  170  or  even  250  mm.;  maximum  breadth  0.90  to  i.o  mm.  Head 
small,  suckers  large.  No  vestige  of  fifth  sucker.  First  prt)gli)liids  brt)ader  than  long;  mature 
proglottids  0.85  mm.  broad  by  0.34  to  0.37  mm.  long;  riin-  proglottids  longer  than  bri>ad  or 
quadrate.     Old  spent  proglottids  up  to  2.0  mm.  long  by  0.4  mm.  broad. 

Genital  pore  at  end  of  first  one-fourth  to  one-half  of  proglottid.    Testes  75  to  So  or  90,  m  a 


43^ 


FRESH-WATER   BIOLOGY 


single  layer.  Vas  deferens  large  mass  of  coils  in  mid-field.  Cirrus-pouch  slender,  nearly 
straight,  muscular,  length  two-fifths  to  one-third  proglottid  width. 

Vagina  always  anterior  to  cirrus-pouch,  never  crossing  latter.  Beginning  region  of  vagina 
narrow.     Uterus  with  20  to  25  lateral  outpocketings. 

In  intestine  of  Lepisosteiis  platostomus.  Illinois. 


Fig.  735.  Proteocephalus  singularis.  a,  Head;  apical  prominence  contracted;  6,  apical  prominence 
extended,  X  50;  c,  ripe  proglottid,  frontal  section  showing  arrangements  of  testes,  vitellaria  and  ovary; 
vagina  and  cirrus-pouch  not  shown,  X  36.     (After  La  Rue.) 


40  (39)     Suckers  round  or  oval  with  smooth  contour. 

Proteocephalus  ambloplitis  (Leidy)  1887. 

Large,  280  to  410  mm.  long,  2  to  2.5  mm.  in  maximum  breadth.  Surface  of  body  rough, 
with  transverse  and  longitudinal  furrows.  Scolex  prominent.  Fifth  sucker  vestigial.  Young 
proglottids  12  to  15  times  broader  than  long.  Mature  and  ripe  proglottids  broader  than 
long,  about  quadrate,  or  rarely  longer  than  broad.  Vitellaria  not  posterior  to  lobes  of  ovary. 
Genital  sinus  at  end  of  first  fourth  of  proglottid.  Uterus  with  15  to  20  lateral  outpocketings 
on  each  side.  Cirrus-pouch  pyriform,  muscular,  two-sevenths  to  two-fifths  of  proglottid 
breadth.  Coils  of  vas  deferens  many,  extending  to  middle  of  proglottid.  Testes  70  to  100  in 
number. 

Intestine  of  Ambloplites  rupestris,  Micropterus  salmoides,  M.  dolomieu,  Amia  calvor  New 
York,  Michigan,  Minnesota,  and  Wisconsin. 


vas 


Fig.  736.     Proteocephalus  ambloplitis.     a,   Head,   X  25.     (After  La  Rue);     b,   ripe  proglottid,  frontal 
section  showing  main  parts  of  male  and  female  reproductive  systems,  magnified,     (After  Benedict.) 


41  (34)     Well-developed  (functional)  fifth  sucker  present 42 


PARAS  [TIC    I  LATWORMS 


437 


42  (43)     Cirrus-pouch  extends  half  way  across  proglottid. 

Proteocephalus  exiguus  La  Rue  191 1. 

Stroliila  short,  slender,  lenKth  9  to  38  mm., 
maxmnim  breadth  0.425  to  0.8  mm.  First 
proglottids  longer  than  broad  or  nearly  quad- 
rate; mature  and  ripe  proglottids  longer  than 
broad,  ripe  proglottids  considerably  larger,  0.680 
to  1. 190  mm.  long  by  0.460  to  0.595  mm.  broad. 
Suckers  0.058  mm.  broad,  0.069  to  0.085  mm. 
long.  Genital  pore  near  middle  of  lateral  mar- 
gin of  proglottid.  Testes  .:i4  to  54  in  number, 
in  one  layer.  Vas  deferens  forming  mass  of 
coils  in  mid-field.  Vagina  anterior  to  cirrus- 
pouch,  crossing  it  near  middle.  Uterus  with  9 
to  14  lateral  pouches  on  either  side. 

In  intestine  of  Coregonus  ni^ripiiuiisX- Prog- 
nathus,  and  C.  artedi,  Lake  Michigan. 


Fig.  737.  Proteocephalus  exiguus.  a.  Head,  su, 
fifth  sucker,  X  93;  b,  mature  proglottid,  X  60 
(After  La  Rue.) 


43  (42)     Cirrus-pouch  less  than  one-third  breadth  of  proglottid. 

44  (45)     Testes  in  one  layer Proteocephalus  pingiiis  La  Rue 


44 

IQI  I. 


Fig.  738.  Proteocephalus  pinguis.  a.  Head  in  dorsal  or 
ventral  view,  X  45;  b,  ripe  proglottid,  till,  lateral  uterine 
pouches,  ventral  view,  X  63.     (After  La  Rue.) 


Strobila  short,  .slender,  length  up  to 
90  mm.,  ma.ximum  breadth  1.24  mm. 
First  proglottids  very  short.  .Mature 
and  ripe  proglottids  nearly  quadrate  or 
in  a  few  ripe  proglottids  length  exceed- 
ing the  breadth. 

(ienital  pore  at  or  near  middle  of 
lateral  margin  of  proglottid.  Testes 
54  to  70,  in  a  single  layer.  Cirrus- 
pouch  short,  stout,  0.13  to  0.14  mm. 
long  by  0.05  to  0.06  mm.  broad,  i  :  ^ 
or  I  :4  in  breadth  of  proglottid.  Va- 
gina anterior,  but  vaginal  ojx'ning  al- 
ways dorsal  to  cirrus-pouch.  Vagina 
crossing  inner  end  of  cirrus-sheath. 
Uterus  with  10  to  14  lateral  pouches 
on  either  side. 

In  intestine  of  Esox  reticidatus  Le 
Sueur,  and  E.  Indus  Linn.,  Maine, 
Michigan,  and  Wisconsin. 


45  (44)     Testes  in  two  layers Proteocephalus  pus  ill  us  Ward  iqio. 


Very  small,  weak;  length  30  to  50  mm., 
maximum  breadth  0.350  mm.  Proglottids 
few.  First  proglottids  broader  than  long, 
mature  proglottids  longer  than  broad,  rijx^ 
proglottids  much  longer  (0.84  to  1.4  mm.) 
than  broad  (0.18  to  0.35  mm.) 

Genital  sinus  at  end  of  first  one-third  to 
two-fifths  of  i^roglottid.  Testes  44  to  70  in 
number,  in  two  layers.  Coils  of  vas  deferens 
few,  anterior  to  cirrus-ix)uch.  Vagina  never 
crossing  cirrus-pouch.  Uterus  with  10  tt)  16 
lateral  pouches  on  each  side. 

Habitat :  Intestine  of  Satmo  srbago  Girard 
and  Crislhomrr  ttamaycush  \Vall)aum;  Se- 
bago  Lake,  Maine,  Lake  Temagami,  On- 
tario. 


Fig.  739.  Proteocephalus  pusillus.  a.  Head,  showing 
fifth  sucker,  X  70;  b,  mature  proglottid,  toto,  X  63. 
(After  La  Rue.) 


438 


FRESH-WATER   BIOLOGY 


46  (33)     Testes  lie  in  two  lateral  fields  between  vitellaria;    parasitic  in  am- 
phibians, aquatic  snakes,  and  lizards. 

Ophiotaenia  LiSi  Rue  igii    .    .   47 

Head  globose  or  somewhat  tetragonal.  No  rostellurn.  ^  No  hooks  or  spines.  Suckers  dr- 
cular  or  oval,  with  margins  entire.  Fifth  sucker  vestigial.  Neck  usually  long.  Testes  in 
two  long  lateral  fields  anterior  to_  ovary.     Musculature  weak. 

In  aquatic  snakes  and  Amphirbia. 


47  (48)     Vagina  always  anterior  to  cirrus-pouch,  not  crossing  latter. 

Ophiotaenia  filaroides  La  Rue  1909. 

Worms  attenuate,  small,  thin,  flat.  Length  80  to  no  mm.,  maximum  breadth  about  0.80 
to  OQO  mm  Suckers  deep,  muscular,  oval,  maximum  diameter  0.165  to  0.184  mm  First 
progiottids  o  30  to  0.36  mm.  broad  by  o.io  to  0.17  mm.  long;  mature  proglottids  quadrate  or 
longer  than  broad;    ripe  proglottids  from  1.6  mm.  to  4.0  mm.  long  by  0.8  mm.  to  0.75  mm. 

Genital  pore  at  end  of  first  fifth  of  proglottid.  Testes  70  to  114  in  number. 
Few  coils  in  cirrus-pouch.  Cirrus-pouch  about  0.22  mm.  long  by  o.ii  mm. 
broad.  Vitellaria  with  large  follicles.  Uterus  with  25  to  35  lateral  pouches  on 
each  side.     (For  structure  of  mature  proglottid  consult  figure  730,  page  425.) 

Intestine  of  Amblystoma  tigriniim  (Green);   Nebraska  and  Kansas. 

Fig.  740.    Ophiotaenia  filarioides.     Head  of  adult,  magnified.     (After  La  Rue.) 


48  (47)     Vagina  either  anterior  or  posterior  to  cirrus-pouch 49 


49  (52)     Genital  pore  anterior  to  middle  of  margin  of  proglottid 5° 


50  (51)     Testes  number  90  to  160.     Ophiotaenia  Idnnbergii  (Fuhrmann)  1895. 


Fig.  741.      Opkwlaenia  idnnbergii.      a.   Head,  b,  mature 
proglottid,  magnified.     (Alter  Fuhrmann.) 

posterior  to  it.     Vagina  never  crosses  cirrus-pouch 


Length  170  to  190  mm.,  breadth  up  to 
1.35  mm.  Scolexo.50too.60mm.  broad. 
Suckers  measure  0.24  to  0.26  mm.  long 
by  0.14  to  0.22  mm.  broad.  First  pro- 
glottids about  0.5  mm.  long  by  0.50  mm. 
broad;  mature  proglottids  0.85  to  i.o 
mm.  square,  or  longer  than  broad, 
measuring  as  much  as  2.5  mm.  long  by 
0.45  to  0.5  mm.  broad.  Ripe  proglottids 
not  observed. 

Genital  pore  situated  at  end  of  first 
one-third  or  two-fifths  of  proglottid. 
Testes  90  to  160  in  number,  extending 
lateral  of  excretory  vessels  and  a  few 
into  midzone.  Cirrus-pouch  0.185  to 
0.280  mm.  long  by  0.05  to  0.085  or  o.io 
mm.  broad,  with  large  mass  of  coils 
Uterus  with  25  to  40  lateral  pouches. 


In  intestine  of  Neciurus  maculosiis  Raf.;  Ohio,  Indiana. 


PARASITIC    FLATWORMS 


439 


51  (50)     Testes  number  150  to  215 


Ophiotacnia  pcrspicua  La  Rue  191 1. 

Length  up  to  360  mm.,  maximum  breadth 
about  2.0  mm.  First  proglottids  short,  mature 
proglottids  quadrate  (2.0  mm.)  or  somewhat  longer 
than  broad,  ripe  proglottids  as  much  as  3.8  mm. 
long  by  1.2  mm.  broad. 

Genital  pore  situated  near  middle  or  at  end  of 
first  third  of  proglottid.  Testes  150  to  215.  Vas 
deferens  in  ripe  proglottids  heavy  mass  of  coils 
reaching  from  end  of  cirrus-p<juch  to  mid-field. 
Ratio  of  length  of  cirrus-pouch  to  proglottid 
breadth  i  :  4  to  i  :  3.  V'agina  anterior  or  pos- 
terior to  but  not  crossing  cirrus-pouch.  Uterus 
with  20  to  30  lateral  pouches  on  each  side. 

Habitat:  Natrix  {Nerodia)  r hombifer  HaWowcW; 
Illinois,  Oklahoma. 


Fig.  742.  G;ilnolaenia  pcrspicua.  a,  Head.  X  23; 
b,  ripe  proRlottid,  showing  uterine  pouches,  and  testes. 
(After  La  Rue.) 


52  (49)     Genital  pore  at  or  near  center  of  margin  of  proglottid. 

Ophiotaenia  gra^idis  La  Rue  191 1, 


utvp 


Very  long  (fragments  200  mm.),  2.75  to  4.25 
mm.  broad  in  ripe  proglottids.  First  proglottids 
much  broader  than  long;  proglottids  with  develop- 
ing sexual  organs  quadrate  or  nearly  so;  ripe  pro- 
glottids quadrate  or  much  longer  than  broad. 
Head  large,  i.o  to  1.2  mm.  broad  at  base  of  suck- 
ers. Suckers  about  0.34  by  0.36  mm.  Testes 
large,  numerous,  200  to  250.  Cirrus-pouch  0.24  to 
0.26  mm.  broad,  0.64  to  0.75  mm.  long,  enclosing 
few  or  no  coils  of  ductus  ejaculatorius.  Uterus 
with  40  to  60  lateral  outpocketings  on  each  side. 

In  intestine  of  Ancislrodon  piscivorus  Holbr., 
locality  not  known. 


Fig.  743.  Ophiotaenia  grandis.  a,  Head,  showinR 
swollen  region  back  of  head,  X  S;  b.  mature  pro- 
glottid, ventral  view  showing  reproductive  organs  and 
ventral  uterine  pores  {utvp).     X  10.     (After  La  Rue) 


S3  (32) 


Many  lappets  or  folds  of  tissue  about  suckers. 

Corallobotliriiim  Fritsch 


[886. 


Scolex  with  four  suckers  situated  on  the  flat  anterior  face  of  the  head.  .Many  irregular 
folds  and  lappets  of  tissue  about  margin  of  anterior  surface;  may  enclose  suckers  as  in  a  corolla. 
Norostellum.     No  hooks  nor  spines.     Neck  broad,  short.     Habitat.    In  Siluridae. 

Marshall  and  Gilbert  report  the  occurrence  of  two  species  m  the  lonuiion  bullhead.  I  have 
an  undescribed  species  taken  from  a  channel-cat  at  Milford,  Neb. 

54  (31)     Vitellaria  condensed,  in  a  single  mass,  in  medullary  layer,  usually 
immediately  posterior  to  ovary,  rarely  anterior  to  it. 

Order  Cyclophyllidea   .    .     55 

Scolex  with  4  cup  or  saucer-shaped  suckers  and  in  the  center  an  apical  organ  or  rostcllum  of 
varied  form.  Hooks  common  on  rostellum,  very  rare  on  suckers.  Segmentation  well  devel- 
oped, only  rarely  absent  (Fimbriariidae);  proglottids  set  free  after  lull  maturity.  No  uterine 
pore;  rarely  a  secondary  connection  to  the  exterior  permits  the  escape  of  ova.  Testes  m  nuxlul- 
lajy  layer,  ordinarily  numerous.     Ovary  bilobed;    vitellarium  compact,  smgle.   near  ovary 


440 


FRESH-WATER    BIOLOGY 


with  shell  gland  between.     Eggs  thin-shelled,  no  lid;    onchosphere  with  one  or  more  mem- 
branes.    Bladder-worm  in  vertebrates  and  invertebrates. 

The  great  majority  of  forms  commonly  designated  Taenia  are  included  here.  Number 
and  form  of  hooks  on  which  older  systems  are  based  form  unrehable  means  for  the  distinction 
of  species.  In  immature  forms  the  organs  utilized  in  this  key  are  undeveloped  and  a  deter- 
mination can  only  be  approximate. 

55  (117)     Body  flattened.     Distinct  and  regular  external  boundaries  corre- 

sponding to  internal  grouping  of  organs  in  the  strobila.     56 

56  (57)     Suckers  carry  on  anterior  and  lateral  surface  auricular  appendages. 
Vitellarium  anterior  to  ovary. 

Family  Tetrabothriidae  Fuhrmann  1907. 

Scolex  unarmed,  without  rostellum.  Neck  short.  Proglottids 
except  oldest  always  much  broader  than  long.  Reproductive  organs 
single  in  each  proglottid.  Genital  pores  unilateral;  genital  cloaca 
deep.  Cirrus-pouch  small  and  nearly  spherical,  united  with  genital 
cloaca  by  muscular  cloacal  canal.  Eggs  with  three  transparent  en- 
velopes.    Adults  in  birds  and  mammals. 


Type  genus. 


Tetrabothrius  Rudolphi  18 19. 


Fig.  744.  Tetrabothrius 
macrocephalus .  Scolex;  mag- 
nified.    (After  Liihe.) 


With  characters  of  the  family. 

Scolex  unarmed,  quadrate.  Suckers  large.  Sexual  pore  always 
dextral. 

The  hosts  are  aquatic  birds,  largely  marine.  Nearly  twenty  species 
are  described,  a  number  of  which  occur  in  North  American  birds: 
(gull,  grebe,  heron,  loon),  that  frequent  fresh-water  bodies. 


57  (56)     Suckers   simple   without   appendages   of   any   sort.     Vitellaria   not 

anterior  to  ovary  but  posterior  to  it,  or  in  the  same  trans- 
verse plane  with  it 58 

58  (59)     Genital  pores  median,  on  flat  surface  of  proglottids. 

Family  Mesocestoididae  Fuhrmann  1907. 

Scolex  without  rostellum  or  hooks.  Suckers  unarmed.  Reproductive  organs  single  in 
each  proglottid.  Genital  pores  median  on  ventral  surface.  Vagina  opens  in  front  of  or  beside 
cirrus-pouch.  Eggs  in  terminal  proglottids  inclosed  in  single  thick-walled  egg-capsule.  Adults 
in  mammals  and  birds. 

Type  genus Mesocestoides  Vaillant  1863. 

With  characters  of  the  family. 

Few  species;  almost  never  in  aquatic  forms.  No  North  American  records  although  the 
genus  occurs  here. 

59  (58)     Male  genital  pores  at  margin  or  very  close  to  it.     Female  pores 

when  present  similarly  located 60 


60  (104) 

61  (103) 

62  (102) 

63  (64) 


Female  genital  pore  present  and  located  near  male  pore.    ...     61 

Uterus  transverse  or  irregular,   not  elongated  in  median  line  of 
proglottid 62 

Reproductive  organs  simple  in  each  proglottid  or  if  genital  pores 
are  double,  the  organs  are  also  double 63 


Scolex  provided  with  three  to  many  rows  of  hooks. 

Family  Dipylidiidae  Liihe  1910. 

No  forms  in  fresh-water  hosts. 

64  (63)     Scolex  provided  with  one  or  two  rows  of  hooks  or  without  any 
hooks 65 


PARASITIC    FLATWORMS  441 

65  (70)     Rostellum  hassock-shaped  with   a  muhitudc  of  very  small   hooks 

arranged  in  a  double  row. 

Family  DavaIxNEidae  Fuhrmann  1907   .    .     66 

Scolex  with  rostellum  usually  broader  than  hi^h  and  armed  with  very  many  minute  hammer- 
shaped  hooks.  Margins  of  suckers  usually  with  small  hooks,  (lenital  organs  usually  single, 
rarely  double  in  each  proglottid.     Testes  numerous.     Onchosphere  with  two  thin  membranes.' 

66  (67)     Uterus  divides  into  numerous  separate  parenchyme-capsules. 

Davainea  R.  Blanchard  i8qi. 

Rostellum  armed  with  double  row  of  hooks;  dorsal  excretory  vessels  present.  RcprcKluctivc 
organs  single  in  each  proglottid.  Genital  pores  unilateral  or  occasionally  irregularly  alternate. 
Uterus  breaks  down  into  egg  capsules  each  containing  one  or  several  eggs.  .Adults  in  mam- 
mals and  birds.  Numerous  species;  mostly  in  scratching  birds.  D.  anatina  is  reported  from 
the  domestic  duck  in  Europe.     No  North  American  records. 

67  (66)     Uterus  not  breaking  up  into  separate  parenchyme-capsules.    .    .     68 

68  (69)     No  parauterine  organ;   uterus  sac-shaped.     Rostellum  broader  than 
_  scolex  with  several  thousand  booklets. 

Opiiryocotyle  Friis  1870. 

Rostellum  broader  than  rest  of  scolex;  suckers 
armed  only  near  anterior  border.  Reproductive  or- 
gans single  in  each  proglottid.  Uterus  sac-like,  per- 
sistent. 

Three  species  in  European  shore  and  water  birds 
some  of  which  occur  in  North  America. 


Fig.  745.     Opiiryocotyle  proleus.     Head   and  neck  with 
retracted  and  extended  infundibulum;   magnified.     (.After 

Stiles.) 

69  (68)  Uterus  coiled  in  posterior  end  of  proglottid;  thick-walled  para- 
uterine organ  in  anterior  region.  Rostellum  small;  with 
not  to  exceed  a  few  hundred  booklets. 

Idiogenes  Krabbe  1868. 

Small  cestodes.  Genital  pores  unilateral.  Cirrus-pouch  very  large,  with  retractor.  Para- 
uterine organ  develops  in  front  of  uterus;  eggs  finally  pass  directly  into  it  from  uterus  and  it 
is  transformed  into  single  thick-walled  egg  capsule.     Adults  in  birds. 

A  few  species  in  water  birds;  none  recorded  as  yet  in  North  .Vmerica. 

70(65)     Rostellum  sac-like,  or  lacking 71 

71  (82)     Not  more  than  four  testes  in  each  proglottid. 

Family  Hymenolepididae  Fuhrmann  1007.   .    .     72 

Scolex  armed  with  8  to  40,  usually  10  hooks,  with  points  directed  i^)steriad  when  at  rest, 
on  a  more  or  less  elongated  rostellum  which  rarely  is  rudimentary  and  unanned.  Genital 
pores  strictly  unilateral  in  entire  strobila.  Genital  ducts  dorsal  to  e.\cretor>-  ducts  and  longi- 
tudinal nerve.  Female  glands  median.  Onchosphere  with  three  membranes,  .\dults  in 
birds  and  mammals. 

72  (73)     In  each  proglottid  normally  4  testes.    .    .   Oligorchis  Fuhrmann  ioo(). 
A  single  species  in  North  America;   not  reported  in  aquatic  birds. 

73  (72)     In  each  proglottid  normally  less  than  four  testes 74 

74(79)     In  each  proglottid  normally  three  testes 7^ 


442 


FRESH-WATER    BIOLOGY 


75  (76)     Strobila   broad,   lancet-shaped.     Ovary  and  vitellarium   ante-poral, 

alongside  of  testes Drepanidotaenia  Railliet  1892. 

Scolex  very  small,  with  8  hooks.     Neck  wanting.     No  accessory  sac  in  genital  atrium. 

Type  species Drepanidotaenia  lanceolata  (Bloch)  1782. 

Adult  in  intestine  of  ducks  and  geese;   cosmopolitan.     Bladder-worm  in  various  Cyclopidae 
and  Diaptomus. 


Fig.  746.     Drepanidotaenia  lanceolata.     Transverse  section    of  proglottid;    u,   uterus;    vt,   vitellaria; 
ov,  ovary;   t,  testes;   vd,  vas  deferens;   sr,  seminal  receptacle;   v,  vagina;   magnified.     (After  Wolffhiigel.) 

76  (75)     Strobila  slender  or  even  filiform.     Ovary  and  vitellarium  ventral  to 
testes  or  between  them 77 


77  (78)     Suckers  entirely  unarmed,  or  at  most  armed  with  hooks  on  margin 
only Hymenolcpis  Weinland  1858. 


Rostellum  well  developed,  rarely  rudimentary 
or  absent.  Accessory  sac  generally  wanting  in 
genital  atrium.  Rarely  as  abnormality  2,  4, 
5,  or  6  testes  in  a  single  proglottid.  Chiefly  in 
land  and  water  birds;  some  species  in  mam- 
mals. 

A  very  large  genus;  about  50  species  occur  in 
aquatic  hosts  found  in  North  America.  Among 
them  a  few  are  definitely  reported  for  North 
America.  H .  compressa  (Linton)  1892  from  the 
scoter  and  canvas-back.  H.  fusus  in  which 
Fig.  747.     Hymenolcpis  megalops.     Dorsal  view     Fuhrmann  places  Linton's  Taenia  filum  from 

of  mature  segment  (no.  172).    Reconstruction  from     gulls  at  Yellowstone  Lake 

rri°t?ako^%rdSS?.5  ^..,»e,a/.^.describedby  Ransom  (withother 

genital  cloaca;    nt,  main  lateral  nerve;    sg,  shell      species  from  land  birds)  from  the  pintail  duck; 

gland;  /,  testis;  tm,  transverse  muscles;  tit,  uterus;      Missouri  River,  Mo. 

vc,  ventral  excretory  canal;  vg.  vagina;  vs,  seminal 

vesicle;    vs',  seminal  vesicle  of  cirrus-pouch;    xpl, 

plexus  of  excretory  vessels;  yp,  yolk  glands.     X  90. 

(After  Ransom.) 

78  (77)     Suckers  armed  on  borders  and  also  in  cavity  with  small  booklets; 
sacculus  accessorius  always  present. 

Echinocotyle  Blanchard  1891. 

Rostellum  armed  with  single  crown  of  ten  slender  hooks  with  dorsal 
root  and  blade  about  equal  in  length  and  ventral  root  rudimentary. 
Suckers  large,  flat,  oval,  poor  in  musculature,  armed  on  borders  and  in 
middle  with  several  rows  of  small  booklets.  Muscular,  spinous  sacculus 
accessorius  always  present.     Adults  in  birds. 

Type  species.    .     Echinocotyle  rosseteri'EXainchdiTdiZgi. 

Five  species  in  shore  and  water  birds  of  Europe.     Hosts  mostly  found     I 
in  North  America  also. 


Fig.  748.     Echinocotyle  rosseteri.     Head  with  extended  rostellum;    X  250. 
(After  Blanchard.) 


PARASITIC    FLATWORMS 
yg  (74)     In  each  proglottid  normally  less  than  three  testes. 


443 

80 


80(81)     Two  testes  in  each  proglottid -O/Wc///^  Clerc  1903. 

Rostellum  with  single  crown  of  ten  hooks  having  long  dorsal  and  short  ventral  roots  or 
exceptionally  very  short  dorsal  root  and  ventral  root  nearly  as  lung  as  the  hladc.  Entire 
surface  of  suckers  may  be  armed  with  minute  spines.  Inner  longitudinal  muscle  layer  con- 
sisting of  8  bundles,  4  dorsal  and  4  ventral.  Two  testes  in  each  proglottid.  Ovary  and  vitel 
larium  always  median.     Adults  in  birds. 

Four  or  more  species  in  European  water  birds.  Most  of  the  host  species  occur  in  North 
America.  D.  acuminata  and  D.  americana  were  both  collected  by  Ransom  from  the  coot  in 
Nebraska. 


Fig.  749.     Diorchis    acuminata,     a.   Hook  from    rostellum;    sexually    mature   scRmcnt;      cp,   cirrus- 
pouch;  ov,  ovary;   t,  testis;  ves  sent,  seminal  vesicle;   yg,  yolk  gland;   magnified,     (.-^fter  Ransom.) 


Fig.  750.     Diorchis  americana.      a.  Hook  from  rostellum;    magnified;    se.xually  mature  segment  at 
high  focus  to  show  male  organs,  dorsal  view;   magnified;  cp,  cirrus-pouch;  ov,  ovar>-;  /,  testes;   vts  sem, 

seminal  vesicle;   yp,  yolk  gland;   magnified.     (After  Ransom.) 


81  (80)     One  testis  in  each  proglottid \ploparaksis  Clerc  1Q03. 


Fig.  751.  Aploparaksis  filum.  Transverse  section 
of  proglottid,  female  reproductive  organs  not  shown; 
X  3,6.  (After  Clerc.)  Hook  from  rostellum,  X  75°- 
(After  Krabbe.) 


Strobila  small  and  slender.  Rostellum 
armed  with  a  single  crown  of  lo  hooks,  with 
ventral  root  as  long  or  nearly  a.s  long  as 
blade.  Suckers  unarmed.  One  testis  dors;il. 
Seminal  vesicle  large.  Ovary  and  vitcUa- 
rium  always  median.     .Vdults  in  birds. 

Type  species. 
Aploparaksis Jil urn  (Goczc)  17S2. 

.V  dozen  species  described  from  avian 
hosts  both  terrestrial  and  aquatic:  nearly 
all  of  the  species  arc  found  in  North  .\mcri- 
can  host  s]K*cies. 


82  (71)     At  least  six  testes  normally  in  each  proglottid 83 


444 


FRESH-WATER   BIOLOGY 


83  (83a)     Rostellum  entirely  lacking.     Scolex  unarmed,  very  muscular. 

Family  Anoplocephalidae  Kholodkovsky  1902. 
Not  found  in  fresh-water  hosts. 

83a  (83)     Rostellum  present  and  armed  with  one  or  two  rows  of  hooks. 

Family  Dilepididae  Fuhrmann  1907   .    .     84 

With  rostellum  armed  with  single  or  double  crown  of  hooks  rarely  in  broken  zig-zag  row, 
exceptionally  rudimentary.  Points  of  hooks  directed  posteriad.  Suckers  unarmed.  Genital 
pores  marginal  (see  84  just  below).  Sex  organs  in  each  proglottid  simple  or  double.  Uterus 
sacculate  or  lobed,  simple. 

Onchosphere  with  three  membranes.  Many  genera  chiefly  found  m  birds,  rarely  m  rep- 
tiles or  mammals. 

84  (85)     Genital  pores  submarginal,  dorsal,  but  never  as  far  as  half  way 

from  margin  to  median  hne. 

Trichocephaloides  Ssinitsin  1896. 

Rostellum  powerful  with  single  crown  of  hooks.  Genital  pores  unilateral,  subdorsal.  Cirrus 
short  and  thick  with  long  bristles;  no  seminal  vesicle.  Testes  few,  in  posterior  region  of  seg- 
ment.    Uterus  sac-like;   eggs  few.     Adults  in  birds. 

Few  species  in  shore  birds;   parasites  not  reported  from  North  America. 

85  (84)     Genital  pores  distinctly  marginal 86 

86  (93)     Genital  pores  uniformly  unilateral 87 

87  (88)     Rostellum  with  single  crown  of  hooks.     Lateriporus  Fuhrmann  1907. 

Rostellum  armed  with  single  crown  of  12  to  16  hooks  (120  to  170M  long),  with  long  dorsal 
and  short  ventral  root,  and  well-developed  blade.  Proglottids  broader  than  long.  Genital 
canals  pass  dorsal  of  longitudinal  excretory  vessels.  Testes  12  to  30  in  number,  situated  pos- 
terior and  lateral  to  ovary  and  xntellarium.  Uterus  sac-Hke,  filling  entire  medullary  paren- 
chyma in  terminal  proglottids.     Adults  in  birds. 

Five  or  more  species,  found  in  Europe  in  Anseriformes;  not  yet  reported  for  North  America. 

88  (87)     Rostellum  with  double  crown  of  hooks;  rarely  rudimentary  and  un- 

armed  89 

89  (92)     No  spines  on  base  of  cirrus 9° 

90  (91)     Testes  not  in  front  of  but  behind  ovary  and  vitellarium. 

Dilepis  Weinland  1858. 

Rostellum  armed  with  double  crown  of  hooks  having  long  dorsal  and  short  ventral  root  and 
long  blade.  Inner  longitudinal  muscle  layer  consisting  of  numerous  bundles.  Proglottids 
broader  than  long.  Genital  canals  pass  dorsal  of  the  longitudinal  excretory  vessels  and  nerve. 
Vas  deferens  coiled,  seminal  vesicle  not  developed.  Testes  in  medullary  portion  typically 
numerous  (40  to  50),  but  may  be  reduced  in  number  (7).  Uterus  sac-Uke  with  few  or  numer- 
ous outpocketings.     Adults  in  birds  and  mammals. 

Many  species  from  various  birds  including  fresh-water  types  found  in  North  Amenca. 
D.  transfuga  from  the  spoonbill  determined  for  North  America  by  Ransom.  D.  unUaterdis 
for  the  green  heron  by  Stiles  and  Hassall,  and  by  A.  J.  Smith;  also  for  the  httle  blue  heron  by 
Leidy. 

91  (90)     Testes  very  numerous,  entirely  surrounding  the  female  glands. 

Cydorchida  Fuhrmann  1907. 

Rostellum  armed  with  double  crown  of  hooks,  which  have  a  very  large  dorsal  root  and  small 
hook  portion.  Genital  canals  pass  between  longitudinal  excretory  vessels.  Cirrus-pouch 
communicates  with  genital  cloaca  by  narrow  canal  opening  upon  large  papilla.  Uterus  ventral, 
growing  laterally  between  the  excretory  vessels  into  the  cortical  parenchyma  and  fiUing  entire 
proglottid.     Adults  in  birds. 

In  heron,  crane,  etc.,  in  Europe.     Not  recorded  for  North  America. 


PARASITIC    FLATWORMS 


445 


92  (89)     Root  of  cirrus  with  one  or  two  pairs  of  powerful  hooks  lying  in 
special  pockets;  genital  canals  pass  between  longitudinal 
excretory  vessels. 

Gryporhynchus  Xordmann  1832. 
(Syn.  —  Acdnthocirrus  Fuhrmann  1907.) 

Genital  canals  pass  between  the  longitudinal  excretory  vessels. 
In  genital  atrium  lateral  to  root  of  cirrus  two  special  pockets  with  one 
or  two  pairs  of  powerful  hooks  in  each.  Uterus  sac-like.  Adults  in 
birds. 

Three  species  or  more  in  herons;  not  reported  from  North  America. 

Fig.   752.      Gryporhynchus    cheilancristrolus.      Proglottid    with    contracted 
cirrus-pouch;  short  heavy  hooks  in  pockets  at  opening  of  cirrus-pouch  into 
genital  cloaca.    Magnified.     (After  Clerc.) 


93  (86)     Genital  pores  not  unilateral  but  alternating 94 

94  (97)     Genital  pores  regularly  alternating 95 

95  (96)     Rostellum  with  single  crown  of  hooks.     Less  than  30  proglottids; 

scolex  large;  no  neck Amocbotaeuia  Cohn  i8qq. 

Proglottids  much  broader  than  long.  Testes  rather  numerous  (12  or  more),  in  posterior 
portion  of  segment.  Uterus  sac-like,  fills  entire  medullary  portion  of  terminal  proglottids. 
Adults  in  birds. 

Four  or  five  species,  some  in  shore  birds  that  occur  in  North  America. 


Fig.  753.  Amoebotaenia. 
Anterior  end,  magnified. 
(After  von  Linstow.) 


Fig.  754.     Amoebotaenia  cuncata.     a.  dorsal  view; 
b,  ventral  view;   magnified,     (.\fter  Cohn.) 


96  (95)     Two  rows  of  hooks  on  rostellum. 


Cvclustcra  Fuhrmann  iqoi. 


Rostellum  with  double  crown  of  hooks.  Longitudinal  musculature  in  three  layers,  (icni- 
tal  canals  pass  between  the  longitudinal  e.\cretor>'  vessels  and  ojx'n  into  a  very  muscular  cloacal 
canal.  Testes  numerous,  scattered  throughout  entire  dorsal  medullar>'  portion  of  proglottid. 
Ovary  and  yolk  gland  surrounded  by  ring-like  uterus  with  secondar\'  branches.  Eggs  with 
two  shells.  Adults  in  birds.  C.  capita,  the  type  species,  is  reported  by  Ransom  as  found  in 
the  roseate  spoonbill  in  North  America. 


97  (94)     Genital  pores  alternate  irregularly 9S 


446 


FRESH-WATER    BIOLOGY 


98  (99)     Uterus  sac-like 


Anomotaeiiia  Cohn  1900. 


Rostellum  with  double  crown  of  hooks,  w'ith  long  dorsal  and  short 
ventral  root,  and  long  blade.  Genital  pores  near  anterior  border  of 
segment.  Genital  canals  pass  between  the  longitudinal  excretory 
vessels  and  dorsal  of  the  nerve.  Vas  deferens  coiled,  seminal  vesicle 
absent.  Testes  numerous,  in  posterior  portion  of  segment  (or  rarely 
laterally  on  both  sides  of  the  female  glands).  Adults  in  birds  and 
mammals. 

]Many  species  from  both  land  and  water  birds  in  Europe.  A .  con- 
stricta  from  the  fish  crow,  determined  for  U.  S.  A.  by  Ransom.  [Many 
European  hosts  of  other  species  are  found  in  North  America. 


Fig.  755. 


Anomoiaenia  constricta.      Male  and  female   reproductive  organs, 
magnified.     (After  Volz.) 


99  (98)     Uterus  branching  and  in  ripe  proglottids  incompletely  divided  intp 
numerous  small  communicating  compartments .100 


loo  ^loi)     One  crown  of  hooks  on  the  rostellum.     Choanotaenia  Railliet  1896. 

Scolex  small.  Rostellum  armed  with  single  crown 
of  hooks  usually  with  long  dorsal  and  short  ventral 
root.  Proglottids  numerous,  rarely  less  than  30; 
oldest  often  longer  than  wide.  Genital  pores  irregu- 
larly alternate  near  anterior  border  of  proglottid, 
(ienital  canals  pass  between  longitudinal  excretory 
vessels  and  dorsal  of  nerve.  \^as  deferens  coiled, 
seminal  vesicle  absent.  Testes  numerous,  in  posterior 
region  of,  or  more  rarely  laterally  on  each  side  of,  the 
female  glands.  Uterus  subdivided  into  numerous 
small  communicating  chambers  incomplctelj'  sepa- 
rated by  partitions  infolded  from  wall  so  that  in  some 
cases  eggs  appear  almost  as  if  isolated  in  parenchyma. 
Adults  in  birds  and  mammals. 

A  dozen   species  or  more  from  North  American 

hosts;    land,  shore  and  water  birds  represented.    Ch. 

^  ^        ^,  .      .  ^     ,.,    ,         zWzmtfj&H/HW  is  common  in  chickens  and  is  recorded 

Fig.    756.       Choanotaenia    mfundibulum    for  North  America  generally.     Ch.  porosa  occurs  in  ?. 

a,   Hook  irom   rostellum;    magnmed;     seg-  ,  r  ^.  °,  .    ,      •'.,    .         ^     ^   j  v      t  •   i. 

ment  showing  reproductive  organs;  magni-    number  of   aquatic  birds;    it  is  reported  by  Linton 

fied.     (After  Ransom.)  from  gulls  at   Yellowstone  Lake. 


loi  (100)     Rostellum  armed  with  double  crown  of  hooks. 

Monopylidium  Fuhrmann  1899. 

Reproductive  organs  single  in  each  proglottid.  Genital  canals  pass  between  longitudinal  ex- 
cretory vessels  and  dorsal  to  longitudinal  nerve  or  to  both  excretory  vessels.  Testes  numerous 
(20  to  40  or  more),  behind  ovary  and  vitellarium  or  laterally  on  both  sides  of  latter.  Vas 
deferens  coiled;  seminal  vesicle  absent.  Uterus  breaks  down  into  egg  capsules,  each  con- 
taining usually  one  egg.     Adults  in  birds. 

A  dozen  species  in  European  hosts  which  include  some  shore  birds  found  in  North  America. 


102  (62)     Reproductive   glands   simple,  central   in   each   proglottid;    ducts 
and  pores  double,  one  set  on  each  side. 

Diploposthe  Jacobi  1896. 

Rostellum  armed  with  single  crown  of  ten  hooks.  Suckers  unarmed.  Inner  longitudinal 
muscle  layer,  except  for  two  or  three  small  bundles  lateral  beyond  excretory  vessels,  developed 
in  median  portion  consisting  of  about  ten  dorsal  and  ten  ventral  bundles  of  unequal  size. 
Outer  longitudinal  muscle  layer  of  numerous  equally  developed  bundles,  interrupted  where 
genital  canals  pass  through.  Outside  thin  layer  of  diagonal  fibers,  at  posterior  end  well- 
developed  muscle  ring.  Genital  pores  marginal,  one  on  each  side.  Testes  few  (3  to  7)  in 
posterior  portion  of  proglottid.     Two  vasa  deferentia.     Seminal  vesicles  present  on  each  side 


PARASITIC    Fl.ATWOKMS  4^7 

armed  with  strong  hooks.     Female  glands  single,  median;    two  vaginae.     Eggs  with  ilirtc 
membranes. 

The  type  species,  D.  laeyis,  from  various  ducks  and  geese  found  in  North  .\mcrica      .\o 
record  of  any  species  on  this  continent. 


vt       ov  vi 

Fig.  757.  Diplopostke  laevis.  Optical  section  of  ripe  proglottid;  vd,  vas  deferens;  /,  testes;  u,  uterus 
vt,  vitellaria;  ov,  ovary;  vs,  seminal  vesicle;  v,  vagina;    X  22.     (After  Jacobi.) 

103  (61)     Uterus  with   median  stem   and  lateral  branches;    female   genital 

glands  in  posterior  end  of  proglottid. 

Family  Taexiid.ve  Ludwig  1886. 
Splex  usually  with  well-developed  rostellum  armed  with  double  crown  of  hcxjks,  rarely  with 
rudimentary  unarmed  rostellum.  Suckers  unarmed.  Terminal  segments  longer  than  broad. 
Reproductive  organs  single  in  each  proglottid.  Cicnital  pores  irregularly  alternate.  Vas 
deferens  coiled,  seminal  vesicle  absent.  Testes  numerous,  scattered.  Double  ovary  poste- 
rior, median,  posterior  to  which  is  the  yolk  gland.  Egg  with  thin  outer  membrane,  and  thick 
brown  radially  striated  inner  shell.     Adults  in  mammals  and  birds. 

Taenia  Linnaeus  1758. 

Forms  rightly  included  here  are  as  adults  characteristic  parasites  of  higher  carnivorous  land 
animals  and  the  larval  forms  (cysticerci)  also  occur  in  land-living  herbivorous  or  omnivorous 
mammals. 

Eggs  are  distributed  widely  by  surface  waters.  Larval  stages  occur  rarely  in  aquatic  mam- 
mals, e.g.,  Cysticcrcus  fasciolaris  the  bladder-worm  of  Taenia  crassico/lis  of  the  cat  wliich  Stiles 
and  Hassall,  and  later  Linton  also,  have  reported  from  the  muskrat. 

104  (60)     Female  genital  pore  not  adjacent  to  cirrus  and  male  pore.   .    .      105 

105  (112)     Proglottids  without  lateral  appendages.     Female  genital  {xjre  is 

entirely  lacking. 

Family  Acoleidae  Fuhrmann  1007   .    .      106 
Thick-bodied   cestodes   with   rostellum   usually  armed.     Proglottids   short.      Musc-ulature 
very  powerful.     Cirrus  sac  very  large;    cirrus  armed  with  strong  spines.     Eggs  with  3  mem- 
branes.    In  birds. 

106(111)     Hermaphroditic  forms 107 

107(110)     ]\Iale  and  female  genital  organs  simple 108 

108  (109)     Testes  numerous;    seminal  receptacle  very  large;    uterus  a  trans- 

verse tube  anterior  to  ovary.     Male  genital  pores  regularly 

alternate icolcus  Fuhrmann  1809. 

Scolex  small  with  armed  rostellum.  Reproductive  organs  single.  Cirrus-pouch  passes 
ventral  of  longitudinal  excretory  vessels  and  nerve.  V'^agina  closed,  functions  as  very  large 
seminal  receptacle.    Adults  in  water  birds. 

Type  species lr()/(7/.s  (/rmc;///.?  Fuhrmann  1899. 

From  the  black-necked  stilt;  parasite  not  reported  from  North  .\merica. 

109  (108)     Testes    few;     seminal    receptacle    very   small;     uterus    encircling 

ovary;  male  pores  irregularly  ahernate. 

Ciyrococlia  Fuhrmann  iSoo. 
Rostellum  armed  with  single  crown  of  hooks  arranged  in  zig-zag  row  having  eight  angles. 
Reproductive  organs  single  in  each  proglottid.  Cirrus  |>nuh  jKisses  In-tween  longitvidina! 
excretory  vessels  and  dorsal  of  nerve.  Cterus  ring-like,  with  numerous  outixHketings.  and 
with  opening  in  terminal  proglottids  both  dorsally  and  ventrally  in  median  line  of  posterior 
margin.     Adults  in  birds. 

In  water  birds;   not  reported  in  North  .Vmerica. 


448  FRESH-WATER    BIOLOGY 

no  (107)  Male  reproductive  organs  double  and  female  single  in  each  pro- 
glottid with  two  vaginae  functioning  as  large  seminal  re- 
ceptacles  Diplophallus  Fuhrmann  1900, 

Large  forms  with  small  scolex  and  armed  ros- 
tellum.  Testes  numerous,  in  two  lateral  fields 
fully  separated  by  median  female  glands.  Cir- 
rus sac  powerful,  cirrus  slender,  very  long. 
Vagina  a  blind  transverse  canal.  Uterus  at 
first  transverse  tube:  later  irregular,  and  finally 
taking  in  entire  medullary  region. 

Type  species. 

Diplophallus  polymorphus 

(Rudolphi)  1819. 

Fig.  758. .  Diplophallus.  Schematic  transverse  Yxom  the  black-necked  stilt;  parasite  not  re- 
section of  ripe  proglottid;  /.testes:  «,  uterus;  sr,  ^^^  r „  -^t ,i     »„ . '^ 

seminal  receptacle;  ..,  ovary;  vt,  vitellaria.    (Afte^  ^^rded  from  North  America. 
Wolffhugel.) 

111  (106)     Dioecious,  entire  strobila  male  or  female;    male  with  a  double 

set,  female  with  a  single  set  of  reproductive  organs  in  each 

proglottid Dioicocestus  Fuhrmann  1900. 

Female  thicker  and  broader  than  male.  Vagina  irregularly  alternating,  reaching  almost  to 
the  edge  of  the  segment.  Testes  numerous,  divided  more  or  less  plainly  into  two  symmetrical 
groups.  Eggs  with  three  envelopes.  ]Male  ducts  paired  in  every  proglottid.  Adults  in 
birds. 

Type  species Dioicocestus  paronai  Fuhrmann  1900. 

Several  species  from  grebe  and  ibis;   parasite  not  recorded  from  North  America. 

112  (105)     Proglottids   carry   lateral   foHate   or   digitate   processes.     Female 

genital  pore,  when  present,  separate  from  marginal  male 
pore.     .    .    Family  Aimabiliidae  Fuhrmann  1907   .    .     113 

Rostellum  with  simple  crown  of  hooks.  Proglottids  short  with  lateral  margins  prolonged 
into  processes.  Musculature  weakly  developed.  Cirrus  sac  large;  cirrus  spinous.  Duct 
united  with  receptaculum  seminis,  designated  as  accessory  vagina,  opens  in  cases  on  surface  or 
on  margin  opposite  male  pore. 

In  water  birds. 

113  (114)     Male  sexual  organs  double  in  each  proglottid.     Accessory  vagina 

with  surface  opening.     Uterus  a  network. 

Amahilia  Diamare  1893. 

Scolex  very  small  with  armed  rostellum.  Male  reproductive  organs  double  with  one  pore 
on  each  side  of  proglottid.  Cirrus  armed  with  strong  spines.  Testes  numerous,  in  median 
field.  Female  organs  median,  single  set  in  each  proglottid.  Uterus  forming  network  con- 
sisting of  dorsoventral  ring  with  dorsoventral  anastomoses.  Accessory  vagina  opening  ven- 
trally,  communicating  (?)  with  canal  from  excretory  system  opening  on  ventral  surface  of 
proglottid  in  median  line.     Adults  in  birds. 

Type  and  only  species imabilia  lafnelligera  (Owen)  i8$2. 

114(113)     Male  organs  single  in  each  proglottid.     Uterus  sac-like. .    .    .     115 

115  (116)     Rostellum    thick,    powerful.     Male    pores    alternate    irregularly. 
Female  pore,  when  present,  on  surface  of  proglottid. 

Schistotaenia  Cohn  1900. 

Rostellum  very  large,  armed  with  heavy  hooks.  Between  rostellum  and  suckers  an  annular 
thickening  covered  closely  with  small  three-cornered  hooks.  Testes  numerous,  dorsal,  poste- 
rior, across  entire  width  of  proglottid,  reaching  maturity  later  than  female  glands.  Ovary 
and  vitellarium  large.  Male  duct  runs  between  excretory  canals,  accompanying  vagina  which 
ends  blindly  near  cuticula. 

Tj^e  species  S.  macrorhyncha  in  the  horned  grebe.  Parasite  not  recorded  from  North 
America. 


PARASITIC   FLATWORMS 


449 


ii6  (115)     Rostellum  long,  slender.     Male  pores  alternate  regularly.     Female 
pore,  when  present,  always  marginal. 

J  atria  Kowalewski  1904. 

Rostellum  with  single  crown  of  10  to  14  large  hooks  and  behind  them 
numerous  rows  of  small  conical  hooks.  Suckers  and  fKjsterior  p<jrtion 
of  head  covered  with  minute  spines.  Segments  not  numerous.  Cirrus- 
pouch  large.  Testes  not  numerous.  Male  and  female  canals  pass  be- 
tween longitudinal  excretory  vessels.  Distal  end  of  vagina  instead  of 
opening  to  exterior  turns  postenad  into  next  following  progh^ttid  and 
opens  into  seminal  receptacle  there.  Seminal  receptacles  median;  ac- 
cessory vagina  present  opposite  cirrus-pouch,  sometimes  with  ojx-ning. 
Adults  in  birds  (Urinatores). 

The  type  species  (Tatria  biremis  Kowalewski  iqo4)  occurs  in  the 
horned  grebe  and  has  not  been  reported  for  North  America.  In  1887 
Leidy  reported  Taenia  scolopendra  Diesing  from  this  host  and  that  species 
is  placed  here  by  some  authors. 


Fig.  759- 


Tatria  biremis.     Forma  major;   proglottids  with  lateral  appendages, 
X  30.    (After  Kowalewski.) 


117(55)     External  division  of  strobila  into  proglottids  lacking 118 


118  (119)  Anterior  portion  of  strobila  folded  and  coiled  to  form  large  pseudo- 
scolex;  strobila  grooved  transversely,  without  true  pro- 
glottid limits.    .    .    Family  Fimbriariidae  Wolfifhiigel  1898. 

Scolex  small,  imstable,  frequently  lost,  with  rostellum  armed  with  single  row  of  hooks. 
Pseudoscolex  conspicuous.  Strobila  with  transverse  grooves  which  produce  appearance  of 
segmentation.  Three  pairs  of  longitudinal  excretory  vessels.  Reproductive 
organs  not  segmentally  arranged.  Genital  pores  marginal,  irregular,  generally 
unilateral.  Testes  numerous,  arranged  in  transverse  rows.  Uterus  not  persist- 
ent, breaking  down  into  a  large  number  of  egg  sacs.  Egg  spindle-shaped  with 
thin  transparent  shell.    Adults  in  birds  (Anserif ormes) . 

Type  genus Fimhriaria  Frolich  1802. 

(Syn.  —  Epision  Linton  1S92.) 

Two  well-known  species  both  occur  in  North  American  water  birds;   a  third, 
F.  plicata  (Linton)  1892  is  recorded  from  the  American  scoter. 

Fig.  760.     Fimhriaria  plicata.      Lateral  view  of  head  and  anterior  part  of  body  of 
smallest  specimen.     X  8.     (After  Linton.) 


119  (118)     Scolex  small,  simple.     Strobila  round  or  nearly  so.    Without  pro- 
glottid boundary  except  at  extreme  posterior  end. 

Family  Nematot.venudae  Liihe  1910  .    .      uo 

Scolex  unarmed,  without  rostellum.  At  extreme  ix)stcri(.r  lilifomi  end  of  strobila  a  few 
separate  proglottids  visible  externally;  these  are  much  longer  than  thick,  sciviratc  readily,  and 
move  about  independently  a  long  time.  Genital  pores  alternate  irregularly.  Cirrus  and 
vagina  pass  dorsal  to  excretory  canals  and  nerve  trunks,  open  into  genital  atrium  marginal 
in  location.     Male  organ  dorsal,  female  ventral. 

In  intestine  of  .\mphibia. 


450 


FRESH-WATER    BIOLOGY 


20(121)     Two  testes  in  each  proglottid N emafo taenia  Luhe  iSgg. 

Strobila  thicker  near  anterior  end  becoming  thinner 
and  eventually  filiform,  circular  in  cross-section.  Neck 
short,  cirrus-pouch  long,  passing  within  longitudinal 
muscle  layer.  Vas  deferens  long,  with  ventral  loop 
between  ovary  and  excretory  canals.  Two  testes, 
dorsal  and  symmetrical.  Vitellarium  almost  exactly 
in  center  of  body.  Ovary  ventral,  nearly  median; 
uterus  horseshoe-shaped,  breaks  up  early  into  numer- 
ous capsules  with  2  to  4  eggs,  usually  3,  in  each  cap- 
sule becoming  ultimately  13  to  30  small  dark  uterine 
capsules. 

Records  of  its  occurrence  in'North  America  are  open 
to  question.  ' 

T>^e  species. 

N ematotaenia  dispar  (Goeze)  1782. 

Fig.  761.  Nematotaenia  dispar.  Transverse  section  of 
ripe  proglottid;  c,  cirrus;  t,  testes;  m,  retractor  muscle  of 
cirrus;  t'/,  vitellaria;  oi',  ovary;  vd,wa.s  deferens;  i',  vagina. 
Magnified.     (After  Fuhrmann.) 


121  (120)     One  testis  in  each  proglottid. 


Cylindrotaenia  Jewell  191 6. 


Strobila  thickest  near  center,  becoming  thinner 
towards  both  ends.  Neck  long.  Single  testis 
round,  on  aporal  side  of  proglottid  just  dorsal  to 
transverse  diameter.  Cirrus-pouch  short,  ending 
at  longitudinal  muscle  layer.  Vas  deferens  short, 
nearly  straight.  Uterus  breaks  up  into  capsules 
each  containing  4  to  6  eggs,  becoming  enclosed 
later  in  two  conical  organs,  one  dorsal  and  one 
ventral,  which  are  large  transparent  uterine  cap- 
sules. 

Type  species. 

Cylindrotaenia  americana  Jewell  1916. 
Perhaps  Taenia  pulchella  Leidy  1851  belongs 
here. 

Fig.  762.  Cylindrotaenia  americana.  Transverse 
section  of  ripe  proglottid;  t,  testes:  vd,  vas  deferens;  c, 
cirrus;  v,  vagina;  ov,  ovary;  vt,  vitellaria.  Magnified. 
(After  Jewell.) 


122  (i)     Larval  forms;  reproductive  organs  undeveloped 123 

Usually  small  and  unsegmented  though  some  bladder-worms  reach  considerable  size  and 
even  show  the  beginning  of  proglottid  formation.  On  the  whole  these  larvae  show  little  or  no 
organ  differentiation  and  are  distinguishable  from  adults  by  the  absence  of  characteristic 
structures.     Most  larvae  are  encysted  but  there  are  numerous  free  forms. 


123  (124)     Four  long  proboscides  covered  with  hooks. 


Very  rare  but  easily  recognized. 


Trypanorhyncha  (p.  434)- 


124(123)     No  proboscides  with  hooks  present 125 

125  (126)     Scolex  and  sucking  organs  hardly  differentiated  at  all  and  the 
latter  when  present  never  more  than  two. 

Larvae  of  Pseudophyllidea. 

(See  also  Sparganum,  p.  434.) 

The  anterior  end  of  these  and  other  larvae  is  often  rolled  in  so  that  its  exact  character  is 
difficult  to  determine. 


PARASITIC    FLATWORMS 
126  (125)     Four  suckers  on  the  scolex  of  the  larva. 


Cystlcercus 


451 


127 


The  head  of  the  larva  is  inverted  so  that  these  suckers  are  in  the  center  „f  the  mass  and  mav 
easily  be  overlooked.  In  the  narrower  sense  the  term  cystlcercus  is  applied  to  the  lar^'e  thin- 
walled  bladder-worm  having  a  cavity  of  considerable  size  filled  with  watery  fluid  in  which  the 
scolex  grows  from  a  polar  papilla  that  subsequently  hollows  out  giving  in  reverse  the  srolov  Af  ih.. 
adult  This  larva  belongs  to  the  terrestrial  fauna  and  occurs  only  SJnl^lly  in  aquatc  form 
hke  the  muskrat  which  have  become  a  part  of  the  acjuatic  fauna  secondarily. 


127  (128)     Entire  larva  solid  parenchyma   tissue, 
apex  at  bottom  of  infolding. 


Scolex   invaginuled   with 
Plcroccrcoid. 


Caudal  region  not  differentiated  at  all  or  only  very  poorly  indi- 
cated. In  general  structure  the  Bothriocephalid  larvae  with  two 
sucking  grooves  are  like  the  true  plerocercoids  with  4  acetabula 

Larvae  prominently  of  Proteocephalidae,  also  of  Cycloi)hyI!idea 
from  reptiles.  One  special  form  known  as  Gryporhynchus  has  been 
identifaed  as  the  larva  of  Dilepis  or  some  allied  genus. 

Fig.  763.  Proteocephahis  plerocercoid;  a,  from  the  body  cavity  b  from 
cyst  suckers  drawn  within  body.  Note  iar-e  end  organ,  shaded;  c\  from 
intestine;   optical  sections,  X  10.     (After  La  Rue.) 


(127)     Spaces  in  larva  between  folds  of  tissue, 
surrounded  by  cyst 


Scolex  in  natural  position,, 
Cxsticcrcoid. 


Usually  with  caudal  appendage  in  a  posterior  hollow  of  the  cyst,  and  on  the  tail  the  embrv- 
onic  booklets  of  the  onchosphere.  In  form  and  texture  the  cyst  varies  greatly.  Calcareous 
bodies  abundant,  mostly  on  the  invaginated  layer  between  the  cyst  and  the  scole.x  which  corre- 
sponds to  the  neck  when  the  larval  head  is  evaginated. 

Very  frequent  among  Cyclophyllidea.  Relationship  between  the  cysticcrcoid  and  the  adult 
may  be  inferred  from  careful  e.xamination  of  the  scolex  and  its  armature. 

No  records  exist  of  the 
presence  in  North  .Ameri- 
ca of  these  forms.  I-'or 
convenience  in  recogniz- 
ing them  a  figure  is  in- 
cluded of  an  abundant 
European  form  likely  to 
occur  here  also  in  similar 
aquatic  hosts.  W  hile 
these  cysticercoids  are 
most  fretjuently  recridid 
from  t\)pepoda.  Ostra- 
coda,  and  other  small 
aquatic  Crustacea,  they 
occur  also  in  l.unibruu- 
liis  and  other  .'■mall  an- 
nelids, and  more  rarely  in 
small  snails  and  slugs. 


Fic.  764.   Drttanidotantia 
fiiu  idtd.    a,  IkkIv  of  Cyili^t's 
<m;»/«5.      containlru-       l.tx  .1 
i.i|><."worm  (c\    ■ 
simc  Iar\-a  wi; 
lon>:  tail,  isol   • 
crustaci-an; 
with  cxtrndf 
nil'iol.     (.\ft(  : 


452  FRESH-WATER   BIOLOGY 


REFERENCES  ON  NORTH  AMERICAN  PARASITIC  WORMS 

IMPORTANT  GENERAL  WORKS 

CoBBOLD,  T.  S.     1864.     Entozoa.     480  pp.     82  figs.     London. 
1879.     Parasites.     508  pp.     London. 

DiESiNG,  C.  M.  1850,  185 1.  Systema  helminthum.  Vienna.  2  vols.;  679 
and  588  pp. 

DujARDiN,  F.  1845.  Histoire  naturelle  des  helminthes,  ou  vers  intestinaux. 
Paris.     654  pp.     Atlas,  12  pi. 

Leidy,  J.  1904.  Researches  in  Helminthology  and  Parasitology.  Smith. 
Inst.,  Misc.  Coll.,  vol.  46,  Art.  Ill,  281  pp.  (Reprint  of  Leidy's  contribu- 
tions from  1845  to  1 89 1.     With  a' bibliography.) 

LiNSTOW,  O.  VON  1878.  Compendium  der  Helminthologie.  382  pp. 
1889.     Nachtrag.     157  pp.     Hannover. 

Looss,  A.  1901.  Zur  Sammel-  und  Conservirungstechnik  von  Helminthen. 
Zool.  Anz.,  24:  302-304,  309-318. 

Smith,  A.  J.  1908.  Synopsis  of  Studies  in  Metazoan  Parasitology.  Univ. 
Penn.  Med.  Bull.,  Feb.,  68  pp.  10  pi. 

Stiles,  C.  W.,  and  Hassall,  A.     1894.    A  PreUminary  Catalog  of  the  Para- 
sites Contained  in  the  Collections  of  the  U.  S.  Bureau  of  Animal  Industry, 
U.  S.  Army  Medical  Museum,  etc.     Vet.  Mag.,  i:  245-253,  331-354. 
1902-1912.     Index-Catalog  of  Medical  and  Veterinary  Zoology.     (Authors.) 
Bur.  An.  Ind.,  Bull.  No.  39;  36  parts,  2766  pp. 

Wright,  R.  R.  1879.  Contributions  to  American  Helminthology,  Proc, 
Can.  Inst.,  n.s.  i:  54-75,  2  pi. 

trematoda 

Braun,  M.     1879-93.     Trematodes.  Bronn's  Klass.  u.  Ord.  d.  Tierreichs, 

Vol.  4,  925  pp.,  34  pi.     Leipzig. 
Cooper,  A.  R.     191 5.    Trematodes  from  Marine  and  Fresh-Water  Fishes. 

Trans.  Roy.  Soc.  Can.,  (3)  9:  181-205,  3  pi. 
Cort,  W.  W.     191 5.     Some  North  American  Larval  Trematodes.    111.  Biol. 

Monogr.,  i:  447-532;  8  pi. 
Looss,  A.     1894.    Die  Distomen  unserer  Fische  und  Frosche.    Biblth.  Zool., 

Heft.  16,  296  pp.,  9  pi. 
1899.    Weitere  Beitrage  zur  Kenntniss  der  Trematoden-Fauna  Aegyptens, 

zugleich  Versuch  einer  natiirlichen  GHederung  des  Genus  Distomum  Ret- 

zius.     Zool.  Jahrb.,  Syst.,  12:  521-784,  9  pi. 
Luhe,   M.     1909.    Parasitische  Plattwiirmer.    I:  Trematodes.     Susswasser- 

fauna  Deutschlands,  Heft  17,  217  pp.,  188  figs. 
Odhner,  T.    1 9 10.   Nordostafrikanische  Trematoden.   I.   Fasciolidea.    Swed- 
ish Zool.  Exp.,  23  A;  170  pp.,  6  pi. 


PARASITIC    FLATWORMS  4^3 

1911-1913.     Zum    naturlichen    System    der    digcncn    Trcmatodcn    I-VI. 
Zool.  Anz.,  vols.  37-42. 
Pratt,  H.  S.     1900.     Synopses  of  North  American  Invertebrates,  XII.     The 
Trematodes.     Part  i.     Heterocotylea.     Am.  Nat.,  34:  645-662;   50  ligs. 
1902.     Part  2.     Aspidocotylea  and  Malacocotylea.     Am.  Nat.,  36:  887-910, 
953-979;  8  pi. 
Stiles,  C.  W.  and  Hassall,  A.     1908.     Index-Catalog  of  Medical  and  \'eter- 
inary  Zoology.     Subjects:    Trematoda  and  Trematode  Diseases.     Hyg. 
Lab.,  Bull.  No.  37,  401  pp. 


CESTODA 

Braun,  M.     1894-1900.     Cestodes.     Bronn's   Klass.  u.  Ord.  d.   Tierreichs, 

Vol.  4,  p.  927-1732,  25  pi.     Leipzig. 
La  Rue,  Geo.  R.     1914.     A  Revision  of  the  Cestode  Family  Proteocephalidac. 

111.  Biol.  Monogr.,  i:  1-350,  16  pi. 
LtJHE,     M.      Parasitische     Plattwurmer.     II.      Cestodes.      Susswasserfauna 

Deutschlands,  Heft  18,  153  pp.,  147  figs. 
Ransom,  B.  H.     1909.     The  Taenioid  Cestodes  of  North  American  Birds. 

U.  S.  Nat.  Mus.,  Bull.  69,  141  pp. 
Stiles,  C.  W.  and  Hassall,  A.     191 2.     Index-Catalog  of  Medical  and  \'cteri- 

nary  Zoology.     Subjects:    Cestoda  and   Cestodaria.    Hyg.   Lab.,   Bull. 

No.  85,  467  pp. 


CHAPTER   XIV 
THE    NEMERTEANS 

By  WESLEY  R.  COE 

Sheffield  Scientific  School  of  Yale  University 

Among  the  fresh-water  animals  of  the  northern  half  of  the 
United  States  occurs  a  slender  Httle  worm  of  a  beautiful  reddish 
color  belonging  to  the  group  of  Nemerteans.  These  worms  can  be 
easily  distinguished  from  the  other  flatworms  (Platyhehninthes) 
by  the  slenderness  of  the  body,  and  from  the  other  groups  of  worms 
by  their  perfectly  smooth,  ciliated  bodies  and  their  leisurely  creep- 
ing movements.  The  presence  of  the  proboscis  armed  with  a 
formidable  calcareous  stylet  which  can  be  thrust  out  of  the  opening 
at  the  anterior  end  of  the  body  is  proof  that  the  worm  is  a  ne- 
mertean. 

These  nemerteans  live  along  the  shores  of  lakes  and  streams, 
as  well  as  in  pools  and  artificial  basins  of  water  and  aquaria.  Quiet, 
shallow  areas  of  water  with  a  dense  growth  of  water  plants  are 
particularly  favorable.  The  worms  may  be  found  creeping  over 
the  stems  and  leaves  of  the  water  plants,  among  the  dead 
leaves  and  debris  at  the  bottom,  on  stones  and  objects  in  the 
water,  and  oftentimes  beneath  the  stones  along  the  shore.  The 
under  sides  of  floating  leaves,  as  Hly  pads,  particularly  those  par- 
tially decayed,  often  harbor  numbers  of  these  tiny  worms.  They 
are,  however,  local  in  distribution  and  are  seldom  found  in  abun- 
dance over  a  very  wide  area.  When  common  in  a  shallow  inlet  a 
few  yards  wide,  a  further  search  for  a  mile  along  the  shore  of  a 
lake  or  stream  may  fail  to  reveal  a  single  specimen. 

The  worms  are  usually  from  lo  to  i8  mm.  in  length  when  fully 
extended,  but  may  contract  to  a  small  fraction  of  their  former 
length.  They  rarely  exceed  i  mm.  in  diameter.  The  color  varies 
considerably,  shades  of  red,  orange,  or  vermiUon  being  most  com- 
mon, while  the  smaller  specimens  are  often  pale  yellowish  or  flesh 
colored.    The  anterior  half  of  the  body  is  more  brightly  colored 

454 


THE   NEMERTEANS 


455 


CP 


cc 


—  LI\J 


than  the  posterior  portion,  where  the  in- 
testinal lobes  and  reproductive  glands 
modify  the  brilliancy  of  the  coloring. 
Some  individuals  have  a  cast  of  reddish 
brown. 

On  the  anterior  end  of  the  bod>'  arc 
usually  six  black  pigment  spots,  or  ocelli, 
arranged  symmetrically  in  three  pairs  {o, 
Fig-  765).  Smaller  specimens  may  have 
but  four  ocelli,  and  occasional  irregularities 
occur  in  which  the  number  may  be  live, 
seven,  or  eight. 

It  is  to  the  internal  organization  of  the 
body,  however,  that  one  must  look  for 
those  characters  which  are  mainly  used 
in  the  classification  of  the  nemerteans. 
These  structures  must  be  studied  in  most 
species  by  means  of  serial  sections,  but, 
fortunately,  the  fresh-water  forms  arc  so 
nearly  transparent  that  the  principal  or- 
gan systems  of  the  body  may  be  studied 
in  the  Hving  animal.  It  is  only  necessary 
to  place  the  worm  on  a  slide  with  a  small 
drop  of  water  and  flatten  the  body  be- 
neath a  cover  glass.  When  such  a  speci- 
men is  examined  under  the  low  powers 
of  a  microscope  the  principal  anatomical 
features  are  easily  made  out. 

Particularly  characteristic  is  the  probos- 
cis, a  strong  muscular  organ  (/>.  Fig.  7O5) 
contained  in  the  rh>-nchococl  and  en- 
closed by  the  proboscis  sheath.  This 
organ  extends  from  the  anterior  extrem- 
ity nearly  to  the  posterior  end  of  the  bod)-. 

Fig.  765.  Sticlwstcmma  ruhrum  (Ix-idyl.    Diapram  of  Ii\  i;:.-  in  !i- 
vidual  flattened  beneath  a  cover  plass.  showinR  inli  r 
i4,anus;   C,  pyloric  cecum;    Ct\  cephalic  furnnv; 
ganglia:  Cponad;  /.intestine;  LiV.  lateral  nerve;  (>.•> 
boscis;  i?,  rhynchodaeum;  /?C,rhynchocoel;  /^A/,  retractor  muscle  of  proboscis;  5,  centr.il  styUt  .m  !  •iv-; 


-  RM 


—  A 


456  FRESH-WATER  BIOLOGY 

Back  toward  its  posterior  third,  the  proboscis  is  armed  with  a 
needle-like  calcareous  stylet  (s)  resting  upon  a  solid  conical  basis. 
Beside  the  central  stylet  there  are  two  lateral  pouches  each  con- 
taining 2,  3,  or  4  accessory  stylets  of  size  and  shape  similar  to  the 
central  stylet.  The  proboscis  is  considerably  longer  than  the  sheath 
in  which  it  hes  coiled  and  to  which  it  is  attached  at  both  ends. 
By  means  of  its  powerful  musculature  it  can  be  thrust  out  of  the 
anterior  end  of  the  body.  This  process  of  eversion  turns  the  ante- 
rior part  of  the  proboscis  inside  out  and  brings  the  central  stylet 
to  the  end  of  the  everted  organ,  where  it  constitutes  a  formid- 
able weapon  of  defense  or  offense.  After  eversion  the  retractor 
muscle  at  its  posterior  end  withdraws  the  proboscis  to  its  original 
position. 

The  mouth  and  proboscis  open  together  through  the  rhyncho- 
daeum  (;-)  at  the  anterior  end  of  the  body.  The  esophagus  leads 
into  a  broad  stomach,  and  this  into  the  intestine  with  its  numer- 
ous lateral  lobes.  At  the  anterior  end  of  the  intestine  a  pair 
of  pyloric  ceca  (c)  extend  forward  to  the  brain.  The  short  rec- 
tum leads  to  the  opening  at  the  posterior  end  of  the  body.  The 
nemerteans  feed  upon  other  worms  and  soft-bodied  animals  of 
various  kinds. 

The  central  nervous  system  consists  of  the  four  cerebral  gangHa 
and  a  pair  of  large  longitudinal  lateral  nerves  (In).  These  are 
easily  seen  in  the  Hving  worm. 

The  excretory  system  extends  the  entire  length  of  the  body  as  a 
series  of  dehcate  tubes  with  several  efferent  ducts  leading  to  each 
side  of  the  body.  The  three  longitudinal  trunks  of  the  blood 
vascular  system  are  often  distinctly  seen  in  the  Hving  animal. 

The  fresh- water  nemerteans  are  hermaphroditic,  and  usually 
protandric.  The  gonads  are  arranged  serially  along  each  side  of 
the  body  between  the  intestinal  lobes.  Each  gonad  bears  both 
male  and  female  genital  products,  which  are  discharged  when 
mature  through  a  small  pore  opening  on  the  side  of  the  body. 
The  male  sexual  elements  are  formed  first,  and  in  the  smaller  and 
evidently  younger  worms  the  gonads  are  filled  with  developing 
spermatozoa.  Later,  and  after  the  discharge  of  a  portion  of  the 
spermatozoa,  the  eggs  begin  their  development. 


THE   NEMERTEANS 


457 


As  a  rule  a  single  egg  is  formed  in  each  gonad,  although  some- 
times there  are  two.  Even  when  the  eggs  are  fully  formed  there 
remains  in  each  gonad  a  portion  of  the  spermatozoa  i)revi(jusly 
formed.  This  fact  has  led  certain  investigators  to  conclude  that 
self-fertilization  may  sometimes  occur.  The  eggs  are  fertilized  after 
deposition,  however,  and  the  gregarious  habits  of  the  worms  pre- 
sumably insure  the  presence  of  spermatozoa  from  other  individuals 
which  may  effect  cross  fertilization  in  whole  or  part. 

The  eggs  are  deposited  in  a  double  string  embedded  in  a  jelly 
which  attaches  them  to  the  water  plants  or  other  objects  on  which 
the  worms  are  found.  They  are  beautiful  objects  by  which  to 
illustrate  the  processes  of  fertilization,  maturation,  cleavage  and 
the  development  of  the  embryo. 

The  worms  may  be  kept  ahve  for  a  long  time  in  aquaria  contain- 
ing water  plants,  and  under  suitable  conditions  will  continue  to 
live  and  breed  year  after  year.  They  thrive  under  the  conditions 
found  in  botanical  gardens,  where  large  basins  of  water  are  used 
in  the  cultivation  of  exotic  water  plants. 

Although  the  nemerteans  are  represented  by  numerous  genera 
and  species  in  the  oceans  in  all  parts  of  the  world,  only  a  few  forms 
occur  in  fresh  water  and  a  few  others  in  moist  places  on  the  land. 

In  North  America  only  a  single  genus  is  known  from  fresh  water, 
and  of  this  genus  the  described  species  are  so  closely  similar  as  tc 
lead  to  some  doubt  as  to  whether  more  than  a  single  .species  is 
actually  represented. 

In  1850  Leidy  published  a  brief  and  imperfect  descrii)tion  of  a 
nemertean  found  in  the  vicinity  of  Philadeli^hia,  which  sj)ecies  he 
described  as  Emea  rubra.  Silliman  later  found  the  same  or  a 
very  similar  species  in  New  York  State,  to  which  he  gave  the  name 
Tetrastemma  aquarium  dulcium,  and  included  Leidy's  species  therein. 
Montgomery,  in  1896,  described  under  the  name  Stichostcmma 
asensoriatum,  a  similar  species  from  Pennsylvania,  while  aj-Jixir- 
ently  similar  forms  have  been  recorded  from  Connecticut,  Illinois, 
Nebraska,  and  Washington.  The  worms  are  thus  known  to  occur 
from  the  Atlantic  to  the  Pacific  coasts  and  have  probably  i)een 
observed  at  numerous  unrecorded  localities  in  the  intervening 
territory. 


458  FRESH-WATER   BIOLOGY 

But  whether  the  nemerteans  from  these  widely  separated  local- 
ities represent  a  single  or  several  distinct  species  is  not  yet  defi- 
nitely known.  Since  fresh-water  nemerteans  similar  to  ours  are 
found  in  England,  Germany,  and  other  parts  of  Europe,  and  in 
Asia  and  Africa,  a  careful  study  of  specimens  from  many  Ameri- 
can localities  is  necessary  to  settle  the  question  of  nomenclature. 
For  it  is  not  improbable  that  some  of  the  locaHties  mentioned 
have  been  stocked  with  forms  transported  from  other  parts  of  the 
country,  or  from  other  quarters  of  the  >^orld.  The  importation 
of  cultivated  water  plants  furnishes  ideal  conditions  for  the  intro- 
duction of  the  nemerteans  associated  with  them. 

A  recent  study  indicates  that  the  species  found  in  Connecticut 
is  identical  with  that  recorded  by  Montgomery  from  Pennsylvania. 
This  species  differs  in  certain  anatomical  details  from  any  of  the 
described  exotic  forms,  but  is  evidently  synonymous  with  Leidy's 
Emea  rubra.  Since  there  is  nothing  in  the  pubHshed  descriptions  of 
specimens  from  other  North  American  localities  to  indicate  a  spe- 
cific distinction  it  is  at  present  possible  to  recognize  but  a  single 
species,  to  which  the  name  Stichostemma  rubrum  (Leidy)  should  be 
applied. 

IMPORTANT    REFERENCES    ON    FRESH-WATER    NEMERTEANS 

BoHMiG,  L.  1898.  Beitrage  zur  Anatomic  und  Histologic  der  Nemertinen. 
[Stichostemma  graecense  (Bohmig),  Geonemertes  chalicophora  (Graff).]  Zcit. 
f.  wiss.  Zool.,  64:  479-564. 

Detailed  account  of  the  structure  of  a  fresh-water  form. 

BtJRGER,  O.     1895.     Die  Nemertinen  dcs   Golfcs  von  Ncapel  und  der  an- 

grenzenden  Mecres-abschnitte.     Fauna  u.  Flora  v.  Ncapel,  Monogr.  22. 

Important  monograph  on  the  European  nemerteans. 

Child,  C.  M.     1901.     The  Habits  and  Natural  History  of  Stichostemma. 

Am.  Nat.,  35:  975-1006. 
Hartmeyer,  R.  1909.     Nemertini.     Die  Siisswasserfauna  Deutschlands,  Heft, 

19:  47-48. 
Montgomery,  T.  H.,  Jr.     1895.    Stichostemma  eilhardi  nov.  gen.  nov.  spec. 
Ein  Beitrag  zur  Kenntnis  der  Nemertinen.     Zeit.  f.  wiss.  Zool.,  59:  83-146. 
Anatomical  study  of  a  fresh- water  nemerteau. 
1896.     Stichostemma  asensoriatum  n.   sp.,  a  Fresh -water  Ncmertean  from 
Pennsylvania.     Zool.  Anz.,  19:  436-438. 

Description  of  a  fresh-water  nemertean  from  Pennsylvania. 


CHAPTER   XV 
FREE-LIVING    NEMATODES 

By  N.   a.    COBB 

U.  S.  Department  of  A zricullure 

Practically  any  collection  of  sand,  mud,  debris  or  aquatic  vege- 
tation, from  standing  or  running  water,  in  any  part  of  the  coun- 
try, will  yield,  on  examination  with  a  hand  lens,  minute  slender 
organisms  which  whip  themselves  about  by  means  of  more  or 
less  rapid  contortions  of  the  whole  body.  This  t}pe  (jf 
movement  identifies  them  as  nematodes;  it  dilYers  from  that 
of  other  small  organisms  in  that,  though  often  vigorous  and  con- 
spicuous, it  is  in  one  plane  only,  the  dorso- ventral  plane  of  the 
body,  and  in  that  the  length  and  proportions  of  the  body  mean- 
while remain  unchanged.  In  pure  water,  moreover,  this  thrash- 
ing about  seems  to  produce  no  locomotion;  the  animal  remains 
in  the  same  spot  unless  among  vegetation,  debris  or  particles 
of  soil.  When  quieted  by  stupefying  or  killing,  these  fresh- 
water nematodes  ("threadworms"  or  "roundworms")  are  seen 
to  be  more  or  less  cyUndroid  unsegmented,  without  locomotor 
appendages,  varying  in  length  up  to  a  centimeter  or  more. 
They  belong  to  a  group  in  the  animal  kingdom  comparable  in 
number  and  importance  with  the  insects;  nematodes  of  other 
sorts  live  free  in  the  soil,  and  in  the  sea,  r.nd  infest  as  parasites 
an  immense  variety  of  plants  and  other  animals.  They  arc  in- 
conceivably abundant.  A  tablespoonful  of  ooze  from  the  bottom 
of  the  ocean  may  contain  thousands  of  specimens.  The  number 
of  nematodes  in  the  top  six  inches  of  an  acre  of  ordinary  arable  soil 
is  shown  by  statistical  calculations  lo  reach  thousands  of  nu'llions. 
The  number  of  eggs  vastly  exceeds  even  that  of  adults;  for  they 
are  usually  very  prolific,  a  single  female  somelinies  producing 
hundreds  of  thousands  of  eggs. 

Even  the  free-living  soil  and  water  nematodes  have  become 
adapted  to  an  astounding  variety  of  habitats;  they  occur  in  arid 
deserts,  at  the  bottom  of  lakes  and  rivers,  in  the  waters  oi  hot 

459 


460  FRESH-WATER   BIOLOGY 

springs  and  in  polar  seas.  They  were  thawed  out  alive  from 
Antarctic  ice  by  members  of  the  Shackleton  expedition.  An  exam- 
ination of  beet  seeds  imported  into  the  United  States  disclosed 
the  presence  on  them  of  several  species  of  nematodes.  The  tap 
water  of  even  well-conducted  cities  often  contains  nematodes. 
Their  microscopic  eggs  and  larvae,  even  more  readily  than  the 
adults,  are  transported  from  place  to  place  by  an  exceedingly  great 
variety  of  agencies.  They  are  carried  by  the  wind,  by  flying 
birds  and  running  animals,  they  float  in  ah  the  waters  of  the  earth, 
and  are  shipped  from  point  to  point  throughout  the  civilized  world 
in  vehicles  of  traflic.  Sometimes  the  eggs  and  larvae  are  so  re- 
sistant to  dryness  that  if  converted  into  dust  they  revive  again 
when  given  moisture,  even  after  as  long  a  period  as  a  quarter  of 
a  century.  There  are  beneficial  nematodes,  though  knowledge  of 
this  phase  of  the  subject  is  in  its  infancy.  Some  nematodes  feed 
exclusively  on  their  injurious  brethren.  Others  devour  baneful 
micro-organisms.  Their  adaptations  in  these  respects  appear  to  be 
similar  to  those  of  insects. 

The  smaU  fraction  of  the  fresh-water  nematodes  of  North  America 
at  present  known,  comprises  only  about  thirty  genera,  but  these 
present  such  a  variety  of  form  that  a  thorough  knowledge  of  them 
insures  a  fair  understanding  of  all  the  free-living  nematodes.* 

The  number  of  nematode  species  is  enormously  greater  than 
commonly  supposed.  Since  most  species  of  vertebrates  are  in- 
fested by  one  or  more  nematodes,  and  with  comparatively  few  ex- 
ceptions a  given  parasitic  nematode  infests  but  one  host,  it  may  be 
estimated  that  more  than  80,000  nematode  species  infest  the  forty 
odd  thousand  species  of  vertebrates.  Insects,  also  much  infested, 
will  add  many  thousands  of  species.  The  molluscs,  crustaceans, 
and  various  groups  of  worms  are  also  infested,  and  investigation 
continues  from  this  source  also  to  augment  the  number  of  known 
species  of  parasitic  nematodes. 

Numerous  as  the  parasitic  species  are,  it  is  certain  that 
the  species  of  nematodes  living  free   in   soil   and   in   water   far 

*  In  an  attempt  to  distinguish  the  parasitic  nematodes  from  the  aquatic  and  soil- 
inhabiting  nematodes,  the  latter  are  usually  assigned  to  the  group  of  free-living  nema- 
todes, —  an  arbitrary  classification  not  based  on  natural  relationships. 


FREE-LIVING  NEMATODES 


461 


outnumber  them;  and  the  number  of  free-Uving  individuals  is 
so  great  that  they  probably  constitute  one  of  the  important 
mechanical  as  well  as  biological  factors  in  soil,  and  in  the  bot- 


Lip , 

Lateral  field 
Pharyngeal  bulb 

Pharynx   , 

Salirary  gland 
Muscular  layer 

Cuticula 

Hair  

Esophagus 

Cuticula 

Nerve-ring 

Duct  of  ventral  gland 

Esophagus. 

Nerve  ring 

Ridge  in  cuticula 

Esophagus   

Stria  of  cuticula 

Sub- cuticula 

Wing  of  cuticula 

Cuticula 

Cardiac  bulb  ... 
Dorsal  field 


Valvular  apparatus 
Its  radial  muscles 
Muscular  layer 
Wall  of  intestine 
Wing  of  cuticula 
Ovum  fit  to  fertilize 


29.  Blind  end  ovary 

30.  Intestine 

31.  Yolk  of  egg 

32.  Nucleus  of  egg 

33.  Shellofegg... 

34.  Internal  lateral  field  ,. 

35.  External  lateral  field 

36.  Intestine      


37.  Copulatory  muscle 

38.  Wing  of  cuticula. 

39.  Copulatory  muscle 

40.  Intestinal  cell    

41.  Accessory  male  organ 

42.  Ejaculatory  duct 

43.  Copulatory  muscle 

44.  Wmg  of  cuticula 

45.  Constriction  in  spiculum 

46.  Right-hand  spiculum 

47.  Distal  end  spiculum     

48.  Accessory  piece 

49.  Caudal  gland  . .   . . 
60    Left  wing  of  bursa 

61.  1st  caudal  gland 

62.  2nd  caudal  gland 

63.  3rd  caudal  gland 

64.  Muscular  wall    

56.   Right  wing  of  bursa 


.   Cephalic  seta 
.    Labial  papilla 
,   Pharyngeal  rib 
.   Pharynx  or  throat 
.   Pharyngeal  tooth 
.   Pharyngeal  bulb 
.   Salivary  gland 
.  Lateral  organ 
,  Esophagus  tube 

Eye,  with  lens 
,   Excretory  pore 
.   Ampulla 
.   Median  bulb 
.   Nerve-rmg 

Ganglion  cells 
,   Duct  of  ventral  gland 
.   Duct  of  lateral  gland 

A  lateral  gland 

Cardiac  bulb 

Valvular  apparatus 
,  Wing  or  ridge  in  skin 

Cardiac  coUum 

Cardia 

Stomach  or  intestine 

Tessellation  of  same 

Cuticula 

Wall  of  intestine 

Ventral  gland 

Striation  in  cuticula 

Ripe  ovum 

Uterus 

Unripe  ovum  in  ovary 

Spermatoioa 

Fertilised  egg  in  uterus 

Blind  end  of  ovary 

Yolk  of  egg 

Vaginal  glund 

Vulva 

Vagina 

Vaginal  gland 

Lateral  field 

Seminal  vesicle 

Wall  of  same 

Spermatozoa 

Copulatory  muscle 

Accessory  male  organ 

Ductus  ejaculatoriuB 

Three  pre-anal  papillao 

Copulatory  muscle 

Proximal  end  spiculum 

Pylorus 

Anterior  ribs  of  bursa 

Anal  gland 

Anus 

Post  anal  papillae 

Caudal  gland 

Median  ribs  of  bursa 

ursa 
Posterior  ritis  of  bursa 
Duct  ofraudul  glandt 
Terminus 


Diagram  of  Nematode  structure. 


Fig.  766. 
Above,  anterior  end  of  female.     Below  posterior  end  of  male. 
(After  Cobb.) 

toms  of  lakes  and  oceans.  The  aquatic  nematode  species  exist 
in  enormous  numbers,  in  both  fresh  and  salt  water,  while  tlic 
number  of  individuals  is  past  computation.    The  unavoidable  con- 


462  FRESH-WATER   BIOLOGY 

elusion  is  that  there  must  be  hundreds  of  thousands  of  species  of 
nematodes. 

Nearly  all  the  tissues  of  the  fresh-water  nematodes  are  compara- 
tively colorless  and  transparent,  and  whatever  decided  color  the 
body  possesses  is  usually  confined  to  the  intestinal  region.  The 
cells  of  the  intestine  itself  are  sometimes  colored  by  the  presence 
in  them  of  granules  of  a  faint  yellowish  or  brownish  tint,  and 
the  middle  portions  of  the  body  are  thus  rendered  yellowish  or 
brownish.  The  color  of  the  ingested  food,  showing  through  the 
tissues  of  the  body,  is  also  sometimes  a  color  factor.  The  food 
varies  in  color  from  nearly  black  to  colorless,  and  the  body  is 
correspondingly  tinted.  Species  feeding  on  the  juices  of  plants 
are  usually  nearly  colorless,  e.g.,  species  of  Tylenchns  and  Aphe- 
lenchus.  A  few  species  possess  colored  eye-spots  near  the  head. 
In  some  species  the  esophagus  contains  yellowish  or  brownish 
pigment. 

Most  genera,  and  even  some  species,  of  fresh-water  nematodes 
have  a  world-wide  distribution.  The  small  size  and  the  vitaHty 
of  the  individuals  favor  their  transportation  in  a  great  variety  of 
ways,  one  of  the  most  efficient  vehicles  being  the  feet  of  flying 
water-fowl.  Possibly  some  of  the  aquatic  species  are  as  resistant 
to  dryness  as  are  rotifers,  and,  as  "dust,"  are  blown  about  in  the 
same  manner.  Certain  species  of  plant-infesting  nematodes  will 
revive  after  many  years  of  desiccation. 

Another  cause  of  this  wide  distribution  is  the  fact  that  fresh- 
water nematodes  adapt  themselves  to  a  great  variety  of  depths  and 
temperatures.  They  are  found  as  near  the  poles  as  are  any  other 
organisms.  They  occur  in  practically  every  body  of  water  where 
extreme  conditions  do  not  preclude  Hfe  of  any  kind.  Few  organ- 
isms are  so  easy  to  find. 

The  outer  covering  of  a  nematode  is  composed  of  a  non-cellular 
layer  usually  divided  into  two  parts,  the  cuticula  and  the  subcutic- 
ula.  These  groups  are  not  easily  defined,  but  the  natural  division 
line  is  probably  between  the  outer  layers  that  are  to  be  shed  at  the 
next  moult,  and  all  the  other  layers.  Thus  the  subcuticula  in  turn 
becomes  the  cuticula.  The  cuticula  is  composed  of  about  three 
layers  and  the  subcuticula  of  about  an  equal  number.     Though 


FREE-LIVING  NEMATODES 


463 


some  of  the  markings  usually  to  be  seen  in  the  cuticula  are  due  to 
sense  organs  or  to  pores,  most  of  them  are  inherent  structural 
markings.  These  markings  are  used  as  specific,  and  in  some  cases 
as  generic,  characters. 

The  cuticula  of  almost  any  species,  if  examined  with  sufficient  care 
will  show  transverse  striations,  ranging  in  the  various  species  from 
a  few  score  to  upwards  of  a  thousand.  m 

Many  species  described  by  earher  writers 
as  destitute  of  these  striations  really 
possess  them.  When  very  fine  the 
transverse  striae  are  best  seen  at  the 
extremities  of  the  organism.  In  some 
genera  the  striae  are  apparently  due  to 
the  constant  bending  of  the  body  in  the 
dorso- ventral  plane.     This  pecuhar  mo-  ^  "^ 

.  .  I'iG.  767.      Diagrammatic   cross-section 

tion,   which  IS   universal  amongr  nema-      ti^^ugh  the  middle  of  a  nematode. 

°  "".  ovary;   tnt,  mtestme;   m.   median 

todes,  and  continuous  from  birth  to  fidd^;  i:t'cutVS^=-S;^^^^ 
death,  unceasingly  stretches  and  then  !u!d"tbmSbn''its":?ri^ 
compresses  the  dorsal  and  ventral  sur-      '^S^:^''^^^<:'\:S:^:'li 

r  A  ^     ^T-        J.*  1  J^  •  course,  in   no  sense  organs,  but  only 

laces.       At     tne     time     when     the     one     is        convenient   descriptive   terms.      The 

,       ,    ,       ,     ,  ,  .  ,  ,_^^  ,  line  shading  between  the  fields  repre- 

stretched  the  other  is  compressed.  This  ^^°ts  muscle  ceiis.  (After  cobb.) 
results  in  characteristic  appearances,  such  as  the  more  pronounced 
striation  of  the  dorsal  and  ventral  surfaces,  the  interruption  and 
variation  of  the  striations  near  the  lateral  lines,  and  the  presence  on 
the  lateral  fields  of  various  longitudinal  striations.  In  some  genera 
the  striations  are  compound,  that  is,  each  transverse  striation  is 
resolvable  into  a  row  of  dot-like  markings,  either  round  or  elongated. 
These  secondary  markings  may  be  again  resolvable,  the  result  being 
a  very  complex  series  of  exceedingly  minute  markings.  The  trans- 
verse striations  are  usually  more  or  less  plainly  interrupted  near  the 
lateral  fines.  Obhque  striae,  such  as  are  to  be  found  in  the  large 
parasitic  nematodes,  sometimes  occur  in  the  fresh- water  species, 
in  some  Mermithidae,  for  instance. 

The  longitudinal  striations  are  of  two  kinds:  (i)  True  stria- 
tions of  the  cuticula  due  to  certain  stiffening  structures  or  ^' wings," 
and  (2)  internal  markings  due  to  the  attachment  of  the  cells  of  the 
muscular  layer  and  of  the  lateral  fields.     The  longitudinal  stria- 


464  FRESH-WATER   BIOLOGY 

tions,  when  they  are  really  cuticular  structures,  are  likely  to  appear 
in  some  multiple  of  four.  Since  they  occur  on  each  side  of  the  two 
lateral  lines,  and,  naturally,  in  a  symmetrical  way,  the  smallest 
number  possible  is  four.  Two  on  each  side  of  each  lateral  line 
would  make  eight  in  all,  a  state  of  things  exemplified  in  Iota.  In 
Diplogaster  the  number  is  about  sixteen  to  thirty-two,  and  ap- 
parently these  numbers  also  prevail  in  some  Dorylaimi. 

The  various  elements  of  the  cuticula  originate  in  certain  cells  in 
the  longitudinal  fields,  which  early  in  the  development  of  the  em- 
bryo become  separated  from  the  ectoblastomere  group  of  cells.  One 
of  the  first  two  somablastomeres,  the  primary  ectoblastomere,  divides 
and  spreads  systematically  over  the  endoblastomeres.  By  further 
divisions  the  primary  ectoderm  thus  formed  gives  rise  among  other 
things  to  the  cuticula.  The  nuclei  of  the  ectoblast  cells  destined 
to  form  the  cuticula  of  the  embryo  arrange  themselves  in  longitudi- 
nal Hnes.  Increasing,  and  functioning  from  these  Hnes  they  become 
specially  active  at  each  moult  in  producing  a  new  layer  of  cuticula. 
At  moulting  time  the  activity  of  the  cuticula-forming  cells  in  the 
lateral  fields  is  indicated  by  an  increase  in  the  size  of  the  nuclei 
and  the  growth  from  them  of  excessively  fine  elements  forming  the 
cuticula.  The  lateral  fields  appear  to  be  the  leading  members  of 
this  group  of  cuticula  builders.  This  is  in  harmony  with  the  greater 
abundance  and  variety  of  the  lateral  cuticular  structures. 

In  the  course  of  its  development  a  nematode  sheds  its  skin 
about  four  times,  —  and  often  appears  to  be  about  as  active 
during  the  moulting  period  as  at  other  times.  In  some  species 
the  changes  that  take  place  at  the  time  of  moulting  are  of  a 
striking  character,  reminiscent  of  the  metamorphoses  in  other 
groups,  though  no  true  metamorphosis  takes  place.  Thus  we  have  ; 
in  the  last  moult  of  the  males  in  some  species  of  Iota  a  marked  alter- 
ation, viz.,  the  loss  of  the  oral  spear.  This  so  alters  the  appear- 
ance of  the  male  that  one  unfamiliar  with  the  facts  would  not  > 
class  the  adult  males  in  the  same  genus  as  the  females. 

During  the  moulting  period  the  cuticula  is  thicker  and  looser,  —  j 
sometimes  very  loose.  The  lining  of  the  mouth  and  esophagus,  j 
as  weU  as  that  of  the  rectum,  is  shed  at  the  same  time  as  the  outer  [^ 
cuticula.    At  this  time,  therefore,  the  mouth  parts  take  on  unusual 


FREE-LIVING  NEMATODES  465 

appearances.  If  the  pharynx  is  armed  with  teeth  these  are  often 
seen  in  dupHcate.  In  a  moulting  Dorylaimus,  for  instance,  one  may 
see  the  old  spear  or  tooth  and  behind  it  a  second  smaller  one,  and 
in  some  cases  even  a  third.  The  nature,  or  the  presence,  of  stria- 
tions  may  become  more  evident,  or  less  evident,  at  the  moulting 
period  than  at  other  times.  Remnants  of  old  skin  attached  to 
newly  moulted  individuals  have  sometimes  given  rise  to  erroneous 
deductions  and  to  errors  in  taxonomy. 

The  nervous  system  centers  in  the  so-called  nerve-ring,  which  in 
free-living  species  encircles  the  esophagus  near  the  middle  of  the 
neck.  This  ring  is  composed  of  interwoven  nerve-fibers  which, 
taken  together  with  the  groups  of  nerve  cells  immediately  in  front 
of  and  behind  them,  form  what  is  undoubtedly  a  rudimentary 
brain.     (See  Rhahdolaimus) 

Eyes,  or  rather  eye-spots,  are  known  in  one  or  more  species  of  the 
following  fresh-water  genera:  Dorylaimus,  Diplogaster,  Spilophora, 
Cyatholaimus,  Chromadora,  and  Monhystera.  The  visual  organs 
in  their  most  complete  form  consist  of  well-defined  subspherical 
cuticular  lenses  placed  in  front  of  collections  of  reddish,  violet,  or 
blackish  pigment-granules.  Usually  two  such  organs  are  placed 
symmetrically,  one  on  either  side  of  the  esophagus,  between  it  and 
the  body  wall,  and  in  a  dorsally  sublateral  position.  Nerves  pass 
backward  from  the  eyes  to  the  nerve-ring.  It  is  doubtful  whether 
the  lenses  form  images  that  are  perceived,  though  no  doubt  the 
more  perfect  of  the  lenses  found  in  nematodes  are  capable  of  form- 
ing excellent  images.  Probably  the  lenses  serve  merely  to  collect 
and  condense  light.  Usually  the  eye-spots  are  mere  collections  of 
pigment  without  lenses.  Eye-spots,  or  what  appear  to  be  such,  may 
occur  embedded  in  the  esophagus.  It  is  probable  that  the  great 
majority  of  species,  even  when  without  specialized  visual  organs, 
perceive  light  by  its  direct  action  on  the  nervous  system.  A 
few  experiments  will  convince  anyone  that  many  eyeless  species 
distinguish  the  direction  from  which  the  light  comes.  There  is  no 
satisfactory  evidence  that  nematodes  hear. 

At  various  points  on  the  surface  of  the  cuticula  there  are  found 
innervated  papillae  and  setae,  which  appear  in  most  cases  to  be  tactile 
organs.     Sometimes,  however,  they  are  associated  with  glands,  as, 


466  FRESH-WATER   BIOLOGY 

for  instance,  in  the  case  of  the  supplementary  organs  of  the  males. 
These  papillae,  hairs,  and  setae  all  belong  to  the  same  general  class  of 
structures,  but  various  terms  are  applied  to  them  in  accordance  with 
their  size  and  location.  The  special  hairs  found  on  and  near  the 
lips  are  known  as  cephaHc  setae,  in  contradistinction  to  the  large 
hairs  or  setae  sometimes  found  at  the  posterior  extremity,  the 

caudal  and  terminal  setae.  The 
setae  are  no  doubt  mainly  tac- 
tile in  function,  though  it  seems 
certain  that  some  of  the  ce- 
phaHc setae  and  papillae  serve 
2        also   as   organs   of   taste   and 

_  Fig.  768.  Head  of  a  nematode  (diagrammatic),  i ,  side  smcll. 
view;   2,  front  view,  showing  triangular  mouth  opening 

in  the  middle.     The  ventral  side  to  the  right  in  i  shows  Xhc  similar  OrSTanS  fOUnd  On 

the  ampulla  and  excretory  duct.     As  the  right  side  01  the  o 

head  is  towards  the  spectator  the  lateral  organ  appears  ^^iC  general  SUrfaCC  of   thc  bodv 

as  a  left-handed  spiral.     The  arrangement  of  the  cephalic  ^^  ^  ^v.xxv.it*.i  ow.j.iu,«^v.  v^i    i,j.xv.  kj\j\j.j 

setae  is  characteristic,  the  lateral  ones  being  single,  while  rjillpH      liPirQ      r%r      cOmatir 

the  submedian  are  in  pairs  whose  members  are  of  un-  **J-C       i-dllCU      llclllb      Ui      SUlllctLlU 

equal  size.    (After  Cobb.)  ^^^^^^      ThcSC  probabty  foUoW  a 

definite  law  in  their  distribution,  but  are  so  small  that  the  exact 
distribution  is  difficult  to  make  out  and  has  been  studied  in  but 
few  cases.  While  it  is  not  estabhshed  that  their  distribution 
accords  with  a  segmentation  theory,  this  matter  is  worthy  of  care- 
ful study.  Sometimes  the  hairs  occur  in  harmonic  repetition  on 
successive  groups  of  annules.  The  papillae  of  the  cuticula  are  setae 
that  do  not  project  beyond  the  surface,  or  not  far  enough  to  entitle 
them  to  be  called  setae.  They  should  not  be  confounded  with 
pores,  or  with  mere  projections  of  the  surface  of  the  cuticula. 
Neither  of  these  latter  are  innervated.  Tactile  structures  sup- 
plementary to  the  sexual  organs  are  found  on  the  tail  end  of  the 
male  both  in  front  of  and  behind  the  anus,  generally  toward  the 
ventral  side.  They  are  much  more  rare  in  the  female,  being 
located,  when  present,  near  the  vulva. 

What  are  known  as  the  amphids  or  lateral  organs  are  of  such 
widespread  occurrence  among  free-Hving  nematodes  as  to  make  it 
seem  certain  that  their  function  is  of  fundamental  importance,  but 
what  the  function  is  remains  a  mystery.  The  amphids  are  two 
lateral,  symmetrically-placed  external  cephaUc  organs.  The  ex- 
terior part  has  the  form  of  a  circle,  spiral,  helix,  or  elongated  figure, 


FREE-LTVING   NEMATODES 


467 


the  helix  or  spiral  being  the  fundamental  form  of  the  main  cuticular 
outer  lateral  markings  that  serve  so  good  a  purpose  in  characterizing 
species.  These  external  markings  are  undoubtedly  in  some  species 
connected  with  internal  series  of  lateral  organs  arranged  in  two  rows, 
one  along  each  lateral  field,  extending  throughout  the  length  of  the 
body.  One  more  or  less  plausible  theory  concerning  the  amphids  is 
that  which  proposes  to  regard  them  as  breathing  organs.  It  is  only 
very  exceptionally  that  they  are  known  to  have  special  direct  con- 
nection with  the  central  nervous  system.  Such  connection  would 
be  expected,  if,  as  some  suggest,  they  are  organs  of  sensation. 
Their  apparent  homologues  found  in  some  parasitic  nematodes 
seem  rudimentary.     Possibly  they  are  organs  of  equiUbration. 

In  describing  the  digestive  system  it  is  necessary  to  consider  the 
mouth  parts,  the  saHvary  or  mouth  glands,  the  esophagus,  the  in- 
testine, and  the  rectum.  Roughly  speaking,  the  mouth  parts  may 
be  divided  into  two  main  groups:  those  adapted  to  biting  and  those 
adapted  to  sucking.  The  various  forms  of  the  pharyngeal  cavity 
in  the  biting  group  are  shown  in  the  adjacent  illustrations,  together 


None  Conoid  Concave-      Cyathiform    Cyathiform, 

conoid  then  Cylindroid 

Fig.  769.    Forms  of  the  pharynx.    (After  Cobb.) 


Cylindroid 


Compound 


with  their  corresponding  nomenclature  (Fig.  769) .  The  formation  of 
the  pharynx  in  the  sucking  groups  is  more  uniform.  The  soft- lipped 
species  are  intermediate  in  form  and  are  adapted  to  seizing  and 
swallowing  various  microscopic  organisms,  both  plant  and  animal. 
The  mouth  cavity  or  pharynx  is  usually  more  or  less  strongly 
lined  with  cuticula,  and  often  furnished  with  cuticukir  parts  serving 
various  purposes  according  to  the  food  habits  of  the  species.  Where 
the  lips  are  muscular  and  mobile,  not  infrequently  they  are  sup- 
plied with  rather  complicated  gripping  organs  arranged  like  the 
jaws  of  a  lathe  chuck.  This  arrangement  of  the  mouth  parts  is 
well  illustrated  in  Enoplus;  the  reverse  motion  for  ripping  tissues 
open  is  shown  in  Ironus  (Fig.  781).  Mononchus  (Fig.  782)  shows 
the  development  of  six  muscular  lips  with  opposing  pharyngeal 


468  FRESH-WATER  BIOLOGY 

teeth  used  in  seizing  prey.  There  are  a  number  of  genera  in  which  the 
pharynx  is  armed  with  from  one  to  three  prominent  teeth  of  prob- 
lematical function.  In  some  of  these  cases  the  teeth  are  the  outlets 
of  an  equal  number  of  glands  located  in  the  wall  of  the  esophagus. 
The  secretions  of  these  glands  are  probably  saUvary  in  nature,  or 
possibly  in  some  cases  venomous,  or  even,  as  has  been  suggested, 
excretory.  These  suppositions  rest  on  structural  and  food-habit 
considerations,  rather  than  on  an  examination  of  the  nature  of 
the  secretions.  The  saliva  theory  is  strongly  supported  by  the 
nature  of  these  glands,  whether  their  form,  number,  position,  or 
structure  is  considered,  but  they  sometimes  empty  through  fang- 
like projections  in  carnivorous  species  that  one  would  think  could 
profit  by  the  use  of  venom  in  much  the  same  way  that  serpents  do. 

The  nematode  esophagus  is  an  organ  of  which  every  cross-section 
is  usually  substantially  circular,  though  the  diameter  may  vary 
much  in  the  various  parts.  The  central  canal  is  usually  trique- 
trous in  cross-section  (Fig.  766).  The  lining  is  uniformly  cuticular 
and  varies  considerably  in  thickness  in  the  various  species.  In  the 
simple  cylindrical  form  of  esophagus,  radial  muscles,  the  contraction 
of  which  accomphshes  the  act  of  swallowing,  everywhere  pass  from 
the  lining  of  the  organ  to  the  exterior  cyHndroid  wall.  The  action  of 
these  muscles  is  peristaltic,  first  creating  the  necessary  suction,  and, 
after  the  food  is  sucked  in,  rapidly  forcing  it  along  toward  the  intes- 
tine.     The  act  of  swallowing  is  often  lightning-like  in  its  rapidity. 

In  addition  to  this  general  radial  musculature  the  esophagus  some- 
times presents  spherical  or  ellipsoidal  muscular  swellings,  or  bulbs, 
often  suppHed  with  a  central  cuticular  valve,  for  exerting  more  pow- 
erful suction  than  could  be  produced  by  the  narrower  tubular  part. 
The  presence  of  bulbs  denotes  certain  methods  of  feeding,  —  either 
the  lips  need  to  be  fastened  securely  to  the  source  of  food  in  order 
to  facilitate  the  stabbing  action  of  the  oral  spear,  or  it  is  necessary 
to  exert  unusual  suction  in  order  to  ingest  the  food.  There  may  be 
one,  two,  or  three  of  these  bulbs,  or  none.  The  corresponding  forms 
of  the  esophagus  are  shown  in  the  accompanying  illustration 
(Fig.  770),  to  which  the  appropriate  names  are  appended.  In  rare 
cases  the  esophagus  is  not  clearly  marked  off  from  the  intestine, 
but  there  nearly  always  exists  between  these  two  parts  of  the  ali- 


FREE-LIVING   NEMATODES 


469 


mentary  canal  a  distinct  constriction,  known  as  the  cardiac  con- 
striction. In  the  immediate  vicinity  of  this  constriction  small 
organs  are  sometimes  found,  apparently  of  a  ^dimdular  naturr, 
though  their  functions  are  still  veiled  in  obscurity.  Here  also  (Kcur 
definite  nerve  cells  which  are  probably  to  be  regarded  as  the  center 
of  an  involuntary  nervous  system. 


Cylindroid        Conoid 


() 


& 


Fusiform        Clavate    Dorylaimoid      Oxyuroid  Rhabditoid   lylcnthui.!  Apbclcndnid 
Fig.  770.    Forms  of  the  esophagus.    (After  Cobb.) 


The  intestine  is  a  tubular  canal  extending  from  the  csophap^J^  to 
near  the  anus.  Usually  rather  uniform  in  diameter,  it  is  occasion- 
ally somewhat  expanded  just  behind  the  esophagus  to  form  a 
rudimentary  stomach,  if  one  may  judge  from  the  histoloi^y  (^f  this 
part  of  the  organ.  The  cells  at  this  part  of  the  intestine  are  often 
markedly  different  in  structure  and  chemical  reaction  from  thosc^ 
farther  back.  In  almost  any  species  a  sufficiently  careful  examina- 
tion will  show  that  some  of  the  anterior  cells  of  the  intestinal  tul)c 
differ  from  those  farther  back,  and  hence  it  appears  certain  that  the 
anterior  part  of  the  intestine  serves  a  digestive  function,  while  the 
remaining  part  serves  as  an  intestine  proper.  There  are  also  well 
differentiated  cells  in  the  wall  of  the  posterior  part  of  the  intestine, 
indicating  here  also  a  subdivision  of  functions. 

The  intestine  ends  in  a  short  tubular  conoid  region  leading  to 
the  anus,  and  known  as  the  rectum.  This  part  is  more  or  less 
muscular  and  serves  to  extrude  the  feces.  In  Dor  vidimus  and  its 
congeners,  just  preceding  the  rectum  there  is  a  short  \ery  distinct 
part  of  the  alimentary  canal  known  as  the  prc-rectum.  In  spite  oi 
the  definiteness  of  its  structure  its  function  is  unknown.  Kmpt\in- 
near  the  anus  there  are  usually  to  be  found  a  number  of  small  unicel- 
lular glands,  called  anal  glands,  perhaps  ser\'ing  as  accessories  in  defc- 


470  FRESH-WATER   BIOLOGY 

cation.     The  anal  muscles  are  muscular  strands  passing  from  tne 
transverse  slit-like  anus  to  the  body  walls  near  the  lateral  fields. 

There  is  no  vascular  circulatory  system.  These  organisms  are  so 
small  that  the  colorless  "blood"  is  aerated  without  the  need  of  special 
vessels.  The  movements  of  the  body  serve  to  propel  the  body-fluid 
irregularly  about  through  the  body  cavity  and  among  the  organs. 

The  main  locomotive  movements  of  nematodes  are  due  to  the 
alternate  action  of  two  antagonistic  sets  of  muscle,  dorsal  and 
ventral,  extending  nearly  the  full  length  of  the  body,  and  acting  on 
the  lateral  thickening  of  the  cuticula  as  a  fulcrum.  The  move- 
ments are  serpentine,  but  in  a  dorso- ventral  plane.  As  the  result- 
ing body-curves  are  usually  wider  than  the  space  between  the 
cover  glass  and  the  microscope  shde,  it  follows  that  the  micro- 
scopical view  of  these  nematodes  is  usually  a  lateral  view. 

Locomotion  is  accompHshed  by  the  aid  of  friction  on  surrounding 
solid  objects,  such  as  the  stems  or  roots  of  plants,  grains  of  sand 
or  other  particles.  Comparatively  few  of  the  aquatic  species  can 
swim,  and  even  these  seem  uneasy  and  frightened  when  they  find 
themselves  floating  free  in  the  water.  ]\Iost  of  the  aquatic  species 
are  supplied  with  three  unicellular  caudal  glands  and  a  terminal 
spinneret,  whose  main,  and  probably  sole,  function  is  to  cement 
the  tail  temporarily  to  various  objects.  From  this  attachment 
as  a  base  the  nematode  moves  its  head  in  various  directions  in 
search  of  food,  or  of  its  mates.  Some  species,  for  instance  some 
species  of  Chromadora,  attach  themselves  alternately  first  by  the 
head  by  suction,  and  then  by  the  spinneret,  executing  movements 
like  those  of  the  common  caterpillars  known  as  ''inch- worms." 

The  excretory  organ  of  the  f  ree-hving  nematodes  consists  of  a  uni- 
cellular* gland,  the  renette,  lying  in  the  body  cavity,  not  far  from  the 
junction  of  the  intestine  and  esophagus.  It  empties  through  a  duct 
leading  forward  to  a  ventral  excretory  pore,  usually  located  some- 
where between  the  Hp  region  and  the  intestine.  There  are  a  number 
of  genera  in  which  the  renette  has  not  yet  been  seen.  Its  homologue 
in  the  large  parasitic  species  is  renal  in  nature, —  at  least  in  one  case. 

Through  the  study  of  the  free-Hving  species  the  supposed  excre- 
tory function  of  the  lateral  fields,  long  beheved  in,  has  been  dis- 

*  Rarely  two  to  many-celled  and  double . 


FREE-LIVING  NEMATODES  ^y  j 


een 


proved.  The  apparent  connection  in  the  parasitic  species  Ijctw 
the  excretory  organ  and  the  lateral  fields  is  incidental,  the  action 
of  the  body  muscles  tending  to  locate  such  long  slender  tubular 
organs  in  the  region  of  least  motion,  namely  the  lateral  region. 
In  these  parasitic  species  the  organ  is  often  bifurcated  a  little  be- 
hind the  excretory  pore  (apparently  on  account  of  the  increased 
size  of  the  whole  organism),  and  thence  backward  the  tubular 
elements  are  attached  to  or  lie  in  or  near  the  lateral  fields.  This 
suggests  that  the  mystery  surrounding  the  excretory  organ  in 
some  of  the  free-living  species  may  perhaps  be  solved  by  search 
directed  toward  the  discovery  of  a  bilaterally  symmetrical  renette. 
Dorylaimus,  a  genus  containing  some  of  the  largest  free-living 
nematodes,  is  a  case  in  point.  The  renette  cell  often  has  smaller 
companion  cells  in  its  immediate  rear. 

The  caudal  glands,  so  common  in  the  tail  end  of  the  free-living 
nematodes,  serve  to  cement  the  tail  end  to  any  convenient  object. 
In  thus  attaching  themselves  nematodes  sometimes  show  great  skill 
and  pertinacity.  The  terminus  of  the  tail  bears  a  minute  spinneret 
through  which  the  secretion  of  the  glands  is  forced  out,  and  by  means 
of  which  its  flow  may  be  regulated,  much  as  in  the  case  of  spiders. 
The  secretion  is  a  cementing  substance  insoluble  in  water.  The 
caudal  glands  are  normally  three  in  number  and  are  usually  located 
single  file  in  the  anterior  part  of  the  tail,  or  somewhat  farther  forward 
in  front  of  the  anus.  Two  of  the  ducts  often  unite  to  form  one  duct ; 
sometimes  all  three  unite.  Just  in  front  of  the  pore  in  the  spin- 
neret the  ducts  may  enlarge  to  form  one  or  more  ampullae.  Caudal 
glands  are  absent  in  most  of  those  species  in  which  the  males  are 
supphed  with  lateral  caudal  flaps  constituting  the  bursa.  It  is 
possible  that  the  secretion  of  the  bursal  ribs,  or  tubes,  is  of  the 
same  general  character  as  that  of  the  three  caudal  glands,  and  that 
these  two  sets  of  glands  are  homologous.  The  ribs  of  the  bursa, 
when  the  full  complement  is  present,  consist  of  three  groups.  This 
is  at  least  suggestive.  The  females  of  such  species  sometimes  have 
lateral  pores  on  or  near  the  tail. 

The  sexual  organs  originate  from  a  few  cells  set  oil  for  the  pur- 
pose early  in  the  development,  which  for  a  time  remain  rather 
quiescent  near  the  center  of  the  body.    As  tlie   nematode   ap- 


472  FRESH-WATER   BIOLOGY 

proaches  maturity  these  sexual  cells  resume  their  activity  and 
begin  to  divide  and  to  produce  a  symmetrically  two-parted  elon- 
gated group  of  cells,  one  part  extending  forward  and  the  other 
backward.  Primarily  the  sexual  organs  of  both  sexes  are  double, 
and  the  normal  development  at  first  always  forecasts  a  double 
organ.  This  forecast  is  often  fulfilled,  but  in  many  species  one  of 
the  halves  has  deteriorated  or  become  vestigial.  Where  this  is 
the  case  the  symnietry  of  the  early  development  is  soon  lost  and 
the  group  of  developing  sexual  cells  then  becomes  one-sided. 

At  the  last  moult,  or  the  penultimate,  the  sexual  opening  in  the 
cuticula  makes  its  appearance.  This  is  always  on  the  ventral  side, 
and  in  the  male  invariably  corresponds  with  the  anus;  in  the  female 
it  is  independent  and  nearer  the  middle  of  the  body,  usually  very 
near  the  middle  when  the  internal  organs  are  double  and  symmet- 
rical, and  farther  back,  or  more  rarely  farther  forward,  when  there 
is  only  one  ovary. 

The  female  sexual  system  is  very  commonly  double,  each  half  of  it 
being  tubular  and  consisting  of  (i)  an  ovary,  (2)  a  seminal  receptacle, 
(3)  a  uterus,  (4)  a  vagina ;  this  latter  of  course  in  common  with  the 
other  half  of  the  apparatus.  These  parts  may  lie  in  linear  succession 
in  the  body  cavity,  or,  as  is  more  often  the  case,  the  series  may  be 
folded  near  its  middle,  that  is,  between  the  ovary  and  the  uterus, 
so  that  the  ovary  is  reflexed  and  extends  back  toward  the  vulva. 

The  more  usual  forms  of  female  apparatus  are  as  follows: 

1.  Of  two  parts,  each  reflexed. 

2.  Of  two  parts,  each  outstretched. 

3.  Single  and  reflexed. 

4.  Single  and  outstretched. 

When  the  organ  is  single  it  may  extend  either  forward  or  back- 
ward from  the  vulva,  though  it  usually  extends  forward.  Letting 
F  represent  the  vulva,  -  an  outstretched  organ,  and  '  a  reflexed 
organ,  the  various  forms  may  be  abbreviated  as  follows : 

*F'  -F-  'F  F»  -F  F- 

and  this  is  the  form  in  which  the  facts  are  presented  in  the  measure- 
ment formulae  for  the  females,  except  that  F  is  replaced  by  the  per- 
centage measurement  figure  representing  the  position  of  the  vulva. 


FREE-LIVING   NEMATODES  47. 

As  the  male  organ  may  be  either  double  or  single,  outstretched 
or  reflexed,  the  corresponding  abbreviations  for  the  usual  forms  of 
male  apparatus  are  as  follows: 

-M  =M  *M  -U  -M- 

and  this  is  the  form  in  which  the  facts  are  presented  in  the  formulae- 
for  males.  As  the  testes  always  he  in  front  of  the  sexual  opening, 
the  datum  point  of  the  reference  signs  in  this  case  is  the  point 
where  the  testes  join  the  vas  deferens,  not  the  sexual  opening,  as 
in  the  females.  The  percentage  figure  representing  the  extent 
of  the  male  sexual  organs  dates  from  the  anus.  Species  with  re- 
flexed  testes  are  comparatively  rare  among  fresh-water  nematodes, 
the  commonest  forms  being  -M-  and  -M. 

The  bhnd,  free,  or  distal  end  of  the  female  sexual  tube  is  usually 
found  to  contain  only  cells  of  extremely  small  size,  observable  with 
difficulty.  In  consequence  Kttle  is  known  about  the  primordial 
sexual  products  in  these  free-living  species.  The  interior  of  the 
main  part  of  this  segment  of  the  tube,  the  ovary,  is  filled  with  devel- 
oping oocytes,  which  generally  soon  arrange  themselves  in  single  file. 
The  oocytes  increase  rapidly  in  size,  so  that  they  are  ripe  by  the  time 
they  reach  the  entrance  to  the  uterus.  At  this  point  they  undergo 
synapsis,  meet  the  spermatozoa,  and  are  fertihzed,  and  then  receive 
their  shells,  cuticular  coverings  acquired  in  the  uterus.  The  sper- 
matozoa usually  collect  together  at  the  end  of  the  uterus,  which,  in 
some  instances,  has  a  special  form  adapted  to  their  reception,  and 
in  all  cases  must  be  at  least  physiologically  adapted  to  attract  and 
retain  them.  Some  species  have  special  receptacles  for  the  sper- 
matozoa in  the  shape  of  large  tubular  branches  of  the  uterus,  — 
genuine  spermathecae. 

The  entrance  to  the  uterus  from  the  ovary  is  narrow,  and  this 
slender  part  of  the  sexual  tube  is  armed  with  delicate  annular 
muscles  adapted  to  moving  the  ova  on  into  the  uterus.  The 
uterus  varies  much  in  size.  Frequently  in  the  small  species  a 
single  egg  completely  fills  it;  in  the  larger  fresh-water  species  each 
uterus  may  become  large  enough  to  carry  a  score  or  more  of  eggs. 
In  the  larger  parasitic  species  this  capacity  is  enormously  greater, 
so  that  the  number  of  eggs  in  the  uterus  may  reach  tens  of  thou- 
sands, or  even  hundreds  of  thousands. 


474 


FRESH-WATER   BIOLOGY 


The  vagina  is  usually  short  and  more  or  less  muscular,  especially 
near  the  vulva,  where  its  wall  is  usually  thicker.  At  the  thickest 
part  it  suddenly  diminishes  in  massiveness,  and  in  the  case  of  the 
double-ovaried  species  forks  to  form  two  short  tubular  branches 
which  join  the  uteri.  The  walls  of  these  two  short  tubes,  as  well 
as  those  of  the  part  nearer  the  vulva,  are  suppHed  with  encircHng 
muscle  fibers  which  by  their  peristaltic  action  force  the  egg  onward 
and  outward  in  the  process  of  deposition.  The  vulva  is  a  trans- 
verse sHt-like  opening  whose  length  varies  up  to  about  one-half  the 
width  of  the  body.  Muscular  fibers  radiate  from  its  cuticular 
margin  to  the  ventral  submedian  parts  of  the  body  wall,  and  serve 
by  their  contraction  to  open  the  orifice. 

The  subspherical  to  elongate  eggs  are  covered  with  cuticular 
shells  of  varying  thickness,  usually  smooth,  but  sometimes  bearing 
projections.  In  the  greater  number  of  fresh-water  species  the  eggs 
are  deposited  before  segmentation  begins,  but  in  some  genera  fully 
developed  embryos  are  formed  in  the  eggs  before  deposition.  A 
few  species  are  viviparous.  The  period  of  gestation  varies  widely. 
In  some  cases  the  formation  of  the  embryo  occurs  within  the 
space  of  a  few  hours  to  a  day  or  two,  in  other  cases  weeks  are 
necessary. 

The  structure  of  the  testes  resembles  that  of  the  ovaries,  but 
the  resulting  sexual  cells,  the  spermatozoa,  are  smaller.  The  pri- 
mordial germ  cells  at  the  bHnd  end  of  the  testis  multiply  to  form 
the  grandmother-cells  of  the  spermatozoa,  which  grow  to  a  con- 
siderable size,  so  that  it  is  usually  easy  to  locate  the  part  of  the 
testis  where  they  are  maturing,  —  generally  the  middle  or  proximal 
part.  These  grandmother-cells,  or  spermatocytes,  have  the  num- 
ber of  chromosomes  characteristic  of  the  males  of  the  species,  and 
they  proceed  to  the  formation  of  the  spermatozoa  by  a  process  of 
sudden  double  division  of  the  chromosomes  such  that  each  sper- 
matocyte gives  rise  in  most  of  the  known  cases  to  four  spermatozoa, 
two  with  half  the  number  of  chromosomes  characteristic  of  the 
females  and  two  with  one  less  chromosome  than  this.  All  these 
spermatozoa  are  supposed  to  be  potent,  but  there  is  a  dearth  of 
experimental  evidence. 

The  oocytes  follow  a  similar  course  but  only  one  of  the  last 


FREE-LIVTNG  NEMATODES  475 

four  female  cells  is  potential,  the  other  three  being  the  so-called 
polar  bodies  which  are  left  at  the  periphery  of  the  egg  to  disinte- 
grate and  disappear.  The  polar  bodies  are  to  be  looked  for  in 
eggs  that  have  just  entered  the  uterus,  and  can  be  observed  to 
advantage  only  in  stained  specimens,  though  they  may  sometimes 
be  seen  in  the  living  material.  The  fundamental  facts  connected 
with  fertilization  and  inheritance  in  animals  were  first  worked  out 
largely  through  the  instrumentality  of  the  eggs  of  various  species 
of  nematodes.     In  this  respect  they  are  classical  objects. 


V 

Fig.  771.  Forms  of  spicula.  i.  Broad,  tapering,  blunt.  2.  Elongate.  3.  Slender.  4.  Setaceous. 
5.  Elongated,  tapering.  6.  Elongated,  arcuate.  7.  Elongated,  bent.  8.  Fusiform,  slightly  arcuate. 
9.   Arcuate,  strongly  cephalated.     10.   Sickle-form.     11.  Hamate.     12.   L-shaped.     (.^fter  Cobb.J 

The  male  intromittent  organs,  the  spicula,  are  usually  two  in 
number,  and  in  nearly  all  free-living  species  the  two  are  identical 
in  form  and  size.  Each  spiculum  is  usually  a  straight,  curved,  or 
bent,  elongated  framework  of  cuticula,  commonly  one  to  two  times 
as  long  as  the  anal  body  diameter.  Exceptionally  it  may  be  very 
long  and  slender.  The  main  portion  of  its  shaft  is  usually  of  uni- 
form size,  while  the  free  or  distal  end  commonly  terminates  in  a 
somewhat  blunt  point,  which,  however,  may  be  variously  modified. 
The  anterior  or  proximal  end  is  often  swollen  or  cephalated,  for  the 
attachment  of  muscles. 

The  muscle  for  protruding  the  spiculum  more  or  less  insheaths 
it,  and  is  attached  to  the  proximal  end  of  the  spiculum  and  to  the 
body  wall,  or  to  an  accessory  piece,  near  the  anus,  so  that  its  con- 
traction moves  the  spiculum  toward  the  anus  and  thus  protrudes 
it.  The  retractor  muscle  is  attached  to  the  proximal  end  oi  the 
spiculum  and  thence  usually  passes  forward  and  toward  the  dorsal 
side  of  the  body,  where  it  is  attached  to  the  body  wall;  its  con- 
traction thus  tends  to  pull  the  spiculum  back  into  the  body.  It  is 
usually  rather  easy  to  observe  these  retractor  muscles  of  the  spicula. 
but  difficult  to  observe  the  protruding  muscles. 

In  order  that  these  muscles  may  act  to  better  ad\'antage  the 
spicula  often  sHde  in  grooved  pieces  of  cuticula  named  the  acces- 


476  FRESH-WATER  BIOLOGY 

sory  pieces.  These  accessory  pieces  are  usually  from  one-fourth  to 
two-thirds  as  long  as  the  spicula  themselves,  and  not  uncommonly 
possess  an  inward  or  backward  extending  apophysis  whose  function 
is  to  anchor  them  firmly  in  position,  or  serve  for  the  attachment 
of  special  muscles.  Long-necked  unicellular  glands  are  often 
seen  to  empty  into  the  cloaca  near  the  distal  ends  of  the  spicula. 
These  probably  serve  a  special  purpose  at  mating  time.  The 
form  of  the  spicula  and  of  their  accessory  pieces  is  useful  in 
distinguishing  the  various  species,  and  as  these  organs  are  usually 
viewed  in  profile  the  various  terms  used  to  describe  them  are 
understood  to  apply  to  this  aspect.  The  various  forms  and  terms 
are  shown  in  the  accompanying  illustrations,  Fig.  771. 

Among  the  male  accessory  organs  the  bursa  is,  in  a  number  of 
genera,  the  m^ost  important,  though  there  is  no  trace  of  it  in  the 
greater  number  of  the  fresh-water  genera.  The  bursa  is  a  thin,  trans- 
parent flap-like  expansion  of  the  lateral  cuticula  of  the  tail  end  of  the 
male,  and  serves  as  a  copulatory  clasping  organ.  It  may  consist  of 
two  distinct  halves,  one  on  each  side  of  the  tail,  and  each  ending  short 
of  the  extremity,  or  the  two  parts  may  extend  to  the  extremity 
and  coalesce  to  form  a  continuous  flap  encompassing  the  tail. 
The  bursa  springs  from  the  submedian  or  lateral  regions,  though  it 
is  usually  on  the  ventral  side  of  the  lateral  lines  and,  furthermore, 
is  bent  toward  the  ventral  side.  Typically  the  flaps  spring  from 
the  body  somewhat  in  front  of  the  anus,  grow  wider  as  they  pass 
backward,  and  reach  their  maximum  development  about  opposite 
the  anus;  thence  onward  they  usually  diminish,  —  though  in  some 
cases  not  very  much.  In  its  maximum  development  the  bursa  may 
possess  flaps  as  wide  as  the  body  itself;  from  this  maximum  it 
varies  to  rudiments  that  may  easily  be  overlooked  (pp.  484,  493). 

The  bursa  functions  as  a  male  clasping  organ  through  the  pres- 
ence of  muscular  fibers  adapted  to  close  it  ventrally,  and  through 
the  presence  of  so-called  ribs  which  appear  to  be  in  the  main,  if  not 
altogether,  tubular  outlets  for  a  cement-like  secretion  used  to 
fasten  the  male  more  or  less  permanently  to  the  female  at  mating 
time.  No  chemical  examinations  have  been  made  of  the  cement 
substances  of  the  bursa  and  the  caudal  glands,  but  both  are  insol- 
uble in  water  and  seem  otherwise  similar.     Some  genera  in  which 


FREE-LIVING  NEMATODES  477 

no  bursa  is  developed,  nevertheless  have  papillae,  as  they  ha\e  been 
called,  located  according  to  the  same  general  law  as  the  riljs  of  the 
bursa.     (Diplogaster,  Cephalobus.) 

One  striking  fact  will  be  forced  on  the  attention  of  the  collector  of 
nematodes  early  in  his  work,  and  that  is  the  comparative  rarit\-  of 
the  males.  In  many  of  the  species  the  males  have  never  been  seen, 
and  in  most  species  the  females  are  from  five  to  twenty  times  as 
common  as  their  mates.  There  is  reason  to  think  that  in  some 
species  the  males  are  very  short-hved,  and  that  this  is  the  reason 
they  are  so  rarely  seen.  The  males  are  often  so  much  smaller  than 
the  females  that  they  are  easily  overlooked,  or  mistaken  for  young, 
so  that  in  such  cases  the  rarity  of  the  males  may  easily  be  over- 
estimated. In  a  few  species  the  males  appear  to  be  more  common 
than  the  females,  at  least  at  times.  Hermaphroditism  and  par- 
thenogenesis are  frequent.      (See  p.  495.) 

As  the  ova  approach  the  narrow  duct  leading  to  the  uterus  they 
rapidly  acquire  yolk  of  a  distinctly  granular  character.  In  the  case 
of  the  numerous  species  having  refiexed  ovaries,  the  oviduct  is 
located  near  the  flexure,  and  is  so  small  and  short  that  it  is  usually 
impossible  to  see  it  except  when  the  organs  are  immature.  Passing 
through  the  oviduct,  the  ovum  enters  the  uterus,  where  for  a  short 
distance  the  cells  of  the  uterine  wall  are  unusually  well  developed, 
apparently  to  furnish  the  material  for  the  shells  of  the  eggs.  Here 
too  the  eggs  are  fertilized.  The  proximal  limit  of  the  shell-gland 
is  often  very  definite.  The  rest  of  the  uterus  is  thin-walled  and 
connects  with  the  vagina  through  a  narrow  muscular  duct,  mainly 
responsible  for  forcing  the  eggs  into  the  outer  world.  The  eggs 
at  the  time  of  deposition  are  usually  soft  and  pliant,  so  that  they 
easily  pass  through  the  vulva,  even  when  relatively  large. 

The  fresh-water  nematodes  are  t>T3ical  of  the  entire  group  of 
free-living  nematodes  in  that  while  most  of  them  arc  oviparous, 
some  are  ovi- viviparous  and  others  viviparous.  The  eggs  in  most  of 
the  known  fresh- water  species  are  smooth  shelled.  In  the  segmen- 
tation the  first  division  is  a  slightly  unequal  one,  one  blastomere  giv- 
ing rise  to  the  somatic  tissues,  the  other  to  the  sexual  organs. 

There  are  various  organs  that  have  been  observed  in  the  free- 
living  nematodes  whose  functions  are  problematical,  such  as  (i)  the 


478  FRESH-WATER   BIOLOGY 

double  organ  in  the  females  only  of  some  species  of  Oncholaimus, 
located  in  the  posterior  part  of  the  body  and  connecting  with  the 
exterior  through  openings  in  the  subdorsal  region;  (2)  the  gland- 
Uke  pair  of  organs  seen  in  the  females  of  Diplogaster,  and  apparently 
also  of  Rhahditis  and  other  related  genera;  and  (3)  the  long-necked 
paired  glands  sometimes  emptying  into  the  male  cloaca.  It  is 
conceivable  that  some  of  these  serve  a  sexual  function,  such  as 
the  secretion  of  a  substance  whose  odor  or  taste  is  of  service  in 
enabUng  the  nematodes  to  locate  their  mates. 
< 88  > 

<  28> 

<  14> 

<  -  -  7'^^^_..-,,,-----——--'^^rzzzzz^,_.---...   V     ,---, : 

^3 17? a       C>-CjO'''..x'l^)  m 

— "^ oii/ • 

Fig  772.  Diagram  in  explanation  of  the  descriptive  formula  used  for  nematodes;  6,  7,8,  10,  6  are 
the  transverse  measurements,  while  7,  i4>  28,  50,  88  are  the  corresponding  longitudmal  measurements. 
The  formula  in  this  case  is: 

7.   14.  28.     50-  88. 
6.     7.     8.     10.     6. 
The  measurements  are  simply  percentages  of  the  length,  and  the  formula,  as  printed  in  the  key,  may 
be  regarded  as  somewhat  in  the  nature  of  a  conventionalized  sketch  of  the  nematode  with  dimensions 

The  measurements  are  taken  with  the  animal  viewed  in  profile;  the  first  is  taken  at  the  base  of  the 
pharynx  the  second  at  the  nerve-ring,  the  third  at  the  cardiac  constriction  (base  of  the  neck  ),  the 
fourth  at  the  vulva  in  females  and  at  the  middle  (M)  in  males,  the  fifth  at  the  anus.     (After  Cobb.) 

It  seems  reasonably  clear  that  fresh-water  nematodes  have 
marked  seasonal  development,  at  least  in  some  species.  Adults 
of  many  species  can  be  found  at  all  times  of  the  year.  Freezing 
does  not  necessarily  kill  them.  Although  the  fresh-water  nema- 
todes are  so  widespread,  and  so  abundant  at  all  seasons,  it  is  not 
always  easy  to  isolate  them  for  examination  without  the  use  of 
special  methods.  Few  of  these  nematodes  exceed  two  to  three  milH- 
meters  in  length,  and  they  are  so  slender  and  transparent  as  to  make 
it  practically  impossible  to  examine  them  without  the  aid  of  a  lens. 

However,  when  special  methods  are  employed  they  may  easily 
be  collected.  A  few  centigrams  of  mud  or  sand  from  a  place  where 
nematodes  are  beHeved  to  exist  is  disseminated  in  a  watch  glass  of 
water,  and  the  sediment  examined  carefully  for  the  characteristic 
wavy  non-progressive  motion  exhibited  by  these  Httle  organisms. 
When  discovered,  the  specimens  are  captured  with  a  fine-pointed 
pipette  or  medicine  dropper  and  ejected  with  a  minimum  of  other 


FREE-LIVING  NEMATODES 


419 


material  into  a  second  watch  glass,  from  which  Ihcy  are  removed  on 
a  very  fine-pointed  needle  and  placed  in  a  drop  of  clear  water  on  a 
microscope  slide.  These  operations  are  best  performed  on  the  stage  Jf 
a  dissectingmicroscope,  under  a  lens  magnifying  five  to  ten  diameters. 
To  collect  specimens  in  large  numbers  it  is  best  to  make  use  of 
more  elaborate  methods.  A  coarse  sieve  with  meshes  two  to  three 
millimeters  across  is  used  to  remove  objects  larger  than  nema- 
todes.    To  gather  the  nematodes,  the  material  that  comes  through 

Fig.  773.  Measuring  the  length  of 
the  camera  lucida  drawing  of  a  nema- 
tode. The  head  end  of  the  drawing 
lies  near  the  left-hand  cuff.  The 
pharynx  is  shown,  and  near  it,  next 
the  knuckle  of  the  httle  finger,  is  the 
oblique  nerve-ring.  The  cardiac  con- 
striction lies  this  side  of  the  end  of  the 
forefinger,  and  the  vulva  on  the 
farther  side.  Mention  should  be  made 
of  the  presence  of  the  error  resulting 
from  the  attempt  to  measure  a  curved 
line  with  a  straight  measure.  The 
aim  should  be  to  reduce  this  error  so 
much  that  it  can  safely  be  neglected. 
One  means  of  reducing  this  error  may 
here  be  mentioned,  namely,  reducing 
the  "step"  of  the  divider  legs  in  pro- 
portion to  the  sharpness  of  the  curv^e 
to  be  measured.  Another  method 
may  also  be  mentioned,  but  it  is  to  be 
used  with  caution,  and  only  as  the 
result  of  experience.  By  a  number  of 
careful   trials  it  will   be  found  that  a 

measurement  nearer  the  truth  can  be  obtained  by  fbllowing  a  path  somewhat  on  the  outside  of  the  curve* 
of  the  median  line  on  the  drawing  or  image  being  measured,  but  care  must  be  exercised  in  adoptinK  this 
method  not  to  overshoot  the  mark.  Where  the  curve  is  sharp  it  is  of  course  safer  to  go  always  a  liltlr  on 
the  outside  of  the  curve.  I  consider  it  to  be  sufficiently  accurate  after  a  little  practice  to  dispense  with 
actually  drawing  in  a  median  line  on  which  to  measure  It  is  easy  to  keep  sufficiently  near  the  miildle 
by  eye.  Of  course,  with  a  reliable  map-measure  all  these  difficulties  dis  ip:ie:ir.  The  map  measurer,  an 
instrument  to  be  had  from  most  dealers  in  drawing  instruments,  has  a  small  milled  wheel  that  may  be  st- 
rolled along  a  crooked  line  as  to  measure  its  exact  length. 

To  obtain  the  percentage  figures  used  as  terms  of  the  formula  simply  divide  each  of  the  various  trans- 
verse and  longitudinal  measurements  by  the  total  length.  Using  a  slide  rule  these  divisions  iKcupy 
only  two  to  three  minutes.     (After  Cobb.) 

this  coarse  sieve  is  passed  through  sieves  of  finer  and  finer  mesh 
until  the  limit  of  fineness  is  reached.  About  the  finest  mesh  ob- 
tainable is  that  of  the  finest  miller's  bolting  silk  (0.25  to  0.5  mm.), 
which,  when  stretched  over  appropriate  rings  made  of  ])ottomless 
dishes  will  allow  fine  mud  to  pass  through  while  it  will  retain  all 
but  the  smallest  nematodes.  By  successive  sif tings  practicall>-  all 
the  nematodes  can  be  secured. 

The  sifting  can  be  supplemented  by  gravity  methods.  Aquatir 
nematodes  are  lighter  than  sand  and  heavier  than  water.  It  tlu' 
water  containing  the  nematodes  be  violently  agitated  and  then  be 
allowed  to  rest  for  a  few  seconds  the  sand  will  have  subsided  to  the 
bottom,  and  the  nematodes  may  be  decanted  off  if  the  pouring  be 
managed  expeditiously.     Then,  if  the  nematode-containing  water 


480  FRESH-WATER   BIOLOGY 

be  allowed  to  rest  for  from  two  to  four  minutes  in  a  vessel  two  to 
three  inches  deep  the  nematodes  will  have  largely  settled  to  the 
bottom  and  the  supernatant  muddy  water  may  be  carefully  de- 
canted away.  The  residue  will  contain  an  abundance  of  nema- 
todes that  may  be  captured  as  described  above. 

Fresh-water  nematodes  are  so  active  that  it  is  practically  impos- 
sible to  examine  them  without  first  anesthetizing  or  kilHng  them. 
They  may  be  rendered  unconscious  by  the  use  of  a  small  amount 
of  chloroform  dissolved  in  water.  Ether,  chloral  hydrate,  tobacco 
smoke  and  other  anesthetics  and  narcotics  are  also  used  in  this 
way.  Specimens  treated  thus  are  wonderfully  transparent,  and 
display  to  a  maximum  advantage  certain  features  of  the  anatomy. 

Permanent  preparations  may  be  made  by  kilUng  and  fixing  with 
Flemming's  solution  or  Bouin's  solution,  washing,  and  then  chang- 
ing to  water  containing  5  per  cent  glycerine  and  very  slowly  evap- 
orating in  a  closed,  preferably  warm,  space  such  that  the  solution 
becomes  fully  concentrated  in  the  course  of  a  few  days.  The 
cuticula  of  some  nematodes  is  so  thin  and  flexible,  and  at  the 
same  time  so  impervious,  that  this  evaporation  process  sometimes 
has  to  be  prolonged  to  several  weeks  to  prevent  crumpling,  but 
many  kinds  can  be  successfully  treated  in  two  to  three  days.  If 
the  specimens  have  been  blackened  by  the  Flemming's  solution, 
they  may  be  satisfactorily  bleached  in  a  few  hours  or  days  by 
adding  a  few  drops  of  dioxide  of  hydrogen  solution  to  the  glycerine 
in  which  they  lie  after  evaporation.  They  are  removed  to  pure 
glycerine  one  by  one  as  they  become  bleached,  and  then  are 
mounted  in  glycerine  jelly.  Specimens  treated  in  this  way  make 
excellent  material  for  examination,  but  may  deteriorate  in  the 
course  of  years.  Again,  the  specimens  may  be  killed  by  suddenly 
heating  in  water  on  a  glass  slide  until  they  become  motionless, 
and  can  then  be  examined  at  once,  or  evaporated  as  above  de- 
scribed in  5  per  cent  glycerine. 

The  residue  from  the  subsidence  and  sifting  methods,  already 
described,  may  be  added  suddenly  to  an  equal  volume  of  boihng- 
hot  concentrated  solution  of  corrosive  sublimate  and  allowed  to  cool. 
When  the  specimens  have  remained  in  chis  solution  for  twenty- 
four  hours  or  more  they  may  be  picked  out  one  by  one  on  the  point 


FREE-LIVING  NEMATODES 


481 


Fig.  774.  Skeleton  camera  lucida  drawitiR  used  to 
compute  the  nematode  formula.  (.After  Cobb.) 
The  head  end  lies  to  the  left.  This  gives  the 
following  formula. 


1-9 


[4.8      46      9S 


,81  mm. 


of  bamboo  splinters  and  differentiated  into  alcohol,  and  thence 
successively  into  acid  carmine  in  70  per  cent  alcohol,  70  per  cent 
alcohol  with  i  to  2  per  cent  hydrochloric  acid,  absolute  alcohol,  oil 
of  cloves  and  Canada  balsam.  The  specimens  thus  treated  arc 
more  permanent  than  those  resulting  from  the  glycerine  treatment 
described  above  and  are  the  only 
satisfactory  ones  for  many  cyto- 
logical  studies.  These  various 
treatments  may  affect  the  relative 
proportions  of  the  organism  dif- 
ferently, especially  those  of  the 
neck.  It  is  therefore  best  when 
noting  measurements  of  specimens  ^.8  52    7.4  10.4  4-3 

for  descriptive  purposes  to  indicate  how  the  specimens  were  treated. 

The  student  cannot  expect  to  examine  the  finer  details  of  the 
anatomy  or  indeed  to  make  satisfactory  progress  without  the  i)atient 
use  of  a  good  oil  immersion  objective  under  favorable  conditions. 

The  formula  is  made  to  convey  much  additional  information,  by 
interspersing  suggestive  signs.  Thus  the  successive  signs  in  the  ad- 
/_   ii_  _iL_^i7 '^rL—^L<i-  ,  8  mm  jaccut  formukc  indicate  lips,'  papillae 

< —       I  2  3  J  '  '        4_i  4  9  1  6 

on  the   lips,-  a  pharynx   of  uniform 
i=  il--tr/^~3i5       T7~~^2jri '  "^  (diameter  without   armature    of    any 

kind,^  no  amphids,'*  a  rcnctte  whose 
excretory  pore  is  located  a  little  behind 
the  nerve-ring,^  about  600  transverse 
striae  resolvable  into  rows  of  dots,® 
no  wings  to  the  cuticula,'^  a  median 
esophageal  bulb  two-thirds  as  wide  as  the  middle  of  the  neck,'**  a 
cardiac  bulb  three-fourths  as  wide  as  the  base  of  the  neck,''  two 
symmetrically  reflexed  ovaries,  occupying  71  per  cent  of  the  length 
of  the  body,^^  no  caudal  glands  or  spinneret, '^  a  single  outstretched 
testis  occupying  63  per  cent  of  the  length  of  the  body,'-  a  bursa 
beginning  in  front  of  the  anus  and  including  the  entire  tail,'^  4 
bursal  ribs  or  supplementary  organs  on  cither  side  in  front  of  the 
anus,  and  5  ribs  on  either  side  behind  the  anus.'^ 

1  Conventionalized  contour  of  the  front  of  the  head.  -  Conventionalized  ((.iin.ur 
of  the  lips.     3  Conventionahzed  outline  of  the  pharynx.     *  Absence  of  mark  indicat- 


TABLE 
Terminology  Relating  to  Strlatlon  of  Cuticula. 


100  down 

260  ± 

SOO  ± 

760  ± 
1000  ± 
1500  up 


Very  coarse 

Coarse 

Rather  coarse 

Rather  fine 

Fine 

Very  fine 

Hone 


482 


FRESH-WATER   BIOLOGY 


KEY  TO  NORTH  AMERICAN  FRESH-WATER  NEMATODA 

1  (64)     Intestine  normal  and  functional  throughout;    anus  present  in  both 

sexes 2 

The  forms  which  are  included  here  are  typical  nematodes.  They  possess  an  alimentary 
canal  which  is  complete  and  functional  during  the  entire  life  of  the  individual.  They  are 
free  living  in  the  adult  as  well  as  in  the  larval  stage  of  existence.  With  the  free-living  forms 
are  sometimes  found  parasitic  forms  so  similar  in  structure  that  a  knowledge  of  their  source  is 
needed  to  determine  whether  the  species  is  parasitic  or  not.  No  note  is  taken  of  the  parasitic 
forms  and  the  following  statements  apply  only  to  the  true  free-living  nematodes. 

They  are  all  relatively  small  in  size  and  so  transparent  that  the  internal  structure  can  be  made 
out  clearly  in  the  Uving  animal.  In  these  respects  as  well  as  in  detail  of  internal  structure  they 
stand  in  distinct  contrast  to  the  other  group  included  under  the  alternative  heading  in  the 
key.     Famihes  which  include  only  parasitic  species  are  not  mentioned  in  this  key. 

2  (13)     Oral  end  armed  with  roptrusile  spear  or  sting 3 

3  (8)     Spear  with  bulbous  base 4 

4  (s)     Cuticula  with  70  to  100  coarse,  retrorse  annules Iota  Cobb. 

Genus  consisting  of  a  considerable  number  of  species,  found  in  swamps  and  in  acid 
soils.  These  nematodes  are  covered  with  retrorse  scales,  or  bristles,  so  that  it  is  practically  im- 
possible for  them  to  move  in  any  other  direction  than  forward.  ^  Near  the  head  the  remarkably 
large  and  powerful  spear  can  be  seen  through  the  skin.  When,  in  order  to  make  punctures,  this 
spear  is  thrust  out,  the  nematode  is  not  pushed  backward,  because  of  the  friction  which  its 
scales  offer  to  surrounding  soil  particles.  But  often  the  males  of  Iota  lose  the  spear  at  the  last 
moult  and  become  relatively  longer  and  more  slender  and  smoother,  and  then  they  look  very 
unlike  the  females. 

Representative  species Iota  octangular e  Cobb  19 14. 

^      14 21 .__2i_ -85"  92^ ^^      Male  unknown.    Habitat:  Dismal  Swamp,  Va. 

C"^    II  12  12./  9  6.  '""'■ 


Fig.  775.  Iota  ocfangulare. 
a,  mouth  opening;  b,  lip  region;  c,  spear  muscles;  d,  shaft  of  spear;  e,  base  of  spear;  /,  cuticular  tube 
ol  esophagus;  g,  nerve-ring;  k,  posterior  portion  of  esophagus;  i,  flexure  in  ovary;  j,  body  muscles; 
k:  cuticula;  I,  one  of  the  eight  longitudinal  rows  of  modified  cuticula;  m,  ovum;  n,  muscles  of  body  wall; 
0,  sublateral  modification  of  the  cuticula;  p,  uterus;  q,  subdorsal  modification  of  the  cuticula;  f,  vulva; 
s,   muscles  of  the  body  wall;  t,  rectum;  u,  anus;  v,  terminus.     (After  Cobb.) 

5  (4)     Cuticula  with  200  or  more  finer  or  almost  invisible  annules 6 

ing  amphids.  ^  Oblique  line,  conventionalized  drawing  of  the  outlet  of  the  excretory- 
duct,  placed  just  behind  the  measurements  relating  to  the  nerve-ring.  ^  Character 
of  the  hne  running  through  the  formula  (see  adjacent  table) ,  and  dots  placed  on  either 
side  of  the  Hne.  ^  Absence  of  short  horizontal  Hnes  above  and  below  main  line,  such 
marks  being  used  when  wings  are  present.  ^  Horizontal  stroke  under  two-thirds  of 
the  nerve-ring  \vidth  measurement.  ^  A  corresponding  stroke  under  three-fourths  of 
the  width  measurement  for  the  base  of  the  neck.  ^^  Single  quotation  marks  around  the 
measurement  indicating  the  position  of  the  vulva,  and  71  used  as  an  exponent.  ^^  Ab- 
sence of  spinneret  mark,  —  an  angular  sign  used  to  indicate  spinneret.  ^  Dash  in 
front  of  the  M  and  63  used  as  an  exponent.  ^^  Curved  marking  under  the  transverse 
anal  measurement,  extending  to  the  end  of  the  formula  line  of  the  male,  ^^  4  and  5 
used  as  sub-figures  before  and  after  the  anal  diametral  measurement  with  ditto  marks 
to  indicate  that  the  ribs  occur  on  both  sides. 


FREE-LIVING  NEMATODES 


483 


Esophagus  with  a  distinct  median  bulb,  and  a  more  or  less  distinct 
posterior  swelling.  Males  with  bursa.  .  Tylenclius  Baslian. 
Genus  consisting  of  numerous  species,  many  of  them  iwrasilit 
in  plants  and  sometimes  highly  injurious.  Aquatic  species  are  rather 
uncommon.  A  single  species  found  parasitic  in  a  marine  alsa 
I  nncipally  owing  to  its  economic  importance  the  genus  has  a  very 
extensive  literature. 


Representative  species. 

/l^       9  8.      __  13.  -81 

V  '.i    '      'l.8'/~     2._  ■      ■      '2  2 

(-  : 


7(6) 


Tylenchus  dipsaci  Kahn  1857. 

8=    2_  ■         "22  '12'  I  5  mm         '^ ''|^.    S[K'cieS      is      fouod 

parasitic  in  onion  and  hya- 
,  —  *]■■  •  -^1  ••'•'..  Mmm.  ^'"^'1  \i\i\h>,  and  in  a  num- 
1'       '9  .2.       -NU  ber  of  other  plants,  and  is 

very  harmful.  The  spear,  h,  i,  Fig.  II,  is  shot  forth  hy  the  musiles. 
/,  and  is  used  to  puncture  the  cells  of  the  h(jst  plant.  The  sjiear  is 
tubular,  and  the  juices  of  the  host  are  sucked  through  the  siK-ar  into 
the  intestine  by  means  of  the  bulb,  c.  Often  referred  to  in  literature 
as  Tylenchus  devaslalrix. 

Habitat:  Europe,  America,  Australia,  and  probably  throughout 
the  temperate  regions. 

Fig.  776.     Tylenchus  dipsaci.  Kiihn. 

I,  a  female;  II.  head  of  the  same  more  highly  magnified;  III.  Uil  of 
a  male;  IV,  view  from  below,  of  the  female  sexual  oi)cnin)z;  \".  cross- 
section  of  the  neck  passing  through  the  median  sucking-bulb;  \  I.  front  vktw 
of  the  penes  and  their  accessory  parts;  VII,  cross-section  through  the  middle  of 
a  female,  showing  how  the  body-cavity  is  filled  completely  by  the  ovary-  (») 
and  the  intestine  (3). 

a,  lip  region;  b,  tip  of  spear;  c,  median  sucking-bulb;  <f,  ncr%T-rinK; 
e,  excretory  pore;  /,  muscles  for  moving  the  spear  forward;  /t,  ixwtcrwr 
esophageal  swelling;  A,  excretory' gland;  i,  hind  end  of  si)car.  thrre-bulbrtl: 
i,  loop  in  ovary;  k,  right  spiculum;  /,  muscles  for  ojjcning  the  vulva; 
m,  the  vulva;  n,  glandular  (?)  bodies;  o,  bursa;  p.  hind  end  of  ovar>-; 
q,  uterus  containing  spermatozoa  and  one  segmenting  egg:  r.  segmentrnK 
egg;  5.  vagina;  /,  the  vulva  or  female  sexual  opening:  «,  blind  end  of  ixsterio' 
rudimentary  ovarv;  v,  intestine,  showing  its  cellular  structure;  ir.  cross- 
section  of  an  egg;  x,  anus;  y,  wings  of  the  cuticula;  z.  cross-section  o(  the 
intestine.     (After  Cobb.) 

Esophagus  with  only  one  swelling,  corresponding  to  the  median  l)ulb  i)f 
Tylenchus.    Males  without  bursa.   .    .  Aphdcnchiis  l^Asu^n 


Genus  consisting  of  numerous  species,  the  niajority  parasitic  in 
plants,  and  often  highly  injurious.  Some  sjx-cics  prthenoKenetk-. 
This  genus  closely  resembles  Tylenchus.  frt)m  which  it  is  distin- 
guished by  the  absence  of  the  bursa  on  the  males,  and  by  the  less 
developed  posterior  portion  of  the  esophagus.  Thi>  latter  Ls  so 
deteriorated  that  it  cannot  be  distinguished  from  the  intestine. 
The  oral  spear  also  is  usually  less  strongly  deyeloix-d  than  in 
Tylenchus,  and  its  posterior  extremity  is  less  likely  to  pn-si-nt 
bulbous  swelhngs.  .\s  in  Tylenchus,  so  here,  some  of  the  spitics 
are  known  to  revive  years  after  haWng  been  dried  up  and  con- 
verted into  "dust."  In  the  dirt  or  dust  adhering  to  seeds  and 
plants  they  are  often  transported  long  distances,  -'^•anv  «'  ln« 
species,  therefore,  are  now  cosraoiJoUtan.  Like  I  yUtuhus,  ihii  genu* 
has  an  extensive  literature. 

Representative    species.  ^  ,  u    o 

Aplielenchns  viicrohiimus  Cohh  1891. 


.5 

$. 

10. 
•  •  i  J  ■/ 

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2.4 

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'  °^      Habitat:  Douglas  Lake, 
Michigan. 


Fig.  777.     Aphelcnchus  microlaimus. 
a,  the  lips;   b,  the  spear;   r.  the  nerve-ring;  J  sucking-bulb;   ''J-f"*^^ 
vote-   f  ventral  gland;  g,  blind  eivl  of  testicle;   h.  inloslinc;   i.  cuticwU  or 
skS  ;•;  spStozoonf*.  right  spiculum  or  penis;    /.   piece  accr^oo'  » 
the  spicula;   m,   anus;  n,  papiUa;   o,   terminus.     (.Vflcr  Ujbb.) 


484 


FRESH-WATER   BIOLOGY 


Representative  species. 


'i-: 

,3  4) 

7  1 

9   1 

-52-58 

97  2 

(M) 

1  6/ 

l_7 

2  1 

1  2 

1- : 

<;  n 

8 

12/ 

11 
1.4 

-MOO 
1   7 

99  3 

8  (3)     Spear  without  a  bulbous  base 9 

9  (10)     Esophagus  with  a  median  bulb;  males  with  bursa. 

Dolichodorus  Cobb. 

This  genus  is  distinguished  from  Tylenchus  by  the  peculiar  lobed  bursa  without  ribs,  by  the 

relatively  long  and  slender  oral  spear  and  peculiar  lip  region,  and  by  the  presence  of  a  double 

sexual  organ  in  the  female.     There  are  few  Tylenchi  the  females  of  which  possess  two  ovaries. 

.    .   Dolichodorus  heterocephalus  Cobb  19 14. 

The    transverse  striie  are    resolvable   with   high 
powers    under    favorable    conditions    into    rows  of 
exxeedingly   minute,    somewhat  irregular   elements. 
The  flaps  of  the  bursa  are  striated  in  much  the  same 
manner  as  the  cuticula,  and  the  margins  of  the 
flaps   are   distinctly   thickened.       The   sper- 
matozoa are  small  and  numerous  and  it  ap- 
pears that  the  reduction  divisions  take  place 
in  a  short  segment  of  the  testis  not  far  from 
the  blind  end.     The  organs  obscurely  figured 
in  connection  with  the  head  appear  to  be  the 
outlets  of  glands  located  in  the  neck. 

The  "cardiac  swelling"  h  appears  to  have 
the  same  structure  as  in  some  species  of  Ty- 
lenchus, in  which  it  is  known  to  be  caused  by 
the  presence  of  glands  exterior  to  the  esoph- 
agus, and  therefore  not  properly  to  be  re- 
garded as  a  cardiac  swelling  of  the  ordinary 
kind.  In  the  Tylenchi  mentioned,  these 
glands  empty  through  a  minute  duct  which 
enters  the  esophagus,  passes  through  the 
median  bulb  on  the  dorsal  side  of  its  valvular 
apparatus,  and,  continuing,  empties  into  the 
pharynx  at  the  base  of  the  spear.  These  so- 
called  salivary  glands  are  designated  at  g  in 
I,  under  Tylenchus  dipsaci  (Fig.  776).  Similar 
structures  may  occur  in  the  present  species. 

Inequality  of  the  ovaries  is  characteristic 
of  a  vast  number  of  species  of  nematodes 
and  may  have  a  deep  morphological  signifi- 
cance. It  is  nearly  always  the  posterior 
ovary  which  is  the  smaller.  Every  degree 
of  inequality  exists  even  to  the  extinction 
of  one  ovary.  The  smaller  branch  may  pro- 
duce smaller  and  what  appear  to  be  inferior 
eggs,  and  may  even  cease  to  function  as  a 
reproductive  organ  and  function  merely  as  a 
minor  part  of  the  other  branch,  serving,  for 
instance,  either  as  an  extension  of  the  uterus, 
or  as  a  seminal  receptacle. 

Habitat:  Douglas  Lake,  Michigan;  Silver 
Spring,  Florida. 

Fig.  778.  Dolichodorus  heterocephalus. 
I,  nearly  side  view  of  a  female;  II,  lateral  view 
of  surface  of  head,  more  highly  enlarged;  III, 
sagittal  section  of  head;  IV,  dorso-ventral  view 
of  head;  V,  front  view  of  head;  VI,  side  view, 
posterior  extremity  of  male;  VII,  ventral  view  of 
posterior  rxtremity  of  female;  VIII,  ventral  view 
of  posterior  extremity  of  male. 

a,  papilla;  b,  cephalic  organ  of  unknown  signiQ- 
cance;  c,  spear;  d,  base  of  spear;  e,  median  bulb; 
/,  nerve-ring;  g,  excretory  pore;  //,  cardiac  swell- 
ing; i,  intestine;  j,  anus;  k,  lateral  caudal  pores; 
/,  terminus;  m,  blind  end  of  posterior  ovary; 
n,  ovary;  o,  left  spiculum;  p,  accessory  piece; 
q,  distal  end  of  accessor^'  piece;  r,  left  flap  of 
bursa;  s,  terminus  oE  male;  t,  ovum;  u,  sperma- 
tozoa; ;•,  vaginal  muscles;  w,  uterus;  x,  vulva; 
i',  anus.     (After  Cobb.) 

10(9)     Esophagus  with  only  an  elongated  posterior  swelling;  no  bursa.    .   11 


FREE-LIVING  NEMATODES 


4S5 


(12)     Pharynx  simple,  male  supplementary  organs  not  in  fascicles. 

Doryldimus  Dujarciin. 
Genus  consisting,  no  flouht.  of  hundreds 
of  species,  and  inhabiting  stjii.  frt-sh  water, 
and,  to  a  limited  extent,  brackish  water. 
They  feed  so  far  as  known  on  vcKetahIc 
matter,  most  commonly,  it  is  hclieve<l.  on 
the  roots  of  jilants  which  they  pierce  by 
means  of  the  hollow  oral  sf>car. 

Representative  species. 

Dorylaimus  Jccuudiis  Cobb  1914. 

[-' 

Habitat: 
ington,  D.  C. 

Fig.  779.     Dorylaimus fecundui. 
At  the  right,  head  and  tail  of  a  fi-m.ilc;  al  the  left, 
tail  end  of  a  male, 
a,  apex   of   spear,    showing'  ohlique  opening: 
b,  papilla  of  the  anterior  circlet;    c,   pantUa  of 
the  posterior  circlet;     d,  guidint'-rinR    for    the 
spear;     e,    commencement    of    the   esophaRus, 
/,     pre-rectum;    g,    rectum;    //,  anus;     i,  anai 
muscles;  j,   caudal    pai)ilhi;    k.    outer  cuticub; 
/,  inner    cuticula;    m,  muscular   layer;    n,  prr- 
rectum;    o,   one  of  the  numerous  oblicjuc  a>|m- 
latory  muscles;    P,  one  of  the  ventral  scries  of 
r,  pair  of  pre-anal  papillae;    5,  retractor  muscles  of  the 
accessory  piece.    (.After  Cobb.) 


4  4 

16 

•4r«« 

% 

.5 

I.I 

lb 

19 

1  I 

.) 

4  8 

17 

-M- 

9» 

2  14  I  4       rf^J  4  '  '  — 

Algae,  Potomac   River,  Wash- 


male  supplementary  organs;  q,  ejaculatory  duct 
spicula;   / 


(11) 


1 

6  4 

19 

•29' 

93. 

.9 

15 

17 

-'• 

1  4 

<> 

13. 

41. 

-M- 

99  7 

8 

3. 

36 

2. 

3-M  4 

muscular  layer;    u,  right  spiculum 

Pharynx  with  complicated  radiate  framework,  male  supplementary 
organs  in  fascicles Aclinohiimus  Cohh. 

Genus  represented  in  all  parts  of  th    world,  and  proposal  for 
species   similar   to    Dorylaimus  labyrinthoslonius,  in   which  the 
pharynx  is  more  or  less  immobile,  radially  striated  and  elabo- 
rately constructed. 
Representative  species. 

Actinolaimus  nidiatus  Cobb  1913. 

The  esophagus  bcjjins 

e.9         13.  41.  -M-  ^1  4  I  mm  "'^    ^     ^"'**^    alx)Ut     OnC- 

''  I "8       T.        n  T.     tmI"  third  as  wide  as  the  cor- 

responding portion  of  the  neck.  It  continues  to  have  this  width 
for  some  distance.  Considerablv  in  front  of  the  middle  of  the 
neck  it  expands  rather  suddenly.  The  cells  of  the  brownish  intc-^- 
tine  contain  granules  of  variable  size,  arranged  so  as  to  give  n.sc 
to  a  rather  obscure  tessellation.  The  tail  of  the  female  is  concave- 
conoid  to  the  hairfine  terminus.  The  tail  of  the  male  is  hemi- 
spherical-conoid. Immediately  in  front  of  the  anus  are  two  ven- 
tral papillae  placed  side  by  side.  In  addition  t(^  these  there  are 
ventral  papillae  arranged  in  three  raised  and  conspicuoiis  groups 
or  fascicles.  These  three  groups  form  a  .scries  whose  length  is 
about  equal  to  the  distance  from  the  jx.stenor  group  to  the  end 
of  the  tail.  The  two  equal,  slightly  arcuate  rather  aculc 
spicula  are  about  twice  as  long  as  the  anal  IkkIv  diameter  The 
surface  of  the  tail  carries  a  number  of  innervate<i  |upillac.  at 
least  as  many  as  six,  and  probably  c|Uite  a  number  of  others. 

Habitat:  Roots  of  plants  and  among  algae  Potomac  River  and 
its  banks,   Arlington   Farm   near  Wiushington,  DC;   Douglas 

Lake,  Mich.  ...  ,.  , 

Fig.  780.     Actttwlamus  radiatus 
lb,  lip  region;   />/>.  innervated  ixipillae;    ph,  phao'nx;  on.  oncho,  of 
spear;  or,  mouth  opening,     (.\ller  Cobb.) 

13(2)     Oral  end  without  protrusile  spear  or  Sting. '-^ 

14  (37)     Pharynx  armed  with  one  or  more  refractive, 


Xv5/^ 


cutKular  tecti 


486 


FRESH-WATER   BIOLOGY 


15  (16)     Number  of  teeth  three,  equal,  small,  mobile,  well  forward  near  the 

mouth.  .  Ironus  Bastian. 
Genus  with  about  six  known 
species,  confined  to  fresh  water, 
though  there  is  a  very  similar 
genus,  Thallasironus  de  Man,  for 
the  reception  of  similar  marine 
forms.  Some  species  hermaphro- 
ditic. Salivary  glands  in  esophagus. 

Representative  species. 

Ironus  americanus 
Cobb  1914. 


16  23  27  29  1.3 

From  the  size  of  the  apparently 
matured  ova  it  is  assumed  that  the 
eggs  are  considerably  elongated. 
It  is  unlikely  that  more  than  one  is 
contained  in  the  uterus  at  a  time. 

Habitat:  Deer  Bottom,  Pikes 
Peak  region,  Colorado. 

Fig.  781.     Ironus  americanus. 

I,  head  and  anterior  portion  of  neck; 
II,  head,  lateral  view  "teeth"  ex- 
truded; III,  head,  "  teeth  "  withdrawn 
with  second  set  formed  in  preparation 
for  the  next  moult;  IV,  tail  end  of 
female. 

a,  one  of  the  three  pharyngeal 
teeth,  shown  extruded;  h,  papilla;  c, 
cephalic  seta;  d,  amphid;  e,  pharynx; 
/,  toothlet;  g,  toothlet;  h,  esophagus; 


f,  lining  of  esophagus;  j,  nerve-rmg; 
k,  intestine;  /,  anus;  in,  caudal  gland; 
n,    terminus.      (After  Cobb.) 

16  (15)     Number  of  teeth  one;  or  more  than  one,  and  unequal 17 

17  (22)     Teeth,  at  least  one  of  them,  usually  massive;  thick,  more  or  less 
papillate  lips  closing  over  the  capacious  pharynx.  •    •    •      18 

Main  tooth  dorsal  (sometimes  all  nearly  obsolete) ;  Hps  thick,  armed 

with  papillae;  no  setae Mononchus  Bastian. 

Genus  of  a  score  or  more  species,  some  in  fresh  water,  others 
in  soil,  where  they  hunt  and  devour  nematodes  and  other  small 
organisms.  The  movements,  especially  those  of  the  head,  are  often 
very  active.  The  males  are  very  rare.  The  name  Mononchus 
indicates  the  presence  of  a  single  pharyngeal  tooth,  but  sometimes 
there  are  one  or  two  additional  teeth;  sometimes  all  are  absent. 
The  relatively  powerful  lips  can  be  everted,  and  are  utilized  to 
grasp  the  prey  and  force  it  against  the  pharjmgeal  teeth.  In  some 
species  the  wall  of  the  pharynx  bears  series  of  minute  rasp-like 
denticulations.    Some  species  are  hermaphroditic. 

Representative  species.     Mononchus  major  Cobb  1893. 


1.6 

6. 

19 

•55' " 

95 

16 

2  2    ■ 

26 

2  9 

1  J      ' 

1  •> 

66 

19 

-M- 

95 

15 

23 

2.9 

2  8 

12-N2  3 

>  3  4nua.,     ^y^  elegant  species  is 
a   soil  inhabitating   form 

>  3  4  mim  sometimes  found  in  wet 
places.  No  American  species  are  figured  as  yet.  The  adjacent  il- 
lustrations are  derived  from  Australian  specimens. 

Fig.  782.  Mononchus  major. 
I  side  view  of  male;  11,  side  view  of  head  of  same;  III,  front  view  of 
head;  IV,  side  view  of  tail;  V,  details  of  male  papillae. 
a  mouth;  h,  lip-papiUa;  c,  lip;  d,  esophagus;  e,  nerve-ring;  /,  phar- 
yngeal tooth;  g,  inner^'ated  papilla  of  skin;  U,  esophagus;  t,  base  of 
phSnx;i,  cardiac  collum;  k,  intestine;  /,  flexure  in  testicle ;.  m  blind 
end  of  testicle;  «,  vas  deferens;  o,  lip;  p,  mouth  opening ;  9,  ejaculatory 
duct-  T  spicula;  s,  ejaculatory  duct;  t,  accessory  piece;  w  post-anal 
papillae!  %,  spicula;  w,  ejaculatory  duct;  x,  ventral  row  male  papillae, 
y,  anus;  2,   three  anal  glands.     (After  Cobb.) 


FREE-LIVING  NEMATODES 


487 


19(18)     Main  tooth  submedian.     Lips  thin;  setae  present 20 

20(21)     Males  without  bursa 0)ic/iolui, nus  DuinuWn. 

%t/Il/      I  Genus  of  numerous  siK-cics.   nearly  all 

marine.  A  few  six-cies  only  in  Ijrackish 
and  fresh  water.  C'osmoixjiilan.  i-xt<ii(J 
ing  well  into  the  ix>lar  sc-as.  Some  attain 
a  length  of  25  to  30  mm.  The  individuals 
sometimes  occur  in  enormous  numln-rs 

The  pharyngeal  teeth  vary  in  iiumUT, 
form,  and  size,  and  atTord  g(M)d  n|m-.  ilk 
characters.  The  segments  of  the  ev.pha- 
gus  frequently  contain  much-hramhcd 
"salivary"  glands  emptying  through  the 
pharyngeal  teeth. 

The  female  sometimes  possesses  a  pecu- 
liar pair  of  relatively  large  organs  of  un- 
known .significance  emptying  through 
pores  toward  the  tail  end. 

Representative  species. 
OncholaimHs  piinctatiis  Cobb  1914. 

7         19  10  ;i  -M.««  tj 

L-**  1.T7       n        Ti  n      ^Tl~'  '  '  ■• 


X897 

Fig.  783.    Oncholahnus 
punctatus. 

a,  thin  flaps  on  margins 
of  lips;  b,  lips;  c,  anterior 
circlet  of  papillae;  d,  poste- 
rior circlet  of  papilla-like 
cephalic  setae;  e.J,  subme- 
dian tooth  or  onchus;  g,  wall 
of  pharynx;  k,  intestine;  i, 
ejaculatory  duct;  j,  spic- 
ulum;  k,  dorsal  tooth  or 
onchus;  /,  amphid;  m,  am- 
pulla of  gland,  emptying 
through  dorsal  onchus,  k; 
n,  rectum;  0,  beginning  of 
esophagus;  ^,  anus;  9,  lin- 
ing of  esophagus;  r,  caudal 
gland;  s,  caudal  papilla; 
t,  ducts  of  the  three  caudal 
glands  ;m,  spinneret.  (After 
Cobb.) 

21  (20)     Males  with  bursa. 

Oncholaimellus  de  Man. 

Much  like  Oncholaimus,  but  males  have  narrow 

bursa.      Spicula    unequal,   or    equal.      Two   species 

known;    the  type  0.  calvadosicus  de  Man  is  marine. 

Representative  species. 

Oncholaimellus  heterurus  Cobb  19 14. 


It  is  rather  difficult  to  obser\'c  the  finer 
details  of  the  cuticul.i  on  account  of  the 
presence  in  it  of  numerous,  dot-like  eU- 
ments,  which  are  arranged  in  loni,itudinal 
groups,  of  which  the  wiclest  are  the  lateral 
groups.  The  longitudinal  arrangement  of 
the  granules  is  continuous  throughout  the 
body,  but  it  is  most  marked  on  the  lateral 
fields.     There  are  six  lips. 

Habitat:  Fresh-water  pt)nds.  Cape 
Breton  Island,  Dominion  of  Canada. 


X4.57 


There  are  six  lips,  each  bearing  on  its  anterior  sur- 
face, near  the  margin  of  the  head,  a  somewhat  out- 
ward pointing,  minute,  innervated  papilla.  The  cells 
composing  the  intestine  contain  scattered  granules, 
which  give  rise  to  a  very  obscure  tessellation,  and  also 
certain  doubly  refractive  granules.  The  posterior 
testis  is  the  smaller.  This  is  a  doubtful  Oncholaimel- 
lus, since  there  are  no  pharyngeal  teeth,  and  the 
amphid  varies  from  that  of  the  type  species,  as  do 
the  spicula,  which  in  the  type  species  are  unequal. 

Habitat:   Fresh-water  pond  near  Ocala,  Fla. 

Fig.  784.  Oncholaimellus  heterurus. 
I,  side  view  of  head;  II,  ventral  view  of  head;  III,  side 
view  of  tail  end  of  male;  IV,  ventral  view  of  anal  region  of 
male,  o,  excretory  pore;  b,  submedian  cephalic  seta;  c, 
pharynx;  d,  left  flap  of  bursa;  e,  esophagus;  /,  left  spiculum; 
g,  accessory  piece;  h,  amphid;  i,  male  [X)st-anal  seta  and  pa- 
pilla; j,  lateral  seta;  k,  spinneret;  /,  thin  lips.    (After  Cobb.; 


488 


FRESH-WATER   BIOLOGY 


22  (17) 

23  (36) 

24  (25) 


Teeth  small,  often  only  one,  then  dorsal;    lips  with  inconspicuous 

papillae;  pharynx  of  moderate  size 23 

Esophagus  with  one  or  two  bulbs 24 

Bulbs  two,  spinneret  absent Diplogaster  M.  Schultze. 

Genus  with  more  than  a  score  of 
known  species,  mostly  found  in  fresh 
water  but  also  in  many  moist  situations 
in  soil  and  between  the  sheaths  of 
grasses,  etc.  Some  species  hermaphro- 
ditic. A  number  of  the  species  appear  to 
be  at  least  facultative  parasites.  They 
are  often  found  in  dead  insects  and  cater- 
pillars, whose  death  they  apparently 
have  caused.  Other  species  are  found 
in  decaying  mushrooms,  animal  excreta 
and  foul  pools.  Many  of  the  species  are 
easily  reared  in  decayed  meat  and  va- 
rious other  culture  media.  Many  thrive 
best  in  the  presence  of  bacteria. 

Representative  species. 
Diplogaster  fictor  Bastian  1865. 


J 

II. 

14. 

'5r« 

88, 

3 

IJ 

M 

...... ^.. 

'4 

.9 

12. 

15. 

-M55 

86  6 

1 

la 

/        IJ. 

1  5 

J-Nl  65 

then  cardiac,  or  none;  spinneret  present 


Striae  resolvable  near  the  head  into 
rows  of  refractive  dots  arranged  in  lon- 
gitudinal as  well  as  transverse  Hnes.  A 
short  distance  behind  the  head  the  longi- 
tudinal rows  arrange  themselves  in  pairs. 
These  pairs  indicate  the  locus  of  about 
twenty-four  longitudinal  cuticular  ribs 
or  wings,  which  extend  from  the  middle 
of  the  neck  to  near  the  anus.  On  the 
tail  these  ribs  again  resolve  themselves 
into  double  rows  of  dots.  The  thin- 
shelled  eggs  appear  to  be  deposited 
before  segmentation  begins,  something 
rather  unusual  in  this  genus. 

Habitat:  Spring,  Washington  Coun- 
try Club,  Chevy  Chase,  Md. 

Fig.  785.     Diplogaster  jidor. 

I,  side  view  of  female;  II,  head  of  the 
same,  seen  in  dorso-ventral  view,  lips  nearly 
closed;  III,  head  of  the  same,  lateral  view, 
lips  nearly  wide  open;  IV^  head  of  the  same, 
lateral  view,  lips  partially  closed;  V,  front 
view  of  mouth,  partially  closed;  VI,  lateral 
view,  posterior  portion  of  a  male  specimen; 
VII,  somewhat  diagrammatic  perspective 
view  showing  markings  of  the  cuticula. 

a,  one  of  the  lips;  b,  one  of  the  six  cephalic 
setae;  c,  amphid;  d,  one  of  the  two  more  or 
less  evertible  pharyngeal  hook -shaped  teeth; 
e,  median  esophageal  bulb;  /,  nerve-ring; 
g,  anus;  h.  rectum;  i,  intestine;  j,  terminus; 
k,  posterior  esophageal  bulb;  /,  nerve  cells; 
m.  renette  cell  (?);  n,  left  spiculum;  o,  lumen 
of  the  intestine;  p',  pre-anal  male  seta; 
P",P"',  ^"",  post-anal  male  setae  and  papil- 
lae; q,  one  of  the  cells  of  the  intestine;  r, 
accessory  piece;  s,  flexure  in  anterior  ovary; 
/,  blind  end  of  anterior  ovary;  y,  vagina; 
w,  synapsis  in  egg  in  the  anterior  uterus; 
.T,  one  of  the  spermatozoa  in  the  vagina; 
y,  uterus;   z,  vulva.     (After  Cobb.) 

26 


FREE-LIVING   NEMATODES 


489 


26  (27)     Lateral  dots  much  accentuated Spilophoni  HjLsiian. 

The   striae    arc    rcs^jlvah'e   into   ruw<   ..f  dots 

which  are  much  accentuated  on  the  latir.il  lu-lds. 

/'  \  _  '         Genus    of    a   score    or    more   known    siKxics, 

aquatic,  mostly  marine. 

Representative  species. 

Spilophora  canadensis  Cobb  19 14. 

Cs       .5.  .  .  .8.  .  .  i    '5  -MM  U4 

(^     2.  4.3/    ■■  .   ij i.-  •  •■\yi  ■>      '■* 

Lateral  wings  (j)  are  very  prominent,  and  pos- 
teriorly are  somewhat  scalariform.  The  females 
have  symmetrically  reflcxed  ovaries. 

Habitat:  Fresh-water  ptjiids,  Cape  Breton  Is- 
land, Dominion  of  Canada. 

Fig.  786.     Spilophora  canadensis. 

a,  mouth  opening;  b,  dorsal  tooth;  c.  pharj-nx;  d. 
base  of  the  pharynx;  e,  esophuKus;  f,  nerve  celL»;  t, 
nerve-ring;  //,  excretory  imre;  /,  valvular  api«ratu<i 
of  the  bulb;  j,  longitudinal  row  of  cuticular  markings 
characteristic  of  the  genus;  k,  intestine;  /,  rencttc  cell; 
m,  nucleus  of  renette  cell;  n,  cell  access<jrv  to  the 
t        »        ti  X300     renette  cell;   o,  blind  end  of  testicle;   p,  reversed  of  the 

striationsof  thecuticula;  (/,  vas  deferens;  r,  spiculum;  i, 
anus;  /,  caudal  gland;  u,  spinneret,     (.\fter  Cobb.) 

Striae  composed  of  dots;  the  lateral  ones  Httle  if  any  accentuated.     28 
Pharynx  without  esophageal  bulb Cyatholaimus  ^iisiv^n. 

PharjMix  is  cup  shaped  then  conoid,  and 
longitudinally  ribbed. 

Genus  of  a  score  or  more  of  aquatic 
species,  nearly  all  marine  but  found  also 
in  brackish  and  fresh  waters.  Cyatho- 
laimi  are  found  in  all  trojiical  and  tem- 
perate seas,  and  the  individuals  are  nu- 
merous. In  most  habitats  lx)th  sexes 
will  be  found.  Diatoms  are  sttmetimcs 
found  in  the  intestine.  Thoush  not 
shown  in  the  species  here  figured,  the  re- 
nette seems  always  present,  and  is  often 
well  developed. 


27  (26) 

28  (29) 


Representative  species. 
Cyatholaimus  truncatus  Cobb  1914. 


i- 


Habitat:  Silver  Springs,  Fla. 

Fig.  787.    Cyatholaimus  trumatui. 
I,  side  view  of  a  female;    II.  side  view  of 
head;     III,   front  view  of  the  same  head; 

IV,  ventral   view  of  anal   region  of  male; 

V,  lateral  view  of  the  siime;  VI.  lateral  view 
in  tl>e  middle  of  tiie  body  showing  cuticular 
markings  and  pores. 

a,  suhmedian  cephalic  seta ;  h.  lal>ial 
papilla;  c,  amphid;  d,  dorsal  to<nh:  <■,  lat- 
eral cephalic  seta;  /,  one  of  the  twelve  ribs 
of  the  vcstihulc;  .?,  small  sul)nie«lian  phar;k-n- 
goal  tooth;  //,  base  of  the  pliar>nx;  i.  ejac- 
ulatory  duct;  j.  intestine;  k.  one  of  the 
four  male  pre-anal  supplementary  orRan.*; 
/,  one  of  the  spicula;  m,  anal  muscles;  ».  one 
of  the  accessor>-  pieces;  o,  ner\c  ring;  p. 
one  of  the  cells  of  the  intestine;  q.  lumen  oA 
the  intestine;  r,  anus;  s,  blind  end  of  re- 
flexed  ovar\-;  /,  egg;  u.  vulv.i;  r.  llexurr 
in  anterior  ovan.';  w,  junction  <>l  tlir  .ivarv- 
and  uterus;  J.  pores  in  the  cutKiila:  y  cme 
of  the  three  caudal  glands;  :.  male  gland  (i). 
(After  Cobb.) 


490 


FRESH-WATER  BIOLOGY 


29(28)  Pharynx  less  conspicuously  ribbed;  cardiac  bulb  distinct.     ...     30 

30  (35)  Dorsal  tooth  well  developed 31 

31  (34)  Pharynx  cyathiform  then  conoid,  joining  esophagus  indefinitely,    s^ 
32(33)  Amphids  spiral,  inconspicuous  sUts  or  none.   .    .Chromadora  BsiStia.n. 

Y«j  Genus,   aquatic,  mostly  marine  but  abundant  in   fresh  waters. 

Twenty  to  thirty  species  known.  Found  in  American  fresh  waters, 
no  species  yet  described.  Species  highly  developed,  usually  of  small 
size.  Many  possess  eye-spots  near  the  head.  The  males  usually 
have  a  number  of  pairs  of  special  unicellular  glands  emptying  through 
slender  ducts  into  the  cloaca.  These  glands  are  usually  arranged  in 
series  of  pairs  toward  the  dorsal  side  of  the  body  some  distance  in 
front  ot  the  spicula.  Amphids,  fairly  well  developed,  usually  difficult 
to  see  because  of  their  peculiar  form  and  position;  far  toward  front 
of  head,  usually  seen  more  or  less  in  profile.  Cardiac  bulb  relatively 
shorter  than  in  Spilophora,  and  not  so  distinctly  subdivided.  Males 
usually-  have  well-developed  series  of  ventral  supplementary  organs; 
such  organs  are  less  common  and  less  well  developed  on  males  of  Spilo- 
phora. Lateral  elements  of  the  transverse  striae  sometimes  modified, 
but  rarely  reaching  degree  of  dififerentiation  shown  in  Spilophora. 

Representative  species.  .   Chromadora  minor  Cobb  1893. 

^        .6  9.       .      tS.  '48'  86.       . 

£     \.i'"yir'-u  48        28  •    Habitat:    Pacific   Ocean, 

^       6       8  3       ,4  _M         89  California,  and  Australia. 

e    \.i  •  ■  a:?/--  •  ij 3'.8  •  ic^i.i  ■>  '-'^  °^ 

Fig.  788.  Chromadora  minor. 
I,  male  of  Chromadora  minor;  II,  one  of  the  ventral  accessory  organs  of  the 
same  nematode;  III  and  IV,  head  and  anal  region  of  the  same  nematode. 
a,  pharj^nx;  b,  eye-spots;  c,  esophagus;  d,  h,  ventral  supplementary  organ; 
e,  nerve-ring;  /,  excretor>' pore ;  g,  gland  of  supplementary  organ;  f,  renette 
cell;  j,  organ  of  unknown  nature,  accessorj-  to  the  renette  cell;  k,  blind  end 
of  testicle;  /,  cephalic  seta;  m,  ribs  of  pharyngeal  opening;  n,  papilla; 
0,  dorsal  tooth;  p,  pharynx;  g,one  of  the  striae  of  the  cuticula;  r,  subcephalic 
seta;  s,  dorsal  eye-spot;  /,  intestine;  z<,one  of  the  ventral  male  supplementary 
organs;  v,  ejaculatory  duct;  u\  one  of  the  supplementary  organs;  x,  anus; 
y,  left  spiculum;  s,  accessory  piece. 

33  (32)     Amphids  spiral,  well  developed Achromadora  Cobb. 

Genus  proposed  for  the  reception  of  Chrom- 
adora minima  Cobb  and  similar  soil  and  fresh- 
water species.  Distinguished  from  Chromadora 
by  the  presence  of  well-developed  spiral  am- 
phids. The  dorsal  tooth  is  farther  back  and 
is  opposed  by  a  small  ventral  "pocket"  as 
shown  in  the  figure  of  Achromadora  minima. 
Species  found,  probably,  in  all  parts  of  the 
world.  Known  from  Australia,  Fiji,  and 
various  parts  of  United  States  and  Europe. 

Representative  species. 

Achromadora  minima  (Cobb)  1914. 


E>. 


10    _  . 


Male  unknown.     Habitat:    Soil,  El  Paso, 
Texas.     Potomac  River,  Washington,  D.  C. 
Fig.  789.     Achromadora  minima. 

I,  lateral  view  of  a  female;  II,  lateral  view, 
cuticular  markings;  III,  lateral  view  of  head. 

a,  cephalic  papilla;  h,  cephalic  seta;  c.  one  of 
the  ribs  of  the  pharynx;  d,  dorsal  pharyngeal 
tooth;  e,  subventral  (?)  phar>mgeal  tooth;  /, 
pharynx;  ,5,  cuticular  markings;  h,  amphid;  f, 
nerve  cell;  j,  nerve-ring;  k,  spinneret;  /,  excretory 
pore;  m,  flexure  of  ovar^^;  n.  one  of  the  caudal  glands; 
0,  blind  end  of  posterior  ovary;  p,  anus;  q,  intestine; 
r,  vulva;  s,  one  of  the  granules  of  the  intestine;  /. 
egg.     (After  Cobb.) 


FREE-LIVING  NEMATODES 


491 


34  (31)     Pharynx  cyathiform  then  prismoid,  ending  behind  very  definitely; 

amphids  distinct.     .    Etkmolaimus  de  Man* 

Genus  of  two  known  sf)ccu>s.  one  Kuroiican  one 
American.  Closely  relatod  to  Chromadora.  from 
which  It  IS  readily  distinguished  by  the  narrow  uniform 
posterior  portion  of  the  pharynx,  which  is  usually 
surrounded  by  a  comparatively  distinct  pharyngi-al 
bulb. 

Representative  species. 

Ethmolaimus  amerkanus  C  obb  1Q14. 


[- 


35  (30) 


Labial  papillae,  apparently  12.  Onchus  thumb- 
shaped,  forward  pointing,  attached  to  a  distinctly 
thickened  rib  of  cuticula  which  extends  from  the  lip 
region  back  to  the  base  of  the  pharynx,  and  is  thicker 
anteriorly  than  posteriorly.  Fully  dcvdoiR-d  ov.i  arc 
nearly  twice  as  long  as  the  body  is  wide,  and  one-third 
as  wide  as  long.  Form,  size,  and  number  of  eggs  un- 
known. 

Habitat:  Spring,  Washington  Country  Club,  Chevy 
Chase,  Md. 

Fig.  790.  Ethmolaimus  americanus.  Lateral  view  of  a 
female,  a,  lips;  b,  minute  dorsal  and  ventral  pharyngeal 
teeth;  c,  one  of  the  four  cephalic  setae;  d.  amphid:  t, 
pharynx;  /,  nerve-ring;  g,  excretory  pore;  h,  nerve  cells; 
i,  cardiac  bulb;  7",  beginning  of  the  intestine;  *,  rcnclle 
cell  (?);  /,  beginning  of  main  portion  of  the  inicstinc;  m.onc 
of  two  pairs  of  unicellular  organs  of  unknown  significance; 
w,  cuticula;  0,  one  of  the  cells  of  the  intestine;  p.  su(x:uticuU; 
q  and  r,  body  cavity;  s,  vulva;  /,  nucleus  of  one  of  the 
muscle  cells;  «,  spinneret;  v,  one  of  the  caudal  glands; 
w,  anus. 

Dorsal  tooth  minute,  amphids  circular.  .    .    .    Mkrolaimus  de  Man. 

Amphids  well  developed. 
Genus  of  few  species  from  Europe 
and  North  .America. 

Representative  species. 

Idkrolaimus  jhrciatilis 
Cobb  1914. 


as 
ii' 


The  eggs  appear  to  be  deposited  be- 
fore segmeiitatinn  begins.  Sfxvimens 
with  one,  and  thn.se  with  two.  (Svarics. 
appear  to  be  about  cnjually  numerous; 
as  no  other  dilTerence  has  been  detected, 
they  are  included  for  the  present  under 
the  same  name  and  description. 

Habitat:    Maple  River,  .Michigan. 
Fig.  791.     Mkrolaimus  ilutidtilis. 

I.  lateral  view  of  female;  II.  head  of 
the  same.  /     u       • 

a.  mouth  opening:  b.  one  ol  the  six 
cephalic  papillae;  c.  one  of  the  four  cephalic 
setae;  </,  one  of  the  small  phar>n»:c.il  tcrlh; 
e,  excretor\-  iwre;  /.  spiral  amphid.  f. 
esophagus;  A.  ner\-e-nng;  1.  car.luc 
bulb:  j.  preliminar>-  portion  ol  the  in- 
testine: k.  renctte  cell;  /.  bodv  i-ivity; 
m  lumen  of  intc->itinc:  w.  one  of  the  cclU 
of  the  intestine;  0.  anus:  /.  lie  mi  re  in 
posterior  ovar>';  Q.  uterus:  r.  blind  rn.l  o 
posterior  ovar^-;  s,  one  of  the  tl.n-r  v.uid*! 
glands;  /.  spinneret:  u,  ckk> 
w,  cuticula. 


.Iva: 


(After  Cobb.) 


492 


FRESH-WATER    BIOLOGY 


36  (23)     Esophagus  plain Cryptonchus  Cobb. 

Iff Y^^^y^^      PP  Differs  from  Cylindrolaimns  de  Man  in  the  form  of  the  amphids, 

and  the  strongly  developed  esophagus  with  its  various  regions,  in 
the  presence  of  a  dorsal  tooth  at  the  base  of  the  pharynx  and  in 
the  absence  of  setae. 


ccm 


Single  species. 


Cryptonchus  nudus  Cobb  1913. 


H 


9  ...^..26; .'?.3'* ?.!.... ..>     I  9  mm       At  a  point  about  two 

"        ^  ^^         '^  body  widths  in  front  of 

the  cardia  the  nature  of  the  esophagus  suddenly  changes,  the 
lining  becoming  notably  less  massive,  and  the  radial  structure 
becoming  relatively  more  massive,  and  at  the  same  time  changing 
its  character,  so  that  there  is  a  rather  striking  contrast  between 
this  short  posterior  section  and  the  main  portion  of  the  esophagus. 
Wing  space  one-third  as  wide  as  the  body.  The  anterior  part  of 
the  intestine  for  a  distance  equal  to  the  body  radius  consists  of 
small  cells  packed  wnth  granules  and  possessing  larger  and  differ- 
ently formed  nuclei.  Eggs  four  times  as  long  as  the  body  is  wide, 
one-fourth  as  wide  as  long,  and  comparatively  thick  shelled; 
uterus  contains  one  at  a  time. 

Habitat:    Found  about  the  roots  of  aquatic  plants,  Potomac 
River,  Arhngton,  and  in  Douglas  Lake,  Mich. 

Fig.  792.     Cryptonchus  nudus.     lb,  lip  region;  pp,  labial  papillae;   am, 
amphid;  ph,  pharynx;  on,  onchus  or  tooth;  oe,  esophagus;  sp,  spinneret. 
XI81         '^^^^^^  Cobb.) 

Pharynx  without  teeth 38 

Esophagus  with  bulbs 39 

Amphids  circular  or  nearly  so ;  pharynx  compound,  much  elongated.  40 
Cuticular  external  marking  of  amphid  circular.    .    .     Plectus  Bastian. 

Genus  of  about  thirty  species  mostly  about  plants.     Some  aquatic,  none  marine.     Some 
species,  perhaps  most,  parthenogenetic  or  hermaphroditic.  Obscure  labial  papillae  usually  present. 

Representative  species Plectus  tubifer  Cobb  19 14. 

74  mm       First  lateral  pore    of   the 
cuticula  immediately  behind 
the    lateral    organs,   whence 
79  mm.  similar,     somewhat    smaller 
pores,    totaUing    about    two 
hundred,  form   four  subme- 
dian  rows.     Six  rounded,  rather  massive  hps  sur- 
round the  short,  napiform  vestibule  leading  to  the 
pharynx.       Amphids     transversely     elongated    or 
roundish,  open  behind.      There  is  an  obscure,  pos- 
terior, more  or  less  closed,   elon- 
gated,     triquetrous       pharyngeal 
^      J     k 


sp 

37  (14) 

38  (49) 

39  (42) 

40  (41) 


2. 

II.     19. 

■49"« 

926 

2.1 

3.4 /—     3_5 

3  2 

2.3 

I  9 

10.              19.2    ■ 

'-Mi* 

91  5 

2. 

•31.^    -3 A 

36 

}'-\i  3 

XZ20 


Fig.  793- 
a,  mouth;  6,  papilla-like  cephalic  setae;  c,  lateral  organ;  J,  pharynx;  e,  posterior  chamber  of  phar\'nx; 
/,  esophagus;  g,  nerve-ring;  h,  excretory  pore;  i,  renette  cell;  j,  glandular  (?)  cell;  k,  cardiac  bulb; 
/,  cardia;  m,  intestine;  n,  blind  end  of  anterior  testicle;  o,  spermatocyte;  p,  flexure  in  posterior  testicle; 
q,  blind  end  of  posterior  testicle;  r,  junction  of  testicles;  s,  vas  deferens;  /,  glandular  (?)  organ;  «, 
muscle  to  one  of  the  three  supplementary  organs;  v,  anterior  supplementary  organ;  w,  spiculum;  x,  anus; 
y,  one  of  the  caudal  papillae;  2,   spinneret,     (.\fter  Cobb.) 


Plectus  tubifer.     Male, 
lateral  organ;   J,  pharynx; 


FREE-LIVING   NEMATODES 


493 


41  (40)     Chitinous  marking  of  amphid  not  circular.  .   .    .    Clironogast€r  Cobb 

Genus  closely  related  to  Plectus,  differing  in  much  elongated  cardia.  connecting  mstcrior 
esophageal  bulb  and  intestine.     Ovary  single  in  Chrono^asler,  double  in  PUclus  ^''''^'■^^' 

ra^     Single  species  known.  .  Chronogaster  gracilis  Col^b  1913.  ^^    ^ 


5 

II.        . 

25. 

•56" 

89 

2 

2  3'- 

2.6 

•         5. 

16 

2 

12 

25. 

-M-" 

92  7 

9 

1.9  /  ■ 

2-i 

2  4 

9~XI   9 

Male  unknown.     Habitat:    Potomac 
River;  Douglas  Lake,  JNIichigan. 


%, 


Figs.  794  and  795.    Clironogastrr  Rraulis. 
a,  lips;  b,  papilla;   c,  cephalic  seta;   </.  phar>'n\: 

e,  esophagus;  /,  posterior  chamln-r  of  i)har>iut; 
g,  problematical  organs;  //,  ner\'e-rin);;  1,  excretory 
pore;  j,  renette  cell;  /,  valvular  a|>i>aratus  in 
cardiac  bulb;  m,  cardia;  n,  intestine;  o.  llcxurc  in 
ovary;  p,  nucleus  of  ovum;  q,  bliml  end  of  ovarj-; 

f,  egg;  s,  vulva;  /,  anus:  u.  c.iuil.il  uLind;  r, 
spinneret.     (After  Cobb.  1 

42(39)     Amphids  apparently  absent;  pharynx  simple 43 

43  (44)     Esophagus  with  two  bulbs;  males  with  bursa. 

Rhahditis  Dujardin. 

Genus  of  numerous  species,  some  parasitic,  especially  in  insects. 
Several  marine  species  and  a  number  in  fresh  water.  Conimon  in 
decaying  matter.  Reproduction  wonderfully  varied,  ranging  from 
parthenogenesis,  through  hermaphroditism  of  varying  degree  to  com- 
plete bi-sexuality.  Many  species  microbivorous.  In  some  siiecies 
there  is  a  marked  alternation  of  generations. 

Bursa  better  developed  in  species  of  Rhahditis  than  in  any  other 
fresh-water  nematodes.  Other  genera  presenting  this  feature  are 
Tylenchus,  Dolichodorus,  and  Oncholaimellus.  Bursa  (Fig.  Ill) 
consists  of  two  thin  lateral  extensions  of  cuticula  containing  rays  or 
ribs,  often  tubular,  constituting  outlets  of  cement  glands,  always 
well  supplied  with  nerve  endings.  Form  of  bursa  and  arrangement 
of  its  rays  form  good  generic  and  specific  characters. 

Representative  species.    Rhahditis  cylindrica  Cobb  1S9S. 

<-_      12  n  _  ^  J7_ 'Ji'l 91L       \%mm. 

<.—      I  2  3J/  4_3  4  9  1.6 

Habitat:  Wet  soils. 


(= 


J6_ 
3.5" 


3.7  4  2^5 


Fig.  796.    Rhahditis  cvUndrica  Cobb. 

I,  side  view  of  female;  II,  side  view  of  attached  male;  III,  ventral  view 
of  male  tail.  .  .     , 

a,  pro.ximal  end  of  spiculum;  h,  lip;  c,  base  of  pharynx;  d,  right  spiculum; 
e,  bursa;  /,  anus;  g,  median  bulb;  h,  nerve-ring;  i,  excretory  pore;  j,  cardiac 
coUum;  k,  intestine:  /,  one  of  the  ribs  of  the  bursa;  w,  egg  containing 
embryo;  m,  flexure  in  ovary;  o,  lips;  p,  pharynx;  9,  segmenting  egg; 
r,  median  bulb;  s,  vulva;  /,  intromitted  spicula;  u,  ejaculatory  duct:  r. 
testicle;  w,  blind  end  of  testicle;  x,  blind  end  of  reflexed  ovary;  y,  intestine, 
z,  anus.     (After  Cobb.) 


wy^ 


494 


FRESH-WATER   BIOLOGY 


44  (43)     Esophagus    with    only    one    well-developed    bulb;      males    without 

bursa 45 

45  (46)     Pharynx  long  and  narrow Rhahdolaimus  de  Man. 

Genus  of  four  known  species,  three  European,  one  American. 

Representative  species Rhahdolaimus  minor  Cobb  1914. 


c= 


77  » 

....... 


The  cuticula  appears  to  be  destitute  of  any  but  very 
fine  transverse  striations,  most  clearly  visible  near  the 
head.  Careful  focussing  appears  to  indicate  the 
presence  on  the  outer  margin  of  the  head  of  almost 
invisible  papilla-like  organs  which  may  perhaps  be 
the  representatives  of  cephalic  setae.  There  are  no 
hps.  The  thin-shelled,  smooth  eggs  are  relatively 
large  and  elongated  and  have  been  seen  in  the  uterus 
one  at  a  time.  They  are  about  four  to  five  times  as 
long  as  the  body  is  wide  and  about  one-fifth  as  wide  as 
long.  They  appear  to  be  deposited  before  segmenta- 
tion begins.  The  eggs  are  so  large  in  proportion  to  the 
size  of  the  ovaries  that  they  push  the  ovaries  first  to 
one  side  and  then  the  other  as  they  develop,  so  that 
both  ovaries  may  occasionally  appear  to  be  either  in 
front  of  or  behind  the  vulva.  The  specimen  figured 
was  so  twisted  that  the  head  presents  the  dorso- 
ventral  view,  and  the  tiny  amphids  (a)  therefore 
appear  in  profile.  The  figure  shows  well  the  typical 
distribution  of  nerve  cells,  large  numbers  in  front  of 
and  behind  the  nerve-ring,  a  smaller  collection  in  the 
cardiac  region,  and  other  collections  in  the  anal  region. 
The  long,  slender  spirmeret  is  characteristic  of  the 
genus. 

The  figure  illustrates  the  general  features  of  the  cen- 
tral nervous  system,  which  in  nematodes  consists  of  a 
ring  of  ner\^e  fibers  encircling  the  esophagus,'and  hav- 
ing connected  with  it  a  number  of  more  or  less  spherical 
nerve  cells,  shown  dark  in  the  figure.  Under  favorable 
circumstances  each  one  of  these  cells  can  be  seen  to  be 
connected  with  others,  and  directly,  or  indirectly,  with 
the  ring  of  fibers.  The  whole,  therefore,  constitutes  a 
rather  complicated,  coordinated  system  of  nerve  cells. 
In  many  species  the  cells,  such  as  those  shown  at  c  and 
h,  are  arranged  in  longitudinal  groups,  and  even  where 
the  groups  are  not  apparent,  as  here,  the  connections 
among  the  cells  are  undoubtedly  systematic  and  cor- 
respond with  the  longitudinal  grouping  that  is  evident 
in  other  genera.  From  the  central  nervous  system 
extend  forward  and  backward  nerves,  —  ventral,  dor- 
sal, lateral,  and  to  a  lesser  extent  submedian,  connected 
by  commissures.  Special  collections  of  nerve  cells 
occur  on  the  ventral  side  near  the  cardia,  vulva,  and 
anus.  The  exterior  indications  of  the  nerves  are  found 
in  papillae  and  setae,  usually  corresponding  in  position 
with  the  main  branches  of  the  ner\'ous  system. 

Habitat:  Mud,  Beach  pool,  Pine  Point,  Douglas 
Lake,  Michigan. 

Fig.  797.    Rhahdolaimus  minor. 

I,  lateral  view  of  female;  II,  head  of  the  same,  showing 
amphid.  The  head  m  I  is  twisted,  so  that  the  amphid 
appears  as  if  ventral,  or  nearly  so. 

a,  amphid;  b,  long,  narrow  phar>-nx;  c,  anterior  group 
ot  nerve  cells;  d,  nerve-ring;  e,  cardiac  bulb;  /,  wall  of 
the  mtestine;  g,  fle.Yure  in  anterior  ovarj^;  h,  posterior 
group  of  nerve  cells;  i,  body  cavity;  j,  lumen  of  intestine; 
k,  ovum;  /,  blind  end  of  posterior  ovary;  w,  egg;  w,  flexure 
in  posterior  ovary;  o,  cuticula;  /),  caudal  glands;  9,  subcuticula; 
r,  vulva;  s,  rectum;  t.  anus;  u,  nerve  cells  (?);  v,  duct  of 
caudal  glands;  w,  spinneret;  x,  lip  region.      (After  Cobb.) 


FREE-LIVING  NEMATODES 


495 


47 


46  (45)     Pharynx  not  long  and  narrow 

47  (48)     Striae  not  resolvable  into  rows  of  dots Cephalohns  Baslian. 

Genus  of  numerous  species,  frequent  about  the  higher  plants,  doubtless  often  at  least  "semi 

parasitic.'      Occasionally  species  in  fresh  water.      Common  in  deaiying  veirctable  maticr 
Some  species  are  parthenogenetic,  others  hermaphroditic.     Found  on  iht-  surface  of  iiw(  t^ 

Cephalobus  resembles  Rhabditis,  but  may  readily  be  distinguished  by  the  form  of  the  r,l,ir\nx 
and  the  nature  of  the  male  caudal  armature.  The  pharynx  of  Cephalobus  is  ahnosi  m-v.-r 
cyhndroid  or  prismoid  as  in  Rhabditis.  On  the  contrary  it  tends  to  tafK-r  more  or  less  reKularlv 
from  the  base  of  the  hps  backward.  Though  simple  in  form  the  pharynx  is  usually  comixjuiKled 
of  two  or  three  series  of  short  cuticula  elements  separated  from  each  (jtluT  by  transverse 
breaks.  In  a  considerable  number  of  species  the  lips  a.-j  mjdiiied  so  as  to  bear  more  or  less 
complicated  forward  pointing  cuticula  appendages. 
Such  forms  are  intermediate  between  the  typical 
Cephalobi  and  other  genera,  such  as  Acrobelcs  and 
Wilsonema.  The  males  of  the  Cephalobi  do  not 
possess  a  bursa,  at  most  showing  faint  indications  of 
such  a  structure.  Nevertheless  the  papillae  or  ribs 
found  accompanying  the  bursa  in  Rhabditis  are  present 
in  Cephalobus,  though  they  sometimes  are  less  numer- 
ous than  on  typical  Rhabdites. 

Not  infrequently  the  ovary  functions  in  the  first 
instance  as  a  testis.  Spermatocytes  appear  in  the 
young  ovary  even  before  an  external  sexual  opening 
exists.  The  developing  spermatozoa  descend  the 
oviduct  and  enter  the  uterus.  Later  the  oocytes  de- 
velop and  are  fertilized  by  the  spermatozoa  previ- 
ously produced  in  the  same  organ,  —  at  least  this 
happens  in  some  instances,  and  hence  is  assumed  to 
happen  in  all.  So  far  no  differences  have  been  dis- 
covered between  spermatozoa  produced  in  this  way 
by  these  syngonadic  females  and  those  produced  by 
the  rarely  occurring  males.  It  is  therefore  fair  to  as- 
sume that  the  sperm  cells  so  commonly  produced 
in  this  way  are  potent.  As  in  Rhabditis  the  renette 
often  takes  the  form  of  two  long  slender  lateral  ducts 
ending  bhndly  near  the  anus.  Some  species  may  be 
revived  after  remaining  months  or  even  years  in  a  dry 
condition. 

Representative  species. 

Cephalobus  suh-elongatus  Cobb  19 14. 

^ 

The  thin,  transparent,  colorless  layers  of  the  naked 
cuticula  are  traversed  by  about  seven  hundred  plain, 
transverse  striae,  resolvable  with  high  powers  without 
very  much  difficulty.  There  are  three  rather  distinct, 
bluntly  conoid  lips,  which  are  rounded  in  front;  each 
of  them  apparently  has  two  inconspicuous  innervated  "^ 

papillae.  The  intestine  is  composed  of  cells  of  such  a 
size  that  probably  only  about  two  are  recjuired  to  build 
a  circumference.  The  nerve-ring  surrounds  the  esoph- 
agus obhquely,  and  is  accompanied  by  nerve  cells,  of 
which  the  greater  number  are  behind  the  nerve-ring 
and  in  front  of  the  cardiac  bulb. 

Habitat:  Moss  Bog,  VV.  End  of  Douglas  Lake,  Mich. 

_  Fig.  798.     Cephalobus  sub-elongatus. 
Lateral  view  of  a  female. 
a,  lips;  h,  pharynx;    c,  anterior  portion  of   esophagus; 

d,  posterior  extremity  of  anterior  portion  of  esophagus; 

e,  nerve-ring;  /,  cardiac  bulb;  g,  beginning  of  intestine; 
//,  one  of  the  cells  of  the  intestine;  /,  lumen  of  the 
intestine;  j,  excretory  pore;  k,  cardiac  valve;  /,  re- 
nette cell;  m,  flexure  in  single  ovary;  n,  cuticula;  o, 
ovary;  />,  spermatozoon  in  uterus;  q,  vulva;  r,  nucleus  in  ^^^ 
ovum;  5,  body  cavity;  t,  anus;  u,  ripe  ovum;  v,  unripe 
ovum;  w,  oocyte;  x,  blind  end  of  ovary;  y,  rectum;  2, 
terminus.    (After  Cobb.) 


t  8 

15. 

23. 

•6151 

94. 

1.6 

3./ 

J-6 

■■4.3" 

M 

496 


FRESH-WATER   BIOLOGY 


48  (47)     Striae  resolvable  into  rows  of  dots,  altered  on  lateral  fields. 

Teratocephalus  de  Man, 

Interesting  genus  of  few  species,  with  movable  cuticular  lips.  Species  have  thus  far  been 
found  only  in  fresh  water  and  wet  soils,  but  the  genus  appears  to  have  a  world-wide  distribution, 
at  least  in  temperate  regions.  Teratocephalus  seems  related  to  Cephalobus  from  which,  how- 
ever, it  differs  strikingly  in  the  formation  of  the  lips  and  pharynx.  It  is  difficult  to  determine 
the  functions  of  the  movable  cuticular  labial  elements  {a).  The  most  reasonable  assumption 
appears  to  be  that  they  are  biting  organs. 

-Representative  species Teratocephalus  cornutus  Cobb  1914. 


The  cuticula  is  traversed  by  about  1500  transverse 
striae,  resolvable  into  rows  of  minute  dots,  which  are 
modified  on  the  lateral  fields.  The  movements  of 
which  the  lips  are  capable  are  plainly  indicated  in 
Figs.  II  and  IV.  The  relatively  large  eggs  are  ex- 
tremely mobile,  so  that  they  pass  out  through  the 
relatively  small  vulva  without  difficulty.  Contact 
with  water,  however,  appears  to  harden  the  shell  so 
that  after  deposition  the  eggs  have  a  more  definite 
and  rigid  form.  These  phenomena  are  characteristic 
of  the  eggs  of  many  genera,  especially  those  in  which 
the  eggs  are  of  relatively  large  size.  In  the  present 
species  the  eggs  are  deposited  before  segmentation 
begins.  The  general  form  of  the  tail,  and  its  termi- 
nus, would  seem  to  suggest  the  presence  of  caudal 
glands,  but  none  have  been  seen. 

The  cardiac  bulb  so  strongly  developed  in  this 
species  is  similar  to  that  found  in  Rhabditis,  Plectus, 
Cephalobus,  etc.  It  consists  of  three  movable  valves 
rolling  against  each  other,  that  can  be  pulled  back- 
ward by  appropriate  muscles.  The  arch  over  them 
meanwhile  remains  rigid;  thereby  a  vacuum  (suction) 
is  produced.  The  minute  striation  on  these  valves 
has  suggested  that  they  are  triturating  organs,  but 
the  food  habits  would  not  seem  to  necessitate  such 
an  assumption.  It  seems  more  likely  that  the 
striations  are  due  to  such  a  disposal  of  the  cuticula 
as  will  give  to  the  organs  the  necessary  strength  and 
eflficiency.  These  valves  act  rapidly,  often  several 
times  per  second. 
Habitat:   Maple  River,  Michigan. 

Fig.  799.     Teratocephalus  cornutus. 
I,  lateral   view   of   a   female;     II,  lateral  view  of  head, 
more    highly    magnified;     III,    front   view   of   head;    I\', 
dorso-ventral   view    showing   lips  wide  open;     V,  cuticula 
showing  lateral  field. 

a,  one  of  the  six  movable,  cuticular  lips;  b,  one  of 
the  four  submedian  cephalic  setae;  c,  amphid;  d,  nerve- 
ring;  e,  excretory  pore;  /,  organ  of  unknown  signifi- 
cance; g,  cardiac  bulb;  h,  intestine;  i,  anus;  j,  rec- 
tum; k,  cuticula;  /,  one  of  the  cells  of  the  intestine; 
m,  lumen  of  the  intestine;  nn,  flexures  in  ovary;  o,  egg; 
p,  vulva;  q,  blind  end  of  posterior  ovary;  u,  terminus. 
(After  Cobb.) 


49  (38)     Esophagus  without  bulbs ....     5c 


50  (57)     Pharynx  none. 


51 


51  (56)     Caudal  glands  and  cephaHc  setae  present 52 


FREK-LIVING  NEMATODES 


52  (55)     Amphids  spiral. 


4Q7 
53 


53  (54)     Male  supplementary  organs  papillate Hastiana  dc  Man. 

Named  in  honor  of  the  English  nematologist  Henry  CharRon  liastiaii,  iSj7-igi4 

Genus  of  slender  nematodes  with  rather  simple  mouth  parts.  M:iK-s  with  a  ventral  row  of 
small  supplementary  organs  extending  over  the  greater  part  of  the  length  of  the  body  Half 
a  dozen  species  known.     Occurs  in  Europe,  America,  JajKin,  and  .\ustralia. 


Representative  species Basliana  exilis  Cobb 


[914. 


P  .4  6       _     19.  -M-O"  92. 

£  ^  T — r2--^-i:4 2:--o^i.T     ''"""• 

The  moderately  thick  layers  of  the 
transparent,  colorless,  naked  cuticula 
are  traversed  by  about  eight  hundred 
transverse  striae,  which  do  not  appear 
to  be  further  resolvable.  These  striae 
exist  in  the  outer  as  well  as  the  inner 
cuticula,  so  that  the  entire  contour  of  the 
body  is  crenate.  Rather  conspicuous 
lateral  wings  are  present,  the  optical 
expression  of  which  is  two  distinctly  re- 
fractive longitudinal  Hues  opposite  the 
lateral  fields,  separated  from  each  other 
by  a  distance  somewhat  greater  than  the 
width  of  one  of  the  annules  of  the  cuticula. 
There  is  a  circlet  of  at  least  six  cephalic 
setae,  of  which  the  four  submedian  are 
the  longer,  and  are  somewhat  longer  than 
the  head  is  wide.  Possibly  each  of  these 
latter  is  accompanied  by  a  shorter  seta, 
thus  making  ten  in  all.  Apparently 
labial  papillae  are  present,  but  they  have 
not  been  sufficiently  clearly  seen  to  per- 
mit of  enumeration.  From  the  rather 
raised  anus  the  conspicuous  rectum, 
which  is  twice  as  long  as  the  anal  body 
diameter,  extends  inward  and  forward. 
The  tail  is  conoid,  but  tapers  more  rapidly 
near  the  acute  terminus.  Nothing  is 
known  concerning  the  renette. 

Habitat:  Fresh  water,  Tynne  Station, 
Fla. 

Fig.  800.     Bastiana  exilis. 

Lateral  view  of  a  male  specimen. 

a,  one  of  the  six  cephalic  papillae;  b,  one  of  the 
posterior  set  of  four  submedian  cephalic  setae; 
c,  one  of  the  anterior  set  of  si.x  cephalic  setae;  d, 
esophagus;  e,  cervical  seta;/,  amphid;  g,  one  of 
the  cells  of  the  intestine;  //,  one  of  the  numerous 
male  supplementary  organs;  /,  blind  end  of  the 
two  testes;  the  two  testes  join  each  other  at  n,  the 
complete  development  of  the  spermatozoa  tak- 
ing place  between  the  locations  indicated  by  / 
and  «;  the  junction  of  the  testes  with  the  vas 
deferens  is  on  the  far  side  of  the  body  and  is 
not  shown;  j,  nerve-ring;  k,  posterior  extrem- 
ity of  esophagus  (pseudo-bulb);  /,  left  spicu- 
lum;  m,  cuticula;  n,  spermatozoon;  o,  anal  mus- 
cle; p,  terminus;  g,  vas  deferens;  r,  intestine. 
(After  Cobb.) 


498 


FRESH-WATER  BIOLOGY 

Male  supplementary  organs  protusile  tubes.    Aphanolaimus  de  Man. 

Genus  of  fresh-water  nematodes, 
of  which  nearly  a  dozen  species  are 
known.     Hermaphroditism  occurs. 

Representative  species. 

Aphanolaimus  spiriferus 
Cobb  1914. 


X 


.5 

'7 

9.    _     20. 
■|.5'     ■     2.1 

•50"«3        & 
■31' 

.2 
.7 

10.     _     14  (?) 
l.l'      ■      2. 

2  4    71 

9 

55  (52) 
i 


-V   c 

Viviparous.  Two  embryos  and  de- 
veloping egg  have  been  seen  in  each 
uterus  at  the  same  time.  Eggs, 
about  as  long  as  body  is  wide,  and 
less  than  half  as  wide  as  long. 

Habitat:  Potomac  River,  Wash- 
ington, D.  C. 

Fig.  801.    Aphanolaimus  spiriferus. 

I,  lateral  view,  anterior  end  of  female; 

II.  lateral  view,  posterior  end  of  female; 

III,  lateral  view  of  head,  more  highly 
magnified;  IV,  male  supplementary 
organ;  V,  lateral  view  of  posterior  ex- 
tremity of  male. 

a,  mouth  opening;  b,  amphid;  c,  lumen 
of  esophagus;  d,  pigmented  eye-spots  (?); 
e,  intestine;  /,  nerve  cell;  g,  rectum;  h, 
nerve-ring;  /,  anus;  k,  esophagus;  /,  cau- 
dal gland;  m,  duct  of  caudal  gland;  n, 
glandular  body  at  base  of  neck;  0,  spin- 
neret; p,  ejaculatory  duct;  q,  intestine;  r, 
anterior  end  of  cloaca;  5,  right  spiculum; 
t,  backward  pointing  accessory  piece;  u, 
nerve  cells  (?);  v,  male  supplementary 
organs.     (After  Cobb.) 

Amphids  circular  or  ellipsoidal Tripyla  Bastian. 

Genus  of  toward  twenty  fresh-water 
species,  some  at  least  carnivorous. 


Representative  species. 

Tripyla  lata  Cobb  1914. 

r    ^  I  J 7_ 20  '»'*'> 8_5_^    2^  ^^, 


7.    „    .7 7_ 20  -M-5» 82  8  .    ,  ,  ^^ 

p '  2 1 — 3-2 Ji Ts — I?sTr\  ^■*'^' 

In  lumen  of  pharynx  at  a  point  re- 
moved from  anterior  extremity  a  distance 
a  little  greater  than  radius  of  head, 
minute  inward-pointing  dorsal  tooth, 
having  a  length  about  equal  to  width  of 
one  of  the  annules  of  cuticula,  proving 
that  pharynx  extends  backward  a  dis- 
tance equal  to  width  of  head.  In  some 
specimens  not  far  behind  this  point  dis- 
tinct transverse  fold  in  lining  of  esopha- 
gus. 

Habitat:  Alpine  Lakes,  Bald 
Mountain,  Colorado. 

Fig.  802.  Tripyla  lata, 
a,  labial  papilla;  b,  lip;  c,  amphid;  d,  sper- 
matozoon; e,  spermatocyte  of  anterior  testis; 
/,  base  of  esophagus,  pseudo-bulb;  g,  nerve- 
ring;  h,  cuticula;  j,  esophagus;  j,  lining  of 
esophagus;  k,  intestine;  /,  posterior  testis; 
w,  male  supplementary  organ;  n,  vas  def- 
erens; 0,  retractor  muscle  of  spiculum; 
p,  right  spiculum;  q,  intestine;  r,  duct  of 
caudal  gland;  s,  caudal  gland;  /,  spinneret. 
(After  Cobb.) 


FREE-LIVING  NEMATODES 


4og 


56  (51)     Caudal  glands  and  cephalic  setae  absent 


.    .     Alaimus  de  Man. 
The  species  of  this  small  kciius  have  a 
rather  simple  structure.     All  are  slender. 
Some  appear  to  be  parthenoKeiictic. 
Representative  species. 

Alaimus  simplex  Cobb  19 14. 

r     .     I?..      .     "■        r-    "  »■«•  92 

I.      .J         .e'^"':9 i  i 6         '    ■■ 


r    .   ;2.  .      7.      _  1$  M  94 

Very  minute  striations  in  subcuticula  at 
extremities,  under  favorable  conditions. 
Obscure  traces  of  lateral  winRs.  Krks  ap- 
parently deposited  before  segmentation  be- 
gins. Whether  two  testes  or  only  one  not 
determined.  Broad,  nninded,  blunt  end  of 
testis,  located  as  far  behind  base  of  neck  as 
latter  is  behind  anterior  extremity. 

Habitat:   Big  Lake,  Fla. 

Fig.  803.    Alaimus  simplex. 

I,  lateral  view  of  a  female;  II,  anterior  ex- 
tremity, lateral  view;  III,  posterior  extremity 
of  a  male,  lateral  view. 

a,  lip  region;  b,  phar>'nx;  c,  amphid;  d, 
amphid,  enlarged;  e,  group  of  spermatozoa  at 
posterior  portion  of  ovarj- ;/,  blind  cnfl  of  ovary; 
g,  male  supplementary  paijillae;  h.  left  spicu- 
lum;  i.  terminus;  7,  submedian  elevation  or  flap 
indicating  rudimentary  bursa;  k,  egg;  /.  vulva; 
w,  nerve-ring;  «,  posterior  extremity  of  esopha- 
gus; p,  modified  cells  of  anterior  intestine;  (j, 
cuticula;  r,  wall;  5,  lumen  of  intestine;  /,  flexure 
in  single  ovary.     (After  Cobb.) 

57  (50)     Pharynx  present 58 

58  (59)     Pharyngeal  cavity  relatively  large,  amphids  very  small  if  any. 

Prismatoldimus  de  Man. 

Well-characterized  genus  consisting  at  present  of  four 
or  five  species.    This  genus  resembles  Monhystera  to  a 
certain  extent. 
Representative  species. 

Prismatolaimus  stenurus  Cobb  1914. 


£= 


Behind  each  amphid,  at  a  distance  equal  to  the  width 
of  two  to  three  annules  of  the  cuticula,  there  is  a  short 
seta.  The  ovaries  are  moved  backward  and  forward 
in  accordance  with  stage  of  development  of  eggs.  These 
latter  appear  to  be  deposited  before  segmentation  begms. 
Notwithstanding  the  slenderness  of  the  tail  caudal  glands 
and  a  spinneret  are  present. 

Habitat:   Roadside  pool,  Douglas  Lake,  Michigan. 


Fig.  804.     Prismatolaimus  stenurus. 


side 


I,  lateral  view  of  a  female;   II.  front  view  of  head:   III, 

Tone'ofthe  six  cephalic  papillae;  6,  one  of  the  ten  ccphalk 
setae;  c,  one  of  the  six  thm  lips;  d,  pharynx;  e  ^mph  1  /. 
lumen  of  the  esophagus;..^-  nerve-nng;  h  cu  .cula;  ••  n"-;''^ 
of  ovum;  j,  vulva;  ^,  bhnd  end  of  l>«Jt«-"r'«^,^."^;'^J ;  '■  ^  ^ 
beginning  of  the  intestine;  n.  one  of  the  cells  of  the  ^^i'"' -;'/f«^ 
Einef  .,  rectum;  />•  ^""^^'Z' «"^  "^^i7,^■:'Sl^l3t"^*'•  '' 
flexure  in  anterior  ovary;  5,  spinneret.     (After  Lobb.) 


500  FRESH-WATER   BIOLOGY 

59  (58)     Cavity  small,  amphids  usually  well  developed. 


60 


60  (61)     Form  of  cavity  conoid,  open  in  front;   circular  amphids  considerably 
behind  it • Monhystera  Bastian. 

A  large,  aquatic  genus  of  which  about  one  hundred  species  are  known.  Many  marine. 
Some  found  in  soil.  Many  species  feed  upon  diatoms.  Probably  no  other  nematode  genus 
is  so  widespread  as  Monhystera.  In  any  collection  from  land  or  from  fresh  or  salt  water  the 
first  specimen  to  come  to  view  often  proves  to  be  a  Monhystera.  The  species  are  very  numer- 
ous and  the  individuals  surprisingly  so.  Brightly  colored  eye-spots  are  more  common  than  in 
any  other  fresh-water  genus. 

Representative  species Monhystera  sentiens  Cobb  1914. 


t=»,i 


6 

7 

.    22. 

-7262 

88. 

6 

■3  1 

43 

48 

31 

7 

9 

.    22 

-M-71 

87. 

6 

29 

3  5 

4  2 

^33 

The  striae  are  more  readily  visible 
toward  the  extremities,  especially  the 
posterior  extremity.  The  lips  appear 
to  be  three  in  number,  and  are  longi- 
tudinally striated  or  fluted.  The 
anterior  portion  of  the  intestine  is 
somewhat  bulbous  in  form,  and  is 
separated  from  the  esophagus  on 
the  one  side  and  the  true  intestine  on 
the  other,  by  a  pair  of  constrictions. 
This  portion  may  perhaps  be  looked 
upon  as  a  strongly  developed  cardia. 
The  lateral  fields  vary  in  width  in 
different  parts  of  the  body.  A  httle 
in  front  of  the  anus  they  are  about 
two-fifths  as  wide  as  the  correspond- 
ing portion  of  the  body,  and  contain 
rather  numerous  scattered  nuclei  of 
such  a  size  that  about  eight  would  be 
required  to  reach  across  the  field. 
A  Httle  farther  forward  the  field  is 
narrower.  Anteriorly  it  is  wider 
again.  The  blind  end  of  the  anterior 
testis  is  located  a  short  distance  behind 
the  nerve-ring,  while  the  blind  end  of 
the  posterior  testis  is  located  about  as 
far  in  front  of  the  anus  as  the  ter- 
minus is  behind  it.  The  testes  are 
broad  and  in  some  parts  appear  to 
fill  up  the  main  portion  of  the  body 
cavity. 

Habitat:  Sand  bar  off  Plummer's 
Island,  Potomac  River. 


Fig.  805.     Monhystera  sentiens. 

I,  side  view  of  a  female;  II,  side  view  of  head  of  the  same;  III,  side  view  of  posterior  extremity  of  a 
male. 

a,  pharynx;  b,  submedian  cephalic  seta;  c,  lateral  cephalic  seta;  d,  spermatozoon;  e,  amphid;  /,  lining 
of  esophagus;  g,  esophagus;  /;,  subcephalic  setae;  i,  lumen  of  intestine;  j,  nerve  cells;  k,  nerve-ring; 
/,  striated  lip  region;  m,  left  spiculum;  n,  cell-nucleus  associated  with  amphid; _  o,  blind  end  of 
single  ovary;  pp,  the  three  caudal  glands;  q,  anal  muscles;  r,  spinneret;  s,  beginningof  intestine;  t,  anus; 
u,  one  of  the  cells  composing  the  intestine;  v,  vulva;  w,  egg,  the  spermatozoa  "d"  being  outside  of  the  egg 
"w";  *,  egg  in  synapsis;  y,  vaginal  glands;  2,  ovum.    (After  Cobb.) 


FREE-LI\^NG   NEMATODES 


;oi 


6i  (60)     Form  of  cavity  various,  closed  in  front,  amphids  opposite  it.      .     (ji 


62  (63)     Lateral  organs  or  amphids  inconspicuous Trilolnis  Bastian. 

Fresh -water  genus  of  which  about  half  a  dozen  species  are  known.     Known  to  fee.l  u[xjn 
diatoms  in  one  case  and  upon  rotifers  in  anotlier.     Hermaphroditism  occurs. 

Representative  species Trilobus  longus  {W\i\y)  1)^,-^1. 


.3 

7. 

19. 

'Ab'iO 

89. 

2  8/ 

3.8 

4.6 

2.3 

3 

8. 

14. 

-M- 

92. 

2,6/ 

3.2 

3.8 

t"N2.7 

source  of  nourishment  of  this  species, 
about  one-fourth  as  wide  as  the  body. 


The  lips  bear  papillae  but  their  numlier  i.<i  not 
„  known.  The  intestine  frequently  contain.s  rliatoms 
in  large  numbers,  indicating  that  these  are  a  comm<jn 
The  longiitudinal  fields  are  distindly  develoi)cd,  and 
From  the  slightly  elevated  vulva  the  vagina  leads  in- 
ward at  right  angles  to  the  ventral  surface  fully  half  way  across  the  body.  The  rcllexwl 
ovaries  pass  about  two-thirds  of  the  way  back  to  the  vulva.  Two  or  tiiree  eggs  may  <Kcur  in 
each  uterus  at  one  time.  These  are  somewhat  ellipsoidal  and  thin  shelled,  being  al)out  two- 
thirds  as  long  as  the  body  is  wide  and  about  two-thirds  as  wide  as  long.  The  eggs  ap[X'ar  to 
pass  through  at  least  the  early  stages  of  segmentation  before  being  deposited.  The  waits  of 
the  vagina  present  the  peculiarity  of  being  very  thick,  and  composed  of  six  to  .seven  tun- 
centric  layers  so  that  the  organ  is  considerably  broader  than  it  is  deep.  Its  intcrnAl  wall 
presents  the  peculiarity  of  staining  strongly  with  carmine. 

Trilobus  longus,  the  only  American  fresh-water  nematode  outside  the  Mcrmithidac  that  had 
been  adequately  characterized  previous  to  the  inception  of  this  chapter,  was  de.scribed  by  the 
famous  Philadelphia  naturalist,  Dr.  Joseph  Leidy,  in  185 1.  At  that  time  extremely  little  wa^ 
known  about  the  free-living  fresh-water  nematodes,  and  no  one  dreamed  of  their  vast  numlxrr 
and  variety.  The  peculiar  male  supplementary  organs  of  Trilobus  did  not  fail  to  attract  atten- 
tion, and  it  is  owing  to  this  fact  that  Leidy's  name  is  associated  with  the  striking  sp)ecic3 
selected  as  a  representative  of  the  genus. 

Habitat:  Mud  about  the  bases  of  aquatic  plants,  in  pools,  ditches,  rivers,  and  lakes  through- 
out the  country. 


Trilobus  longus. 


T,  male;  II,  head,  lateral  view;  III,  head,  lateral  view;  IV,  head,  ventral  view;  V.  anterior  supple- 
mentary organ;  VI,  posterior  supplementary  organ;  VII,  two  supplementary  organs  from  an  exceptional 
female. 

a,  lateral  seta;  b,  papilla;  c,  submedian  seta;  d.  pharynx;  r,  lateral  organ;  /,  toiUh;  .c.  toj)lh;  *•  «^Jj|J': 
agus;  /,  nerve-ring;  i,  excretory  pore;  k,  body  muscles;  /,  glandular!?)  organs;  w.  intestine;  «•  W'"'| 
end  anterior  testicle;  0,  testicle;  p,  junction  of  testicles;  q,  blin.l-cnd  posterior  testicle;  r.  va>  *>^'^'^: 
5,  nerve  of  supplementary  organ;  t,  cavity  of  supplementary^  organ;  u,  left  spiculum  r.  acccs^  r>  piece, 
w,  the  three  caudal  glands;  x,  anus;  y,  terminus;  z,  aix-x  of  supplementary  organ.      K.\\\cx  Couu.; 


;o2 


FRESH-WATER  BIOLOGY 


63  (62)     Lateral  organs  or  amphids  more  or  less  conspicuous  spirals  or  circles. 

Anonchus  Cobb. 

Genus  of  which  a  single  species  is  known.     There  are  indications  of  folds  surrounding  the 
mouth  opening,  so  that  in  all  probability  the  lips  may  be  opened  outward  as  in  Mononchus. 

Single  species  known Anonchus  monhystera  Cobb  igis ■ 


pe  jy--3------3  7--'^j--®|^^->     I  mm.       Lateral    fields   occupied    by   about   forty  internal 

ellipsoidal  bodies,  rather  equally  spaced  in  two  series. 

Y=<f  *---i^^^^: ?* ^^->     I.  mm.  Cardia  slender,   as  long  as  the  neck  is  wide.     The 

~      ^'         ■'       ''         ^'    ''^^'  twenty  tubular  male  supplementary  organs  are  con- 

tinued to  the  head  by  a  series  of  about  seventy  minute  ventral  depressions. 
Habitat:  Mud  about  the  roots  of  aquatic  plants,  Potomac  River. 


XI39 


Fig.  807.    Anonchus  tnonhystera. 


Fig.  808.    Anonchus  monhystera. 


a,  mouth  opening;  b,  pharynx;  c,  cephalic  seta; 
d,  lateral  organ;  e,  esophagus;  /,  cellular  body  in 
lateral  field;  g,  nerve-ring;  h,  excretory  pore; 
i,  cardia;  j,  anterior  end  of  intestine;  k,  renette 
cell;  /.lumen  of  intestine;  m,  blind  end  of  testicle; 
n,  testicle;  0,  spermatozoa;  p,  one  of  the  numerous 
supplementary  organs;  q,  anus;  r,  accessory  piece; 
s,  one  of  the  caudal  glands;  /,  terminus;  u,  right 
ppiculum.    (After  Cobb.) 


a,  mouth  opening;  b,  cephalic  seta;  c,  chitinous 
element,  anterior  portion  of  pharynx;  d,  pharynx; 
e,  spiral  amphid;  /,  radial  musculature  of  esoph- 
agus; g,  lumen  of  esophagus;  h,  cuticula;  i, 
ampulla  of  gland  (?);  j,  body  wall.     (After  Cobb.) 


FREE-LIVING  NEMATODES  -o^ 

64  (i)     Posterior  region  of  intestine  atrophied;  anus  vestigial  or  absent. 

Family  Mermithidak  .    .     65 

The  forms  included  in  this  group  are  of  some  size,  being  notably  larger  than  those  in  the 
first  section  of  the  nematodes.  These  often  reach  lo  to  20  cm.  in  length  They  are  more 
or  less  opaque  so  that  the  mternal  structure  cannot  usually  be  determined  by  sut>cr 
fjcial  exammation  of  the  living  ammal.  The  intestinal  region  of  the  alimentary  canal' is  re- 
duced to  a  mere  cord  of  cells  without  any  cavity,  or  may  be  entirely  wanting  for  a  |>ortion  of 
the  length.  The  anus  if  discernible  at  all  in  the  female  has  the  form  of  a  mere  shillow  dcnl 
in  the  external  surface  of  the  cuticula  to  which  the  vestigial  remnant  of  the  intestine  is  attachctl 
In  the  male  the  terminal  portion  of  the  intestinal  canal  persists  as  the  genital  duct  cloaca  an<l 
the  anus  functions  as  its  orifice,  but  the  intestinal  tube  is  atrophied  in  front  of  the  ixiint  at 
which  the  sexual  canal  joins  it.  These  forms  are  parasitic  in  larval  life  and  do  not  feed  during 
the  adult  stage  of  their  existence.  The  latter  may  be  passed  either  in  water  or  in  the  stA\ 
though  the  species  are  more  frequently  reported  from  the  latter.  By  virtue  of  likeness  iti 
habit  and  to  some  extent  also  in  external  form  Mermithidae  are  often  regarded  as  related  to  the 
"hair  snakes"  (Gordiacea)  to  which,  however,  they  bear  no  real  structural  resemblance.  They 
are  the  so-called  "cabbage  worms  "  which  from  time  to  time  enjoy  transient  newsjjaper  notoriety 
on  account  of  their  supposed  poisonous  character  whereas  really  they  are  harmless. 

The  American  Mermithidae  are  very  little  known.  The  following  key  to  the  cstablishwl 
genera  will  be  of  service  to  the  student  in  allotting  any  of  his  discoveries  to  the  proper  genua 

65  (66)     Hypoderm  with  only  two  longitudinal  fields;    cuticula  with  criss- 

cross fibers;  spicula  two N  comer  mis  von  Linstow. 

66  (65)  Hypoderm  with  more  than  two  longitudinal  fields 67 

67  (78)  Longitudinal  fields  six 58 

68  (73)  Cuticula  without  criss-cross  fibers 69 

69  (70)  Spicula  two Mesomermis  Daday. 

Representative  species Mesomermis  virginiana  Cobb  iqi 4. 

There  are  minute  longitudinal  striations  throughout  the  body.  These  are  interrupted  on  the 
lateral  jines  where  there  is  a  distinct  wing.  There  is  no  distinct  pharynx.  The  mouth  pore  is 
very  minute  and  is  located  a  little  toward  the  ventral  side  of  the  middle  of  the  front  of  the  head. 
The  cuticula  is  penetrated  on  the  head  by  a  number  of  innervations  which  end  in  minute  depres- 
sions on  the  surface  of  the  head.  Near  the  mouth  opening  there  is  one  of  these  depressions  on 
the  dorsal  side,  and  apparently  a  similar  one  on  the  ventral  side,  while  nearer  the  outer  margin 
of  the  head  there  are  two  ventral  submedian  and  two  dorsal  submedian  similar  depressions. 
Pores  occur  also  here  and  there  on  the  body,  as  well  as  on  the  neck.  The  lateral  organs  present 
the  following  appearance  when  seen  from  the  side:  They  appear  to  project  from  the  surface 
of  the  body  very  slightly,  beginning  as  a  tube  having  a  length  about  one-third  as  great  as  the 
corresponding  diameter  of  the  head.  This  tube  has  very  thin  walls,  and,  a  short  distance  in. 
apparently  near  the  surface  of  the  body,  a  second  element  appears  in  the  form  of  a  circle  inside 
that  representing  the  contour  of  the  outer  tube.  This  appears  to  constitute  a  sort  of  core  In 
the  midst  of  which  are  a  number  of  refractive  elements,  resembling  ner\x-  fibers,  which  pass  in- 
ward and  backward  toward  the  lumen  of  the  esophagus.  Some  of  these  elements  are  longer 
than  others.  The  focus  passing  inward  picks  up  one,  then  two,  then  several  more,  st)  that  by 
the  time  a  view  is  obtained  that  is  wholly  inside  the  body  there  are  seen  a  half  dozen  or  more 
of  these  elements.  It  is  impossible  in  this  view  to  pick  up  the  internal  connections  of  thes<- 
refractive  elements.  The  lateral  fields  are  about  one-third  as  wide  as  the  body.  The  tail  of 
the  male  bears  several  series  of  innervated  papillae.  These  papillae  are  arranged  on  the  ventral 
submedian  Hnes  as  .well  as  on  the  ventral  line.  The  ventral  papillae  just  in  front  of  and  jii^t 
behind  the  anus  are  double.  In  the  submedian  rows  there  are  four  on  the  tail  — one  opjjosite 
the  anus,  one  a  little  farther  back,  a  third  near  the  middle  of  the  tail,  and  a  fourth  considerably 
farther  back.  In  front  of  the  anus  on  each  side  there  are  eight  submedian  papillae  occupying  .1 
distance  more  than  twice  as  great  as  the  length  of  the  tail;  the  distance  between  the  successive 
papillae  increases  with  the  distance  from  the  anus,  so  that  the  space  between  the  st-venth  and 
eighth  is  about  two-thirds  as  great  as  the  diameter  of  the  body.  Of  the  median  papiltu;  on  the 
tail  there  are  three,  two  near  the  anus  and  one  just  in  front  of  the  middle  of  the  tail,  with  |x)s 
sibly  a  fourth  farther  back.  Of  the  median  papillae  in  front  of  the  anus  there  are  two  near  the 
anus,  and  ten  additional  ones  about  coextensive  with  the  submedian  papillae,  and  distributiti  in 
the  same  manner.  There  are  two  outstretched  testes,  the  posterior  a  little  shorter  tli.m  tin- 
anterior. 

Co   A 6   -  "  -M-«        %.  Habitat:    Cranberry  bog,  Arlington  Farm,  \irpini.i. 


504 


FRESH-WATER  BIOLOGY 


^ 


m 


mi 


rx  334  , 


Fig.  809.     Mesomennis  virginian.i. 


a,  mouth  opening;  h,  anterior  circlet  cephalic  papillae;  c,  posterior  circlet 
cephalic  papillae;  d,  pharyngeal  tube;  e,  outer  margin  lateral  organ;/,  strands, 
lateral  organ;  g,  esophagus;  h,  papilla;  i,  unicellular  organs  of  uniinown  signif- 
icance; j,  nerve-ring;  k,  esophagus;  /,  intestine;  m,  ejaculatory  duct;  n,  body 
wall;  0,  one  of  the  oblique  copulatory  muscles;  p,  one  of  the  submedian  sup- 
plementary organs;  q,  one  of  the  ventral  supplementary  organs;  r,  spiculum; 
5,  one  of  the  caudal  ventral  supplementary  organs;  t,  subventral  caudal  sup- 
plementary organ.     (After  Cobb.) 


X  120 


Fig.  810.    Mesomermis  virginiana. 


a,  mouth  opening;  b,  lateral  organ;  c,  esophagus;  d,  nerve-ring;  e,  posterior  end  esophagus;  /,  intestine; 
g.  blind  end  anterior  testicle;  h,  testicle;  i,  junction  of  testicles;  ;,  intestine;  k,  blind  end  posterior 
testicle;  /,  ventral  supplementary  organs;  m,  submedian  supplementary  organs;  »,  oblique  copulatory 
muscles;  0,  spiculum.     (.After  Cobb.) 


FREE-LIVING  NEMATODES 

70  (69)     Spiculum  single. 

71 

71(72)     Vagina  of  the  adult  cylindroid,  S-shapcd.    .    .    Li mnomcrmis  D.i&^y. 

72(71)     Vagina  tubular  (?)  not  S-shaped P sc ud 0 mc rm i s  ^kM^n 

73  (68)     Cuticula  with  criss-cross  fibers.  ... 

/4 

74(77)     Vagina  of  the  adult  S-shaped 

75  (76)     Spiculum  single Paramermis  von  LinstoNv. 

76  (75)     Spicula  two Mermis  Dujardin. 

77  (74)     Vagina  of  the  adult  not  S-shaped BaUiymcrmis  Daday. 

78  (67)     Longitudinal  fields  eight -g 

79(80)     Cuticula  without  criss-cross  fibers H ydromcrmis  CorU. 

80  (79)     Cuticula  with  criss-cross  fibers Eiuncrmis  Dadav. 


IMPORTANT  REFERENCES   ON  FREE-LIVING  NEMATODES 

Bastian,   C.     1865.     Monograph  of  the  Anguillulidae.     Trans.   Linn.  Soc, 

Lond.,  25:   73-84;   5  pi. 
BuTSCHLi,  O.     1873.     Beitrage  zur  Kenntnis  der  freilebenden  Nematodcn. 

Nova  acta  caes.  leop.,  36:   144;   11  pi. 
Cobb,   N.   A.     1913.      New    Nematode    Genera    Found    Inhabiting    Frc-sh- 

Water  and  Non-Brackish  Soils.    Jour.  Wash.  Acad.  Sci.,  3:  432-444. 
1914.     The  North  American  Free-living  Fresh-Water  Nematodes.    Trans. 

Amer.  Micr.  Soc,  2>i\  69-134;  8  pi. 
De  Man,  J.  G.     1884.     Die  frei  in  der  reinen  Erdc  und  im  susscn  Wasser 

lebenden  Nematoden  d.  Niederlandischen  Fauna.     206  pp.;  34  pl- 
Jagerskiold,  L.  a.     1909.     Freilebende  Siisswasserncmalodcn.     Siisswasscr- 

fauna  Deutschlands,  Heft  15;  46  pp.;  65  figs. 
Maupas,  E.     1899.     La  mue  et  I'enkystement  chez  les  Nematodes.     Arch. 

zool.  exper.  (3),   7:   562-628;  3  pl. 
1900.      Modes  et   formes  de    reproduction   des   Nematodes.      .\rch.    zcx>I. 

exper.  (3),  8:  462-624;   ir  pl. 
MicoLETZKY,   H.     19 13.     Freilebende   Susswassernematoden   der   O.^talpen 

Sitzber.  Kais.  Akad.  Wiss.  Wien,  Math.-natunv.  Kl.,  Abt.  I,  122  :  in 

122,  543-548. 
Steiner,  G.    1913-1914.     Freilebende  Nematoden  aus  der  Schweiz.     Anluv. 

Hydrobiol.  und  Planktonk.,  9:  259-276,  420-438. 


CHAPTER   XVI 
PARASITIC    ROUNDWORMS 

By  henry  B.  ward 

Professor  of  Zoology  in  the  University  of  Illinois 

The  roundworms  or  Nemathelminthes  constitute  a  group  of 
convenience  into  which  are  put  three  classes  that  have  Httle  in 
common  except  general  external  appearance.  But  even  in  this 
feature  differences  of  a  real  character  appear  on  closer  examination 
and  the  study  of  internal  anatomy  fails  to  show  any  intimate 
agreement  in  the  fundamentals  of  structure.  The  three  classes 
embraced  in  this  phylum  are  the  Nematoda  or  true  roundworms, 
the  Gordiacea  or  hairworms,  and  the  Acanthocephala  or  probos- 
cis roundworms.  All  agree  in  the  elongated  generally  cyKndrical 
form,  and  in  the  uniform  or  monotonous  external  appearance. 
The  Nematoda  show  nearly  always  some  taper  toward  one  or  both 
ends,  being  thus  spindle-shaped  rather  than  truly  cyKndrical,  and 
possess  a  smooth,  glistening,  colorless  external  surface.  The  Gor- 
diacea are  larger,  more  uniformly  cyKndrical  with  blunt  rounded 
ends  and  an  exterior  at  least  faintly  colored  in  whole  or  in  part. 
The  Acanthocephala  show  a  roughened  surface  sometimes  with 
imperfect  rings  around  the  body,  and  the  form  usually  Kke  a 
carrot  is  always  somewhat  irregular.  These  differences  are  general 
and  subject  to  exception  but  with  practice  one  can  usually  separate 
members  of  the  three  groups  at  sight,  and  the  structure  is  so  differ- 
ent that  it  is  wise  to  consider  each  group  separately  in  an  inde- 
pendent section  of  the  chapter. 

Biologically  the  three  classes  show  certain  contrasts.  The  Nema- 
toda include  many  free-Kving  forms  and  many  others  purely 
parasitic,  but  most  of  the  latter  have  brief  free-living  stages  during 
which  they  achieve  the  transfer  to  a  new  host.  The  Gordiacea  are 
parasitic  during  early  Kfe  and  spend  the  adult  existence  free  in 
water  bodies.  The  Acanthocephala  are  among  the  most  highly 
specialized  of  parasites  as  they  have  no  free-living  stages  at  all 

506 


PARASITIC   ROUNDWORMS  .q- 

and  as  there  is  no  trace  of  an  alimentary  canal  at  any  sta^c  of 
development. 

In  collecting  parasites  one  may  find  adult  Xcmatoda  and 
Acanthocephala  side  by  side  in  the  same  intestine  but  the  latter 
rarely  occur  outside  the  alimentary  canal  and  nematodes  often  do. 
The  Gordiacea  are  parasitic  in  larval  stages  normally  in  the  Ixxly 
cavity  of  Insecta  and  are  found  only  infrequentl\-  in  other  hosts. 
They  are  most  commonly  found  as  adults  in  general  a(|uati(  col- 
lecting and  are  well  known  even  to  the  casual  observer  of  life  in 
ponds  and  ditches  under  the  popular  designation  of  "  Hair  Snakes." 

The  technic  of  handling  the  roundworms  is  not  simple.  Para- 
sitic nematodes  are  collected  in  the  manner  already  described  for 
parasites  in  general  (p.  368),  but  owing  to  the  very  resistant  cutic- 
ula  and  delicate  structure  of  these  worms  great  care  is  necessary 
to  avoid  injuring  specimens  seriously.  Those  which  are  loose  can 
be  picked  up  with  a  fine  camel's  hair  brush.  This  instrument  is 
most  convenient  in  the  handling  of  small  species.  Many  species  are 
so  firmly  attached  to  the  intestinal  wall  that  it  is  difficult  to  remove 
them  without  injury.  Gentle  manipulation  if  prolonged  will  usu- 
ally loosen  the  hold,  but  the  body  is  easily  lacerated  by  grasi)ing 
it  with  forceps  other  than  very  lightly  or  the  mouth  parts  are  often 
torn  by  pulling  the  worm  too  hard.  Encysted  forms  should  be 
freed  from  the  cyst  under  a  dissecting  lens  with  fine,  sharp  needles. 
A  very  good  needle  is  made  of  a  glass  rod  drawn  out  to  a  point. 
Most  nematodes  are  very  sensitive  to  changes  in  osmotic  pressure 
and  are  badly  disfigured  by  rapid  changes.  Living  specimens 
should  not  be  put  into  distilled  water  or  normal  salt  solution. 
Tap  water  is  fairly  good  and  for  nematodes  from  fresh- water  fish 
a  0.3  per  cent  salt  solution  is  best,  but  material  should  not  be 
left  in  such  a  fluid  longer  than  absolutely  necessary. 

The  resistant  cuticula  prevents  the  entrance  of  cold  killing 
solutions  so  thoroughly  that  these  worms  live  even  hours  in  lluids 
that  kill  other  parasites  promptly.  Hot  fluids  coagulate  the  body 
proteins  and  preserve  specimens  well  extended.  Xo  successful 
methods  of  narcotization  have  yet  been  worked  out.  The  killing 
fluid  recommended  by  Looss  is  all  in  all  most  useful;  it  is  made 
by  adding  to  alcohol  (70  to  85  per  cent)  from  5  to  10  [>er  cent 


5o8  FRESH-WATER    BIOLOGY 

glycerine.  This  fluid  is  heated  over  a  flame  in  a  beaker  or  thin 
watch  glass  until  it  begins  to  volatiUze,  or  more  precisely  to  a 
temperature  of  56°  to  60°  C.  The  worms  in  a  minimum  amount 
of  fluid  are  dropped  into  the  beaker,  whereupon  most  forms 
straighten  at  once.  Specimens  are  preserved  permanently  in  this 
mixture  and  by  allowing  it  to  evaporate  slowly  one  can  bring  them 
gradually  into  strong  glycerine  in  which  they  can  be  studied.  This 
method  is  especially  good  for  mounting  in  to  to.  For  histological 
details  nematodes  should  be  killed  in  a  mixture  containing  equal 
parts  of  acetic  acid,  alcohol,  and  water,  which  has  been  saturated 
with  corrosive  subHmate  and  to  which  has  been  added  0.25  per  cent 
osmic  acid. 

Formol  can  be  used  to  advantage  only  in  the  lactophenol  quick 
method.  Nematodes  are  killed  in  2  to  5  per  cent  formol  and  after 
lying  there  2  hours  are  gradually  transferred  to  a  solution  com- 
posed of  I  part  glycerine,  i  part  lactic  acid,  i  part  phenol,  and  2 
parts  water.  The  transfer  should  be  timed  to  bring  them  at  the 
end  of  6  hours  into  the  pure  solution. 

Lactophenol  specimens  are  mounted  in  the  same  fluid  in  a  pre- 
pared cell.  Glycerine-alcohol  material  is  mounted  in  strong  glycer- 
ine into  which  it  has  been  carried  gradually  by  evaporation.  When 
material  must  be  stained  and  embedded  for  sectioning,  or  mounted 
in  balsam,  treatment  is  very  difficult  and  results  are  uncertain.  In 
general  ah  changes  must  be  gradual  and  as  deliberate  as  possible. 
The  simplest  method  is  to  employ  a  string  siphon  made  by  placing 
three  stender-dishes  in  a  stair-step  series,  with  the  worms  in  the 
middle  dish  and  the  fluid  into  which  they  are  to  be  transferred  in 
the  top  dish  while  the  waste  flows  into  the  bottom  dish.  String 
siphons  lead  into  and  out  of  the  center  dish  and  the  amount  of  the 
flow  is  regulated  by  the  size  of  the  string. 

The  differentiator  (Fig.  811)  is  a  very  valuable  aid  in  nematode 
technique.  Worms  are  placed  in  the  small  tube  a  and  the  tube  h 
is  filled  with  the  fluid  into  which  they  are  to  be  transferred.  The 
very  fine  tip  regulates  the  flow  of  the  fluid.  When  in  absolute 
alcohol  they  can  be  taken  out  and  brought  into  a  clearing  fluid 
by  the  siphon  method,  or  the  differentiator  may  safely  be  used 
by    extending    the    fine    tip    e,    and    leaving    out    the    mixing 


PARASITIC   ROUNDWORMS 


509 


chamber.  The  best  clearing  fluids  are  synthetic  oil  of  wintcrgreen 
(methyl  saHcylate)  and  xylol.  As  stains,  Delal'icld's  hematoxylin, 
EhrHch's  acid  hematoxyUn,  and  Mayers'  para- 
carmine  give  good  results.  For  sections  the  first 
two  are  advised,  also  a  stain  made  by  saturating 
a  one  per  cent  phenol  solution  with  thionin. 
Special  methods  were  worked  out  on  the  nerv- 
ous system  by  Goldschmidt.  Nematodes  may 
also  be  studied  by  staining  intra  vitam  by 
thionin  without  phenol  and  by  methylene 
blue. 

When  specimens  are  to  be  transferred  to  bal- 
sam or  damar,  it  is  wise  to  pierce  the  body 
wall  with  a  fine  needle.  Some  skill  is  necessary 
to  avoid  injury  to  internal  organs.  When 
transferring  the  worms  to  thin  balsam  place 
them  in  paper  cups  and  allow  the  medium 
to  dialyze  into  them.  Sections  are  difficult  to 
make  but  possible  by  the  use  of  very  hard 
parafhn  and  great  care  in  making  the  transfers. 
Vacuum  embedding  is  helpful  in  securing  good 
infiltration. 

For  Gordiacea  the  alcohol-glycerine  method 

Til  •  II-  iiG.Bii.    iJin 

IS    useless;    on    the  whole   the   corrosive  subli-   for dchydratin*:. 

voir;   b.  ol)jcct  holders;  c, 

mate-acetic  mixture  works  best,  but  should  be   ^^^}-"  ^"''  r^Kuiation  dr- 

^  vice;    J.    s;ifclv    tube;    *. 

used  warmed  to  56°  or  60°  C.     In  other  respects   J^^iShoriu-i Jl 


Fig. 81 1.    Differentiator 


here  also. 


The  re»- 
I  meters 

the   instructions   for    nematode    technic    apply   ISdTn'^thc  &".  Tui 

filling  avoid   bunhlcs       t. 
end  piece  of  ditTerentiator 

The  Acanthocephala  are  best  killed  and  fixed    pi[-ce  \i"diiTcrcntutor  fJr 

^  .  .  .  alcohols.     (After  MaK'.ith.) 

in  the  corrosive  sublimate-acetic   mixture   and 

In  general   methods 


do  not  come  out  well  in  glycerine-alcohol, 
used  for  flatworms  work  well  with  these  forms  also,  but  for 
more  precise  results  on  any  of  the  roundworms  each  worker 
must  develop  a  special  technic.  (Compare  further  Looss, 
Ransom,  Magath.) 

The  following  distinctly  artificial  key  ma\'  be  used  to  separate 
the  three  classes  of  Nemathehninthes;  it  must  be  supplemented  by 


5IO 


FRESH-WATER    BIOLOGY 


reference   to  the   longer   discussion  in   the  opening  paragraph   of 

this  chapter. 

A  (B)     With  anterior,  protrusible  proboscis  covered  with  rows  of  recurved 

hooks Class  Acantbocephala  (page  542) 

B  (A)     Without  proboscis  at  anterior  end C 

C  (D)     Adult  free-living,  aquatic,  long,  cylindrical,  with  posterior  end  bifid 

or  bluntly  rounded Class  Gordiacea*  (page  535) 

The  family  of  the  Mermithidae  (page  534)  agrees  in  some  of 
these  particulars  with  the  Gordiacea,  although  the  structure  shows 
that  these  species  are  true  Nematoda  and  not  Gordiacea;  they  are 
readily  distinguished  by  the  acutely  pointed  posterior  end  and 
terrestrial  habit. 

D  (C)  Adult  usually  spindle-shaped,  tapering  rather  than  cyHndrical.  Pos- 
terior end  never  bifid  or  bluntly  rounded,  usually  acutely 
pointed,  occasionally  peculiarly  modified  in  form. 

Class  Nematoda   .    .    E 
E  (F)     Free-living  during  entire  life  cycle.     Adults  small,  transparent. 

Free-living  Nematoda  (page  459) 
F  (E)     Parasitic  during  most  or  all  of  the  life  cycle.     Larvae  small,  transpar- 
ent; adults  variable  in  size,  often  more  or  less  opaque. 

Parasitic  Nematoda 
Parasitic  Nematoda 

The  nematodes  are  easily  recognized  by  their  appearance,  which 
has  given  them  the  common  name  of  round-  or  threadworms. 
Most  of  them  are  small,  measuring  only  a  few  millimeters  in  length 
and  a  fraction  of  a  milhmeter  in  diameter,  and  resemble  a  fragment 
of  a  violin  string.  A  few  of  the  larger  sorts  reach  a  length  of 
several  centimeters  or  even  a  meter. .  The  external  surface  is  usu- 
ally smooth  and  glistening  and  the  body  is  not  divided  into  joints 
or  segments.  In  some  cases  a  fine  surface  striation  is  present 
which  appears  under  a  lens  as  delicate  circular  grooves;  the 
exterior  may  also  bear  irregular  beaded  tubercles  or  fine  scales, 
spines,  or  hairs.  When  present  these  are  usually  confined  to 
certain  regions  and  the  remainder  of  the  surface  has  the  typical 
nematode  appearance. 

The  body  tapers  slightly  towards  one  or  both  ends  and  only 
very  rarely  can  one  find  marked  differences  in  diameter  or  dis- 

*  Some  authors  designate  the  class  Nematomorpha  and  rank  the  Gordiacea  as  an 
order  under  it. 


PARASITIC    ROUNDWORMS 

tinguish  adjacent  regions  by  other  prominent  features.  As  a  rule 
the  anterior  end  is  sHghtly  blunter  whereas  the  posterior  end  i>  more 
pointed.  The  uniformity  of  external  appearance  is  very  charac- 
teristic of  nematodes.  This  creates  an  impression  of  monotony 
in  structure  and  renders  their  classification  difficult.  The  smaller 
forms  are  somewhat  transparent  in  life  but  the  larger  species  are 
opaque. 

One  may  also  recognize  a  nematode  easily  by  its  peculiar  type 
of  movement,  which  in  a  Hquid  medium  consists  of  a  more  or  less 
rapid  and  violent  coifing  and  twisting  alternately  right  and  left 
without  appreciable  progress,  but  is  modified  by  the  presence  of 
sofid  particles  in  the  fluid  into  a  powerful  serpentine  nioxemcnt 
winding  in  and  out  among  the  debris.  This  grows  in  etTectiveness 
as  the  material  becomes  more  nearly  sofid  and  the  particles  are 
less  readily  pushed  aside  by  the  twisting  of  the  worm. 

In  external  features  the  parasitic  species  appear  somewhat  dif- 
ferent from  the  free-living  forms.  On  the  whole  they  are  much 
larger,  thicker  and  more  opaque.  Few  species  are  as  minute  as 
free  forms  and  only  these  minute  types  approach  the  free  species 
in  transparency.  The  external  form  is  also  more  monotonous 
since  the  delicate  hairs  and  scales  that  distinguish  free  species  arc 
almost  entirely  wanting.  Eyes,  amphids,  and  setose  tactile  organs 
such  as  already  described  for  free-Hving  t>pes  are  not  present  in 
parasitic  species. 

Parasitic  nematodes  occur  in  nearly  afi  w^ater-living  vertebrates; 
they  are  also  often  found  in  insects.  In  crustaceans  and  worms  they 
are  much  less  frequent  and  in  any  other  forms  their  presence  is  un- 
usual. While  adult  forms  are  found  in  aU  hosts,  yet  the  immature 
stages  are  more  frequent  in  hosts  from  the  lower  groui)s  nuntit)netl 
and  less  common  in  the  higher  vertebrates.  The  encysted  worms 
are  usually  larval  forms.  The  adults  frequent  commonly  the 
alimentary  canal,  though  some  species  occur  regularly  in  con- 
nective tissue  and  rarer  types  in  other  parts  of  the  bodw  IjicxstiMl 
larvae  may  be  found  almost  anyw^here. 

In  structure  the  parasitic  threadworms  manifest  great  similar- 
ity to  the  free-living  species  and  in  view  of  the  detailed  treatment 
given  the  latter  in  the  last  chapter  it  will  be  necessary  in  the  prcs- 


512 


FRESH-WATER   BIOLOGY 


ent  general  discussion  to  refer  prominently  only  to  points  of  con- 
trast or  to  features  peculiar  to  parasitic  forms.  For  further 
structural  details  the  student  should  consult  that  discussion  which 
should  be  read  in  connection  with  the  following  description.  Some 
parasitic  nematodes  are  apparently  indistinguishable  from  free- 
living  species,  others  are  classed  in  the  same  genera  or  families, 
but  there  are  also  large  groups  that  contain  no  free-living  species 
and  are  highly  modified  for  a  parasitic  existence.  In  general  the 
smaller  transparent  species  show  the  greatest  similarity  to  the  free- 


FiG.  8i2.  Ascaris  lumhricoides .  a,  top  view  of  head;  dorsal  Up  with  two  sensory  papillae  and  ventra 
lips  with  one  each;  the  shaded  areas  indicate  the  muscle  attachment,  b,  lateral  view,  showing  ventral 
lips.  Magnified.  (After  Leuckart.)  Camallanus  ancylodirus.  c,  ventral  view  of  head,  X  i35;  <^>  lateral  view 
of  head,  X  135.  (Original.)  Necator  americanus.  e,  head  of  young  male,  dorsal  view,  X  160;  /,  head  of 
young  female,  from  the  right,  X  160.     (After  Looss.) 

living  species  whereas  the  large  opaque  forms  depart  most  widely 
from  that  type.  In  general  organology,  microscopic  structure  of 
cells  and  their  arrangement  in  layers,  as  well  as  in  fundamental 
features  of  reproduction  and  development,  the  parasitic  nema- 
todes agree  substantially  with  the  free-living  forms  and  manifest 
their  recent  differentiation  from  them. 

The  anterior  end  or  "head"  of  a  nematode  is  usually  slightly 
truncated  or  bluntly  rounded  and  shows  under  a  lens  the  presence 
of  lips,  papillae,  spines,  teeth  and  other  special  structures. 

In  reality  the  numerous  modifications  of  the  anterior  end  may 


PARASITIC   ROUNDWORMS 


513 


be  reduced  to  a  few  fundamental  types  (Fig.  812).  In  the  first 
the  tip  of  the  body  is  unarmed  or  at  most  provided  wiili  a  few 
minute  papillae  arranged  around  the  mouth  opening  wliich  is  a 
minute  circular  orifice.  In  a  second,  three  lips  are  present,  a  large- 
dorsal  and  two  smaller  ventro-lateral,  which  border  a  l.rian;;ular 
mouth.  In  a  third,  the  oral  aperture  is  a  dorso-ventral  slit  guar(le<l 
by  two  lateral  jaws  often  called  lips  but  very  distinct  in  form  and 
function  from  the  triple  labia  of  the  second  type.  In  the  fourth 
class  one  finds  a  hollow  cup-shaped  capsule  with  an  entire  margin 
which  in  lateral  aspect  resembles  the  jaws  of  the  third  type  but  is 
very  unlike  them  in  general  plan.  The  capsule  is  a  powerful 
sucking  organ,  the  jaws  act  as  a  grasping  organ  like  a  vise  or  pin- 
cers, the  lips  are  weaker  and  more  varied  in  movement.  These 
main  types  of  oral  apparatus  are  modified  in  so  manv  directions 
that  it  is  often  difficult  to  comprehend  the  general  t}'pe  inNoKcd 
in  a  compKcated  case. 

The  mouth  cavity  may  be  tubular,  funnel-shaped,  or  even  ex- 
panded into  a  globular  or  oval  capsule  or  pharynx.  Following 
this  region  comes  the  esophagus  which  is  either  muscular  or 
capillary.  The  muscular  type  is  prominent,  thick  walled,  and  tri- 
angular in  cross  section  (Fig.  813,  a),  with  the  muscle  fibers  perjKMi- 
dicular  to  the  lumen.  By  the  contraction  of  these  tibrrs  the 
cavity  is  enlarged   and   the  a 

organ  acts  as  a  pump  to 
draw  in  food.  The  esophagus 
may  be  differentiated  into 
two  regions,  one  clearly  mus- 
cular and  the  other  granu- 
lar, or  the  single  muscular 
region  may  have  large  (sali- 
vary?) gland  cells  in  its  wall. 
It  is  frequently  terminated  by  a  spherical  bulb  which  contain>>  a 
valvular  apparatus.  In  some  cases  this  bulb  is  double.  The 
cavity  is  fined  by  an  inturned  layer  of  the  external  cuticula  wliieh 
terminates  at  the  bulb.  This  is  the  type  of  esophagus  found  in 
free-living  forms  (see  Chapter  XV,  p.  461,  Fig.  766).  The 
capifiary  esophagus  (Fig.  813,  b),  consists  of  a  minute  clfitinous  tube 


Fig.  813.  a,  Aiuylosiomu  diunlcnaU.  Trans-srction  vi 
the  esophagus,  magnified,  (.\ftcr  Looss.)  b.  Truknuima 
conlortum.  Transverse  section  of  esophagus,  magnified. 
(After  von  Linstow.) 


5U 


FRESH-WATER   BIOLOGY 


surrounded  by  a  row  of  granular  cells  but  without  muscle  elements. 
It  does  not  terminate  in  a  bulb  though  the  end  of  the  cell  row  may 
be  slightly  enlarged. 

The  esophagus  opens  directly  into  the  following  region  which  is 
commonly  termed  the  intestine.  It  is  the  digestive  portion  of  the 
canal  and  is  without  any  cuticular  Hning.  The  cavity  is  of  con- 
siderable size  and  Hned  by  large  cells  rich  in  protoplasm.  This 
region  changes  gradually  into  the  narrow  terminal  section  of  the 
canal,  known  in  the  female  as  the  rectum,  or  in  the  male  as  the 
cloaca,  since  the  duct  of  the  sex  gland  joins  it  to  form  a  common 
passage  way. 

The  tail  is  ordinarily  sharply  pointed  though  sometimes  the 
point  is  short  and  in  other  cases  long  drawn  out.  The  anal  open- 
ing is  ventral,  a  Httle  anterior  to  the  tip  of  the  body.  In  a  few 
instances  the  anus  is  terminal  and  the  tail  is  rounded  or  of  peculiar 
form.  In  several  families  its  true  character  is  obscured  in  the 
male  because  lateral  wings  or  folds  of  cuticula  cover  it.  These 
folds  may  be  low,  narrow,  keel-hke  ridges  along  the  sides  or  may 
have  developed  into  wide  semi-circular  wings  forming  together  a 
clasping  organ  known  as  the  bursa.  Protoplasmic  strands  in  the 
wings  appear  like  ribs  of  an  umbrella;  they  vary  in  form  and 
number  and  are  much  used  in  the  diagnosis  of  species.  Numerous 
papillae  occur  on  the  ventral  surface  of  the  male  both  in  front  of 
and  behind  the  anus.  They  vary  greatly  in  size  and  arrangement 
in  different  species  and  constitute  another  useful  feature  in  the 
determination  of  genera  and  species.  A  prominent  cup-shaped 
sucker  is  found  on  the  ventral  surface  in  front  of  the  anus  in  some 
species  and  one  can  often  see  in  the  body  behind  the  anal  orifice  a 
few  large  unicellular  structures  which  are  interpreted  as  glands. 

Between  the  head  and  the  tail  there  are  very  few  external  fea- 
tures to  be  noted.  A  minute  excretory  pore  Hes  in  the  mid- ventral 
line  not  far  from  the  middle  of  the  esophagus.  In  the  female  the 
sexual  pore  also  is  found  on  the  ventral  surface;  in  some  famiUes 
it  is  near  the  head,  in  others  near  the  tail,  and  again  in  the  center  of 
the  body.  Its  location  is  an  important  characteristic  in  defining 
the  various  groups. 

A  circumesophageal  nerve  ring  with  lateral  gangha  is  a  conspic- 


PARASITIC   ROUNDWORMS  -j- 

uous  feature  in  most  nematodes.  It  lies  not  far  from  the  excretory 
pore,  a  short  distance  behind  the  anterior  end  of  the  esophagus. 

A  cross  section  of  the  body  shows  on  the  exterior  the  thick 
non-cellular  cuticula;  within  it  the  hypoderm  or  sub-cuticuhi 
which  is  cellular  but  without  cell  walls.  This  layer  is  thin  except 
at  the  median  and  lateral  fields  which  arc  visible  externally  as 
faint  streaks  and  hence  often  called  "Hues'';  here  it  projects  inward 
between  the  muscle  cells.  The  major  part  of  the  body  wall  con- 
sists of  the  muscular  layer,  a  single  layer  of  large  cells  with  hjngi- 
tudinal  but  no  circular  or  cross  fibers;  these  cells  have  a  con- 
spicuous protoplasmic  body  on  the  inner  side  next  the  body  cavity. 
The  muscle  layer  is  divided  into  four  areas  separated  by  the  median 
and  lateral  fields  of  the  hypodermis;  rarely  the  presence  of  sub- 
median  fields  makes  eight  such  muscle  areas.  Each  of  the  four 
muscle  areas  may  contain  many  muscle  cells  (the  Polymyaria) 
or  be  limited  to  a  longitudinal  series  of  two  muscle  cells  (the 
Meromyaria) . 

The  cuticula  of  nematodes  is  usually  said  to  be  "  chitinous ''  but 
as  this  layer  is  soluble  in  alkalis,  digested  by  the  action  of  en- 
zymes, and  contains  a  very  high  percentage  of  nitrogen,  it  is  not 
chitin;  it  has  been  correctly  designated  as  cornein  by  Reichard. 
Glycogen  occurs  in  large  amount  in  nematode  tissues  and  is  sup- 
posed to  furnish  them  oxygen  and  energy. 

The  body  cavity  is  large  but  not  lined  by  a  peritoneal  epithe- 
lium. It  is  in  fact  formed  by  the  breaking  down  of  connective 
tissue  cells,  the  remnants  of  which  may  still  be  observed  in  well 
preserved  specimens,  especially  at  the  anterior  end.  Both  repro- 
ductive and  digestive  organs  are  free  in  this  ca\'ity  since  mesen- 
teries are  lacking.  In  full-grown  worms  the  space  of  the  body 
cavity  is  almost  entirely  filled  by  the  greatly  enlarged  and  nuich 
convoluted  reproductive  organs  which  press  upon  each  other,  the 
ahmentary  canal,  and  the  body  wall  so  as  to  leave  only  small 
irregular  cavities  here  and  there. 

The  reproductive  system  is  exceedingly  simple.  In  both  sexes 
it  has  the  form  of  a  long  tube  in  which  the  various  regions  are 
continuous  and  only  slightly  distinguished  from  each  other  in  form. 
The  fine  inner  end  of  the  tube  produces  the  reproductive  cells. 


5l6  FRESH-WATER  BIOLOGY 

eggs  or  sperm.  In  the  female  the  fully  developed  eggs  are  pushed 
into  a  slightly  larger  region  in  which  fertiHzation  takes  place. 
Sometimes  the  fertihzed  eggs  are  provided  with  a  heavy  shell  and 
are  soon  ejected  to  carry  out  their  development  in  the  outer  world. 
In  other  cases  they  are  retained  in  a  sac-like  uterus  until  devel- 
opment is  more  or  less  advanced.  In  certain  families  the  entire 
development  is  carried  out  within  the  uterus  and  the  female  brings 
forth  living  young.  The  organs  in  these  cases  differ  in  length 
and  capacity  rather  than  in  fundamental  structure. 

In  the  male  the  reproductive  system  consists  of  but  a  single 
tube,  emptying  as  already  stated  into  the  cloaca,  whereas  the 
windings  of  the  tube  lie  in  the  body  in  front  of  this  region.  In 
the  female  the  tube  may  be  single  but  is  most  frequently  double 
or  Y-shaped.  The  short  stem  of  the  Y  connects  with  the  female 
pore,  the  branches  extend  in  coils  into  the  body.  One  branch 
may  pass  anteriad  and  the  other  posteriad  or  both  may  He  nearly 
parallel  in  the  same  part  of  the  body.  One  branch  may  be  greatly 
reduced  and  by  its  final  disappearance  give  to  the  system  the  form 
of  a  single  tube  such  as  is  found  in  the  male.  Various  intermediate 
stages  occur. 

In  connection  with  the  terminal  portion  of  the  male  duct  are 
usually  found  pieces  of  cuticula  shaped  like  hooks  or  needles,  and 
known  as  the  spicules.  There  may  be  only  one  spicule  or  if  two 
are  present  they  may  be  equal  or  unequal.  Finally  an  accessory 
piece  furnishes  in  some  species  a  link  or  groove  in  which  the  spicules 
proper  are  held  and  through  which  they  are  extruded.  These 
spicules  are  easily  seen  both  on  account  of  their  high  refractive 
index  and  because  in  many  preserved  specimens  they  project 
conspicuously  from  the  anal  opening.  In  transparent  forms  the 
student  may  detect  under  the  microscope  the  spicule  sac,  dorsal 
to  the  intestine,  in  which  the  spicules  are  housed  and  also  special 
sets  of  muscles  by  which  they  are  operated.  The  number, 
length,  and  exact  shape  of  these  organs  serve  as  features  for  specific 
diagnoses. 

The  development  of  parasitic  nematodes  introduces  all  varia- 
tions from  extreme  simpUcity  to  some  of  the  most  complex  life 
histories  known  among  animals.     The  early  development  is  simple. 


PARASITIC   ROUNDWORMS  517 

Within  the  egg-shell  is  formed  in  direct  fashion  a  minute  worm 
which  on  hatching  displays  the  main  features  of  nematode  struc- 
ture. This  embryo  may  require  weeks  or  months  for  its  growth 
and  may  wait  within  the  shell  for  years  before  it  is  passively  intro- 
duced into  a  new  host;  or  it  may  break  out  from  the  shell  and  spend 
a  period  in  moist  earth  or  water  awaiting  the  time  when  in  one 
way  or  another  it  is  brought  into  a  suitable  host.  In  most  cases 
the  embryo  of  a  parasitic  nematode  spends  a  brief  i)eri(Kl  at  least 
as  a  free-living  larva,  and  always  in  an  aquatic  environment,  but 
this  may  be  semi-fluid  mud  as  well  as  open  water.  Frecjuently  it 
undergoes  in  this  stage  or  earlier  the  first  of  the  four  character- 
istic molts  and  within  the  cast  cuticula  of  the  embryonic  form 
enters  upon  a  resting  stage  well  protected  against  drying  out. 
In  this  condition  it  may  be  transported  by  wind  or  water,  or  at- 
tached to  other  objects,  even  such  living  agents  as  the  feet  of 
reptiles^  birds,  or  mammals,  and  thus  be  carried  far  in  attaining 
the  location  where  by  some  chance  it  is  introduced  into  the  body 
of  a  new  host.  When  this  new  host  is  reached  it  may  be  the  same 
as  the  original  host  in  which  case  further  molts  bring  the  wonn  in 
a  short  time  to  the  adult  condition.  In  other  instances  the  larva 
reaches  an  intermediate  host  in  which  it  becomes  cnc\sted  in 
muscles  or  viscera  and  after  a  period  of  growth  is  read}-  for  transfer 
to  the  final  host.  This  change  involves  the  consumption  of  the 
flesh  with  the  encysted  larva  by  a  suitable  final  host,  whereupon 
digestion  sets  the  worm  free,  the  active  development  is  resumed, 
and  the  adult  form  reached  after  a  period  of  growth. 

Most  often  the  larval  parasite  is  taken  into  a  new  host  with 
water  or  food.  In  some  cases  the  free-living  larva  docs  not 
depend  on  chance  to  carry  it  but  gains  entrance  by  its  own  activ- 
ity. Thus  the  hookworm  larva,  Hving  in  moist  earth,  when  brought 
suitably  in  contact  with  the  skin  of  an  available  host  burrows  into 
it  and  completes  its  Ufe  history  during  its  devious  wanderings  in 
that  host. 

As  an  illustration  of  the  life  history  of  a  typical  aciuatic  species 
may  be  taken  the  development  of  Camallaniis  lacustris,  formerly 
often  designated  Cucullanus  elegans.  This  development  was  worked 
out  and  described  by  Leuckart  somewhat  as  follows: 


5i8 


FRESH-WATER  BIOLOGY 


The  female  is  viviparous  and  produces  myriads  of  young.  The 
larva  at  birth  (Fig.  814,  a)  has  an  awl-shaped  tail  equal  to  one- third 
the  total  length;  no  trace  of  the  adult  lips  are  seen;  the  esophagus 
is  simple,  as  also  the  intestine,  and  a  single  cell  is  the  only  trace  of 
genital  organs  present.     A  boring  spine  lies  dorsal  to  the  mouth. 


Fig.  814.  Development  of  Camallanus  lacuslris;  a,  youngest  stage  of  larva;  b,  second  stage  from  body 
cavity  of  Cyclops;  c,  at  end  of  second  stage  showing  jaws  forming;  d,  third  stage  with  larval  jaws  complete. 
Magnified.     (After  Leuckart.) 


The  larva  soon  gains  entrance  to  a  small  aquatic  animal  {e.g., 
Cyclops)  through  the  mouth  and  bores  its  way  into  the  body 
cavity  where  the  first  molt  occurs.  After  this  the  worm  {h)  has 
grown  in  size,  lost  its  long  tail  in  part  and  acquired  a  bipartite 
esophagus.  A  period  of  growth  follows  towards  the  close  of  which 
the  Hps  of  the  adult  are  laid  down  (c)  and  the  second  molt  dis- 
closes an  oral  armature  {d)  which  though  smaller  and  differently 
marked  than  that  of  the  mature  worm,  yet  displays  its  likeness 
even  to  the  beginning  of  the  dorsal  and  ventral  labial  tridents  so 
conspicuous  in  the  adult  Camallanus.  The  genital  area  is  still  in- 
significant and  the  tail  carries  three  small  spines  near  the  tip  which 
survive  in  the  adult  female  only.  The  double  esophagus  is  fully 
differentiated  even  to  the  valve  cells  at  the  lower  end  and  the 
nerve  ring  is  well  developed. 

In  summer  these  changes  require  only  3  days  but  in  winter  they 
may  last  3  weeks.  No  further  change  ensues  until  the  parasites  are 
brought  into  the  alimentary  canal  of  a  suitable  fish  host.  Here 
set  free  from  the  larval  host  by  digestion,  the  worm  grows  rapidly 
to  I  mm.  in  length,  molts  and  assumes  the  sexually  differentiated 


PARASITIC   ROUNDWORMS 

form  of  the  adult.  Ten  to  fourteen  days  after  introduction  into  i 
fish  the  young  worms  have  become  fully  matured  and  pair. 

In  most  cases  the  larval  Camallanus  is  introduced  directly  into 
the  final  host  from  the  first  intermediate  host,  but  in  others  cn- 
cystment  in  a  second  intermediate  host  becomes  an  enforced  pre- 
liminary to  the  attainment  of  the  final  host.  This  takes  place 
when  the  intermediate  host  is  eaten  by  some  species  other  than 
the  final  host;  the  larva  is  set  free  by  digestion  but  immediately 
encysts  again,  usually  in  the  intestinal  wall.  Such  erratic  encysted 
larvae  occur  in  a  wide  variety  of  unusual  hosts  (Seurat). 

Too  many  complications  enter  into  individual  cases  to  be  dis- 
cussed in  detail  here.  It  is  necessary  to  mention  briefly,  however, 
one  type  of  Hfe  history  of  a  different  character.  Among  the 
Filariidae,  the  adult  is  parasitic  in  the  connecti\'e  tissues  or  body 
cavity  of  the  host  and  is  viviparous.  The  embryos  are  produced 
in  enormous  numbers  and  invade  the  blood  stream  from  which 
they  are  drawn  out  by  biting  insects  such  as  the  mosquito.  After 
a  period  of  development  in  the  mosquito  they  escape  into  the  final 
host  when  the  insect  is  biting  again,  and  now  are  ready  to  develoj) 
into  the  adult  parasite.  In  this  case  no  part  of  the  life-history  is 
spent  in  the  outer  world  and  the  only  link  which  connects  the  life- 
history  to  aquatic  biology  is  the  intermediate  host  which  may  be, 
like  the  mosquito,  a  typical  aquatic  organism  in  early  life. 

The  nematode  life  histories  which  have  been  parti}-  worked  out 
are  mostly  those  of  the  parasites  of  man  and  the  domestic  animals. 
Almost  nothing  is  known  of  the  development  of  j)arasites  from 
characteristic  aquatic  hosts  and  the  held  offers  enticing  oppor- 
tunities to  the  student. 

Concerning  other  phases  in  the  biology  of  parasitic  nematodes 
little  or  nothing  has  been  ascertained.  Observations  are  too 
scanty  to  furnish  data  on  their  length  of  life,  on  seasonal  variation, 
or  on  factors  that  influence  their  frequency.  Their  distribution 
evidently  cannot  transcend  that  of  the  hosts  and  in  many  cases 
falls  far  short  of  conforming  to  that,  but  the  conditions  which 
aftect  such  variations  are  beyond  safe  conjecture. 

No  satisfactory  outline  for  the  classification  of  parasitic  nema- 
todes has  yet  been  worked  out  and  the  very  imperfect  knowledge 


520  FRESH-WATER    BIOLOGY 

of  North  American  forms  makes  it  impossible  to  do  more  than 
group  the  few  records  available  into  an  arbitrary  key.  A  natural 
classification  lies  far  in  the  future  and  collecting  in  any  region  will 
surely  result  in  extending  greatly  the  Hst  of  species  included  in  the 
subjoined  key.  Parasites  from  terrestrial  hosts  have  not  been 
included  in  the  synopsis;  doubtless  many  of  them  depend  upon 
water  for  their  transfer  during  a  free-living  stage  from  one  host  to 
another  and  some  of  them  may  even  utilize  aquatic  species  as  in- 
termediate hosts,  just  as  the  guinea  worm  larva  occurs  in  a  fresh- 
water copepod  and  reaches  the  human  host  in  drinking  water. 
The  nematode  parasites  of  fishes,  amphibians,  and  aquatic  species 
among  reptiles,  birds,  and  mammals  may  safely  be  assigned  to  the 
fresh-water  fauna.  They  are  included  here  so  far  as  described  from 
North  America. 

Undoubtedly  the  larvae  of  the  hookworms  {Ancylostoma  duode- 
nale  and  Necator  americanus  of  man;  Uncinaria  stenocephala  of 
the  dog),  of  the  parasite  of  Cochin  China  diarrhoea  {Strongyloides 
stercoralis),  and  of  many  other  parasites  which  occur  in  North 
America  are  aquatic  organisms  and  live  for  considerable  periods 
in  pools  of  water  or  in  moist  earth,  awaiting  an  opportunity  to 
gain  entrance  into  a  suitable  host.  Yet  as  immature  forms  they 
can  be  differentiated  with  great  difficulty  if  at  all,  and  do  not  show 
the  structural  features  that  characterize  the  adults  to  which  they 
belong.  Hence  they  are  only  noted  collectively  in  the  subjoined 
key.  The  adults  which  parasitize  land  animals  are  not  included 
in  the  list. 

KEY  TO  NORTH  AMERICAN  PARASITIC   NEMATODA 

I  (4)     Immature.     Sexual  organs  only  partly  developed,  if  at  all. 

Agamonema  Diesing  185 1    .    .      2 

A  collective  name  for  the  group  of  imperfect,  larval  nematodes  not  yet  developed  so  that 
the  worms  can  be  definitely  classified.  Many  such  forms  occur  encysted  in  fish,  and  the  group 
was  originally  proposed  to  hold  fish  parasites.  Now  it  is  used  to  include  all  agamic  nema- 
todes that  cannot  be  referred  to  a  more  definite  group.  The  rudiment  of  the  sexual  organs 
can  usually  be  seen  as  a  large  cell  or  a  discrete  mass  of  a  few  cells,  lying  near  the  center  of  the 
worm.  In  older  individuals  this  sexual  rudiment  has  begun  to  grow  out  into  a  long  cord  of 
cells  which  marks  the  place  of  the  future  reproductive  system.  In  these  forms  the  Hps,  papil- 
lae, and  other  features  of  special  adult  structure  are  wanting  or  only  generally  and  indefinitely 
laid  down.  Sometimes  distinct  characters,  such  as  the  three  lips  of  the  Ascaridae  which  are, 
nowever,  easily  confused  with  similar  conditions  in  other  groups,  may  enable  one  to  assign 
these  immature  forms  to  a  definite  family,  subfamily,  or  genus,  and  other  collective  names 
are  then  applied  to  such  forms,  e.g.,  Agamomermis.  These  larval  forms  are  very  similar  and 
are  apt  to  be  confused  because  of  their  general  resemblances. 


PARASITIC   ROUNDWORMS  rji 

2  (3)     Free-living  in  moist   earth  or  water.      Many  embryonic  and  lar\'al 

stages  of  parasitic  nematodes. 

Not  distinguishable  from  free-living  nematodes  except  by  exact  data  cotK erninc  sneiific 
forms  which  are  available  only  in  a  few  cases.  Such  are  the  larvae  of  the  human  h(.<.kif.,rms 
{Ancylostoma  duodenale  or  Necator  amertcanus),  of  Strongyloidcs  stcrcoraiis  known  to  Ik-  nrcsi-nt 
generally  in  infected  areas.  They  depend  for  their  development  uixjn  the  opixjrtunilv  of 
entering  a  new  human  host.  ' 

3  (2)     Encysted  in  the  viscera  or  flesh  of  various  fishes. 

Agamonema  capsular ia  ( Rudolph i)  1802. 

The  name  covers  what  is  probably  a  wide  variety  of  different  species  from  difTert-nt  source* 
Thus  worms  under  this  name  are  listed  from  migratory  fishes,  and  these  arc  very  likely  to 
represent  encysted  larvae  of  marine  adults;  and  also  from  fresh-water  fishes  in  which  case 
they  are  doubtless  of  fresh-water  origin.  The  descriptions  of  these  forms  arc  brief.  Rcneral 
and  inadequate  to  differentiate  larval  forms  of  different  genera. 

Among  the  other  species  recorded  from  North  America  are: 

Agamonema  papilligerum,  a  single  specimen  of  which  was  found  by  Leidy  in  Philadelphia, 
in  the  body  cavity  of  a  pike.     Later  regarded  by  him  as  young  FUaria  solilaria. 

Agamonema  piscium  from  the  white  fish,  listed  by  Stiles  and  Hassall  in  the  collection  of  the 
Army  Medical  Museum. 

Such  forms  may  be  found  in  other  hosts  than  fishes  like  the  embryos  recorded  by  Ix-idy  as: 

Nematoideum  integumenti  lumbriculi  limosi,  encysted  in  the  skin  of  a  mud-inhabiting  annelid. 

4  (i)  Mature.     Sexual  organs  developed;  worms  active,  not  encysted.   .    .     5 

Most  adults  are  easily  recognized  as  the  eggs  can  be  seen  in  the  female  and  the  sperm  ma.s8 
in  the  male.  The  open  sexual  pore  in  the  female  and  the  spicules  in  the  male  when  exsertcd 
aid  in  reaching  a  diagnosis. 

5  (6)     Small  transparent  nematodes;    in  general  appearance  identical  with 

free-living  forms.     Few  eggs  in  uterus. 

Not  a  very  satisfactory  means  of  separating  this  group  from  certain  species  in  the  subse- 
quent divisions  which  approach  rather  closely  to  the  brief  description  of  the  key  line  above. 
In  case  of  doubt  regarding  a  specimen  the  student  should  try  also  the  latter  alternative,  6  (5) 
of  the  key. 

These  forms  are  all  minute  (less  than  S  to  6  mm.  long).  Furthermore  they  are  simple  in 
structure  and  not  easy  to  differentiate  from  free-living  species.  They  possess  a  double  es<iph- 
ageal  bulb  and  ventral  glands  often  in  lieu  of  lateral  excretory  canals.  The  male  has  two 
similar  spicules  and  in  some  cases  a  bursa.  The  female  sexual  pore  is  found  in  the  posterior 
half  of  the  body  and  the  uterus  contains  only  a  few  thin-shelled  eggs. 

One  family,  the  Anguillulidae,  includes  the  vinegar  eel,  the  paste  eel,  various  plant  para- 
sites of  some  economic  importance,  and  many  free-living  forms.  These  do  not  show  any  alter- 
nation of  generations  in  the  life  history. 

Only  group  containing  animal  parasites. 

Family  Angiostomid.ak  iiraun  1S05. 

Characterized  by  heterogony.  Otherwise  very  much  hke  the  .\nguillulidae.  and  united 
to  them  by  many  authors.     Parasitic  generation  contains  no  males. 

Only  genus  recorded  for  North  America.   .    Angiostomd  Dujanlin  1845. 

Representative  species  in  North  America. 

Angiostoma  nigrovcnositm  ((ioczc)  iSoo. 

In  Biifo  lentiginosiis;  lung.  District  of  Columbia.  Listed  by  Stiles  and  Hassall  under  the 
name  Rhahdonema  nigrovenosum  as  in  the  Bureau  of  .\nimal  Industry  C»»llection. 

6  (5)     Nematodes  larger  than  free-living  species;    almost  always  distinctly 

less  transparent  and  often  even  oi)aque.     I'tcrus  contains 

many  eggs ^ 

The  unsatisfactory  character  of  the  key  at  this  point  has  already  been  noted.  The  n«na- 
todes  which  follow  are  usually  well  differentiated  parasites,  recognizable  by  one  or  another 
typical  structure  not  present  in  the  previous  group.  They  are,  however,  distinguishable  irora 
the  latter  only  in  general  aspect  and  the  key  is  open  to  doubt  in  a  few  cases. 


522  FRESH- WATER   BIOLOGY 

7  (75)     Esophagus  prominent,  muscular,  with  triradiate  lumen. 

Suborder  Myosyringata  .  .     8 

8  (15)     Bursa  present  in  male  and  conspicuously  developed 9 

9  (14)     Male  with  broad  bursa  traversed  by  system  of  rays.     Buccal  cap- 

sule usually  well  developed  in  both  sexes. 

Superfamily  Strongyloidea  Weinland  1858   .    .      10 

With  the  spherical  buccal  capsule  may  easily  be  confused  the  bivah^e  oral  armature  of 
some  of  the  Spiruroidea.  The  former  presents  in  cross-section  an  unbroken  circle,  or  oval. 
The  latter  is  distinctly  composed  of  two  pieces  interrupted  along  Unes  of  division.  In  the 
former  the  mouth  opening  is  a  ring  that  may  be  dentate  or  serrate  but  is  still  complete;  in  the 
latter  the  mouth  opening  is  a  sht  having  at  opposite  points  two  deep  acute  angles.  A  buccal 
capsule  is  wanting  in  the  three  forms  described  here. 

The  bursa  in  the  strongyles  is  a  conspicuous  broad  flaring  organ,  supported  generally  by 
six  paired  rays  and  one  unpaired  median  ray,  all  extending  outwards  from  a  common  center 
much  Hke  the  ribs  of  an  umbrella. 

Only  a  very  few  strongyles  have  been  reported  in  North  America  from  aquatic  hosts  and  these 
few  are  not  representative  of  the  majority  of  the  group  to  which  belong  the  hookworms  and 
other  well-known  and  abundant  parasites  of  land  animals.  The  three  species  cited  here  are  in 
truth  so  unlike  typical  strongyles  that  it  is  difficult  to  bring  them  into  the  key. 

Since  the  group  is  very  large  and  complex  and  only  three  species  are  to  be  considered  here 
no  effort  has  been  made  to  outline  the  famihes  or  the  numerous  other  subdivisions.  The 
key  is  merely  a  convenient  way  of  separating  these  few  species.  It  is  not  unlikely  that  other 
genera  are  represented  in  the  same  and  other  aquatic  hosts. 

10(11)     In  reptiles  and  amphibians.   .    .    .   Strongylus  auricularis  Zeder  iSoo. 

No  buccal  capsule;  30  longitudinal  ridges  on  the  body.  Spicules  bifid  or  trifid  at  the  distal 
end. 

Reported  by  Leidy  in  1856  from  the  intestine  of  Bufo  americana  and  Cistudo  Carolina  in 
Philadelphia.  No  other  data  accompany  the  record  so  that  it  cannot  be  verified  at  present. 
At  least  two  species  are  included  in  European  records  under  this  name. 

The  genus  Strongyliis  is  grouped  by  Railliet  and  Henry  under  the  family  Strongylidae,  sub- 
family StrongyUnae,  tribe  Stronglyeae. 

Ransom  is  uncertain  as  to  the  genus  in  which  Zeder's  or  Schneider's  species  should  be  placed 
but  thinks  they  evidently  belong  in  the  family  Trichostrongylidae.  Probably  Leidy's  form 
will  fall  in  the  same  group. 

11  (10)     In  mammals 12 

12  (13)     From  frontal  sinus  of  aquatic  carnivore. 

Filar  Old  es  van  Beneden  1858. 

Railliet  and  Henry  include  this  genus  in  the  subfamily  Metastrongylinae. 

Only  species  known     .    .      Filaroides  mustelarum  van  Beneden  1858. 

No  description  of  the  North  American  form  has  been  given  as  yet.  Identified  as  European 
species  from  host  and  effect. 

In  frontal  sinuses  of  various  Mustelidae:  skunk,  weasel,  mink,  and  otter,  from  northeastern 
North  America.     Produces  large  asymmetrical  postorbital  swellings. 

13  (12)     From  intestine  of  aquatic  rodent. 

Trichostrongylus  jiherius  Barker  and  Noyes  191 5. 

Capsule  absent  in  both  sexes.  Male  2.8  mm.  long,  0.013 
to  0.09  mm.  broad.  Bursa  with  broad  lateral  lobes  and 
narrow  dorsal  lobe.     Spicules  short  and  heavy. 

Female  4.7  mm.  long,  0.03  to  0.135  mm.  broad.  Vulva 
near  posterior  end.  Eggs  oval,  0.059  by  0.036  mm.,  shell 
thick. 

Intestine  of  muskrat.     Nebraska. 

The  genus  Trichostrongylus  is  type  of  the  subfamily  Tri- 
chostrongylinae. 

Fig.  815.     Trichostrongylus  fiberius.    Posterior  end  of  male.    X  iSo* 
(After  Barker.) 


PARASITIC   ROUNDWORMS  3,3 

14  (9)     Male  with  bell-shaped  bursa  encircling  posterior  end;  no  sunrwrlinu 

ribs  in  bursa.     No  buccal  capsule. 

Family  Dioctopiiymidae  Raillici  1015. 

Mouth  surrounded  by  one  or  two  circles  of  papillae,  6.  ,2.  or  ,8  in  number.  Ks.,phi«u. 
very  long,  without  bulb.  One  ovary;  vagina  very  lonL-.  Vulva  near  anleriur  n.d  anu^ 
terminal  in  female.  One  long  spicule.  Eggs  with  very  Lhick  pitted  shells  Lar«c  worms 
in  some  genera  armed  with  spines  near  anterior  end.  ' 

Only  genus  parasitic  in  North  American  aquatic  hosts. 

Dioctopliymc  Collel-.Meygret  i.Ho:. 

Anterior  end  unarmed;  mouth  surrounded  by  six  papillae. 

Only  species  known Dioctophytnc  rcualc  (Coc^.q)  i-jSi. 

Color  blood  red;  six  circumoral  papillae  and  150  al..ng  latrral  lines 
Male  up  to  40  cm.  long,  4  to  G  mm.  broad.  Anus  terminal,  surmundcd 
by  circular  bursa  without  ribs.  Spicule  5  to  6  mm.  long.  Female  up 
to  I  m.  long,  and  12  mm.  broad.  Anus  crescentic,  terminal.  Sex  p.irc 
only  50  to  70  mm.  from  anterior  tip.  Uterus  single.  Eggs  oval-  shell 
brown,  very  thick,  deeply  pitted  except  at  poles. 

In  pelvis  of  kidney  of  seal,  otter,  dog.  wolf,  etc.  Rare  in  man 
Reported  from  mink  and  dog  in  Pennsvlvania  bv  Leidy.  Found  in 
dogs  at  Chicago,  Illinois.     Intermediate  host  probably  a  fish. 

The  giant  among  nematodes;  a  dangerous  and  little  known  para>itc 

Another  form  which  may  belong  here  was  collected  in  Florida  by 

Wyman  from  the  water-turkey  or  snake-bird  and  described  as  -nearly 

Fir  Srfi     ninrfnt,hv,„P    ^f  ^^t  i(ientica.l  With  Eustrongylus  papillosus  lYxv^lnK  \n  Plolus  ankiniia 

renal^.  '  Ante^Sr^nd  of    ^JP^,  Brazil."     The  species  last  mentioned  was  included  in  the  genus 

female.  X3.  (After  Riley    ^ystnchis  by  Mohn,  but  as  the  identihcation  of  Wvman  was  not  final 

and  Chandler.)  it  is  impossible  to  enter  Uystrichis  papillosus  definitely  among  North 

American  species. 

15  (8)     Bursa  absent  or  weakly  developed  in  male.     True  buccal  capsule 

wanting 16 

Compare  the  discussion  under  9  (14)  in  this  key.  The  caudal  alae,  often  but  incorrectly 
called  a  bursa,  when  present  consist  of  long,  narrow  wings  not  projecting  conspicuously  from 
the  body  but  parallel  to  it  and  not  supported  by  radiating  ribs,  but  having  at  most  a  scries 
of  canals  at  right  angles  to  the  body. 

16(51)     Very  long,  slender  forms,  with  or  without  lips 17 


17  (26)     Esophagus  slender,  simple,  no  bulb. 

Superfamily  Filarioidea  Weinland  1858  .    .     18 

The  anterior  end  is  usually  plain  and  no  lips  are  present  though  in  some  cases  a  few  minute 
oral  papillae  can  be  recognized.  The  esophagus  has  only  a  single  region.  The  posterior  end 
of  the  male  is  rolled  into  a  close  spiral  of  two  or  more  coils.  The  vulva  lies  far  anteriati  and 
the  forms  are  usually  ovoviviparous.  The  group  as  now  conceived  is  much  m»tre  sharply  lim- 
ited than  formerly. 

18  (19)     Anus  wanting  in  adult;   vulva  lacking  in  adult  female. 

Family  Dracunculidae  Lcipcr  iqi.:. 

The  famous  guinea-worm  of  man  known  since  ancient  times  belongs  in  this  group.  After 
impregnation  the  sexual  pore  disappears  and  no  trace  of  it  has  been  found  in  the  adult.  I  he 
females  grow  to  a  relatively  enormous  size  coincident  with  the  development  of  great  numliers 
of  minute  embryos  which  fill  the  uterus.  The  larvae  develop  in  aquatic  organisms,  prob- 
ably Copepoda,  Ostracoda,  etc. 

Only  North  American  genus 7r///// wmvmj  Diesing  186 1. 

Mouth  surrounded  by  four  low  papillae.  No  buccal  cax-ity.  Esophagus  funnel-shaped  at 
origin.  One  esophageal  gland  with  large  nucleus.  Polymyarian.  I'terus  broad,  traversing 
entire  body,  with  short  ovary  at  each  end.     Embryos  develop  in  uterus.     No  anus,  vulva,  or 


524  FRESH-WATER   BIOLOGY 

vagina  present  in  adult.     Male  much  smaller  than  female;    with  two  spicules  and  accessory 
piece.     Females  parasitic  in  body  cavity  of  Teleostei. 

Single  North  American  species  recorded. 

Ichthyonema  cylindraceum  Ward  and  Magath. 

Male  unknown,  probably  minute.  Mature  female  loo  mm.  long,  of  nearly  equal  diameter 
(0.48  mm.)  everywhere.  DeUcate,  semi-transparent,  and  very  fragile  owing  to  thin  body 
wall.  Lateral  lines  broad,  light  colored,  conspicuous.  No  hps  or  papillae.  Esophagus  1.09 
mm.  long,  0.066  mm.  in  diameter.  Vulva  and  vagina  atrophied,  no  vestiges  discernable. 
Female  impregnated;  uterus  crowded  with  undeveloped  ova  almost  spherical,  44  m  in  diameter. 

In  abdominal  cavity  of  Perca  flavescens;  Lake  St.  Clair. 


Fig.  817.    Ichthyonema  cylindraceum.    Anterior  end  of  female.     X  35-     (After  Ward  and  Magath.) 

19  (18)     Anus  present  in  adult;  vulva  persistent  in  female. 

Family  Filariidae  Claus  1885. 

A  large  group  not  well  known  and  imperfectly  subdivided  into  a  number  of  subfamilies, 
leaving  many  other  forms  still  unplaced.  Most  of  the  species  are  connective  tissue  parasites 
and  the  majority  inhabit  terrestrial  hosts. 

Forms  that  have  not  been  described  from  this  family  exist  in  North  American  aquatic  hosts. 
Those  recorded  are  few  in  number  and  imperfectly  known.  The  following  classification  is 
purely  temporary.  The  genus  Filar ia  has  been  used  as  a  convenient  receptacle  for  all  slender 
roundworms  that  did  not  show  conspicuous  features  of  external  anatomy  adequate  to  place 
them  definitely  elsewhere.  Unless  the  proper  location  of  a  species  could  be  determined  clearly 
it  has  been  left  imder  this  general  heading  even  though  its  original  location  in  this  genus  appears 
to  have  been  an  error. 

Type  genus FzYar/a  0.  F.  Miiller  1787   .    .     20 

Among  the  forms  recorded  as  "Filaria^'  are  some  that  have  no  usable  description  or  in  a 
few  cases  none  at  all  and  must  be  recognized,  if  at  all,  by  their  host,  habit,  or  geographic 
location.  Such  are  ^^Filaria  ardearum"  Stiles  and  Hassall  1894,  cited  from  Ardea  herodias, 
in  Leidy  Collection. 

Filar  ia  atnphiumae  Leidy  1856  encysted  in  the  stomach  wall  of  Amphiiima  means;  alcoholic 
specimens  in  Philadelphia. 

Filaria  cistudinis  Leidy  1856  from  the  heart  of  Cistudo  Carolina,  Pennsylvania. 

Filaria  spec.  Leidy  1882,  a  red  worm  from  the  musculature  and  peritoneum  of  the  black  bass. 

Filaria  nitida  Leidy  1856  from  Rana  pipiens;  later  from  fish  and  reptiles.  "Probably 
yoimg  of  F.  solitaria."     (Two  species  ?) 

20  (25)     Anterior  end  without  lips 21 

21  (22)     Anterior  tip  lacks  both  lips  and  papillae. 

Filaria  wymani  Leidy  1882. 

No  lips  or  papillae.  Female  65  by  0.5  mm.,  sexual  pore  near  center  (?);  viviparous.  Eggs 
0.02  mm.  long;    embryos  0.15  mm.     Male  half  as  large,  with  coiled  caudal  end;    one  spicule. 

Coiled  on  back  of  cerebrum  of  Plotus  anhinga  in  Florida.  Males  rarer  than  females.  Prob- 
ably not  Pelecitiis  {Filaria)  helicinus  (Molin  i860)  with  which  Leidy  later  identified  it. 

22  (21)     Anterior  tip  with  minute  papillae 23 

23  (24)     Oral  papillae  in  two  series  of  4  to  6  each. 

Filaria  solitaria  Leidy  1856. 

Body  cylindrical,  rose-red  with  more  deeply  tinged  extremities.  Length  up  to  150  mm., 
breadth  i  mm.  Slightly  narrower  towards  both  ends.  Tail  obtuse;  anus  terminal,  trans- 
verse, with  prominent  lip.     Esophagus  tortuous,  one-sixth  length  of  body. 

Beneath  dorsal  skin  of  Rana  pipiens;  also  in  muscles  of  Anguilla  chrysypa  in  Delaware 
River.  In  peritoneum  of  Chelonura  serpentina,  Emys  serrata,  and  Esox  reticulatus.  Most 
frequent  during  winter  and  spring.     Railliet  thinks  two  species  are  involved. 


PARASITIC   ROUNDWORMS 


24  (23)     Only  two  small  conical  papillae  near  moulh. 

Filaria  physdura  Bremser  181 1. 

Living  worm  pink  with  brown  intestine  and  white  uteri  prominent      Femak-  10  f 
long,   I  to   1.5  mm.  broad     Head  obtuse.     Mouth  with  two  small  conical  pa.X-  '  MaTil 
35  mm.  long,  0.615  mm.  broad;    tail  curved  with  short  quinquecostatc  alac  which  arc  oil 
mm.  long.     Spicule  recurved.  ^^  °--*S 

In  abdomen  of  kingfisher;   Pennsylvania.     "Determination  not  positive"  (Lcidy). 

25  (20)     Anterior  end  provided  with  two  lips.     Each  lip  carries  two  blunt 

hooks Filaria  cingula  von  Linslow  u)02. 

Length  15  to  25  cm.,  diameter  0.53  mm.  Anterior  end  bluntlv  rounded;  dorsal  and  vi-ntraJ 
triangular  hps  with  two  blunt  hooks  in  each.  Cuticula  embossed  with  low  rounded  trans^ 
verse  ridges  on  dorsal  and  ventral  surfaces.  Pharynx  narrow,  0.375  mm.  Iomk  with  bulbous 
enlargement  at  end.  Esophagus  triangular,  15  by  0.13  mm.  Lateral  fields  broad  Two 
ovaries.     Vulva?     Embryos  0.33  by  0.014  mm.     Viviparous. 

In  skin  of  Cryptobranchus  allegheniensis;  Ohio  river.  Identification  with  von  Linstow'j 
meager  description  uncertain. 


Fig.  818.  Filaria  cingula.  Optical  section  of  the  two  anterior  millimeters;  /,  lips;  p.  pharyngeal  bulb; 
0,  ovary;  e,  esophagus;  u,  uterus;  h,  hooks;  r,  ridges.     Magnified  about  50.     (After  Kreckcr.J 

26  (17)     Esophagus  with  two  separate  regions,  more  or  less  difTercntiatc<I. 

Superfamily  Spiruroidea  RaiUiet  and  Henry  10 15     .   .     27 

The  mouth  has  two  lips,  or  is  without  any.  Esophagus  with  partition  dividinR  it  int<j  two 
regions  which  may  be  differentiated  as  anterior  muscular  and  posterior  granular  region,  and 
may  be  much  alike  in  appearance. 

Male  with  lateral  alae  near  posterior  end  of  body.  Alae  in  general  long,  not  much  if  any 
wider  than  body,  without  ribs  or  radiate,  branching  supports. 

Most  of  these  forms  were  previously  included  with  the  Filarioidea  from  which  they  an-  most 
easily  distinguished  by  the  double  esophagus. 

27  (42)     Anterior  end  simple,  without  prominent  lateral  valve-like  lips.   .      28 

28  (41)     Tail  in  female  simple,  not  modified  in  the  form  of  a  sucker-like 

structure 


29(40)     Male  with  preanal  papillae  and  without  vent  nil  ridges.  30 

30  (37)     Preanal  papillae  in  male  single  not  stalked  and  paired,  also  tew  in 

number Family  Spiruridae  Oerley  1SS5   .    .     31 

There  are  several  subfamilies  which  contain  numerous  parasites  of  terrestrial  hosts. 

31  (34)     Anterior  end  plain,  unornamented  by  external  ridges  or  frills. 

Subfamily  Spirurinae  Raillict  IQ15   ■    •     ^^ 
The  mouth  has  two  small  lips,  or  none.    The  pharynx  is  simple  or  wanting.     The  \ulva  is 
at  the  center  of  the  body,  or  anterior. 


526 


FRESH-WATER  BIOLOGY 


32  {^7,)     Mouth  without  lips. 


Fig.  818.  Haplonmea  im- 
mutatum.  Anterior  end  show- 
ing lateral  alae.  X  22.  (After 
Ward  and  Magath.) 


Male  without  caudal  alae. 

Haplonema  Ward  and  Magath. 

Anterior  end  flexed  or  coiled,  provided  with  lateral  alae. 

Esophagus  muscular,  without  bulb,  divided  into  two  regions  by- 
partition  near  center.  Posterior  end  of  male  without  bursa,  with 
two  pairs  of  preanal  papillae  and  three  pairs  of  postanals. 
Spicules  two,  equal.  Vulva  near  center  of  body;  ovary  double, 
laid  in  transverse  loops  near  anterior  and  posterior  ends.  Ovipar- 
ous. 

Only  North  American  species. 

Haplonema  immutatiim  Ward  and  Magath. 

Body  moderately  robust.  Males  10  mm.  long,  0.2  mm.  broad; 
females  15  mm.  long,  0.31  mm.  broad.  No  lips  present;  three 
minute  oral  papillae.  Esophagus  divided  about  equally;  anterior 
and  posterior  regions  not  distinctly  differentiated.  Spicules  0.75 
mm.  long,  0.02  mm.  broad,  fiat,  ribbon-shaped.  Eggs  65  by  45  tx, ' 
with  moderately  thick,  smooth  shell.  Vulva  five-eighths  of 
length  from  anterior  tip. 

From  intestine  of  Amia  calva;  Lake  St.  Clair,  Michigan,  and 
Fairport,  Iowa. 


33  (32)     Mouth   with   w^ell-developed   lips.     Male  with   caudal   alae  joined 

anteriorly  across  ventral  surface  of  body. 

Physaloptera  Rudolphi  1819. 

Mouth  elongated  dorsoventrally;  bounded  by  2  lateral,  thick  Hps  each  carrying  a  toothed 
process  and  2  broad  submedian  papillae.  Caudal  end  of  male  with  lateral  alae  and  10  pairs 
of  papillae,  of  wnich  4  are  stalked  and  in  each  ala,  whereas  6  are  sessile  and  on  body.  Spicules 
2,  unlike.     Vulva  in  anterior  region.     Eggs  very  thick-shelled. 

Species  reported  in  North  America  but  not  adequately  known. 

Physaloptera  constrida  Leidy  1856.     In  stomach  of  Tropidonotus  sipedon;   Pennsylvania. 
Also  Physaloptera  contorta  Leidy  1856.     In  stomach  of  numerous  turtles;   Pennsylvania. 

34  (31)     Anterior  end  with  sinuous  cuticular  thickening  or  cervical  frill. 

Subfamily  Acuariinae  Railhet,  Henry,  and  Sisoff  191 2. 

Anterior  end  provided  with  bands,  epaulets,  or  similar  ornaments.  Mouth  with  two  simple 
lateral  Ups,  pharynx  and  esophagus  differentiated  into  two  distinct  regions.  Caudal  end  of 
male  with  lateral  alae;  four  pairs  of  preanal  papillae;  postanals  variable.  Eggs  with  thick 
shell,  containing  embryos  when  deposited. 

In  digestive  tract  of  birds.    A  numerous  and  varied  group. 


Only  genus  yet  recorded  in  North  American  aquatic  hosts. 

Acuaria  Bremser  181 1 


ZS 


The  cervical  frill  consists  of  two  or  four  simple  or  complex  loops  draped  from  the  tip  of  the 
head  back  over  the  anterior  region  of  the  body.  Vulva  in  posterior  region.  Two  imequal 
spicules.     In  esophagus,  crop,  or  gizzard  of  birds.     Often  called  Dispharagus  in  records. 


35  (36)     With  trifid  cervical  papilla. 


Acucria  triaenucha  (Wright)  1879. 


Male  unknown.  Female  10  mm.  long,  0.43  mm.  broad.  With  cervical  frill; 
lateral  loops  0.18  mm.  from  anterior  end  at  top  and  extend  0.405  mm.  posteriad. 
Cervical  papilla  a  trident  spine,  at  base  0.06  mm.  from  end  of  frill,  and  0.06 
mm.  long.     Eggs  27  by  18  fx. 

Single  female  taken  from  gizzard  of  Botaurus  minor  in  Canada  by  R.  Wright 
and  described  as  Filaria  triaenucha. 


Fig.  819.     Acuaria  triaenucha.     Cervical  papilla.     X  233.     (After  Wright.) 


PARASITIC   ROUNDWORMS  -27 

36  (35)     No  trifid  cervical  papilla  present. 

Acuaria  ardcac  (A.  J.  Smith)  i.^o^. 

Male  unknown.  Female  17  by  0.7  mm.  Two  lateral  lips,  each  with  double  papillae  From 
base  of  each  lip  two  promment  submedian  ridges  on  surface  extend  posteriad  nearly  to  ccntt-r  lA 
body,  then  dorsad  and  ventrad  respectively  to  join  similar  lines  on  opixjsiic  side.  Ksi.phaifu* 
2  mm.  long,  in  two  sections:  anterior  narrow  region  o.S  by  0.05  to  o.oy  mm.,  ixjstrrior  widrr 
region  1.2  by  0.2  mm.  Anus  0.35  from  tip  of  tail  which  is  bent  strongly  dorsjid.  Vulva  nt-.ir 
center  of  body;  no  eggs  developed. 

In  Ardea  herodias.     Described  originally  as  Dispharagiis  ardeae  by  A.  J.  Smith. 

37  (30)     Preanal  papillae  in  male  numerous,  grouped  in  pairs  and  stalked. 

Family  Thelaziidae  Raillict  1916. 

Head  naked  or  provided  with  cuticular  thickenings  or  helmet-like  covering.  Mouth  with 
2  to  6  very  small  lips  or  without  any,  followed  by  a  long  vestil)ule  or  a  short  butial  capsule. 
Esophagus  composed  of  two  distinct  regions.  Males  with  or  without  lateral  alac  in  caudal 
region,  with  a  linear  row  of  numerous  preanal  papillae,  often  paired;  postanal  i)apillae  lc*« 
numerous;  2  spicules,  almost  always  unequal.  Female  with  double  uterus;  vulva  variable 
in  location.     Oviparous  or  viviparous. 

Only  genus  in  North  American  aquatic  hosts. 

Cystldicola  Fischer  1797    .    .     38 
No  valid  record  exists  for  the  European  C.  Jarionis  in  North  .\merica. 

38  (39)     In  air-bladder  of  salmonid  fishes. 

Cystldicola  stigmatiira  (Leidy)  1886. 

Length:  male,  12  to  25  mm.;  female,  20  to  40  mm.  Width:  male,  0.25  mm.;  female,  0.4s 
mm.  Mouth  circular  with  2  minute  lateral  teeth.  Buccal  capsule  tubular,  0.12  to  0.2.J  mm. 
long.  -  Anterior  region  of  pharynx  0.5  to  0.6  mm.  by  0.054  Tnm.,  posterior  region  2.1  to  2.\ 

mm.    by  o.i    mm.     Male   with 

narrow   lateral    membranes   on 

caudal  end  ;    5   pairs  of  single 

postanal    papillae,    9    pairs    of 

double  preanal  papillae.      Two 

unlike  spicules;    one  slender  oS 

to  0.9  mm.  long,  o.oi  mm.  wide; 

other  trowel-shapeti,  0.16  mm. 

Fig.  820.     Cystldicola  stigmatura.      Anterior  end  of  female.      X  85.    \q^^    q  jg  ^im    wide        Female 

(After  Ward  and  Alagath.)  s^^^;^,  ^^^e  near  center  of  Ixxly ; 

uterus  with  anterior  and  posterior  branches  both  well  developed  and  symmetrical.     Ova  thin 

shelled,  containing  developed  embryo  when  laid,  44  by  27  /x. 

In  air-bladder  of  Great  Lakes  trout,  white  fish,  and  lake  herring.  Lake  Eric,  Lake  St. 
Clair,  Lake  Michigan,  Lake  Ontario  (Leidy). 

In  half  or  more  of  fish  examined.  Reported  by  Wright  as  Ancyracanthus  cystidkola  and  by 
Leidy  as  Filaria  stigmatura. 

39  (38)     In  heart  of  white  fish Cystldicola  scrrata  (Wright)  1S79. 

Length  11  mm.  With  several  small  teeth  around  anterior  end  instead  of  two  as  in  former 
species.  Only  a  single  specimen  found  by  Ramsay  Wright  at  Toronto.  I'erhaps  an  imma- 
ture specimen,  either  migrating  in  blood  stream,  or  accidentally  introduced  into  this  peculiar 
location. 

40  (29)     Male  with  conspicuous  ventral  ridges  near  posterior  end;    preanal 

papillae  absent  or  inconspictious.     Body  spinous. 

Splnltcctiis  Fourment  1S83. 

Mouth  without  lips  or  papillae.  Except  at  extreme  tip  the  body  is  encircli«d  in  the  ante- 
rior half  or  more  by  rows  of  spines  pointing  backward.  The  ventral  surface  in  the  male  carnes 
several  parallel  series  of  rugosities  just  anterior  to  the  anus. 

Representative  North  American  species. 

Splnltcctiis  gracilis  Ward  and  ALigalh. 

Mature  female  17  to  19  mm.  long,  0.14  broad;  male  12  mm  long,  0.075  mm  broad.  ^}^^f 
130  rows  of  spines  with  40  to  50  in  each  row.     .Interior  tip  free  from  spmes  for  o.n  mm.  in 


5^8 


FRESH-WATER   BIOLOGY 


female,  o.i  in  male.    Vulva  one-fourth  total  length  from  caudal  tip.     Spicules  two,  large, 
heavy,  unequal.     Ova  41  by  24  n,  thick- waUed. 
In  intestine  of  black  crappie,  sheepshead,  and  white  bass  at  Fairport,  Iowa.    Abundant. 


Fig.  821.     Spinitectus  gracilis.     Anterior  end  of  female.     X  220.     (After  Ward  and  Magath.) 

41  (28)     Posterior  end  in  female  modified  to  form  a  sort  of  sucker  by  which 
the  parasite  is  attached  to  the  stomach  wall. 

Hedruris  Nitzsch  1821. 

Head  with  4  lips:  2  lateral,  slender,  each  with  2  papillae;  2  median,  thinner,  overlapping 
laterals  almost  completely.  Vulva  near  anus.  Tail  of  female  modified  to  form  with  included 
spine,  the  caudal  tip,  an  adhesive  organ  or  sucker.  Eggs  elhptical,  with  lid-like  areas  at  both 
pointed  poles,  contain  developed  embryos.  Male  spirally  wound  around  female.  Tail  strongly 
compressed  laterally:  6  pairs  postanal  papillae,  i  pair  just  preanal.  Spicules  2,  similar,  very 
short,  apparently  grown  together. 

Tj^e  species Hedruris  androphora  Nitzsch  1821. 

RefX)rted  from  Amhlystoma  mexicana  and  Nanemys  guttata  by  Stiles  and  HassaU.  The  form 
described  by  Leidy  in  1851  as  Synpleda  pendula  certainly  belongs  in  this  genus  if  not  in  this 
species. 

Also  recorded Hedruris  siredonis  Baird  1858. 

In  British  Museum  collection.  From  "stomach  of  Siredon  mexicanus  from  Mexico."  Male 
not  found. 


42  (27)     Anterior  end  provided  with  heavy,  lateral,  valve-shaped  lips. 


43 


43  (48)  Lips  red  or  brown,  very  conspicuous.  Esophagus  with  two  well 
differentiated,  distinctly  separated  regions.  No  preanal 
sucker  in  male. 

Family  Camallanidae  RaiUiet  and  Henry  1915   .   .    44 

Body  nearly  cylindrical,  with  heavy  oral  armature  having  the  appearance  of  a  bivalve  shell, 
which  is  really  2  thick,  lateral,  valve-hke  lips  probably  functioning  as  jaws  and  not  a  buccal  cap- 
sule. Each  valve  marked  by  longitudinal  ridges  terminating  at  the  inner  margin  of  the  mouth 
in  minute  teeth.  Mouth  an  elongated  oval;  inner  opening  of  oral  cavity  to  esophagus  round, 
encircled  by  hea\y  basal  ring  of  chitin.  Several  (2  to  4)  hea\y  chitinous  rods  diverge  from 
common  center  at  each  side  of  capsule  along  sides  of  body  beneath  cuticula,  forming  a  fork 
or  "trident." 

Esophagus  bipartite,  anterior  region  muscular,  club-shaped;  posterior  dark,  granular  (gland- 
ular?); valve  to  intestine. 

Tail  of  male  surrounded  by  narrow,  poorly  developed  caudal  alae  with  stalked  papillae.  A 
single  spicule  with  accessory  piece  or  two  nearly  equal  spicules.  Female  sexual  pore  towards 
center  of  body.     Viviparous;   embryos  develop  in  Crustacea  and  insect  larvae. 

Parasitic  in  aUmentary  canal  of  fishes  and  reptiles. 

Single  genus  known Cawa//awM.y  RaiUiet  and  Henry  191 5. 

These  forms  are  often  cited  as  Cucullanus  and  Dacnitis.  RaiUiet  and  Henry  have  recently 
cleared  up  the  confusion  previously  existing  in  the  group. 


PARASITIC   ROUNDWORMS 


520 


44  (45)     With  anterior  end  bent  ventrad. 

Camallaniis  ancylodirus  W  ar.l  and  Maguih. 


Mature  female  25  mm.  lonp,  0.56  mm.  broad:  male  iq  mm  l.mir  o  ..s 
mm  broad.  Oral  armature  in  female  0..42  to  o.hH  mm.  Iohk  by  o"ih  to 
0.187  mm.  broad;  in  male  0.126  mm.  lonK  by  0.12  mm.  bn.a.i.  Trident 
with  3  or  4  roots,  in  female  0.21  and  in  maleo.iSmm  I..11L'  si.i.  nl.-,  „.- .rl. 
equal.     Vulva  three-fifths  of  length  from  anterior  end 

In  intestine  of  German  carp.     Fairport,  Iowa. 


Fig.  822.     Camallanus  ancylodirus.     Head  of  male. 
Magath.) 


X  70.     (.After  W  ar.l  and 


45  (44)     With  anterior  end  attenuated,  not  bent ^6 


46  (47)     Vulva  one-third  total  length  from  anterior  tip.     No  spines  on  caudal 
tip Camallanus  oxycephalus  Ward  and  Magalh. 

Female  slenderer  than  preceding  species,  25  mm.  long,  0.27  mm.  broad,  straight  through 
entire  length.  Oral  armature  smaller.  First  esophagus  0.47  by  0.085  mm.;  second  0.57  mm. 
wide.     Male  unknown.     In  intestine  of  white  bass  and  black  crappie. 


Fig.  823.     Camallanus  oxycephalus.     Anterior  part  of  female.  X  70.     (.After  Ward  and  Magath.) 


47  (46)     Vulva  behind  center  of  body.     Three  small  spines  on  caudal  lip  of 
female Camallanus  trispi)wsus  (Xa:'\(\\)  185  i. 

Mouth  large,  valves  with  8  radiating  lines  on  each  side  of  unstriated  median  band,  makins 
16  rays  on  each  valve.  Male  6  mm.  long,  0.12  to  0.16  mm.  broad.  .\nus  o.oS  mm.  from  laudal 
tip.  Two  spicules,  0.12  and  0.43  mm.  long.  Fem.ale  12  mm.  long,  0.24  to  0.27  mm.  liroad 
First  esophagus  0.38  by  0.12  mm;  second  0.46  mm.  long.  .\nus  0.022  mm.  from  caudal  tip 
which  bears  three  minute  points.     Vulva  with  prominent  lips. 

In  small  intestine  of  Emys  guttata,  E.  reticulata,  E.  scrpala,  Chclydra  .urpcutitta.  Thiladcl- 
phia  (Leidy). 


48  (43)     Lips  not  conspicuous;    esophageal  regions  similar  in  structure,  mn 
sharply  separated.     Male  with  preanal  sucker. 

Family  Cucullaxid.ae  Slossich  iSgS 

Mouth  eUiptical,  with  long  axis  dorso-ventral,  bounded  by  two  lateral  valves  recalling  those 
of  Camallanus.  Esophagus  pestle-shaped  but  without  bulb,  two  regions  appear  alike  in 
structure,  short,  separated  only  by  transverse  partition.  Male  without  caudal  alae;  two 
equal  spicules;  preanal  sucker  without  horny  ring.  Female  with  vulva  not  far  from  center 
of  body. 

In  intestine  of  fishes. 

There  are  in  North  America  numerous  species  of  this  genus.  Only  a  few  have  been  descrihcd 
adequately.  In  the  past  these  forms  have  often  been  recorded  as  Dacnilis  Dujardin  1S45 
and  assigned  to  the  Heterakidae. 


530 


FRESH-WATER   BIOLOGY 


49  (50)     With  anterior  end  bent  dorsad.     No  intestinal  cecum  present. 

Cucullanus  O.  F.  Miiller  1777. 
Anterior  end  flexed  dorsad  60  to  90  degrees.     Spicules  with  accessory  piece.     Ovary  double. 

Representative  species  in  North  America. 

Cucullanus  clitellarius  Ward  and  Magath. 
Body  uniform  in  diameter  except  for  clitellar-like  swelling  i  mm.  long,  and  1.5  mm.  from 
anterior  tip.  On  each  oral  margin  three  small  papillae.  Male  10  mm.  long  by  0.38  mm. 
broad.  Esophagus  1.45  by  0.12  to  0.22  mm.  Spicules  gouge-shaped,  1.62  by  0.035  mm.; 
accessory  piece  dagger-shaped,  0.06  by  0.015  mm.  Two  small  preanal  papillae;  4  pairs  of 
postanals.  Females  12  to  17  by  0.5  mm.  Esophagus  1.6  by  0.13  to  0.32  mm.  Vulva  two- 
thirds  of  length  from  anterior  end.  Uterus  and  ovary  double.  Ova  63  by  46  /x. 
In  intestine  of  lake  sturgeon;   Lake  St.  Clair. 


50(49)     Anterior  end  straight : 


well-developed  intestinal  cecum  present. 

Dacnitoides  Ward  and  Magath. 

Much  like  Cucullanus  except  that  anterior  tip  is  not  flexed,  an  accessory 
piece  is  lacking  and  only  a  single  ovary  is  developed.  The  intestine  pos- 
sesses a  prominent  cecum  extending  anteriad  to  the  nerve  ring. 

Representative  species  in  North  America. 

Dacnitoides  cotylophora  Ward  and  Magath. 

Male  4  to  6  mm.  long,  0.2  mm.  broad.  Each  lateral  valve  with  anterior 
marginal  cuticular  thickening  bearing  3  papillae.  Esophagus  0.5  to  o.6_  by 
0.06  to  0.12  mm.  Boundary  between  esophageal  regions  at  nerve  ring. 
Spicules  0.89  by  0.005  mm.  Caudal  papillae:  one  pair  on  anterior  margin 
of  sucker,  four  pairs  between  sucker  and  anus,  a  single  medial  papilla  just 
in  front  of  anus  and  four  pairs  postanal. 

Female  4  to  5.5  mm.  long,  0.28  mm.  broad.  Anus  0.14  from  posterior 
tip  with  4  slender  spines  midway  between.  Vulva  one-eighth  of  total  length 
behind  center  of  body.  Posterior  uterine  branch  has  no  ovary.  Ova  65 
by  40  jLt. 

In  intestine  of  yellow  perch  and  wall-eyed  pike;  Lake  St.  Clair. 

Fig.  823a.  Dacnitoides  cotylophora.  Head  of  female,  showing  oral  armature, 
esophageal  regions,  intestine,  cecum,  and  anterior  coils  of  ovary.  X  57-  (After 
Ward  and  Magath.) 

51  (16)     Stout  bodied  forms  with  conspicuous  lips 52 

52  (55)     Two  heavy  lips.     Body  covered  on  anterior  region  at  least  with 

dentate  or  spinous  plates. 

Family  Gnathostomjdae  Railliet  1893. 

Body  covered  in  whole  or  part  by  circles  of  dentate  cuticular  plates.  Anterior  tip  enlarged, 
provided  with  simple  spines,  separated  by  nuchal  constriction.  Two  large  fleshy  lips. 
Esophagus  large,  muscular.  Vulva  behind  middle  of  body.  Two  equal  spicules.  No  bursa. 
In  male  two  pairs  of  preanal  papillae  and  two  postanals. 

Type  genus Gnathostoma  Owen  1836   .    .     53 

Entire  body  or  anterior  end  covered  with  abundant  spines,  often  many  pointed.     Head 
separated  by  circular  constriction,  with  circles  of  simple  spines.     Two  large,  fleshy  lips.     Spic- 
ules 2,  unequal;   vulva  behind  center  of  body.     Male  with  two  pairs  of  postanals. 
Two  species  reported  from  North  American. 

53  (54)     Anterior  plates  palmate  with  eight  spines  each. 

Gnathostoma  horridum  (Leidy)  1856. 
Female  66  mm.  long,  3  mm.  broad.     Male  unknown. 

Taken  from  stomach  of  Alligator  mississippiensis  in  Georgia  and  originally  described  by 
Leidy  as  Cheiracanthus  horridus. 

54  (53)     Anterior  plates  tridentate.     .    .    .     Gnathostoma  sociale  (Leidy)  1858. 
Female  30  mm.  long,  1.5  mm.  broad.     Male  24  mm.  long,  i  mm.  broad. 

Taken  from  stomach  of  mink  {Putorius  vision)  in  Philadelphia  and  originally  described  by 
Leidy  as  Cheiracanthus  socialis. 


PARASITIC   ROUNDWORMS 


531 


55  (52)     Relatively  thick,  heavy-bodied  forms.     Mouth  with  three  lips,  more 

or  less  conspicuous.     Always  oviparous. 
Superfamily  Ascaroidea  Railliet  and  Henry  U)is 

One  large  dorsal  and  two  smaller  ventral  lips,  right  and  left  of  medial  line;  secondary  lips 
(mterlabia)  may  be  uitercalated.  Buccal  capsule  never  present.  Dorsal  lip  l>car8  rcinilarlv 
two  papillae  and  ventral  lips  one  each.     Lips  rarely  greatly  reduced  {or  aljscni:-'). 

56  (68)     Polymyaria.     Usually  'arge  opaque  species 57 

For  discussion  of  term  Polymyaria  see  page  515. 

57  (67)     Lips  prominent.     No  ventral  sucker  in  male. 

Family  Ascaridae  Cobbold  1864   .    .     58 
Male  usually  has  two  spicules.     Female  with  abruptly  conical  posterior  end. 

Type  genus l^a/m  Linnaeus  1758. 

No  fringes  or  tentacles  on  the  lips.  A  large  and  complex  group.  DilTcrontiatcd  usually  on 
the  basis  of  the  form  of  the  lips  which  present  many  modifications  in  minor  details. 

A  number  of  forms  have  been  recorded  under  the  name  Ascaris  which  are  so  inade(juatcly 
described  that  their  exact  systematic  position  must  depend  on  their  redi-scovt-ry  and  further 
study.     Such  are: 

Ascaris  longa  Leidy  1856  of  which  a  single  female  specimen  was  taken  from  the  intestine 
of  the  wood  ibis  in  Georgia. 

Ascaris  penita  Leidy  1886  from  the  intestine  of  the  terrapin. 

Ascaris  cylindrica  Leidy  1849  from  the  intestine  of  Helix  allernata  in  Pennsylvania. 

Ascaris  entomelas  Leidy  185 1  from  the  lungs  of  Rana  halecina,  which  the  description  says 
is  "not  Ascaris  nigrovenosa  Zeder"  (  =  Angiostoma  nigrovenositm  q.v.). 

Ascaris  tenuicollis  Rudolphi  1819,  from  the  stomach  and  intestine  of  Alligator  mississippi- 
ensis  or  encysted  on  viscera.     Reported  frequently. 

Probably  most  of  these  do  not  belong  in  the  genus  Ascaris  in  the  strict  sense  and  ver>'  likely 
not  in  the  family  of  the  Ascaridae  as  at  present  defined.  These  species  are  not  well  known 
and  often  determinations  have  evidently  been  based  on  general  factors  that  are  not  truly 
diagnostic. 

58  (59)     Lips  relatively  small,  without  intermediate  lobes;  dental  plates  with 

serrate  edges  on  inner  margins. 

Ascaris  lanceolata  Molin  i860. 

Male  20  to  25  by  0.5  mm.;   female  25  to  40  by  0.8  mm. 

Lips  much  like  those  of  Ileterakis.  Tail  of  male  with 
oval  groove  on  ventral  surface,  and  parallel  longitudinal 
furrows  on  dorsum;  lateral  to  these  merely  cuticular  folds 
(weakly  developed  alae?).  Papillae:  about  ly  |)reanal 
and  12  postanal  with  one  row  of  long  papillae  in  an  arc. 

In  stomach  of  Alligator  mississippiensis.     (leorgia. 

Fig.  824.      Ascaris  lanceolata.     Dorsal  lip,  inner  aspect.     X  80. 
Ventral  view  of  tail  of  male.     X  6.    (After  von  Draschc.) 

59  (58)     Lips  well  developed;  with  intermediate  lobes  or  interlabia.      .    .     60 

60  (64)     With  serrate  dental  plates  on  inner  border  of  lips 61 

61  (62,  63)     Tail  of  male  with  6  pairs  of  postanal  papillae. 

Ascaris  sidcata  Rudolphi  18 10. 

Male  35  mm.  long;  female  97  to  too  mm.  lon^. 
Body  attenuate  anteriorly,  distinctly  ringixl.  Lijw 
very  large,  hexagonal;  lobes  indistinct;  interlabia 
very  small.  Tail  of  male  with  6  postanal  papillae 
and  many  (±64)  preanals.  Bursa  broad.  Eggs 
irregularly  elliptical,  large. 

Reported  in  1887  by  Leidy  from  the  stomach  i^ 
terrapin,  Pennsylvania. 

Fig.  825.      Ascaris  sulcata.      Dorsal  \ncw  of  lips,  and  po*" 
tenor  end  of  male.    Magnified.    (After  Sio&ucb.) 


532 


FRESH-WATER    BIOLOGY 


62  (61,  63) 


Tail  of  male  with  4  pairs  of  postanal  papillae. 

Ascaris  ardeae  Smith  1908. 

Female  up  to  80  mm.  long  and  1.8  mm.  broad. 
Head  rounded  with  3  prominent  lips  and  well-marked 
interlabia,  Superior  lip  with  finely  denticulate  anterior 
and  lateral  borders.  Tail  acutely  conical,  vulva  30  mm. 
from  head.  Ova  0.105  to  o.ii  mm.  by  0.096  too. x  mm.; 
shell  colorless  marked  by  thick-set  pits. 

Male  72  mm.  by  1.5  mm.  Spicules  double,  equal, 
brownish,  1.3  mm.  long.  Tail  incurved,  bluntly  rounded 
with  small  acutely  conical  tip.  Papillae:  2  pairs  on 
conical  tip  also  2  pairs  postanal  and  5  pairs  or  more 
preanal. 

In  Ardea  herodias. 
^      „  .       .        .       ,  -  ,    .  Much  like  A .  serpentulus  Rudolphi  reported  by  Leidy 

Fig  820.     Ascans  ardeae      Lateral  view    f         ^^^^  j^     ^       Probably  Leidy 's  record  concerns  this 
of  anterior  end,  showing  two  of  the  lips  •  t-u*.  a  i     t   i  iii.ju/\ 

(partly  in  profile)  and  two  of  the  interlabia.     ^P^i^^^?-,    J^e  true  A .  serpentulus  was  collected  by  A. 
Ventral  surface  of  male  tail.      (Note  the    J-  Smith  from  a  European  crane  m  the  Philadelphia 
second  pair  of  papillae  from  tip  of  tail  as    Zoological  Gardens, 
uncertain.)  Magnified.  (After  A.  J.  Smith.) 

63  (61,  62)     Tail  of  male  with  3  pairs  of  postanal  papillae. 

Ascaris  microcephala  Rudolphi  1819. 

Male  15  to  45  mm.,  female  45  to  70  mm.  long.  Body  greatly 
attenuated  anteriorly.  Lips  quadrangular,  with  anterior  margin 
concave  and  angles  projecting.  Interlabia  as  long  as  lips.  Cer- 
vical papillae  in  dorsal  and  ventral  lines.  Tail  of  male  obliquely 
truncated;  papillae  small,  3  postanal  and  31  preanal.  Ova  72  by 
59  M- 

In  crop,  esophagus,  stomach  and  intestine  of  various  herons, 
and  bittern.     Florida  to  Canada. 


Fig.  827.      Ascaris  microcephala.      Dorsal  view  of  head. 
(After  von  Linstow.) 


Magnified. 

64  (60)     Without  serrate  labial  plates 65 

65  (66)     With  interlabia Ascaris  helicina  MoHn  i860. 


Male  6  to  8  by  o.i  to  0.2  mm.;  female  13  to  28  by  0.3 
to  I  mm._  Three  interlabia.  Lips  almost  quadrangular 
with  auricles  on  anterior  corners.  Tail  of  male  with  5 
postanal  and  4  large  lateral  preanal  papillae.  Vulva  an- 
terior, or  almost  in  center  of  body. 

In  stomach  of  Alligator  mississippienis. 


Fig.  828.     Ascaris  helicina.      Dorsal   lip,   inner  aspect.     X  55- 
Tail  of   male.     X  85.     (After    von   Drasche.) 


66  (65)     Neither  interlabia  nor  dental  plates  in  oral  armature. 

Ascaris  miicronata  Schrank  1790. 

Length  52  mm.,  breadth  0.75  mm.  Body  much  attenuated  anteriorly.  Lateral  membrane 
broad  on  head,  disappears  on  neck.  Greatest  breadth  of  upper  lip  twice  its  length;  base 
broader  than  anterior  margin;  lateral  margins  divided  into  anterior  straight  and  posterior 
arcuate  portion.     Tail  of  male  with  2  rows  of  preanal  papillae  on  each  side. 

From  Alligator  mississippiensis.     Listed  by  Stiles  and  Hassall  in  Leidy  Collection. 

67  (57)     Lips  distinct,  not  large.     Male  with  ventral  sucker  near  anus. 

Family  Heterakidae  Railliet  and  Henry  1914. 

None  known  from  aquatic  hosts.  Likely  to  be  confused  with  Cuadlanus  {cf.  page  530)  which 
has  a  preanal  sucker  without  horny  ring.  There  are  in  North  America  numerous  species  of 
this  genus. 


PARASITIC   ROUNDWORMS  533 

68  (56)     Meromyaria.     Small  transparent  forms 6^ 

For  discussion  of  term  Meromyaria  sec  page  515. 

Lips  simple,  inconspicuous.  Vulva  anterior.  Caudal  end  of  female  distinctly  clorujale 
separated  from  Ascands  by  some  authors.  '  wunRaic. 

69  (70)     Without  esophageal  or  intestinal  cecum. 

Family  OxvuRroAE  Coblx)ld  1864. 

The  few  North  American  records  cannot  be  safely  assijmed  on  the  basis  of  the  pn-vnt  div 
tmction  between  this  family  and  the  next.  Consequently  they  are  left  where  they  were  olacrd 
originally.  ' 

Among  forms  recorded  from  North  America  which  cannot  be  placed  at  present  owing  to 
imperfect  knowledge  of  their  structure  are: 

Oxyuris  dubia  Leidy  1856  reported  from  Bufo  americanus  and  SaJamatuIra  rubra.  .Male 
unknown. 

North  American  genus Spironouni  U-idy  1856. 

Mouth  surrounded  by  circular,  papillated  lip.  Tail  of  male  spiral,  acute.  tulxTcubtc. 
Spicules  two,  curved,  ensiform,  costate.  Tail  of  female  conical,  acute.  Vdva  at  posterior 
third. 

Type  species Spironoura  aracilc  WuW  \^s6. 

Female  16  by  0.25  mm.;  male  8  by  0.25  mm.  with  two  rows  of  three  papillae  on  tail.  Found 
in  stomach  of  Emys  serrata  and  Siredon  mexicanus. 

Also  recorded Spironoiira  affiiic  Lcidy  1858. 

Female  9  by  0.4  mm.;  male  6  by  0.3  mm.,  with  two  papillae  on  each  side  of  tail  near  end. 
Foimd  in  cecum  of  Cistudo  Carolina. 

70  (69)  With  cecum  on  esophagus  or  intestine,  or  on  both. 

Family  Heterocheilidae  Railliet  and  Henry  1915  .    .     71 

71  (74)  With  papillae  on  tail  of  male  and  with  ceca  on  both  esophagus  and 

intestine Co»/racoec«w  Railliet  and  Henry  191 2. 

72  (73)     Without  circle  of  spines  on  tail. 

Contracoeciim  spicidigcnim  (Rudolphi)  i8oq. 

Male  18  to  qo  mm.,  female  .^o  to  154  mm. 
long.  Lipssinall;  interlabia  well  dcvel»»pcd 
with  a  small  notch  at  outer  margin.  Intes- 
tine with  diverticulum  at  anterior  end.  Tail 
of  male  with  7  postanal  pajiillae  many  (  ±  40) 
^^\\%J^  lyyy  preanals  in  2  lateral  series.      Spicules  very 

long,  usually  well  extended,  and  recur\'«i. 
V^ulva  anterior.  Ova  irregularly  reticulate 
0.1 1  to  0.12  mm.  long. 

Reported  by  Leidy  in  iS5r>.  1SS2.  and  i8<>8 
^       „  ^  .     ,.  »        .  J   from  the  stomach  of  ct)rmorant.  white  and 

Fig.  82g      Contracoecum  spiculigerum      Anterior  end   j  pelicans,  and  water  turkev,      \l,r^A., 

and  tail  of  male.     Magnified.     (After  Stossich.)         t     n  k  ta 

73  (72)     With  circle  of  spines  on  tail. 

Contracoecum  adunca  (Rudolj^hi)  1809. 

Male  30  to  31  mm.,  female  .^o  to  65  mm.  long.     Weak  lateral 
cuticular  membranes.     Linstow  says  interlabia  are  present.     hM.ph- 
agus  with  cecum  extending  posteriad  o.h  mm.,  and  intestme  with 
similar  extension  0.41  mm.  anteriad.     Tail  of  male  sh..rt.  conical 
coiled;   27  preanal  papillae  in  simple  series,  and  3  postanals.      I  ip  ol 
tail  ringed  with  tine  spines.      Spicules  long  (1.92  mm.).  c«jual,  some- 
what enlarged  at  proximal  end.  ,     ,     .       «  1       • 
In   intestine   and    pyloric   appendages   of   shad       I  ^"^V"^-'"'** 
Fig.  830.     Coniraoecum    Maine      Probably  of  marine  origin  though  taken  from  tish  m  ircsn 
adunca.      Dorsal    view    of    „„f_-.  ' 
upper  lip.  Magnified.  (After    wai:er. 
von  Linstow.) 


534 


FRESH-WATER   BIOLOGY 


74  (71)     Without  papillae  on  tail  of  male  and  with  single  intestinal  cecum. 

Hysterothylacium  Ward  and  Magath. 

Anterior  end  with  narrow  lateral  wings.  Lips  three,  not  prominent.  Esophagus  long, 
slender,  with  terminal  bulb.  Intestine  with  short  simple  cecum  at  anterior  end,  extending 
posteriad.     Males  with  two  equal  spicules.     Females  unknown. 

Type  species.    .    .     Hysterothylacium  hrachyuriim  Ward  and  Magath. 

Male  32  mm.  long;  maximum  width  0.66  mm.  Lateral  ala  one-quarter  width  of  body. 
Esophagus  3.1  mm.  long,  o.i  to  0.13  mm.  broad;  bulb  with  three  teeth;  cecum  0.94  by  0.08 
mm.     Spicules  0.72  mm.  long,  0.045  mm.  wide.     Pyriform  sperm  vesicle  prominent. 

In  stomach  of  black  bass;  Lake  St.  Clair. 

75  (7)     Esophagus  slender,  non-muscular;    lumen  a  capillary  chitinous  tube 

traversing  a  row  of  granular  cells. 

Suborder  Trichosyringata   .    .      76 

76  (77)     Anus  lacking;    alimentary  canal  non-functional  in  adult.     Adults 

free  living Family  Mermithidae  Braun  1883. 

These  forms  are  only  distantly  related  to  aquatic  biology  as  the  adults  occur  free  in  soil,  or 
less  often  on  plants  as  the  famous  "cabbage-snake."  The  early  hfe  is  spent  as  a  parasite  in 
the  body  cavity  of  some  insect  or  crustacean  from  which  they  occasionally  escape  into  an 
apple  or  other  peculiar  environment. 

They  are  very  slender,  greatly  elongated,  threadworms  in  which  the  ahmentary  canal  is 
transformed  in  the  adult  into  a  fat  body.  The  eggs  are  spherical,  with  two  peculiar  stalked, 
tasselated  appendages  at  the  poles.  The  adults  are  fully  considered  in  the  chapter  on  Free- 
living  Nematodes  (consult  page  503). 

The  Mermithidae  are  often  confused  with  Gordiacea  to  which  they  bear  a  certain  superficial 
resemblance.     The  differences  are  discussed  later  (page  535). 

77  (76)     Alimentary   canal   complete  and  functional.     Adults  always  para- 

sitic.   .    .     Family  Trichinellidae  Stiles  and  Crane  1910. 

Esophagus  formed  by  capillary  tube  traversing  chain  of  cells.  Anterior  region  of  body 
slender,  posterior  region  swollen.  Anus  terminal.  Male  with  single  spicule  (or  none?). 
Female  with  one  ovary.     Vulva  near  junction  of  anterior  and  posterior  body  regions. 

The  well  known  human  parasite,  Trichinella  spiralis,  commonly  called  trichina,  is  included 
in  this  group  though  in  another  subfamily  from  the  following. 

Subfamily  Trichurinae  Ransom  191 1    .    .     78 

78  (79)     Anterior  region  of  body  very  slender  and  much  longer  than  posterior 

region Trichuris  Roederer  and  Wagler  1761. 

In  North  American  aquatic  host. 

Trichuris  opaca  Barker  and  Noyes  191 5. 


Male  22  to  28  mm.  long;  anterior  region  13  to  19  mm. 
long,  0.06  to  o.oS  mm.  thick;  posterior  region  7  to  9  mm. 
long,  0.14  to  0.16  mm.  thick.  Spicule  2  mm.  long;  sheath 
0.18  mm.  long,  0.07  mm.  in  diameter. 

Female  22  to  30  mm.  long;  anterior  region  18  to  19 
mm.  by  0.06  to  0.07  mm.;  posterior  region  10  to  11  mm. 
by  0.23  to  0.25  mm.  Vulva  between  first  and  second  an- 
terior eleventh  of  posterior  region. 

Duodenum  of  muskrat.     Nebraska. 


Fig.  831.     Trichuris  opaca.      Posterior  end  of  male.      X  20. 
(Atter  Barker ) 


/m  m. 


PARASITIC   ROUNDWORMS  5^j; 

79  (78)     Anterior  region  not  much  slenderer  than  posterior  region  and  equal 

to  it  in  length  or  shorter Ca  pillar  id  Zv^lt  i>kx^. 

In  North  American  aquatic  host. 

Capillaria  ransomia  Barker  and  Xoyes  1915. 

Length  19  to  20  mm.;  breadth  of  male  o.oi  to  0.03  mm.,  of  female  0.02.'  to  0065  mm 
Bursa  of  male  small,  with  2  lateral  lobes.  Spicule  1.36  mm.  Ions,  0.007  mm.  bruad.  Vulva 
in  anterior  fourth  of  body.     Eggs  0.05  by  0.02  mm.  with  prominent  plugs. 

Duodenum  of  muskrat.     Nebraska. 


GORDIACEA 

The  Gordiacea  are  familiar  to  all  as  the  hairworm.s  or  "hair 
snakes"  frequently  found  in  the  country  in  drinking'  trou-^dis. 
springs,  brooks,  ponds,  or  indeed  any  body  of  water,  lar<^c  or  sfikiII. 
In  general  appearance  these  worms  are  very  much  like  the  nema- 
todes but  the  more  fully  their  internal  organization  has  become 
known  by  study  the  less  they  seem  to  resemble  that  group  in  de- 
tail, and  the  present  tendency  is  to  separate  them  as  an  independ- 
ent class.     Some  even  make  the  group  an  independent  phylum. 

The  body  resembles  a  bit  of  fine  wire  or  a  tough  root  libir  in 
appearance.  It  is  nearly  cylindrical,  usually  with  blunt  or  rounded 
anterior  end  and  a  caudal  extremity  of  modified  form,  often  swollen, 
lobed,  or  curled  in  a  loose  spiral. 

Certain  nematodes,  especially  Mermis  which  occurs  free  in  soil 
in  the  adult  stage,  resemble  the  hairworms  so  much  externally  that 
they  are  often  confused  with  them.  The  two  ditTcr  greatly  in 
internal  structure  and  somewhat  in  less  important  external  lea- 
tures;  but  by  their  pointed  anterior  end,  tapering  body,  and 
smooth,  finely  striated  and  somewhat  transparent  cuticula  the 
true  nematodes  are  usually  easily  distinguished  from  the  Ciordi- 
acea  with  blunt  head,  cylindrical  body,  and  roughened,  ordinarily 
also  papillate,  irregular  cuticula.  Mermis  in  particular  is  most 
readily  distinguished  by  the  pointed  posterior  end  and  when  alive 
by  the  active  anterior  region. 

In  the  Gordiacea  a  single  orifice  serves  as  the  common  outlet  of 
the  reproductive  and  alimentary  systems,  alike  in  both  sexes;  it  is 
located  near  the  posterior  end.  There  are  no  lateral  lines  and  the 
male  never  possesses  spicules. 

These  animals  are  so  opaque  that  little  or  no  internal  structure 
is  visible  on  examination  either  with  the  naked  eye  or  with  the 


536 


FRESH-WATER    BIOLOGY 


aid  of  a  microscope.  The  most  of  the  features  on  which  classifi- 
cation is  based  are  external  and  must  be  regarded  as  arbitrary 
and  trivial.  The  internal  structure  can  be  studied  only  with 
difficulty  by  complicated  technic  and  may  be  passed  here  without 
description. 

In  one  respect  the  Gordiacea  differ  from  the  parasitic  worms 
heretofore  considered:  the  adults  are  free-Hving  and  it  is  only  the 
young  stages  which  carry  on  a  parasitic  existence.  Probably  the 
free  aquatic  stage  is  merely  a  reproductive  period,  even  though  it 
is  prolonged  for  several  weeks  or  months.  The  worm  when  loaded 
with  eggs  is  round  and  plump,  but  the  spent  female  is  often  wrinkled 
and  flattened. 

Gordius  deposits  its  eggs  in  a  long  white  or  grayish  cord  which 
may  be  several  feet  long  and  apparently  many  times  the  bulk  of 
the  female  worm.  In  some  species  the  cord  breaks  up  into  shorter 
pieces.  The  vv^orms  are  often  observed  in  knotted  masses,  con- 
sisting of  two  or  more  worms  coiled  together.  In  some  cases  at 
least  they  are  coiled  about  the  egg  strings  and  remain  for  many 
days  in  this  position,  thus  in  a  sense  exercising  protection  over  the 
developing  embryos.  It  is  commonly  said  that  the  Gordiacea  de- 
posit their  eggs  in  brooks  or  other  running  water,  but  I  have  found 
some  species  in  abundance  on  water  plants  and  in  knotted  masses 

along  the  shore  of  Lake  St.  Clair,  Lake 
Erie,  and  Lake  Michigan.  Rarely  I 
have  seen  a  conspicuous  windrow  of 
adult  worms  and  egg  masses  extending 
for  some  distance  along  the  water's 
margin  of  an  inland  lake  and  probably 
washed  up  there  by  wave  action.  The 
minute  embryo  (Fig.  832)  which  hatches 
from  these  eggs  after  a  brief  period 
possesses  a  conspicuous  proboscis  and 
set  of  hooks  at  the  anterior  end.  By 
this  powerful  boring  apparatus  the  em- 
bryo forces  its  way  into  some  aquatic 
insect,  often  the  ma3^y  larva.  Further  changes  are  not  known 
except  that  in  the  body  cavity  of  various  adult  insects,  such  as 


Fig.  832.  Enibroyo  of  Paragordius 
varius  with  extended  proboscis,  X  looo. 
(After  Montgomery.) 


PARASITIC    ROUXDWOkMS  -,- 

beetles,  grasshoppers,  and  crickets,  are  found  well-^rown  and  iKMrl\- 
mature  larvae  of  the  hairworms.  On  escaping  into  the  water  from 
these  insects,  the  worms  become  sexually  mature  and  the  lyclc  is 
completed.  Villot  denied  the  necessity  of  an  intermediate  hcjst, 
but  others  have  held  that  the  hairworm  undergoes  two  and  pt-r 
haps  more  changes  of  host  during  the  complete  life  cycle.  When 
the  worm  escapes  from  an  insect  it  swims  about  actively  in  the 
water  but  even  where  the  capillary  esophagus  is  not  closed  so  that 
the  taking  of  food  is  absolutely  precluded,  the  worms  i)rol)ahly 
take  no  nourishment  in  the  aquatic  stage. 

Hairworms  in  an  early  or  late  larval  condition  have  been  re- 
corded as  parasites  not  only  in  the  insects  cited  above  but  also  less 
frequently  in  spiders,  oligochaetes  [Lumbriculus) ,  snails,  and  rarely 
in  distomes,  fish,  and  amphibians  (?).  In  the  last  three  t>pes  their 
presence  is  no  doubt  purely  accidental.  Adults  in  the  free-living 
stage  have  been  reported  a  number  of  times  as  human  parasites. 
Here  their  presence  is  also  fortuitous  and  is  doubtless  due  to  the  ac- 
cidental swallowing  of  specimens  in  water  or  in  food  eaten  uncooked. 

The  number  of  species  of  Gordiacea  in  North  America  is  not 
large  and  thanks  to  the  splendid  work  of  Montgomery  the  group 
is  well  known.  The  following  synopsis  is  based  on  his  papers. 
The  range  of  species  has  been  somewhat  increased  b\'  my  own  col- 
lections from  regions  not  represented  in  his  records.  I  have  also 
been  given  valuable  unpubHshed  data  by  H.  G.  May.  Even  yet 
there  are  no  records  from  the  southeastern  or  northwestern  United 
States  and  only  a  single  record  each  from  Canada  and  Alaska. 
The  absence  of  records  from  any  region  indicates  lack  of  study  in 
that  region  rather  than  scarcity  of  material. 

Only  three  well-marked  genera  are  known:  Gordius,  Ghordodcs, 
and  Paragordius,  all  of  which  are  represented  in  this  continent. 

KEY  TO   NORTH   AMERICAN   GORDIACEA 

I  (8)     Anterior  region  distinctly  attenuated,  coming  nearly  to  a  point ;  usu- 
ally lighter  than  the  rest  of  the  body  and  without  a  dark 

ring Clwrdodcs  Crcplin  1847    .    .      2 

Caudal  end  simple,  not  lobed;  in  female  somewhat  enlarged.  External  surface  complicatctl; 
several  types  of  areoles  present.  , 

Because  the  males  and  females  are  distinctly  unlike  in  external  appearance  thoy  come  oui  .1^ 
separate  groups  in  the  key.  The  cross  references  carry  the  student  back  to  the  other  >ex  n 
each  case.  It  will  be  noted  that  the  key  Une  which  ultimately  determmes  the  sik-ocs  is  usually 
alike  in  both  sexes. 


538 


FRESH-WATER   BIOLOGY 


2  (5)     Caudal  end  slenderer  than  preceding  region  of  body,  with  tendency  to 
roll  into  spiral  form (Males  of  Chordodes)   .    .     3 

The  cloacal  orifice  is  ventro-median  and  the  ventral  surface  possesses  a  shallow  furrow  or 
groove  from  this  orifice  to  the  posterior  extremity. 


(4)     Cuticular  areoles  longer  than  high;    small  circular  pits  upon  and  be- 
tween them.   .    .     Chordodes  occidentalis  Montgomery  1898. 

For  female  of  this  species  consult  6  in  this  key. 

Male  up  to  255  mm.  long,  1.5  mm.  broad.  Color  light  brown  to 
black;  tip  of  head  yellowish  white.  A  western  species;  Montana, 
Wyoming,  CaHfomia,  Arizona,  Texas,  Mexico. 

An  Acridiid  is  known  to  serve  as  host  for  this  species. 


Fig.  833. 


Head  and  surface  areoles  of  Chordodes  occidentalis  J  .     Highly 
magnified.     (After  Montgomery.) 


4  (3)     Cuticular  areoles  higher  than  long. 

Chordodes  morgani  Montgomery  1898. 

For  female  of  this  species  consult  7  in  this  key. 

Male  64  to  220  mm.  long.  Color  dull  chocolate  brown,  except  anterior  end  which  is  always 
white.  Papillae  of  several  types;  the  most  regular  conical  with  short  spine,  and  the  highest 
papillae  with  a  few  spines  on  the  summit  of  each  being  typical. 

The  species  manifests  a  high  degree  of  individual  and  sexual  variation.  Recorded  from 
Pennsylvania,  Maryland,  Michigan,  Ohio,  Florida,  Iowa,  and  Nebraska.  C.  puerilis,  origi- 
nally described  from  two  males,  belongs  here. 

A  Blattid  is  known  to  serve  as  host  for  this  species. 


.'^HMXV^AvUvHV^ 


■^'^--''^--A      M^    fui^ 


Fig.  834.  Cuticula  of  Chordodes  morgani  9 
in  transverse  section.  Highly  magnified.  (After 
Montgomery.) 


Fig.  835.  Cuticula  of  Chordodes  morgani 
J  in  transverse  section.  Highly  magnified. 
(After  Montgomery.) 


5  (2)     Caudal  end  swollen,   somewhat  knob-shaped;    also  marked  off  by  a 
slight    constriction.      No    tendency   to    roll   into    a    spiral. 

(Females  of  Chordodes)   .    .     6 

The  females  of  Gordius,  which  may  easily  be  confused  with  these,  never  have  more  than  a 
sHght  swelling  at  the  caudal  end  and  this  is  not  marked  off  by  a  constriction. 


(7)     Cuticular  areoles  longer  than  high;    small  circular  pits  upon  and  be- 
tween them    .    .       Chordodes  occidentalis  Montgomery  1898. 


For  male  and  range  of  this  species  consult  3  in  this  key. 
Anterior  region  much  attenuated;   head  pointed.     Areoles  low. 
darker  neck  ring  and  black  mouth  spot. 


Color  yellowish  brown  with 


7  (6)     Cuticular  areoles  higher  than  long. 

Chordodes  morgani  Montgomery  1898. 

For  male  and  range  of  this  species  consult  4  in  this  key.  The  variable  papillae  are  also 
noted  there. 

Female  up  to  222  mm.  long.  In  the  largest  females  the  cuticula  in  surface  view  is  like  that 
of  the  males,  except  that  the  large  papillae  are  less  numerous.  Color  averages  lighter  than  in 
the  male. 


PARASITIC   ROUNDWORMS 


539 


«  (i)     Anterior  region  very  slightly  or  not  at  all  attenuated.     Tir,  white  usu-illv 
followed  by  a  distinct  dark  ring '       '    ' 

Caudal  end  lobed;  in  feniale  if  not  lobed  then  of  uniform  caliber  with  Ixxly  or  sliKhily  en- 
larged, but  not  set  oflf  by  a  distinct  constriction.  MiKnii>  cn- 

9  (lo)     Anterior   region   slightly   attenuated,   tip   obliquely   truncate-    dark 
ring  very  broad Paragordius  Camerano  iSg;. 

Caudal  end  trilobed  in  female  and  only  bilobed  in  male.  All  males  of  Gordius  also  have  the 
caudal  end  bilobed. 

Montgomery  rightly  emphasized  the  absence  of  cloacal  musculature  in  the  male  and  the 
exceedingly  long  cloaca  in  the  female  as  most  significant  generic  features  to  which  the  taudaJ 
lobes  were  subordinate  in  value.     For  mere  diagnostic  purposes  the  latter  are  convenient. 

Only  species  in  North  America.  .    .     Paragordiiis  varius  ''Leidy)  185 1. 

Males  more  slender  and  considerably  longer  than  females;  up  to  350  mm.  lonR.  o  9  mm 
wide;   female  up  to  290  mm.  long,  2  mm.  wide. 

The  long  trilobed  tail  of  the  female,  the  long  cylindrical  caudal  lobes  in  the  male,  the  obliquely 
truncated  head,  and  the  usually  very  dark-colored  ring  around  the  head  make  its  identification 
easy. 

Montgomery  found  the  larva  only  in  Achaeta  abbreviala  (Gryllus  assimilis).  Found  by 
Minnie  E.  Watson  in  the  same  host  at  Urbana,  Illinois,  and  by  H.  G.  May  in  the  same  host 
and  also  in  Nemobius  Jasciatus  at  Douglas  Lake,  Michigan. 

From  New  England  to  New  York,  Virginia  (and  southward?;  it  is  reported  from  (;uatemab): 
also  Kansas  and  CaUfornia.  I  have  specimens  from  Lake  Erie,  Lake  St.  Clair,  Lake 
Michigan,  and  Nebraska. 


e 


Fig.  836.  Paragordius  varius.  a,  lateral  aspect  of  head.  X  25.  (Originat)  ft.  vfnlr.il  view  of  uil. 
X  25.  (Original.)  c,  dorsal  view  of  tail  (female).  X  25.  (After  Stiles.)  «/,  surface  view  of  cuticulm  in 
male  and  e,  in  female.     Highly  magnified.     (After  Montgomery.) 

10  (9)     Anterior  region  not  attenuated,  tip  usually  rounded. 

Gordius  lAwnwcns  \-]S^       •      ^^ 
Caudal  end  bilobed  in  male;   simple,  not  enlarged  in  female. 

11(22)     Caudal  end  bilobed,  spirally  inroUed.    .    (Males  of  (TorJ;;/^)    .    .      i: 


12  (13)     Arcuate  cuticular  ridge  anterior  and  lateral  to  cloacal  p<irc. 

Gordius  alasccnsis  Montgomery  kx)?. 
Female  not  known;   male   120  mm.  lonp.  slen- 
der,  cylindrical.     Head  roundi-tl.     Cau<l.il  lol>os 
without  hairs  or  spicules.     .Aretiles  irreRular.  in- 
terconnected.     Color  dark   brown    with   darker 
[Oj'^J       neck  ring. 

Fig  8?7.  Gordius  ulufcrnsis.  CuticuUr  arrolr*. 
lateral  and  ventral  views  of  tail.  Magnifictl.  l-Mtcr 
Montgomer>'.) 


S40 


FRESH-WATER    BIOLOGY 


13(12)     No  cuticular  ridge  anterior  and  lateral  to  cloacal  pore 14 

14  (15)     Behind  cloacal  pore  sharp  V-shaped  ridge. 

Gordius  villoti  Rosa  1882. 

For  female  of  this  species  consult  23  in  this  key. 
This  species  was  described  by  Montgomery  as  G. 
aquaticus.      Several   subspecies   have   been  distin- 
guished.    In  the  typical  form  the  cuticula  is  marked 
with  large  light  spots. 

Male  up  to  655  mm.  long,  1.3  mm.  broad,  equal 
in  diameter  throughout;  both  ends  obtuse;  no  true 
areoles  present. 

From  Canada,  New  England,  New  York  to  South 

Carolina;  westward  to  South  Dakota,  Montana,  and 

California;   south  to  Oklahoma,  Texas  and  Mexico. 

1  iG.  838.     Gordius  villoti  $  ;  ventral  view  of       Various  Acridiidae  serve  as  hosts  for  this  species. 

anterior  and  posterior  ends  of  body.    Magnified.  Also  found  in  Locustidae  by  H.  G.  May. 

(After  Montgomery.) 

15  (14)     Cuticula  behind  cloacal  pore  without  sharp,  V-shaped  ridge.  .    .      16 

Paragordius  varius  which  miglit  be  confused  here  is  readily  distinguishable  by  the  trun- 
cated anterior  end. 

16  (17)     On  each  side  of  cloacal  pore  a  longitudinal  Hne  of  hairs. 

^-N  Gordius  lineatus  Leidy  1851. 


For  female  of  this  species  consult  28  in  this  key. 
Male  up  to  278  mm.  long,  0.6  mm.  broad;  very  slender.     Pale 
yellow  or  buff  in  color;   areoles  small.      Perhaps  only  a  young 
form  of  G.  villoti.     Most  of  the  specimens  taken  from  springs. 
Fig.  839-  Gordius  lineatus  $  ;    j^g^  York,  Pennsylvania,  Maryland,  Michigan, 
anterior  and  posterior  ends,  and 
surface  view  of  cuticula.     Mag- 
aified.     (After  Montgomery.) 

17  (16)     No  line  of  hairs  along  side  of  cloacal  pore;  head  not  obliquely  trun- 

cated      18 

18  (21)     Conical  spicules  behind  cloacal  aperture 19 

19  (20)     Caudal  lobes  short,  thick,  and  nearly  conical. 

Gordius  densareolatus  Montgomery  1898. 


For  female  of  this  species  consult  29  in  this  key. 

Male  up  to  290  mm.  long,  i  .1  mm.  broad.  Body  robust.  Conical  spines 
on  ventral  surface  of  caudal  lobes.  Color  deep  chocolate,  with  black 
ring  about  cloacal  aperture.     Wyoming,  Montana,  California. 


Fig.  840.      Gordius  densareolatus  $  .      \'entral  view  of  posterior  end. 
(After  Montgomery.) 


Magnified. 


20  (19)     Caudal  lobes  nearly  cylindrical. 

Gordius  longareolatus  Montgomery  1898. 

Female  of  this  species  unknown. 
Male  115  mm.  long,  0.5  mm.  broad.     Longitudi- 
nally arranged  elongate  areoles  characteristic  and 
^^  =  ==^^        of  rounded-conical  form  without  median  groove. 
'=^^^'^.^='       No  hairs  between  areoles.     Color  deep  olive  brown; 
'^  •=-^-  ^=        tip  of  head  white.     California. 

Fig.  841.  Gordius  longareolatus  $  ;  head,  tail  in  ven- 
tral aspect,  and  cuticular  areoles.  Magnified.  (After 
Montgomery.) 


PARASITIC   ROUNDWORMS 

21  (i8)     No   conical  spicules  behind  cloacal  aperture;    caudal  lobes  cylin- 
^^^^^^ Gordius  pliilyccp/uilus  Monigomcry  iii()». 

For  female  of  this  spcdcs  n.Msult  ^o  in  tlii>  key 
Male  up  to  216  mm.  Iomk,  i  mm.  broad.  The  flattened 
anterior  end  is  characteristic,  l.ut  MontRomery  fuund  one 
specimen  apparently  of  G.  densarrolalus  with  this  feature  and 
could  explain  it  only  as  a  hybrid  form.  Canada.  iVnnsvl- 
vania,  and  Guatemala.  ' 


Fig.  842.      Gordius    plalycephalus    t 
aspect.      Magnified.      (Aft 


^  ,    head  and   ui!    in  vcntr&I 
ter    Montgomery.) 


2  2  (11)     Caudal  end  straight,  not  enlarged  nor  lobed. 

(Females  of  Gordius)    .    .     23 
Compare  5  in  key. 

2;^  (24)     No  elevated  cuticular  areoles  on  surface  of  body. 

Gordius  villoti  Rosa  1882. 
For  male  and  range  of  this  species  consult  14  in  this  key. 
.  Largest  female  705  mm.  long,  1.9  mm.  broad.  One  variety  {G.  villoti  diffifilis  .Mont- 
gomery) has  cuticular  areoles  at  the  ends  of  the  body  only.  The  other  varieties  arc  like  the 
males  marked  with  hght  spots  or  plain.  Montgomery  found  some  points  of  difference  from 
the  European  type,  and  the  American  form  may  prove  on  further  study  to  be  a  sep.-irale 
species. 

24  (23)     Elevated  cuticular  areoles  cover  the  entire  surface  of  the  body.      25 

25  (26)     Paired  dark  stripes  occur  in  median  lines. 

Gordius  leidyi  Montgomery  i8q8. 

Male  of  this  species  is  unknown.  Female 
295  mm.  long,  1.5  mm.  broad.  .Sharply  dis- 
tinguished from  all  other  species  in  the  genus 
by  the  peculiar  truncated  form  of  the  jxtstcrior 
end  and  the  two  narrow  parallel  stripes  of 
intense  reddish  brown  in  the  median  line  of 
the  dorsal  groove. 

In  the  Leidy  collection;  source  unknown. 

Fig.  843.     Gordius  leidyi  9  ;  head  and  tail  in  (lor- 
sal  aspect.     Magnified,     (.^fter  Mont^jomco') 

26  (25)     Dark  stripes  in  median  lines  arc  lacking ^7 

The  tmknown  female  of  Gordius  longareolatus  probably  falls  here. 

27  (30)     Areoles  not  elongated  in  long  axis  of  body;  head  not  tlailened.  .     i8 

28  (29)     Areoles  close-set,  tending  to  produce  longitudinal  ridges. 

Gordius  lineatus  Leidy  ii^5i. 
For  male  and  range  of  this  species  consult  16  in  this  key.  .    «      1 

Female  up  to  283  mm.  long,  0.8  mm.  broad;    Hke  male  very  slender.     Deeper  buff  color  as 

against  the  pale,  transparent  yellowish  white  of  the  male.     In  the  female  the  cloacal  onticc  u 

surrounded  by  a  narrow  reddish-brown  ring. 

29  (28)     Areoles  more  or  less  confluent,  tending  lo  produce  transverse  rows; 

head  usually  cylindrical.  ,    ^ 

Gordius  dcnsareoliilus  yUmif^omvry  iSgS. 

For  male  and  range  of  this  species  consult  19  in  this  key.  ....       ,  ,,        .1     u^u* 

Female  up  to  3Q5  mm.  long,  1.7  mm.  broad.     Body  roI)ust.     Head  white   followi-d  by  I  Rht 
buff  ring  and  broad  reddish  brown  ring;  cloacal  pore  surrounded  l>y  thm  black  ring  and  "r.ua«  r 
circular  reddish  brown  area;   body  generally  chocolate  or  yelU)wish  brown,     t  l.vu.ii   ■■- 
in  a  ventral  depression. 


o-PA 


542  FRESH-WATER    BIOLOGY 

30  (27)     Areoles  not  elongated,  usually  separated;    head  usually  flattened; 

interareolar  groups  of  fine  hairs. 
Gordius  platycephalus 

Montgomery  1898. 

""^oc^j"  Yor  male  and  range  of  this  species  cbnsult  21 

in  this  key.  Female  up  to  335  mm.  long,  1.4 
mm.  broad.  Posterior  end  slightly  enlarged. 
Color  brown;  tip  of  head  lighter;  dark  ring 
around  neck. 

Fig.  844.  Gordius  platycephalus  ^  ;  head  in  dorsal 
aspect,  tail  in  ventral  aspect,  and  surface  view  of 
cuticula.     Magnified.     (After  Montgomery.) 


ACAN  THO  CEPHALA 

The  Acanthocephala  or  proboscis  roundworms  constitute  a  most 
remarkable  group  both  in  the  extreme  adaptation  to  the  parasitic 
habit  which  they  manifest  and  in  the  unique  structure  which  pre- 
sents Httle  or  no  parallel  to  any  other  type  of  animal.  Most  of 
them  are  small,  measuring  only  a  few  millimeters  in  length  although 
the  common  parasite  of  the  pig,  Gigantorhynckus  hirudinaceus 
(commonly  called  Echinorhynchus  gigas),  reaches  a  length  of  15 
cm.  in  the  male  and  30  to  50  cm.  in  the  female. 

In  form  they  are  elongate,  roughly  cyUndrical,  or  spindle-shaped 
but  with  several  distinct  regions  that  give  the  body  an  irregular 
form.  These  regions  are  a  retractile  proboscis  armed  with  hooks, 
a  neck,  and  a  body  proper.  When  examined  living  the  body  is 
often  flattened  or  slightly  bent,  and  displays  a  surface  irregularly 
roughened  or  marked  by  transverse  ridges  of  varying  size.  When 
removed  to  normal  salt  solution  or  preserved  in  other  fluids,  they 
tend  to  assume  a  smooth  rounded  form,  sometimes  with  slight 
regular  annulations  that  suggest  segmentation  but  in  fact  do  not 
extend  beyond  the  dermal  layer. 

At  the  anterior  end  the  proboscis,  which  is  retractile  and  in  pre- 
served specimens  often  partly  or  wholly  withdrawn  into  the  body, 
presents  a  variable  form  being  in  various  species  cyHndrical,  glo- 
bose, filiform,  spindle-shaped,  and  even  more  complex;  it  may  be 
long  or  short,  straight,  oblique,  or  at  right  angles  to  the  long  axis. 
The  particular  form  is  characteristic  of  the  genus  or  species  and  useful 
in  diagnosis.     The  proboscis  bears  always  a  considerable  number  of 


PARASITIC   ROUNDWORMS  -43 

recurved  hooks  which  are  arranged  in  rows.  One  can  distinguish 
both  longitudinal  and  circular  rows  and  as  the  hooks  alternate 
they  form  a  quincunx  pattern.  The  number,  form,  and  arrange- 
ment of  the  hooks  are  again  diagnostic  features.  Usually  the  hooks 
are  strongly  recurved  but  they  may  be  almost  straight  and  often 
the  form  varies  from  tip  to  base  of  the  proboscis.  The  form  of  the 
root  is  also  subject  to  variation  in  different  species.  In  a  few  cases 
the  hooks  differ  on  the  dorsal  and  ventral  sides  of  the  proboscis. 

In  most  species  a  neck  intervenes  between  the  proboscis  and  the 
body  proper.  It  is  nearly  always  unarmed  and  usually  short.  At 
times  it  is  externally  very  sharply  marked  off  from  the  \hhW  or 
again  difficult  to  distinguish.  Internally  a  cuticular  fold  or  >rp- 
tum  divides  the  hypoderm  of  the  proboscis  and  neck  completely 
from  that  layer  in  the  body.  The  circular  insertion  of  a  retractor 
muscle  at  this  point  also  separates  these  regions  from  each  other. 

The  body  proper  forms  the  major  part  of  the  animal.  It  is 
usually  unarmed  but  may  bear  small  spines  of  definite  form  and 
arrangement  on  some  portion  of  the  external  surface. 

The  body  wall  has  on  the  exterior  a  thin  cuticula  which  is  not 
conspicuous  as  in  nematodes.  The  subjacent  hypoderm  possesses 
in  one  group  a  few  very  large  and  prominent  nuclei  which  were 
seen  by  early  investigators  though  their  true  nature  was  not  divined. 
These  nuclei  usually  show  as  sweUings  or  prominences  on  the  sur- 
face. In  most  Acanthocephala,  however,  the  hypoderm  has  many 
small  nuclei  which  cannot  be  seen  on  casual  observation.  Two 
elongate  organs,  the  lemnisci,  are  projections  of  the  h>poderm 
posteriad  into  the  body  cavity.  They  originate  at  the  line  be- 
tween neck  and  body  proper  and  vary  in  size  and  form  in  dilTerent 
species.  Their  function  is  unknown.  The  body  wall  contains  a 
system  of  lacunae  which  is  conspicuous  both  in  living  and  pre- 
served specimens  as  two  longitudinal  vessels  with  smaller  anasto- 
moses usually  numerous  and  irregular. 

The  proboscis  sheath,  usually  a  closed  muscular  sac.  is  attached 
at  the  base  of  the  proboscis,  or  rarely  inside  that  organ.  The  j>ro- 
boscis  can  be  inverted  into  the  sheath.  The  brain  lies  within  thr 
sheath  concealed  between  the  retractor  muscle-.  Its  precise  loca- 
tion may  be  determined  by  the  retinacula,  a  pair  of  nerve  cords 


544  FRESH-WATER    BIOLOGY 

passing  from  it  directly  through  the  sheath  and  obhquely  to  the 
body  wall. 

No  trace  of  an  alimentary  system  has  been  found  in  the  adult 
or  in  any  stage  of  development.  Nutrition  is  thus  provided  for 
entirely  by  absorption. 

The  sexes  are  separate  in  all  cases.  The  genital  pore  in  both  is 
at  or  very  near  the  posterior  tip.  The  male  is  smaller  and  more 
slender  than  the  female  and  often  distinguished  externally  by  a 
bell-shaped  bursa  that  surrounds  the  genital  pore.  This  is  a  mus- 
cular fold  which  is  held  within  the  body  except  at  coition  and 
may  be  forced  out  by  the  contraction  accompanying  the  preser- 
vation of  the  specimen.  Two  oval  testes  He  usually  in  the  center 
of  the  body  one  behind  the  other.  Farther  back  is  a  group  usu- 
ally of  a  few  large  cells,  the  cement  glands. 


Fig.  844.  Acanthocephalus  ranae.  Entire  female,  br,  brain;  bu,  copulatory  bursa;  c?  cement  glands; 
cr,  cement  receptacle;  inr,  invertor  of  neck  region;  /,  lemniscus;  pr,  proboscis  receptacle;  /»/,  postenor 
testis;  re,  retinacula;  rpr,  retractors  of  proboscis  receptacle;  si,  suspensory  ligament;  ta,  anterior  testis. 
X  30.     (After  Van  Cleave.) 

In  the  female  a  Hgament  extends  through  the  center  of  the  body 
cavity  from  end  to  end.  The  ovary,  which  is  present  only  in  the 
larval  stage,  produces  great  numbers  of  ova  that  later,  surrounded 
by  a  heavy  covering  of  three  distinct  membranes,  float  free  in  the 
body  cavity.  A  complicated  apparatus  known  as  the  uterine  bell, 
located  in  the  body  cavity  near  the  posterior  end,  performs  rhyth- 
mic contractions  that  discharge  from  the  body  all  well-developed 
embryos  and  return  to  the  body  cavity  all  that  are  not  sufficiently 
matured. 

The  Hfe  history  of  Acanthocephala  is  almost  unknown.  Those 
parasitic  in  terrestrial  hosts  develop  probably  without  any  rela- 
tion to  the  aquatic  fauna  as  Gigantorhynchus  hirudinaceus  of  the 


PARASITIC   ROUNDWORMS 


545 


pig  finds  its  intermediate  host  in  terrestrial  beetle  larvae.  Of 
forms  from  aquatic  hosts  it  is  inferred  that  the  ripe  embryos  dis- 
charged into  the  water  with  the  feces  of  the  host  attain  by  chance 
a  suitable  intermediate  host  which  is  probably  a  crustacean  or  in- 
sect and  in  that  develop  to  the  end  of  the  larval  stage.  When 
this  intermediate  host  is  eaten  by  the  final  host  the  parasite  reaches 
the  place  in  which  it  can  complete  its  development. 

Almost  no  records  have  been  pubUshed  of  Acanthocephala  from 
North  American  fresh-water  hosts.  My  own  collections  and  re- 
cent papers  by  Van  Cleave,  to  whom  I  am  indebted  also  for  valu- 
able unpubUshed  data,  give  at  best  an  imperfect  survey  of  the 
field.  The  system  used,  which  follows  in  the  main  Llihe's  work,  is 
also  confessedly  artificial  and  incomplete. 


KEY  TO  NORTH  AMERICAN  ACANTHOCEPHALA 

1  (lo)     In  hypoderm  and  lemnisci  only  a  few  giant  nuclei. 

Family  NEOECHiNORHYNCHmAK  Ward   . 

Primitive  Acanthocephala  with  hypoderm  consisting  of  a  syncytium  in  which  arc  six  giajil 
nuclei,  ordinarily  arranged  so  that  five  lie  in  the  mid-dorsal  line  and  one  in  the  mid- ventral. 
One  lemniscus  contains  two  giant  nuclei  and  the  other  only  one.  These  nuclei  are  usually 
conspicuous  on  external  examination. 

Proboscis  sheath  contains  only  a  single  layer  of  muscles.  Cement  gland  a  compact  maf s. 
Neck  lacking.  Muscles  weakly  developed.  Lacunar  system  with  simple  circular  connec- 
tions. 

2  (9)     Proboscis  globose,  or  nearly  so;  with  three  circles  of  hooks. 

Neoechinorhynchus  Stiles  and  Hassall  1005   .    .     3 

Proboscis  short,  globose,  with  few  hooks.  Hooks  of  anterior  row  much  larger  than  those  \j. 
center  and  basal  rows.     Cement  gland  with  eight  nuclei. 


3  (4)     Twelve  hooks  in  each  circle. 

Neoechinorhynchus  gracilisentis  (Van  Cleave)  IQI.^ 

Body  small,  tapering  slightly  toward  both  ends,  bent 
into  a  crescent.  Mature  females  1.7  to  4  mm.  lonff: 
maximum  width  0..5S  mm.  just  anterior  to  centi-r  of 
body.  Males  1.5  to  ,^  mm.  long,  ma.xinuim  l)rcadth  o.j 
mm.  Proboscis  slightly  longer  than  wide  w^ilh  con- 
striction between  second  and  third  row  of  hooks. 
Hooks  delicate,  in  anterior  rt)W  curved  15  ui  17^ 
long,  in  middle  row  1 2  to  1 5  M  long,  m  basal  row  nearly 
straight,  15  to  20/i  lonK-  Knibryos  spmdlo  shaped.  36 
to  40 M  long  by  10 m  broad  .     .    ,„•     •    u- 

.       .         In  intestine  and  ceca  of  hickory  shad;  llUnois  Kirer. 
Fig.  845.  Neoechinorhynchus  gracilisentis.  n^fr^Kf^r  tr^  \Ttv 
Proboscis.    X9S;    hooks  and  embryos,    X   OctoDer  lo  iua\  . 
310.     (After  Van  Cleave.) 


4  (3)     Six  hooks  in  each  circle. 


546  FRESH-WATER   BIOLOGY 

5  (8)     Terminal  hooks  over  go  (x  long.     Embryos  under  50  ju  long 6 


6  (7)     Body  8  to  32  mm.  long.     Embryos  very  small. 

N eoechinorhynchiis  emydis  (Leidy)  1852. 


Fig.  846.     Neoechinorhynchus  emydis. 
X  75;  hooks    and    embryos,     X  230. 
Cleave.) 


Proboscis, 
(After  Van 


Body  much  elongated,  cylindrical.     Female 

10  to  32  mm.  long,  0.7  mm.  in  maximum 
width.  Male  8  to  11  mm.  long  by  0.7  mm. 
broad.  Proboscis  globose,  0.175  mm.  long. 
Hooks  large,  in  anterior  row  strongly  recurved, 
95  to  103  /x  long,  in  middle  row  49  to  59  /x 
long,  in  basal  row  35  to  54  11  long,  nearly 
straight.     Embryos  very  small,  oval,  16  by 

11  fX. 

Originally  described  by  Leidy  from  the  in- 
testine of  various  species  of  Emys  from 
Pennsylvania  and  Maryland.  Frequent  in 
M alacoclemmys  geographicus  (Lesueur)  and 
Pseudemys  elegans  Max  from  the  lUinois 
River. 


7  (6)     Body  2  to  13  mm.  long.     Embryos  about  40  n  long. 

Neoechinorhynchus  tenellus  (Van  Cleave)  1913. 


Neoechinorhynchus    tenellus. 
75;    hooks     and     embrj-o, 


Body  small,  both  ends  curved  strongly  ventrad. 
Posterior  two-thirds  of  body  markedly  attenuated. 
Female  3.5  to  13  mm.  long,  0.6  mm.  in  maximum 
breadth;  males  2  to  8  mm.  long,  0.5  mm.  broad.  Pro- 
boscis nearly  cylindrical,  0.150  mm.  long  by  0.135  vara. 
wide.  Anterior  hooks  90  to  iio^u  long,  heavy;  middle 
hooks  38  /i  long;  basal  hooks  27  /x  long.  Embryos 
37  to  45  by  12  to  16  M- 

Intestine  of  Esox  lucius  L.  from  Lake  Marquette 
near  Bemidji,  Minnesota. 


X  230.     (After  Van  Cleave.) 


8  (5)     Terminal  hooks  usually  less  than  90  ix  long.    Embryos  over  50  m  long. 

Neoechinorhynchus  cylindratus  (Van  Cleave)  19 13. 


Fig.  848. 
X75 
Van  Cleave.) 


Large,  straight-bodied.  Female  10  to  15  mm. 
long,  0.7  mm.  in  maximum  width,  just  behind 
proboscis.  Male  4.5  to  8.5  mm.  long,  0.5  to  0.7 
mm.  in  maximum  breadth  near  anterior  end. 
Proboscis  slightly  broader  (0.172  mm.)  than 
long  (0.15  mm.).  Anterior  hooks  79  to  97  ^ 
long,  heavy,  strongly  recurved,  center  hooks 
37 /x  long,  basal  hooks  21  to  25 /x  long.  Em- 
bryos 49  to  51  )U  long  by  15  to  21  fx  broad. 

In  intestine  of  Micropterus  salamoides  (La- 
cep.).  Pelican  Lake,  Minnesota,  and  of  An- 
guilla  chrysypa,  Woods  Hole,  Massachusetts. 


PARASITIC   ROUNDWORMS 


547 


9  (2)     Proboscis  long. 


Numerous  irregular  circles  of  about  six  hooks  each. 

Tanaorhamphus  Ward. 

The  extreme  length  of  the  proboscis  and  the  larRc  number  of  hooks 
serve  to  contrast  this  with  the  previous  closely  related  genus  H.xAs 
in  the  anterior  row  are  not  conspicuously  larger  than  those  following. 
The  cement  gland  has  16  nuclei. 

Only  species  known. 

Tanaorhamphus  longirostris  (Van  Cleave)  igij. 

Body  robust,  posterior  end  flexed  slightly  ventrad.  Females 
average  6.2  mm.  long,  and  0.63  mm.  in  maximum  bn-adth  Males 
average  4  mni.  long,  and  0.47  mm.  in  ma.ximum  breadth,  i'roboscis 
cyhndrical  with  slight  constriction  one-third  distance  from  ba.se  to 
outer  end,  bent  ventrad  60  degrees.  Hooks  in  about  20  circular 
rows  of  six  to  ten  hooks  each.  Anterior  hooks  54  M  long,  successive 
hooks  gradually  smaller  until  within  a  few  rows  of  the  base  where 
they  become  abruptly  smaller;  basal  hooks  16  m  long.  Embryos 
oval  27  ^i  long  by  8  to  10  )u  broad. 

In  intestine  of  hickory  shad  from  Illinois  River;  not  abundant  but 
probably  most  frequent  in  summer  and  wanting  in  January  to  .April. 


Fig.  849.     Tanaorhamphus  longirostris.     Proboscis,  X  75;  embroyos    X210 
(After  Van  Cleave.) 

10(1)     In  hypoderm  many  small  nuclei,  not  conspicuous  externally.     .    .      n 
The  proboscis  sac  has  a  double  muscular  wall. 

11  (36)     Proboscis  and  neck  simple,   without  bulbous  enlargement  even  in 

fully  developed  specimens 12 

12  (27)     Hooks  in  each  circular  row  all  alike;  no  contrast  between  different 

sides  of  proboscis 13 

13(24)     Proboscis  sheath  attached  at  posterior  end  of  proboscis 14 

14(19)     Body  of  parasite  entirely  free  from  spines  at  all  points 15 

15  (16)     Retinacula  emerge   from   proboscis   sheath   at    blind   posterior  end 

which  contains  ganglion.     Acanthocephalus  Koelreuter  1771. 
In  marine  and'  fresh-water  fishes  and  Amphibia,  larvae  in  Isopoda. 

Representative  North  American  species. 

Acanthocephalus  ranac  (Schrank)  17S8. 

Body  elongate,  club-shaped,  largest  near  neck.  Proboscis  short,  cylindrical.  Twelve  rows 
each  with  6  or  7  hooks  which  are  60,  70,  80  and  50  fi  long.  Embryos  \io  ^l  long  by  13  ^  broad. 
This  European  species  has  been  identified  by  Van  Cleave  who  showed  that  it  is  apparently 
rare  in  this  country. 

From  intestine  of  Diemydylus  viridescens  taken  near  Baltimore,  Maryland. 

16  (15)     Retinacula  emerge  from  lateral  walls  of  proboscis  sheath;   ganglion 

distinctly  anterior  to  bhnd  posterior  end  of  sheath. 

Echinorhynchus  Zocga  ly-jO   .    .     17 

Neck  wanting  or  very  short;  proboscis  long,  cylindrical,  bent  ventrad.  Hooks  numerous, 
much  alike  throughout  except  that  roots  grow  shorter  and  disappear  in  later  rows. 

In  marine  and  fresh-water  fishes. 

Nearly  every  new  species  described  from  this  continent  has  been  assigned  to  this  genus, 
many  of  them  erroneously.  Several  good  species  in  North  America.  Abundant  in  whitefish 
and  lake  trout  from  the  Great  Lakes. 


548 


FRESH-WATER   BIOLOGY 


17  (18)     Embryos  from 
a  e 


5  to  108  M  long. 

Echinorhynchus  thecatus  Linton  1892. 

Body  cylindrical  ,  slightly  curved;  proboscis  curved  also. 
Female  11  to  26  mm.  long;  width  0.51  to  0.89,  anteriorly  0.8 
to  1,4  mm.  in  maximum,  0.52  to  i  mm.  posteriorly.  Male  7 
to  12  mm.  long;  width  0.39  to  0.69  anteriorly,  0.59  to  0.95  in 
maximum,  0.37  to  0.75  posteriorly.  Hooks  in  24  to  31  trans- 
verse and  1 2  longitudinal  rows  surrounded  by  prominent  collars. 
Embr>'os  85  to  108  fx  long  by  18  to  22  fx  broad.     (Graybill.) 

In  ahmentary  canal  and  body  cavity  of  Micropterus  dolo- 
mieu,  Ambloplites  rupestris,  Amia  calva,  and  Roccus  lineatus. 
Great  Lakes  and  eastern  waters. 


Fig.  850.  Echinorhynchus  thecatus.  a,  hooks  from  ventral  side  of 
proboscis  near  base;  b.  hook  from  ventral,  i.e.,  concave  side  of  probos- 
cis; c,  hooks  from  dorsal,  i.e.,  convex  side  of  proboscis.  X  150-  (After 
Linton.) 

18  iiyj     Embryos  from  115  to  165  ix  long.  .     Echinorhynchus  salvelini  Linkins. 

Male  7  to  9  mm.  long,  0.82  to  1.27  mm.  broad.  Fe- 
male loto  17  mm.  long,  1.2  to  1.6  mm.  wide.  Proboscis 
armed  with  26  circular  rows  of  8  hooks  each.  Hooks 
alternate  in  adjacent  rows.  Basal  hooks  39  to  50 /x 
long;  hooks  in  middle  and  anterior  regions  44  to  68  /i' 
long,  those  with  basal  processes  83  fj.  long.  Embryos 
115  to  165  ^l  long  by  20  to  25  fx  wide. 

From  lake  trout;  Lake  Michigan. 


Fig.  851.     Echinorhynchus  salvelini.     Optical  section  through 
anterior  region  of  bodJ^     X  60.     (After  Linkins.) 


19  (14)     Spines  on  body  at  some  point  at  least,  usually  at  anterior  end.  .     20 

20  (23)     Body  tapers  regularly  towards  both  ends.     Proboscis  in  line  with 

axis  of  body.     Posterior  limit  of  spines  alike  on  dorsal  and 
ventral  surfaces 21 

21(22)     Cement  glands  tubular Poly morphus  Liihe  igii. 

Fine  spines  on  skin  of  anterior  body.  Just  behind  the  limit  of  these  spines  a  conspicuous 
annular  constriction.  Type  species  P.  minutiis  (Goeze)  from  various  European  water  birds. 
At  least  one  species  yet  undescribed  from  North  American  Anseriformes. 

22  (21)  Cement  glands  irregularly  ovoid.  (Males  and  some  females  or 
young  specimens.) Filicollis  Liihe  191 1. 

Compare  number  37  in  this  key. 

The  males,  the  young  females  and  even  some  adult  females  of  certain  species  have  a  proboscis 
that  departs  only  slightly  from  the  usual  type,  being  a  little  enlarged  but  not  conspicuously 


PARASITIC    ROUNDWORMS 


549 


set  off  from  the  neck.     In  the  type  species,  FilicoUis  analis,  a  European  form  not  yet  definitely 
reported  for  North  America,  the   adult  female  has  the  proboscis  enlarged  to  a  thin-walled 
spherical  bladder  which  bears  the  hooks  on  its  anterior  aspect  in  a  series  of  radiating  lines. 
Representative  North  American  species. 

FilicoUis  bolulus  Van  Cleave  iqi6. 
This  peculiar  form  found  in  water  birds  has  been  reported  from  the  eider  (Somatcria  dresseri) 
from  Maine.  Although  the  range  of  the  bird  carries  it  (rarely)  as  far  west  as  Colorado,  yet 
the  particular  parasite  may  not  be  native  to  fresh  waters.  Acanthocephala  of  this  general 
type  have  been  reported  from  North  .\merican  ducks  under  the  name  of  '' Echinorhynchus 
polymorphus." 


Fig.  852.     FilicoUis  bolulus.     Female  with  tip  of  proboscis  slightly  inturned.     X  10.    Male,  neck  re- 
tracted, body  spines  not  shown.    X  i7-     (After  Van  Cleave.) 

23  (20)     Body  club-shaped,  anterior  end  enlarged.     Proboscis  bent  ventrad. 

forming  an  angle  with  axis  of  the  body.     Spines  extend 
further  posteriad  on  ventral  surface  than  on  dorsal. 

Corynosoma  Liihe  1004. 

The  peculiar  form  and  the  unusual  distribution  of  spines  on  the  body  serve  to  identify  the 

members  of  this  genus  which  is  apparently  limited  in  the  adult  stage  to  fish-eating  birds  and 

mammals,  chiefly  seal.     The  genus  is  mainly  marine  but  Van  Cleave  has  a  record  of  a  species 

from  birds  at  Yellowstone  Lake. 

24  (13)     Proboscis  sheath  attached  at  center  of  proboscis. 

Family  Centrorhynchidae  Van  Cleave  1916  .    .     25 
The  proboscis  sheath  starts  from  near  the  center  of  the  proboscis  wall.     The  mature  forms 
are  parasitic  in  the  intestine  of  birds. 

25  (26)     Proboscis  receptacle  two  layered:    retractors  penetrate  its  posterior 

rounded  tip Centrorhynchiis'Luhc  iqii. 

Three  long  tubular  cement  glands. 

Only  North  American  species. 

Centrorhynchiis  spinosus  \'an  Cleave  1Q16. 

Female  20  mm.  long,  0.6  mm.  broad  anteriorly.  0.5 
mm.  posteriorly.  Proboscis  0.65  mm.  long  constricted  at 
insertion  of  proboscis  receptacle  with  hooks  of  2  tyjx^s  in 
30  longitudinal  rows  of  about  24  hooks  each. 

In  intestine  of  Ilerodias  egretla  from  District  of  Colum- 
bia (?). 

Fig.  853.  Ccntrorliyiultus  spinosus.  Proboscis  and  anterior 
region  of  body,  showing  also  insertion  of  [iroboscis  receptacle 
and  location  of  the  retractors  of  the  receptacle  with  reference 
to  the  wall.     X  26.    (After  Van  Cleave. ) 

26  (25)     Proboscis  receptacle  single  layered;   retractors  pass  through  its  sides 

some  distance  anterior  to  posterior  tip. 

Mcdiorhynchus  Win  Cleave  1Q16. 
Nerve  gangUon  near  center  of  proboscis  receptacle.     In  male  8  round  or  pyriform  cement 
glands.     Proboscis  hooks  distinctly  of  two  types.     Proboscis  receptacle  not  cylindrKal  in  form. 
Known  species  mostly  in  land  birds  but  one  record  concerns  the  Carolina  rail,  /  orzana  Caro- 
lina, that  might  have  been  infected  from  an  aquatic  intermediate  host. 


550  FRESH-WATER   BIOLOGY 

27  (12)     Hooks  not  alike  on  ventral  and  dorsal  surfaces  of  proboscis.   .    .     28 

28  (29)     Hooks  differ  in  form,  especially  of  root,  but  not  in  size.     Body  uni- 

formly cylindrical  or  nearly  so. 

Rhadinorhynchus  Liihe  191 1. 

Hooks  of  dorsal  surface  with  much  shorter  root,  also  slenderer  and  less  curved  than  those  on 
ventral  surface.  In  marine  fishes  almost  exclusively,  but  present  in  trout  from  eastern  states. 
Species  yet  undcscribed. 

29  (28)     Hooks  differ  noticeably  both  in  form  and  size.     Body  very  large 

and  slender,  with  marked  enlargement  near  anterior  end. 

Arhythmorhynchus  Liihe  191 1    .    .     30 

Body  in  front  of  enlargement  covered  with  fine  spines.  Proboscis  very  long,  enlarged  at 
center,  oblique  to  body  axis.     Adults  in  intestine  of  birds. 

30  (31)     Hooks   on   mid- ventral   surface   of   proboscis    conspicuously   larger 

than  any  others. 

Arhythmorhynchus  trichocephalus  (R.  Leuckart)  1893. 

Body  very  slender.  Length  5  to  8  cm.,  diameter  0.5  to  0.8  mm.  Ovoid  swelUng  2.3  to  2.9 
mm.  behind  neck  with  length  of  1.6  to  2.4  mm.  and  breadth  of  0.6  to  1.4  mm.  Anterior  to 
swelling  many  dermal  spines  28  to  35  ju  long.  Proboscis  with  20  longitudinal  rows  and  19  or 
20  transverse  rows  of  hooks. 

From  Florida;   host  unknown. 

31  (30)     Hooks  on  mid-ventral  surface  of  proboscis  not  conspicuously  larger 

than  others 32 

32  {t,2,)     Large  hooks  exceed  100  ^t  in  length. 

Arhythmorhynchus  uncinatus  (Kaiser)  1893. 

Length  4  to  6  cm.,  diameter  i  to  1.2  mm.  Ovoid  sweUing  about  5  mm.  behind  neck;  0.6 
mm.  in  front  of  sweUing  prominent  annular  enlargement  i  to  1.4  mm.  long,  1.7  to  2  mm.  in 
diameter  and  covered  thickly  with  small  spines.  Proboscis  with  18  transverse  and  18  longi- 
tudinal rows  of  hooks. 

From  Florida;  host  unknown. 


33  (32)     Large  hooks  not  more  than  50^1  long. 


34 


34  (35)     Eighteen  longitudinal  rows  of  hooks. 

Arhythmorhynchus  hrevis  Van  Cleave  19 16. 

Female  6  to  12  mm.  long,  3  mm.  wide.  Male  5  to  6  rrm. 
long,  I  to  1.5  mm.  wide.  Neck  naked.  Body  just  back  of 
neck  with  few  small  spines.  Proboscis  0.665  mrn-  long,  0.23 
mm.  wide  at  base,  0.19  mm.  at  tip,  0.34  mm.  at  center.  Em- 
bryos 76  to  100  n  by  24  to  30  ju.  Middle  shell  heavy,  with 
rounded  swelling  at  each  pole. 

From  bittern  {Botaurus  lentiginosus);  Baltimore,  Mary- 
land. 


Fig.  854.     Arhythmorhynchus  brevis.     Anterior  end  of  body.     X  40- 
..(After  Van  Cleave.) 


PARASITIC   ROUNDWORMS 


551 


35  (34)     Proboscis  with  sixteen  longitudinal  rows  of  hooks. 

Arhythmorhynchus  pumilirostris  Van  Cleave  1916 

Female  up  to  30  mm.  long,  and  1.5  mm.  broad.  Proboscis  0.45 
mm.  long,  0.114  mm.  wide  at  base,  0.095  mm.  at  tip,  0.18  mm  at 
center.  Embryos  65  to  89  /*  long,  18  /x  broad.  Middle  shell  with 
evagination  at  each  pole. 

Yrova.  hiti^xn  {Botaiiruslentiginosus);  Washington  D.  C. 


Fig.  855. 


Arhythmorhynchus    pumilirostris.     r  ofile,    anterior    end 
body.     X  95-     (After  Van  :  leave.) 


36  (11)     In  anterior  region  of  mat'\e  specimens  prominent  bulbous  enlarge- 
ment, separated  Irom  body  by  slender  cyHndrical  neck.     37 

The  bulb  is  embedded  in  the  intestinal  wall  or  may  even  be  in  the  body  cavity  when  the 
slender  region  traverses  the  wall  connecting  with  the  body  of  the  parasite  in  the  intestine.  In 
handling  such  material  the  proboscis  may  easily  be  partly  or  completely  torn  ofiF,  and  the  para- 
site is  then  difficult  to  identify  as  the  characteristic  bulb  at  least  is  gone. 


37  (38)     Bulb  consists  of  the  proboscis, 
bulb  in  radial  lines. 


Hooks  on  the  anterior  face  of  the 
(Females  of)  FilicoUis  Liihe  191 1. 


Representative  North  American  species. 

FilicoUis  hotidus  Van  Cleave  1916. 

In  females  thus  far  reported  under  this  name  for  North  America  the  bulb  is  wanting;  it  may 
be  present  in  older  specimens  and  in  fact  is  described  in  specimens  recorded  under  the  name 
E.  anatis  which  may  belong  here. 

Compare  number  22  in  key. 

38  (37)     Bulb  consists  of  anterior  part  of  neck  only.     Proboscis  extends  an- 
teriad  from  bulb.      .    .    .    Pomphorhynchus  MonticelH  1905, 

Proboscis  long,  cylindrical,  with  many  hooks.  Neck  very  long,  expanded  in  anterior  region, 
slender,  cyHndrical  in  posterior  portion.  In  intestine  of  fishes;  one  of  the  commonest  types 
in  European  fresh-water  hosts.  Not  infrequent  in  North  American  fresh-water  fishes;  species 
not  described. 

IMPORTANT   REFERENCES   ON  NORTH  AMERICAN  PARASITIC 

ROUNDWORMS 


GENERAL   WORKS 

See  also  list  in  Chapter  XIII,  page  452 
1 89 1.     Die  Nemathekninthen.    Heft  i,  120  pp, 


Hamann,  0 

Heft  2,  120  pp.,  II  pi.     Jena. 
Leuckart,    R.     1876.     Die    menschliche    Parasiten. 
Acanthocephala].     882  pp.,  401  figs.     Leipzig. 


Vol. 


,  10  pi.     1S05. 
2    [Nematoda, 


552 


FRESH-WATER    BIOLOGY 


NEMATODA 


Brasche,  R.  von.  1882-3.  Revision  der  in  der  Nematoden-Sammlung  des 
K.  K.  zoologischen  Hofcabinetes  befindlichen  Original-Exemplare  Die- 
sing's  und  Molin's.  Verb,  zool.-bot.  Ges.  Wien,  32:  1 17-138,  4  pi.;  ^t,: 
107-118,  3  pi;  33:   193-218,  4  pl- 

Hagmeier,  A.  1912.  BeitragezurKenntnisder  Mermithiden.  Zool.  Jahrb., 
Syst.,  32:  521-612,  5  pl. 

Hall,  M.  C.  1916.  Nematode  Parasites  of  ^Mammals,  etc.  Proc.  U.  S. 
Nat.  Mus.,  50:  1-258,  I  pl. 

LiNSTOW,  O.  von.  1909.  Parasitische  Nematoden.  Siisswasserfauna  Deutsch- 
lands,  Heft  15,  p.  47-81. 

Magath,  T.  B.  1916.  Nematode  Technique.  Trans.  .Amer.  Mic.  Soc,  35: 
245-256. 

Railliet,  A.  and  Henry,  A. 

191 5.  Sur  les  Nematodes  du  genre  Camallanus  Raill.  et  Henry,  191 5 
(Cucullanus  auct.,  non  Mueller,  1777).  Bull.  soc.  path,  exot.,  Paris,  8: 
446-452. 

Ransom,  B.  H.  1911.  The  Nematodes  Parasitic  in  the  AHmentary  Tract  of 
Cattle,  Sheep,  and  other  Ruminants.     Bur.  An.  Ind.,  Bull.  127,  132  pp. 

ScHNEroER,A.     1866.     Monographic  der  Nematoden.     357  pp.  28  pl.    Berlin. 

Seurat,  L.  G.  1916.  Contribution  a  I'etude  des  formes  larvaires  des  Nema- 
todes parasites  heteroxenes.     Bull.  sci.  France  et  Belgique,  49:  297-377. 

Stossich,  M.  1896.  II  genere  Ascaris  Linne.  1897.  Filarie  e  Spiroptere. 
1899.     Strongyhdae.     Trieste. 

Ward,  H.  B.  and  Magath,  T.  B.  19 16.  Notes  on  Some  Nematodes  from 
Fresh- Water  Fishes.     Jour.  Parasitol.,  3:  57-64,  i  pl- 

gordiacea 

Montgomery,  T.  H.,  Jr.  1898.  The  Gordiacea  of  Certain  American  Col- 
lections.    Bull.  Mus.  Comp.  Zool.  Harvard,  32:  23-59,  15  pl. 

1898a.  The  Gordiacea,  etc.  Pt.  H.  Proc.  Cal.  Acad.  Sci.,  (3)  i:  333-344, 
2  pl. 

1899.  Synopses  of  North  American  Invertebrates.  II.  Gordiacea  (Hair 
worms).     Amer.  Nat.,  $$:  647-652. 

ACANTHOCEPHALA 

LiJHE,  M.     191 1.     Acanthocephalen.      Siisswasserfauna  Deutschlands,  Heft 

16,  60  pp.,  87  figs. 
Van   Cleave,  H.  J.     1913.     The  Genus  Neorhynchus  in  North  America. 

Zool.  Anz.,  43:  177-190. 
1915.     Acanthocephala  in  North  American  Amphibia.     Jour,  Parasitol.,  i: 

175-178. 


CHAPTER    XVII 
THE    WHEEL    ANIMALCULES    (ROTATORL\) 

By  H.  S.  JENNINGS 

Professor  of  Zoology,  Johns  Hopkins  University 

The  Rotatoria  or  Rotifera  are  perhaps  the  most  characteristic 
group  of  fresh-water  animals,  and  at  the  same  time  the  most 
attractive  and  beautiful.  They  are  everywhere  abundant  in  fresh 
water,  but  are  rare  elsewhere.  With  their  varied  and  fantastic 
forms,  their  brilliant  colors  and  lively  manners,  the}-  have  long 
been  the  favorites  of  amateur  microscopists.  Some  of  the  older 
observers  have  expressed  themselves  with  great  enthusiasm  in 
regard  to  these  creatures.  Eichhorn  (1781)  who  discovered  Sieph- 
anoceros  in  1761,  calls  it  the  "crown  polype,"  and  Kkens  this  "in- 
comparable animal"  to  a  pomegranate  blossom.  Of  Floscidaria  he 
says,  "Now  I  come  to  a  very  wonderful  animal,  which  has  very 
often  rejoiced  me  in  my  observations:  I  call  it  the  Catcher:  ex- 
traordinarily artistic  in  its  structure,  wonderful  in  its  actions,  rapid 
in  capturing  its  prey."  Eichhorn's  account  of  the  capture  of  prey  is 
excellent:  "Its  head  was  a  widespread  net  .  .  .  with  points  which 
had  little  round  balls  on  their  tips;  so  it  awaits  its  prey;  when  a 
little  animal  came  into  this  net  or  hollow  basin,  then  it  conMil- 
sively  drew  the  neck  a  little  together,  as  if  to  find  out,  as  it  were, 
whether  it  had  really  gotten  its  booty;  then  it  suddenly  folded  the 
net  together  and  pushed  the  prey  into  its  body,  where  one  could 
still  see  it  plainly.  .  .  .  And  I  have  often  seen  it  exactly  as  in 
[Fig.]  K\  then  it  looked  terrible,  no  lightning  stroke  can  rush  from 
the  clouds  into  the  air  so  quickly  as  this  little  animal  fiercely  struck 
together  the  two  hooks  when  it  noticed  a  prey  in  its  outspread 
net." 

The  rotifers  are  minute,  chiefly  microscopic  animals.  Their 
most  characteristic  feature  is  the  ciliated  area  at  or  near  the  ante- 
rior end  of  the  body,  serving  as  a  locomotor  organ  or  to  bring  food 
to  the  mouth.  Taken  in  connection  with  the  lack  of  cilia  on  other 
parts  of  the  body  (save  in  rare  cases  at  the  posterior  end),  this 

553 


554  FRESH-WATER   BIOLOGY 

ciliated  area  or  corona  serves  as  a  rule  to  distinguish  a  rotifer  at 
once  from  any  other  many-celled  animal  Hving  in  fresh  water. 

The  extreme  diversity  of  form  and  organization  in  different 
rotifers,  though  constituting  the  greatest  charm  of  their  study, 
makes  it  almost  impossible  to  give  a  formal  definition  of  the  group. 
Even  the  most  characteristic  feature,  —  the  cihated  corona,  — 
is  in  a  few  cases  lacking.  The  form  of  the  body  varies  extremely, 
from  spherical  in  Trochosphaera  (Fig.  947)  to  the  excessively  atten- 
uated form  of  Rotifer  neptunius  (Fig.  960),  the  fiower-Hke  shape  of 
Stephanoceros  (Fig.  937),  or  the  spiny,  turtle-like  figure  of  Poly- 
chaetus  (Fig.  905). 

Yet  one  can  give  a  characterization  that  will  be  true  for  the  great 
majority  of  the  rotifers.  The  body  is  as  a  rule  somewhat  elon- 
gated, with  the  cihated  corona  at  the  anterior  end ;  it  is  extended  at 
the  posterior  end,  behind  and  below  the  cloacal  opening,  to  form  a 
stalk,  or  tail-like  appendage  known  as  the  foot.  This  frequently 
ends  in  two  small  pointed  toes.  There  is  a  well-developed  ali- 
mentary canal,  with  a  muscular  pharynx,  containing  complex  jaws. 
There  is  a  simple  excretory  system,  while  circulatory  and  respira- 
tory systems  are  lacking.  The  nervous  system  consists  of  a  prom- 
inent brain  and  of  certain  nerves  and  sense  organs.  The  sexes  are 
separate,  and  the  male  is  usually  a  minute,  degenerate  creature, 
lacking  the  alimentary  canal. 

Rotifera  may  be  found  wherever  there  is  fresh  water.  Lakes, 
pQnds,  and  streams  harbor  them  in  immense  number  and  variety. 
Swamps  and  marshes  swarin  with  them.  Wayside  pools,  drains, 
and  even  the  dirty  water  that  stands  in  barnyard  holes  about 
manure  heaps,  are  proKfic  sources  of  rotifers.  The  mud  of  eave- 
troughs,  the  bottoms  of  funeral  urns,  the  cavities  found  in  the  axils 
of  the  leaves  of  certain  mosses,  —  all  these  are  famous  collecting 
grounds  for  the  rotifer  hunter.  A  few  rotifers  are  parasitic,  some 
externally,  some  internally.  A  few  live  in  salt  water,  but  they  are 
much  less  abundant  in  the  ocean  than  in  fresh  water. 

In  giving  an  account  of  the  structure  and  life  of  the  rotifers,  it 
will  be  well  to  have  in  mind  at  first  some  representative  type ;  then 
the  variations  found  in  other  rotifers  may  be  traced.  The  typical 
rotifers,  as  well  as  the  commonest  ones,  are  those  belonging  to  the 


THE  WHEEL  ANIMALCULES  (R0TAT0RL\) 


:>:>:) 


great  family  of  Notommatidae,  and  there  is  much  reason  to  believe 
that  all  other  rotifers  have  been  derived  from  forms  essentially 
similar  to  those  found  in  this  family.  The  different  members  of 
the  Notommatidae  are  so  much  alike  that  it  is  hardly  necessary 
to  select  precisely  some  one  species  for  a  type.  But  it  will  be  well 
in  following  this  account  to  have  in  mind  such  an  animal  as  Proalcs 
(Fig.  856),  or  Notommata  truncata  (Fig.  857,  yl  and  B),  or  Co  pens 


o — 


OM 


mg- 


^m 


Fig.  856.     Proales  werneckii  Ehr.,  a  typical  notommatoid  rotifer.     A,  Female,  dorsal  view.      X  400. 
B,  Male,  side  view.     For  explanation  of  letters,  see  Fig.  857.  X  600.     (.\fter  Rousselet.) 

pachyurus  (Fig.  857,  C).     For  convenience  one  can  refer  to  any 
member  of  the  Notommatidae  as  a  notonimatid. 

The  notommatids,  though  the  most  abundant,  are  as  a  rule  the 
least  conspicuous  of  the  rotifers.  They  have  usually  a  nearly 
cylindrical  body,  often  somewhat  swollen  behind,  and  with  a 
slender  posterior  foot  (/)  ending  in  two  toes  (/).  Most  of  them  are 
found  swimming  about  amid  vegetation  or  creeping  o\'er  its  sur- 
face. Like  all  other  living  things,  these  rotifers  are  bundles  of 
activity.     They  are  busily  engaged  in  carrying  on  many  processes. 


556 


FRESH-WATER   BIOLOGY 


internal  and  external;  in  meeting  and  solving  the  problems  which 
the  world  presents.  And  it  is  almost  surprising  to  note,  when  the 
matter  is  first  examined  from  such  a  standpoint,  how  nearly  the 
objects  of  the  stri^  ings  of  almost  any  lower  group  resemble  those 
of  the  highest.  To  get  proper  food  and  oxygen;  to  find  or  construct 
a  proper  place  to  dwell;  to  arrange  for  the  production  and  growth 
of  the  young;    to  protect  one's  self  and  one's  progeny  from  ene- 


FlG.  8s7.  Notommatoid  rotifers.  A ,  Notommata  truncata  Jennings,  side  view.  X  300.  B,  same,  dorsal 
view.  X  300.  C,  Copeus  packyurus  Gosse.  X  150.  The  letters  in  Figs.  856  and  857  have  the  follow- 
ing signification:  6r,  brain;  c,  cloaca;  co,  copulatory  organ;  ct,  contractile  vacuole;  e,  eye;  ea;,  excretory 
organs;  /,  foot;  fc,  flame  cell;  gg,  gastric  glands;  in,  intestine;  la,  lateral  antennae;  m,  mouth;  mg, 
mucous  glands  of  foot;  ms,  muscles;  mx,  mastax;  0,  esophagus;  ov,  ovary;  sg,  sahvary  glands;  sp, 
spermarium;   st,  stomach;   t,  toes.      (.After  Weber.) 

mies  and  from  the  forces  of  nature,  —  these,  and  the  activities 
growing  out  of  them,  form  the  groundwork  of  Hfe  in  the  lowest  as 
well  as  the  highest  creatures.  In  studying  the  rotifers,  it  will  be 
best  to  look  upon  them  as  Hving  things  and  to  ask:  What  processes 
and  activities  are  they  carrying  on?  And  what  apparatus  do  they 
use  in  these  activities?    Thus,  one  is  led  to  take  up  in  order  the 


THE   WHEEL  ANIMALCULES   (ROTATORIA)  557 

various  systems  of  organs,  to  notice  their  variations  and  modifica- 
tions, and  the  uses  they  serve. 

Perhaps  the  chief  concern  of  all  organisms  is  to  provide  material 
for  carrying  on  the  complicated  chemical  processes  that  are  going 
on  within,  —  that  is,  to  get  food  and  oxygen.  How  does  the 
rotifer  accomplish  these  ends? 

This  is  done  mainly  by  the  aid  of  the  ciliated  surface  at  the 
anterior  end,  —  the  corona.  The  cilia  of  this  region  are  fine,  hair- 
like processes  which  are  in  constant  motion.  They  strike  back- 
ward more  strongly  than  forward,  so  that  they  cause  a  current  to 
pass  backward  from  in  front  of  the  animal  to  its  mouth,  and  thence 
over  the  surface  of  the  body  (Fig.  858).  In  the  simplest  notommatids 


\  \  N 

N    ^ 

*^ 

Fig.  858.  Currents  of  water  caused  by  the  cilia  of  a  rotifer.  The  dotted  area  shows  how  material  lyin? 
in  front  of  the  rotifer  is  drawn  out  in  the  form  of  a  vortex  to  its  mouth.  (The  rotifer  is  Proales  sordida  Gosse, 
from  a  figure  by  Dixon-Nuttall.) 

the  corona  is  a  mere  flattish  disk  on  the  ventral  side  of  the  anterior 
end,  covered  uniformly  with  short  ciha  (Fig.  859).  In  other  rotifers 
there  are  great  variations  in  the  size  and  arrangement  of  the  cilia; 
these  variations  will  be  taken  up  later.  The  water  current  pro- 
duced by  the  corona  has  a  number  of  different  uses: 

1.  It  continually  renews  the  water  that  bathes  the  surface  of  the 
animal,  thus  insuring  a  constant  supply  of  fresh  oxygen.  The 
oxygen  thus  supplied  is  absorbed  by  the  entire  surface  of  the  ani- 
mal, apparently,  for  there  are  no  special  respiratory  organs. 

2.  The  current  brings  to  the  mouth  any  particles  of  food  that 


558 


FRESH-WATER   BIOLOGY 


may  be  floating  in  the  water,  or  that  are  easily  washed  from  sur- 
rounding objects.  The  mouth,  situated  in  the  posterior  part  of 
the  corona,  opens,  and  so  admits  or  seizes  such  food  as  is  adapted 
to  the  rotifer.  In  many  rotifers  the  cilia  are  the  chief  direct  agents 
in  obtaining  food,  and  in  practically  all  species  they  are  either 
directly  or  indirectly  of  the  greatest  importance  for  this  function. 
A 


Fig.  859.     Corona  of  Proales  tigridia  Gosse.     A,  surface  view,  from  ventral  side.     B,  side  view. 
m,  mouth.     (After  Wesenberg-Lund.) 

3.  In  place  of  bringing  food  and  oxygen  backward  to  the  rotifer, 
the  cilia  may  carry  the  animal  forward  to  new  supphes  of  these 
necessities.  This  is  the  case  in  all  free-swimming  rotifers;  the  ciha 
are  the  main  organs  of  locomotion.  In  thus  moving  the  animals 
about,  the  ciha  of  course  play  as  important  a  part  in  food-getting 
as  when  they  bring  the  food  to  the  rotifer.  In  most  species  the 
ciha  act  in  both  ways  at  once,  bearing  the  animal  forward  and  the 
food  backward,  so  that  the  two  meet. 

4.  The  water  currents  remove  the  products  of  respiration  and 
excretion,  which  the  rotifer,  Hke  other  animals,  is  continually 
giving  off.  Carbon  dioxide  is  doubtless  given  off  over  the  whole 
surface  of  the  body,  while  other  waste  products  are  discharged  by 
the  contractile  vesicle  (see  p.  561).  If  these  waste  products  were 
allowed  to  accumulate,  they  would  be  most  injurious. 

While  these  are  the  main  uses  of  the  cilia,  they  assist,  in  a  num- 
ber of  rotifers,  in  other  important  operations,  such  as  the  con- 
struction of  a  tube  or  nest. 

The  further  course  of  the  food  may  now  be  followed.  The  mouth, 
situated  in  the  posterior  part  of  the  corona  (Fig.  859,  w),  leads  into 
a  cavity  with  thick,  muscular  walls,  known  as  the  mastax  (Figs.  856 
and  857,  mx) .  The  mastax  is  armed  with  a  complicated  set  of  jaws, 
which  have  little  resemblance  to  jaws  found  anywhere  else  in  the 
animal  kingdom.     They  are  known  as  the  trophi  (Fig.  857,  i4,  tr). 


THE   WHEEL   ANIMALCULES   (ROTATORIA)  559 

The  trophi  consist  of  a  number  of  pieces,  so  arranged  that  two  main 
parts  may  be  distinguished.  There  is  a  middle  portion,  somewhat 
fork-shaped,  which  is  known  as  the  incus  (Fig.  860,  in),  and  two 
lateral  parts  known  as  the  mallei  {ma). 

In  the  middle  portion  or  incus  may  be  distinguished  a  single 
basal  piece,  comparable  to  the  handle  of  the  two-tined  fork;  this 
basal  piece  is  known  as  the  fulcrum  {fu,  Fig.  860).     The  two  blade- 
like pieces  resting  on  it,  i.e,  the  tines  of  the  fork,  are  the  rami  ira). 
A  B 


ma.: 
-rnu. 


~mu. 


Fig.  860.  Trophi  or  jaws  of  rotifers.  ^,  Malleate  type.  (From  Wesenberg-Lund,  after  Hudson  and 
Gosse.)  B,  Forcipate  type,  from  Z)ig/e«a/orc//>a/a  Ehr.  (After  Gosse.)  /m,  fulcrum;  in,  incus;  m<i,  mallei; 
mil,  manubrium;   ra,  ramus;   un,  uncus. 

The  rami  are  joined  to  the  fulcrum  in  such  a  way  that  they  may 
move  back  and  forth,  like  the  blades  of  a  pair  of  shears.  They 
often  bear  teeth. 

In  the  lateral  parts  or  mallei  one  may  likewise  distinguish  two 
parts.  The  basal  piece,  serving  as  a  sort  of  handle,  is  known  as  the 
manubrium  (Fig.  860,  mu).  Joined  to  the  top  of  this,  but  placed 
nearly  at  right  angles  to  it,  is  the  piece  known  as  the  uncus  {iin)\ 
the  two  unci  usually  lie  across  the  tops  of  the  rami,  their  points 
meeting  in  the  middle.  Each  uncus  may  bear  one  or  more  points, 
or  a  number  of  sharp  ridges  serving  as  teeth.  The  food  passes 
between  the  teeth  of  the  unci  and  rami  and  is  cut  and  ground  by 
them.  The  jaws  are  worked  by  muscles  which  are  attached  to 
the  manubria  and  to  other  parts  of  the  apparatus;  these  muscles 
make  up  the  main  part  of  the  mastax. 

In  different  rotifers  the  trophi  vary  much  in  the  form  and  rela- 
tive development  of  the  t>T)ical  parts;  this  is  true  even  within  the 
Notommatidae.  There  are  two  main  lines  of  divergent  develop- 
ment: (i)  In  many  rotifers  the  parts  of  the  trophi  become  thick 
and  stout;  the  unci  are  broad  plates  bearing  a  number  of  ridges. 
Such  jaws  are  used  mainly  for  grinding,  and  are  said  to  belong  to  the 


560 


FRESH-WATER   BIOLOGY 


malleate  type  (Fig.  860,  ^),  on  account  of  the  great  development  of 
the  mallei.  (2)  In  other  species  all  parts  of  the  trophi  are  long  and 
slender;  the  unci  end  in  a  single  sharp  point,  which  may  be  thrust 
out  of  the  mouth  to  seize  upon  living  prey.  The  two  rami  Hke- 
wise  form  a  pair  of  strong,  blade-Kke  jaws.  Such  trophi  are  said 
to  belong  to  the  forcipate  type  (Fig.  860,  B) ;  they  are  found  in  active 
rotifers  of  predatory  habits.  There  exist  many  modifications  of 
these  two  types,  and  many  jaws  intermediate  between  the  two. 
Both  types  of  jaws  are  found  in  the  Notommatidae. 

The  mastax  usually  bears  near  its  posterior  end  a  pair  of  small 
glands  that  are  known  as  salivary  glands  (Fig.  856,  sg).  From  the 
mastax  the  food  passes  into  the  slender  esophagus  (Figs.  856  and 
857,  0),  which  leaves  the  mastax  on  its  dorsal  side.  Through  the 
esophagus  the  food  reaches  the  large  stomach  (st),  where  digestion 
takes  place.  Attached  to  the  anterior  end  of  the  stomach  are  the 
two  large  gastric  glands  (gg).  From  the  stomach  the  undigested 
remnants  of  the  food  pass  back  into  the  straight  slender  intestine, 
and  thence  to  the  outside  at  the  cloacal  opening  (c).  This  lies  on 
the  dorsal  side  of  the  body,  above  the  foot. 

The  body  cavity  is  enclosed  by  but  a  single  layer  of  cells,  which 
form  the  body  wall,  so  that  each  cell  is  bathed  on  its  outer  surface 
by  the  outer  water  and  on  its  inner  surface  by  the  fluid  of  the  body 
cavity.  By  this  arrangement  the  processes  of  respiration  are 
made  very  simple.  Oxygen  doubtless  passes  from  the  surround- 
ing water  through  the  single  layer  of  cells  into  the  body  fluid,  while 
the  waste  carbon  dioxide  produced  within  is  given  off  in  the  same 
way  to  the  outside. 

The  nitrogenous  waste  products  are  not  so  easily  eliminated  as 
is  the  carbon  dioxide;  for  removing  these  the  rotifers  have  a  set  of 
excretory  organs.  These  consist  of  fine  tubules  running  through 
the  body  cavity  at  the  sides  of  the  alimentary  canal  (see  Fig.  857, 
ex,  and  Fig.  861).  On  each  side  there  are  usually  two  tubes,  one 
with  thick  walls  (a),  the  other  with  very  thin  ones  (b).  These  two 
are  usually  connected  (c)  in  the  anterior  part  of  the  rotifer.  They 
commonly  bear  at  intervals  along  their  course  certain  minute 
club-shaped  organs  (Figs.  85 7 ,  5 ;  86 1  ,/c) .  These  are  closed  at  their 
free  ends,  and  contain  within  them  either  a  vibrating  membrane 


THE   WHEEL   ANIMALCULES    (ROTATORIA) 


561 


or  a  bunch  of  long  cilia.  The  membrane  or  the  bunch  of  cilia  is 
always  in  rapid  movement,  giving  the  appearance  of  a  minute 
flame,  so  that  these  structures  are  called  flame  cells.  The  cilia  or 
membrane  doubtless  serve  to  propel  a  current  through  the  tubes. 
In  many  rotifers  a  transverse  tube  in  the  head  region  unites  the 


Fig.  86r.  Excretory  organs.  .1,  LAcinularia  socialis  Ehr.,  showing  the  thin-walled  tube  a,  the  thick- 
walled  tube  b,  the  transverse  connecting  tube  c,  and  the  flame  cells /c.  Modified  from  a  figure  by  Hlava. 
B,  Excretory  tubules  of  right  side  in  Floscularia  campanulata  Dobie.  cv,  contractile  vesicle;  fc,  tlame 
cells.     (After  Montgomery.) 

thin-wafled  tubes  of  right  and  left  sides.     Often  all  the  tubes  are 
convoluted  in  their  course. 

There  is  reason  to  believe  that  the  walls  of  the  tubes  absorb  the 
nitrogenous  waste  matter  from  the  fluid  of  the  body  cavity.  This 
waste  matter  passes  backward,  driven  by  the  flame  cells,  to  the  region 
of  the  cloaca  (Figs.  856,  857,  c).  Here  is  found  in  most  rotifers  a 
small  sac  into  which  the  tubes  from  both  sides  enter.  This  sac  opens 
along  with  the  intestine  into  a  small  cavity  known  as  the  cloaca. 
The  sac,  or  contractile  vesicle  (cv),  as  it  is  called,  contracts  at 
intervals,  expelling  to  the  outside  the  fluid  with  which  the  tubes 


a 


Fig.  862.     Spiral  path  followed  by  swim 

— ■ ■'ifer.  as  seen  in  D'      "     ''     ' 

(After  Jennings.; 


ming  rotifer,  as  seen  in  Diurella  tiKris 
MUller.      -■-       -       - 


FRESH-WATER   BIOLOGY 

have  filled  it.  The  contractions  take 
place  frequently,  so  that  a  large  amount 
of  fluid  is  expelled. 

Besides  its  organs  for  the  nutritive 
processes,  the  rotifer  has  of  course  or- 
gans for  causing  and  controlling  move- 
ments. The  chief  organ  of  locomotion 
is  the  cihated  corona.  By  its  aid  the 
rotifer  may  either  creep  along  over 
surfaces,  or  swim  freely  through  the 
water.  When  swimming  freely  the  ro- 
^  tifer  usually  revolves  on  its  long  axis, 
so  as  to  follow  a  spiral  course  (Fig.  862). 
Changes  of  form  and  movements  of 
parts  of  the  body  are  brought  about 
i  by  many  slender  muscles  (Fig.  857,  C, 

I  ms).    These  muscles  are  either  applied 

closely  to  the  body  wall  or  pass  from 
the  body  wall  through  the  body  cavity 
to  other  parts.  The  muscles  are  often 
striated. 

An  important  organ  for  producing  or 
guiding  motion  is  found  in  the  foot 
with  its  toes.  The  foot  of  the  notom- 
matid  is  usually  short;  it  is  nothing 
more  than  that  part  of  the  body  be- 
hind the  cloaca.  It  usually  tapers 
somewhat,  but  is  not  clearly  marked 
off  from  the  rest  of  the  body,  as  it  is 
in  some  rotifers  of  other  families.  At 
its  posterior  end  it  bears  side  by  side 
the  tapering,  pointed  toes,  which  are 
usually  small  in  the  Notommatidae. 
The  toes  serve  as  a  steering  apparatus 
in  swimming,  and  as  points  of  sup- 
port and  attachment  in  creeping.  For 
attachment  the  toes  are  supplied  with 


THE   WHEEL   ANIMALCULES   (ROTATORL\)  563 

two  glands  lying  in  the  foot  (Figs.  856  and  857,  mg);  these  secrete 
a  sticky,  tenacious  mucus,  which  may  be  discharged  either  at  the 
tip  of  the  toes,  or  at  their  base,  so  as  to  flow  out  over  their  surface. 
By  this  mucus  the  rotifer  may  attach  itself  loosely  to  objects  of 
various  sorts,  so  that  the  movements  of  its  cilia  may  continue  to 
bring  food  to  the  mouth  without  carrying  the  rotifer  away  from 
its  anchorage.  Often  the  mucus  is  drawn  out  to  form  a  long 
thread,  like  that  produced  by  a  spider;  from  this  thread  the  rotifer 
remains  as  it  were  suspended,  swinging  about  from  side  to  side  at 
a  distance  from  the  point  of  attachment,  but  not  breaking  away 
from  it  completely.  At  times  the  rotifer  spins  out  behind  it  a 
thread  of  mucus  "as  it  progresses  slowly  through  the  water;  this 
thread  steadies  its  course  and  keeps  it  connected  with  its  point  of 
departure.  The  foot  and  toes  are  modified  in  many  ways  in  other 
groups,  as  will  be  seen  later. 

For  controlling  motion  the  rotifer  has  a  nervous  system  and  a 
number  of  sense  organs.  The  chief  part  of  the  nervous  system  is  a 
large  gangHon  known  as  the  brain  (br),  lying  on  the  dorsal  side, 
just  above  the  mastax,  at  the  anterior  end.  From  the  brain 
nerves  pass  in  many  directions  to  the  various  organs  of  the  body. 

Several  different  kinds  of  sense  organs  are  found  in  the  rotifers. 
In  some  part  of  the  anterior  end,  usually  attached  to  the  brain, 
there  are  usually  one  or  two  red  pigment  spots;  these  are  supposed 
to  be  organs  of  light  perception,  and  are  known  as  eye-spots  (e). 
In  a  few  cases  three  or  more  of  these  are  found.  Sometimes  the  eye- 
spots  are  not  attached  directly  to  the  brain,  but  are  connected  with 
it  by  nerves  (for  example,  in  the  genus  Rotifer).  The  eye-spots 
sometimes  bear  on  their  anterior  surfaces  hemispherical  cr}'stalline 
lenses.     In  some  rotifers  eye-spots  are  lacking. 

Many  rotifers  bear  sense  organs  of  various  kinds  on  the  corona 
(see  for  example  the  corona  of  Synchacta,  Fig.  ^S^,  or  of  Ilydatina, 
Fig.  906,  B).  Such  sense  organs  are  less  common  in  the  Notomma- 
tidae  than  in  more  specialized  rotifers. 

Almost  all  rotifers  have  a  pair  of  sense  organs  on  the  sides  of 
the  body  behind  the  middle;  these  are  known  as  the  lateral  an- 
tennae (Fig.  857,  C,  la).  Either  another  antenna,  or  a  pair  of  ihem, 
is  found  on  the  dorsal  surface  of  the  head,  just  above  the  brain; 
these  are  known  as  the  dorsal  antennae  (Figs.  856  and  857,  da). 


564  FRESH-WATER   BIOLOGY 

The  organs  of  reproduction  are  still  to  be  considered.  Most  of 
the  rotifers  commonly  seen  are  females,  as  the  males  are  very 
minute  and  rare.  In  the  Notommatidae,  as  in  most  other  rotifers, 
there  is  a  single  large  reproductive  body,  commonly  spoken  of  as 
the  ovary,  or  sometimes  as  the  germarium.  This  Hes  ventral  to  the 
intestine,  in  the  posterior  third  of  the  body  (Figs.  856  and  857,  ov). 
It  consists  of  two  portions,  of  different  functions.  The  large  part 
contains  a  small  number  of  large  nuclei,  often  just  eight;  this  por- 
tion prepares  the  yolk  for  the  developing  Qgg,  so  that  it  is  called 
the  vitellarium.  At  one  end  or  side  of  this  vitellarium  is  a  small 
mass  containing  many  minute  nuclei.  From  this  part  the  egg 
develops,  the  small  nuclei  becoming  each  the  nucleus  of  an  egg. 
This  part  is  known  as  the  germarium,  since  it  produces  the  egg  or 
germ.  From  the  ovary  a  thin-walled,  sac-like  passageway,  the 
oviduct,  leads  backward  to  the  cloaca;  by  it  the  egg  is  discharged. 
The  oviduct  can  be  seen,  as  a  rule,  only  with  great  difficulty. 

In  most  rotifers  the  males  are  small  and  degenerate.  But  in 
some  of  the  Notommatidae,  as  well  as  in  a  few  other  species,  they  are 
nearly  as  well  developed  as  the  females,  and  resemble  them  in 
structure.  In  Proales  werneckii  (Fig.  856),  which  lives  within  Vau- 
cheria  filaments,  the  male  is  as  large  as  the  female,  but  the  ali- 
mentary canal  is  not  quite  so  well  developed.  In  Rhinops  vitrea 
(Fig.  863),  the  male  is  smaller  than  the  female  but  not  otherwise 
degenerate,  while  in  the  aberrant  rotifers  known  as  the  Seisonacea 
males  and  females  are  alike,  save  for  the  reproductive  organs.  In 
most  other  rotifers  the  minute  males  either  lack  the  ahmentary 
canal  entirely  or  have  only  vestiges  of  it  (see  Fig.  864).  In  all 
cases  in  the  male  in  place  of  the  ovary  is  found  a  sac,  the  sperma- 
rium  (sp),  in  which  many  spermatozoa  are  seen  swimming  about. 
The  sac  extends  backward  as  a  large  tube,  ending  in  a  ciliated 
opening  from  which  the  spermatozoa  are  discharged.  That  por- 
tion of  the  tube  bearing  the  opening  may  be  protruded  as  a  copu- 
la tory  organ. 

The  chief  structures  of  a  typical  rotifer  have  now  been  described, 
mainly  as  shown  in  the  Notommatidae.  Next,  the  Rotifera  as  a 
whole  will  be  surveyed  and  the  different  groups  examined  rapidly 
to  note  how  these  differ  from  the  notommatids  and  from  one  an- 


THE   WHEEL   ANIMALCULES    (ROTATORIA) 


565 


other.  Such  a  survey  gives  strongly  the  impression  that  the  other 
rotifers  have  been  derived  by  various  modifications  from  rotifers 
having  in  general  the  characteristics  of  the  Notommatidae.  Space 
will  not  permit  setting  forth  in  detail  the  grounds  for  this  impres- 
sion, nor  will  it  allow  describing  the  many  forms  transitional  be- 
tween the  Notommatidae  and  other  groups.      But  in  giving  an 


Fig.  863.  Male  oi  Rhino ps  vitrea, 
Hudson,  showing  presence  of 
the  alimentary  canal,  co,  cop- 
ulatory  organ;  mx,  mastax;  0, 
esophagus;  sp,  spermarium; 
St,  stomach.  X  400.  (After 
Rousselet.) 


Fig.  864.  Male  of  Copeus  pachyurus  Gos.se, 
showing  absence  of  alimentary  canal,  br, 
brain;  co,  copulatory  organ;  5/>,  sperma- 
rium.    X  260.     (After  Dixon-Nuttall.) 


account  of  the  other  rotifers,  they  will  be  grouped  about  the  No- 
tommatidae in  the  way  which  appears  to  be  called  for  by  the  facts.^ 

1  This  follows  mainly  Wesenberg-Lund  (1899),  who  has  developed  a  classification 
of  the  Rotifera  based  on  their  origin  from  Notommatoid  forms.  While  this  classifi- 
cation has  not  thus  far  been  commonly  employed,  the  same  can  be  said  of  any  other 
classification  that  has  been  proposed.  The  writer  is  convinced  that  the  classification 
given  by  Wesenberg-Lund  is  the  only  really  natural  one  and  that  its  use  is  a  great 
aid  to  an  understanding  of  the  Rotifera;  he  has  therefore  employed  it.  It  should  be 
noted,  however,  that  the  arrangement  here  given  differs  in  many  details  from  that  of 
Wesenberg-Lund,  as  the  advance  of  knowledge,  or  the  writer's  own  experience,  seems 
to  require.  No  scheme  of  classification  can  be  completely  li.xed  until  knowledge  of 
the  organisms  to  be  classified  is  infinitely  more  complete  than  is  the  present  knowledge 
of  the  Rotifera. 


566  FRESH-WATER  BIOLOGY 

1.  Notommatidae.  It  will  be  helpful  first  to  notice  some  of  the 
chief  variations  of  type  among  the  Notommatidae  themselves. 
The  simplest,  most  undifferentiated  rotifiers  that  exist  are  those 
commonly  classed  in  the  genus  Proales.  They  have  small,  soft 
bodies,  nearly  cylindrical,  and  obscurely  segmented  externally 
(Fig.  856).  The  foot  and  toes  are  short.  The  corona  is  a  uniformly 
ciliated,  nearly  plane  surface  on  the  ventral  side  and  anterior  end 
(Fig.  859).  These  rotifiers  are  small,  sluggish  creatures,  very  numer- 
ous, but  not  differing  greatly  among  themselves,  so  that  the  species 
are  hard  to  distinguish  and  students  of  the  rotifiers  have  paid 
little  attention  to  them.  In  other  species  of  the  Notommatidae 
the  corona  has  become  differentiated  in  a  peculiar  way,  forming 
the  so-called  auricles;  these  species  are  classed  mainly  in  the  genus 
Notommata.  The  auricles  are  portions  of  the  ciliated  area  set  off 
prominently  on  each  side  of  the  corona  and  bearing  stronger  cilia 
(Fig.  857,  jB)  ;  they  serve  to  enable  the  animal  to  move  more  rapidly. 
In  the  simplest  cases  the  auricles  are  directly  continuous  with  the 
rest  of  the  ciliated  disk,  as  in  Notommata  aurita  (Fig.  878) .  In  other 
cases  there  i*s  a  space  without  ciHa  between  the  disk  and  the  auri- 
cles (Fig.  881).  The  auricles  are  commonly  kept  contracted  when 
the  animal  is  creeping  about,  so  that  their  existence  would  not  be 
suspected.  But  when  the  animal  prepares  to  swim  through  the 
water  it  unfurls  these  auricles  and  sails  away.  The  species  of 
Notommata  are  more  active  than  Proales,  and  there  are  greater 
differences  among  the  different  members  of  the  genus. 

2.  Synchaetidae.  A  Kne  of  divergence,  consisting  essentially  in  a 
greater  development  of  those  characteristics  of  Notommata  which 
give  it  rapidity  of  movement,  leads  to  the  production  of  what 
is  commonly  classed  as  a  different  family,  —  the  Synchaetidae 
(Fig.  880).  In  Synchaeta  the  entire  corona  is  very  large, 
occupying  the  large  end  of  the  cone-shaped  body,  while  the 
auricles  are  highly  developed,  forming  powerful  swimming  organs 
which  are  set  off  at  a  distance  from  the  remainder  of  the  co- 
rona. By  the  aid  of  these  auricles  the  species  of  Synchaeta  dash 
about  with  such  rapidity  that  they  can  hardly  be  followed  with  the 
microscope.  (See  the  monographic  study  of  the  Synchaetidae  by 
Rousselet,  1902.) 


THE   WHEEL   ANIMALCULES    rROTATORL'\)  567 

A  further  development  of  this  line  is  seen  in  Polyarthra  (Fig.  882). 
Here  powerful  swimming  organs  have  developed  in  the  form  of 
appendages  along  the  sides  of  the  body,  while  the  auricles  have  dis- 
appeared. The  animal  never  attaches  itself,  so  that  the  disap- 
pearance of  the  foot  is  complete.  In  Anarthra  (Fig.  885)  we  fmd 
precisely  a  Polyarthra  that  has  not  yet  developed  the  appendages, 
or  that  has  lost  them  (?). 

Synchaela  and  Polyarthra  are  typical  open-water  rotifers,  consti- 
tuting important  elements  of  the  plankton. 

To  introduce  the  families  of  Rotifera  next  to  be  considered,  it 
is  necessary  to  return  to  certain  features  of  the  Xotommatidae. 
Many  of  the  species  of  that  family  show  a  very  slight  tendency  to 
a  stiffening  of  the  cuticula,  so  that  the  body  retains  a  somewhat 
definite  form,  often  a  little  angular.  Such  notommatids  are  classed 
in  the  genus  Furcularia  (Fig.  870).  These  are  usually  more  active 
than  Proales  or  Notommata,  and  have  longer,  stiffer  toes.  By 
accentuation  of  these  features  of  Furcularia,  and  by  further  spe- 
cialization, there  are  formed  several  families  of  free-swimming 
rotifers : 

3.  Salpinidae.  The  cuticula  becomes  more  hardened,  and  three 
or  four  longitudinal  furrows  are  formed,  one  in  the  dorsal  middle 
line,  one  on  each  side,  and  sometimes  a  weak  one  in  the  ventral 
middle  line.  Thus  there  is  produced  a  sort  of  armor  or  lorica, 
composed  of  three  or  four  plates  (Figs.  886,  887).  Such  loricas  are 
seen  in  most  pronounced  form  in  Salpina  (Fig.  886).  But  every 
possible  intermediate  gradation  exists,  leading  from  Furcularia  to 
Salpina.  The  intermediate  steps  are  mostly  classed  in  the  genus 
Diaschiza  (Fig.  887);  here  the  cuticula  is  only  sHghtly  stitlened,  and 
the  longitudinal  clefts  are  httle  marked.  The  species  of  Diaschiza 
are  many  of  them  hardly  distinguishable  from  Furcularia  or  even 
from  Notommata;  they  were  formerly  classed  in  these  two  genera. 
In  Salpina  the  lorica  is  strongly  developed  and  bears  long  spines 
or  teeth.  Diplois  and  Diplax  stand  between  Diaschiza  and 
Salpina,  having  strong  loricas  but  no  teeth.  There  is  thus  a 
continuous  series  from  the  Notommatidac  to  Salpina.  The  Sal- 
pinidae are  common  amid  vegetation.  (See  the  Monograi)h  on 
Diaschiza  by  Dixon-Nuttall  and  Freeman,  1903.) 


568  FRESH-WATER  BIOLQGY 

4.  Euchlanidae.  Another  line  of  divergence  leads  from  the  No- 
tommatidae,  probably  likewise  through  Furcularia,  to  Distyla^ 
Cathypna,  Monostyla,  and  Euchlanis,  —  forming  the  family  Euch- 
lanidae. The  first  steps  in  this  series  are  seen  in  those  species  of 
Distyla  in  which  the  body  is  soft,  wrinkled,  and  only  a  little  flat- 
tened (Fig.  890).  In  the  extended  condition  these  are  hardly  to  be 
distinguished  from  small  species  of  Furcularia.  But  when  re- 
tracted there  is  a  tendency  to  form  lateral  furrows  along  the  side, 
while  a  sharp  edge  is  seen  in  front  (Fig.  890,  B).  In  other  species  of 
Distyla  (Fig.  891)  these  differentiations  are  permanent  and  the  cutic- 
ula  forms  an  evident  lorica,  consisting  of  a  dorsal  and  a  ventral  plate. 
This  line  of  evolution  shows  its  highest  development  in  Euchlanis 
(Fig.  893).  The  Euchlanidae  are  common  among  aquatic  vegetation. 

5.  Coluridae.  This  group  resembles  the  Euchlanidae,  but  has 
probably  developed  from  the  Notommatidae  separately.  The 
hardened  cuticula  here  forms  a  soHd  lorica,  open  at  each  end  for 
head  and  foot;  sometimes  the  cuticula  is  not  hardened  on  the 
ventral  surface.  A  portion  of  the  lorica  extends  out  over  the 
head  as  a  sort  of  hood  (Fig.  901).  Metopidia  (Fig.  901),  Colurus 
(Fig.  900),  and  Stephanops  (Fig.  899)  are  the  principal  genera;  they 
are  all  minute,  creeping  about  among  plants  and  debris. 

6.  Rattulidae.  A  fifth  Hne  of  divergence  leads  from  the  Notom- 
matidae to  thegenera  Diurella  (Fig.  895)  send Rattiilus  (Figs.  896, 897). 
The  cuticula  of  the  nearly  cylindrical  body  becomes  hardened  over 
nearly  the  entire  surface,  so  as  to  form  a  curved,  pipe-like  structure, 
with  openings  for  the  protrusion  of  head  and  foot.  The  less  differ- 
entiated RattuHdae  (Diurella,  Fig.  895)  resemble  greatly  the  lower 
Notommatidae,  ha\dng  the  cuticula  only  a  httle  stiffened  and  toes 
differing  but  Httle  from  those  of  Furcularia.  But  this  Kne  runs  into 
extremely  bizarre  forms.  The  animals  tend  to  become  unsymmet- 
rical,  the  organs  of  the  right  side  being  smaller,  while  the  body 
becomes  in  some  cases  twisted  into  a  segment  of  a  spiral.  The 
right  toe  becomes  enormously  extended  to  form  a  long  rod-like 
structure,  while  the  left  toe  nearly  disappears  (Figs.  896,  897).  The 
right  side  of  the  tifophi  (Fig.  898)  becomes  smaller  than  the  left. 
The  Rattulidae  are  common  among  vegetation.  (See  the  mono- 
graph of  this  family  by  the  present  writer  (Jennings,  1903).) 


THE    WHEEL   ANIMALCULES    (ROTATORIA)  569 

7.  Dinocharidae.  Scaridium  (Fig.  903)  is  perhaps  essentially  a 
Furcularia  which  has  developed  a  long  foot  and  long  toes,  for  leap- 
ing (compare  Furcularia  longiseta,  Fig.  871).  Dinocharis  (Fig.  904) 
and  Polychaetus  (Fig.  905)  are  perhaps  further  developments,  some- 
what divergent,  along  the  same  line.  All  these  animals  are  given  to 
springing  about  wildly  by  the  aid  of  powerful  strokes  of  the  foot 
and  toes;  the  same  habit  is  found  in  various  species  of  Furcularia. 

Next  may  be  taken  up  a  line  of  divergence  from  the  central 
Notommatidae  that  leads  to  some  extraordinary  forms.  It  pro- 
duces the  great  families  of  the  Hydatinidae,  the  Notopsidae,  the 
Ploesomidae,  and  the  Brachionidae,  with  their  relatives.  Here  de- 
velopment has  proceeded  both  toward  greater  strength  and  activity 
and  toward  protective  armor,  so  that  the  result  is  to  produce  some 
of  the  most  powerful  and  ferocious  rotifers  that  exist. 

8.  Hydatinidae.  The  close  connection  with  the  Notommatidae 
is  seen  in  the  Hydatinidae.  The  well-known  rotifer  Hydatina  senta 
(Fig.  906)  was  formerly  classed  with  the  Notommatidae.  It  has  a 
soft,  segmented  body,  small  foot  and  toes,  ventral  corona,  —  all  as 
in  the  primitive  genus  Proales.  But  the  corona  (Fig.  906,  B)  is 
large  and  differentiated  in  a  way  that  is  characteristic  for  the 
families  making  up  the  present  group.  Around  the  outer  edge  of 
the  corona  the  cilia  form  a  prominent  wreath,  while  about  the 
mouth  is  another  series  of  ciHa  so  interrupted  as  to  form  three 
groups,  one  dorsal  and  two  lateral  (Fig.  906,  B).  In  the  region 
between  the  outer  and  inner  series  of  cilia  are  certain  prominences 
(three  in  Hydatina),  on  which  the  cilia  have  become  long,  stitT 
setae,  doubtless  serving  as  sense  organs.  The  coronal  area  between 
the  parts  thus  far  mentioned  retains  in  Hydatina  senta  a  portion  of 
the  covering  of  fine  ciHa  primitively  found  in  Proales;  in  most  other 
members  of  this  group  these  fine  cilia  have  quite  disappeared. 
The  jaws  are  of  the  peculiar  type  shown  in  Figure  906,  C. 

9.  Notopsidae.  The  next  step  in  differentiation  is  seen  in  Notops 
{ox  Hydatina)  hrachionus  (Fig.  909).  The  cuticula,  while  still  soft, 
has  become  a  little  stiffened,  so  that  the  body  tends  to  hold  its 
form;   the  foot  is  more  prominent. 

The  next  steps  seem  to  be  as  follows:  Notops  clavulatus  (Fig.  912) 
and  Triphylus  lacustris  (Fig.  908)  are  rotifers  showing  still  the  soft 


570  FRESH- WATER   BIOLOGY 

body  of  the  Notommatidae,  but  approaching  the  definite  permanent 
form  found  in  Ploesoma.  The  corona  (Fig.  912,  ^)  is  much  like  that 
of  Hydatina,  save  that  the  fine  ciliation  of  the  general  surface  has 
disappeared.  Notops  pelagicus  (Fig.  910)  shows  a  further  step  in 
the  same  direction;  the  cuticula  is  here  stiffened  to  form  a  thin 
transparent  lorica,  of  sufficient  stiffness  to  form  angles  and  teeth, 
though  with  by  no  means  the  thickness  and  soHdity  found  in 
Ploesoma  and  Brachionus. 

From  Notops  pelagicus  it  is  but  a  short  step  in  one  direction  to 
Gastropus  and  Ploesoma,  in  another  to  Brachionus. 

10.  Gastropodidae.  The  transition  from  Notops  to  Gastropus  is 
shown  hy  Gastropus  hyptopus  (Fig.  915),  which  was  originally  con- 
sidered a  species  of  Notops,  and  which  if  it  stood  by  itself  would 
still  be  placed  in  that  genus.  The  lorica  is  here  soft,  the  body 
short  and  thick.  The  lorica  becomes  more  marked,  and  the  other 
pecuHarities  more  pronounced  in  the  other  species  of  Gastropus, 
Gastropus  stylifer  (Fig.  917)  forming  the  extreme  in  this  direc- 
tion. 

11.  Anapodidae.  Probably  derived  from  forms  similar  to  Gas- 
tropus by  a  process  of  reduction  are  the  species  of  Ana  pus  (Fig.  911), 
in  which  the  foot  is  lacking,  the  corona  small  and  simple. 

12.  Ploesomidae.  The  species  of  Ploesoma  (Figs.  918  to  920)  are 
closely  related  to  Notops  and  Gastropus.  Ploesoma  truncatum  (Fig. 
920)  shows  a  lorica  only  a  little  stronger  than  that  of  Notops  pel- 
agicus, and  resembhng  that  of  Gastropus  hyptopus,  though  it  has 
many  irregular  wrinkles.  In  other  species  of  Ploesoma  the  lorica 
becomes  stronger  and  marked  in  very  pecuHar  ways.  Ploesoma 
lenticulare  (Fig.  918)  and  P.  hudsoni  (Fig.  919)  are  among  the  most 
active  and  powerful  of  the  predaceous  Rotifera.  They  tear  their 
w^ay  through  the  water  at  a  furious  rate,  darting  from  side  to  side, 
and  seizing  and  devouring  with  their  powerful  jaws  other  rotifers 
with  which  they  come  in  contact.  The  Ploesomidae  are  among  the 
most  important  plankton  organisms. 

13.  Brachionidae.  From  Hydatina  and  Notops  to  Brachionus 
the  step  is  perhaps  still  shorter  than  to  Gastropus  and  Ploesoma. 
In  Brachionus  (Figs.  922,  923)  the  three  prominences  that  surround 
the  mouth  in  Hydatina  and  Notops  (see  Figs.  906,  910)  have  become 


THE  WHEEL  ANIMALCULES   (ROTATORIA)  571 

much  developed,  so  that  they  stand  high  above  the  general  surface 
of  the  corona  (Fig.  923).  They  partly  enclose  a  sort  of  funnel, 
open  on  the  ventral  side,  which  leads  down  to  the  mouth.  In 
most  species  of  Brachionus  the  integument  has  become  very  thick 
and  hard,  so  as  to  form  a  stout  lorica,  often  bearing  spines  or  teeth 
(Fig.  921).  But  Brachionus  mollis  Hempel  (Fig.  925)  marks  the 
transition  in  this  respect,  the  integument  being  merely  a  little 
stiffened  and  without  spines  or  teeth.  In  Brachionus,  as  in  Ploesoma 
and  Gastropus,  the  stout  foot  is  marked  with  rings.  The  jaws  are 
constructed  on  much  the  same  plan  throughout  all  these  groups. 

The  Brachionidae  are  among  the  most  numerous  of  the  rotifers 
found  in  ponds  and  pools  amid  vegetation.  Some  of  the  species 
are  extremely  variable. 

14.  Anuraeidae.  An  offshoot  of  the  Brachionidae  is  found  in  the 
Anuraeidae  (Figs.  913,  916).  The  general  organization  is  the  same 
as  in  Brachionus,  but  the  foot  has  been  lost,  though  in  the  males 
(Fig.  913,  C)  it  is  retained.  The  lorica  shows  in  some  species  of 
Notholca  a  tendency  to  run  into  bizarre  forms  (Fig.  916).  The 
Anuraeidae  are  among  the  commonest  of  the  rotifers  of  the  plank- 
ton; they  vary  extremely  with  seasonal  and  other  changes. 

15.  As  plane  hnidae.  The  group  diverging  by  way  of  Hydatina 
is  now  left,  and  another  offshoot  of  the  Notommatidae  taken  u[). 
In  the  Asplanchnidae  the  body  remains  soft,  but  becomes  large  and 
inflated,  while  the  foot  disappears;  the  jaws  are  of  a  remarkable 
type  known  as  the  incudate  (Fig.  929,  B),  and  the  alimentary  canal 
loses  its  posterior  opening  (see  Fig.  929,  A),  the  undigested  waste 
being  disgorged  through  the  mouth.  But  one  finds  in  all  these 
respects  forms  transitional  between  the  Notommatidae  and  the 
Asplanchnidae.  Thus,  Asplanchnopus  (Fig.  927)  retains  the  foot, 
though  it  lacks  the  intestine,  and  has  the  characteristic  jaws  of  this 
family.  Harringia  (Fig.  928)  retains  not  merely  the  foot,  but  like- 
wise the  intestine.  Its  corona  is  like  that  of  As  plane  Jnia  while  its 
jaws  (Fig.  928,  B)  are  squarely  intermediate  between  the  usual  form 
and  the  incudate  type  characteristic  of  Asplanchna.  The  t}pical 
incudate  jaws  consist  mainly  of  the  very  large  incus  (fulcrum  and 
rami),  the  mallei  having  nearly  or  quite  disappeared;  but  in  Har- 
ringia all  the  typical  parts  of  the  jaws  are  clearly  seen. 


572  FRESH-WATER  BIOLOGY 

The  typical  Asplanchnas  are  beasts  of  prey,  the  jaws  forming  a 
great  pair  of  forceps  which  can  be  thrust  from  the  mouth  to  seize 
other  large  animals.  Asplanchna  herrickii  de  Guerne  and  A.  pri- 
odonta  Gosse  (Fig.  929)  are  important  elements  of  the  plankton  of 
lakes.  In  the  Great  Lakes  they  sometimes  swarm  so  densely  that 
a  net  dipped  into  the  water  captures  thousands.  Other  species  of 
the  Asplanchnidae  Hve  among  water  plants. 

16-18.  Floscularida.  Now  come  certain  groups  of  rotifers  that 
seem  at  first  view  to  differ  markedly  in  almost  every  respect  from 
the  notommatids.  The  Flosculariidae  (Figs.  933  to  936)  live  attached 
in  tubes.  The  foot  has  become  a  stalk  for  attachment;  there  are 
no  toes.  The  corona  is  immensely  large,  forming  a  great  lobed 
net  of  thin  membrane,  which  can  be  spread  widely  and  serves  to 
capture  Hving  prey;  the  mouth  Hes  in  the  center  at  the  bottom  of 
this  net.  The  ciUa  about  the  edge  of  the  corona  have  become  enor- 
mously long  and  slender  rods  or  threads,  which  do  not  beat  as  cilia 
usually  do,  but  may  be  moved  about  so  as  to  aid  in  entanghng  prey. 
In  connection  with  the  method  of  feeding  on  large  animals  thus  cap- 
tured, the  alimentary  canal  (Fig.  934)  has  become  greatly  devel- 
oped. The  upper  part  of  the  coronal  net  forms  a  great  funnel,  called 
the  infundibulum  (i),  partly  closed  off  below  by  a  ring-like  fold, 
the  diaphragm  (d),  which  has  about  its  edge  an  interrupted  cir- 
clet of  cilia.  The  opening  through  the  diaphragm  leads  into  a 
second  chamber,  the  vestibulum  (v),  at  the  bottom  of  which  is  the 
mouth  (w).  From  the  mouth  there  hangs  the  slender  esophageal 
tube  (o)  ending  freely  below.  The  food  after  passing  through  this 
reaches  a  third  large  cavity,  the  proven triculus  (pr) .  It  is  only  at 
the  posterior  part  of  this  that  the  mastax  (mx)  and  jaws  are  reached; 
so  that  all  thus  far  seen  corresponds  merely  to  the  short  mouth 
cavity  lying  in  front  of  the  jaws  in  other  rotifers.  The  trophi 
(Figs.  934  and  933,  D)  are  pecuKarly  modified,  the  unci  forming  a 
pair  of  two-tined  forks  which  are  the  main  part  of  the  jaws,  though 
the  other  typical  parts  can  be  distinguished. 

The  Flosculariidae  include  two  genera,  Floscularia  (Figs.  933  to 
936)  and  Stephanoceros  (Fig.  937).  The  numerous  species  are  found 
abundantly  seated  in  transparent  tubes  attached  to  plants;  they 
are  among  the  most  attractive  objects  known  to  microscopists 


I 


THE   WHEEL   ANIMALCULES    (ROTATORL\)  573 

(cf.  p.  553).  Of  Stephanoceros  there  is  but  one  species  (Fig.  937), 
while  of  Floscularia  there  are  many,  varying  extremely  in  the  form 
of  the  corona.  A  few  species  have  become  free  and  swim  about 
in  the  open  water  (Fig.  935).  The  fact  that  they  bear  their  tubes 
with  them  shows  that  the  free  Hfe  has  been  secondarily  acquired, 
after  the  animals  had  become  adapted  to  the  attached  condition. 
All  young  Floscularias  swim  about  for  a  time  by  means  of  moving 
cilia,  just  as  do  other  rotifers.  The  males  (Fig.  933,  B)  are  free- 
swimming  throughout  life. 

What  relationship  have  the  Flosculariidae  to  the  typical  rotifers 
found  in  the  Notommatidae?  It  must  be  remembered  that  not 
all  Flosculariidae  have  the  extraordinary  forms  shown  in  Figs.  933 
and  937.  In  some,  the  borders  of  the  corona  are  not  drawn  out 
into  lobes,  but  are  smooth,  as  in  other  rotifers  (see  Fig.  936).  In 
others  the  ciha  of  the  coronal  edge  are  all,  or  partly,  short  and  beat 
regularly,  like  those  of  other  rotifers;  and  about  the  mouth  is  the 
same  circlet  of  cilia  found  in  other  rotifers.  Such  Floscularias 
approach  much  more  nearly  to  the  typical  Notommatidae  than  do 
the  extreme  developments  along  this  Hne  seen  in  Stephanoceros 
and  certain  species  of  Floscularia. 

Furthermore,  among  close  relatives  of  the  notommatids  are  cer- 
tain rotifers  that  seem  to  show  transitional  stages  leading  to  the 
Flosculariidae.^  In  Microcodides  and  in  Microcodon  (Fig.  931),  the 
corona  is  formed  on  essentially  the  same  plan  as  in  the  Floscularias, 
and  there  are  other  peculiarities  that  seem  to  show  that  these  are 
transitional  forms.  In  Microcodon,  as  in  Floscularia,  the  corona 
is  the  broadest  part  of  the  body;  it  has  elevated  edges,  approaching 
the  net  formation,  and  the  mouth  is  in  its  center,  with  an  inter- 
rupted circlet  of  cilia  about  it.  The  foot  in  Microcodon  as  in  Flos- 
cularia forms  a  sort  of  long  slender  stalk,  not  ending  in  toes.  But 
in  Microcodon  it  ends  in  a  sharp  point,  while  in  Floscularia  it  ends 
in  a  disk;  this  is  doubtless  because  the  fonner  is  still  a  free  animal, 
while  the  latter  is  attached.  It  is  a  most  suggestive  fact  that  Mi- 
crocodon frequently  places  itself  in  the  upright  position,  with  the  toe 
attached  by  a  thread  of  mucus,  and  thus  remains  for  a  time  in  a  cer- 
tain spot;  such  habits  might  readily  lead  to  pemianent  attachment. 
1  These  important  considerations  are  due  to  VVeseaberg-Lund  (1899)  • 


574 


FRESH-WATER   BIOLOGY 


All  together,  Microcodon  seems  to  form  a  link  between  the  Flos- 
culariidae  and  the  Notommatidae.  Microcodon  itself  is  closely 
connected  with  the  Notommatidae  by  the  transitional  species  be- 
longing to  the  genus  Microcodides  (Fig.  932).  These  have  corona, 
body,  and  toes  more  nearly  on  the  notommatoid  plan.  The  two 
genera  make  up  the  family  Microcodonidae. 

Specialization  going  even  beyond  that  in  the  Flosculariidae  is 
seen  in  Apsilus  (Fig.  938)  and  AtrocJms  (Fig.  939).  In  these  ex- 
traordinary rotifers  the  ciha  have  been  completely  lost.  The 
comphcated  structure  of  the  alimentary  canal  shows  their  close 
relationship  to  the  Flosculariidae.  In  the  young  the  ciha  still 
exist,  and  the  animals  swim  about  by  their  aid. 

19-22.  Melicertida.  Another  group  of  extraordinary  and  at- 
tractive rotifers  is  that  of  which  Melicerta  (Fig.  948)  is  the  repre- 
sentative. These  were  formerly  classified  with  the  Flosculariidae, 
the  two  forming  the  group  Rhizota.  But  it  is  evident  that  the 
two  famines  differ  widely,  and  that  the  group  Rhizota  is  not  a 
natural  one.  The  Mehcertidae  are  found,  hke  the  floscules,  at- 
tached to  aquatic  plants,  often  in  great  numbers.  Many  live  in 
tubes,  and  the  species  of  Melicerta  manufacture  their  tubes  in  a 
most  interesting  manner,  as  is  well  described  in  Hudson  and  Gosse 

(1889). 

The  most  important  peculiarity  of  the  Mehcertidae  is  perhaps 
the  corona.  This  is  a  large  disk,  bare  within,  but  having  around 
its  outer  edge  a  series  of  strong  ciha,  just  as  in  many  other  rotifers. 
But  in  this  group  is  found  a  special  pecuHarity.  This  outer  wreath 
is  differentiated  into  two  series  of  cilia,  running  parallel  around  the 
disk  (Fig.  865).  The  inner  series  has  much  larger  ciha  than  the 
outer  one,  and  between  the  two  is  found,  in  most  cases,  a  groove. 
This  groove  is  often  hned  with  fine  ciha.  Along  the  groove  small 
food  particles  are  carried  to  the  mouth,  situated  on  the  ventral 
side.  In  some  genera  the  disk  is  drawn  out  to  form  two,  four, 
or  eight  lobes,  giving  the  animal  an  extraordinary  appearance 
(Fig.  950);  in  other  cases  it  is  nearly  circular  (Figs.  865,  951,  952). 
Throughout  this  group  the  jaws  are  of  a  pecuKar  type  (Fig.  866), 
known  as  the  malleo-ramate.     As  a  rule  the  animals  have  two  eyes. 

The  more  extreme  types  of  this  group  seem  to  stand  far  from 


THE  WHEEL  ANIMALCULES    (ROTATORIA) 


575 


the  typical  free-swimming  rotifers.  Yet  again,  as  in  most  other 
cases,  free-swimming  species  form  a  transition  to  these  extreme 
types.  One  finds  the  same  peculiar  corona,  the  same  remarkable 
type  of  jaws,  and  various  other  features  in  common  with  the 
MeHcertidae,  in  a  number  of  free-swimming  rotifers.  These  in- 
clude the  gmQrsiPterodina  (Fig.  942),  Pomp  holy  x,  Pedalion  (Fig.  946), 


Fig.  865.     Corona  of  Lacinularia  socialis  Ehr.,  to  show  the  two  wreaths  of  cilia. 
B,  Side  view.     (After  Wesenberg-Lund.) 


A,    Dorsal  view. 


Triarthra  (Fig.  944),  and  Tetramastix  (Fig.  945).  These  rotifers  are 
the  only  ones  that  have  corona  and  jaws  Hke  those  of  the  Meli- 
certidae,  and  they  agree  with  them  in  many  other  particulars. 
Thus,  all  have  two  eyes,  while  most  other  rotifers  have  but  one. 
In  all  there  is  either  no  foot,  or  it  is  a  pecuhar  one,  lacking  the 
characteristic  toes.  In  Pterodina  the  foot  ends  in  a  bundle  of 
cilia,  and  this  is  Hkewise  true  of  the  young  of  the  jMeHcertidae.     In 


Fig.  866.     Malleo-ramate  jaws.     A,  Jaws  of  Melicerta  ringens  Schrank.     (.\fter  Weber.)     B,  Jaw3 
of  Pterodina  caeca  Parsons.     (After  Rousselet.) 

many  MeHcertidae  there  is  below  the  mouth  a  peculiar  fold  of  in- 
tegument forming  the  so-called  ''chin"  which  plays  a  part  in  the 
formation  of  the  pellets  used  for  building  the  tubes.  This  chin 
is  hkewise  found,  in  a  sHghtly  less  developed  condition,  in  Pedal- 
ion  (Fig.  946,  ch)  and  in  Triarthra,  while  nothing  of  the  sort  is 
found  outside  the  present  group.  The  remarkable  similarity  of 
corona,  jaws,  eyes,  and  other  features  seems  to  demonstrate  clearly 
that  all  these  free-swimming  rotifers  are  closely  related  to  each 
other  and  to  the  MeHcertidae. 


576  FRESH-WATER    BIOLOGY 

The  free-swimming  members  of  the  group  have  developed  a 
number  of  striking  external  peculiarities,  due  to  differences  in  the 
mode  of  life.  Pterodina  (Fig.  942)  has  a  flat  body,  protected  by  a 
hard  cuticula  forming  a  lorica;  this  shape  aids  it  greatly  in  swim- 
ming. Pedalion  (Fig.  946)  has  developed  six  great  limbs  which  Hke- 
wise  aid  it  in  swimming.  Similar  Hmbs,  but  in  a  simpler  condition, 
are  seen  in  Triarthra  (Fig.  944)  and  Tetramastix  (Fig.  945).  In  these 
genera  the  function  of  the  limbs  seems  to  be  mainly  to  protect  the 
animals  from  being  swallowed  by  such  predatory  beasts  as  As- 
planchna.  One  often  sees  an  Asplanchna  attempt  to  swallow  one  of 
these  at  a  gulp,  but  the  prey  at  once  extends  its  long  appendages  in 
all  directions,  and  these  frustrate  the  attempt.  The  male  of  Pedalion 
(Fig.  946,  B)  has  simple  appendages  and  bears  a  striking  resemblance 
to  one  of  the  simpler  species  of  Triarthra  (Fig.  944,  B). 

An  extraordinary  offshoot  of  the  Meticertidae  is  seen  in  the 
spherical  rotifer  Trochosphaera  (Fig.  947).  In  the  corona,  the  jaws, 
the  lack  of  a  foot,  and  various  other  features  it  agrees  essentially 
with  the  MeHcertidae,  though  its  external  form  is  very  different. 

23-25.  Bdelloida.  This,  the  last  group  of  rotifers,  includes  mainly 
the  genera  Rotifer  (Figs.  958,  960),  Philodina  (Fig.  959),  Callidina 
(Fig.  961),  Microdina  (Fig.  962),  and  Adineta  (Fig.  957).  They  are 
somewhat  worm-Hke  animals,  often  creeping  like  leeches,  and  found 
in  great  numbers  amid  aquatic  vegetation.  They  are  specially 
abundant  in  Sphagnum  and  other  wet  moss  or  moss-like  plants;  an 
immense  number  of  species  particularly  of  Callidina  are  found  in 
such  places. 

This  group  differs  widely  from  the  typical  rotifers  in  many  points. 
The  typical  corona  of  the  Bdelloida  is  a  highly  differentiated  struc- 
ture consisting  mainly  of  two  flat  disks  borne  on  stalks  and  with 
cilia  about  their  edges  (Fig.  959,  etc.).  When  the  ciHa  are  in  mo- 
tion these  two  disks  give  the  appearance  of  two  revolving  wheels. 
It  is  to  this  that  the  name  wheel-animalcule,  and  the  Latin  terms 
rotifer  and  rotator  are  due;  the  Bdelloida  were  the  first  rotifers  to 
attract  the  attention  of  microscopists.  The  base  of  the  stalks 
bearing  the  disks  is  often  clothed  with  short  ciha.  On  the  dorsal 
side  of  the  corona  there  is  a  long  tentacle. 

The  foot  ends  as  a  rule  in  three  or  four  minute  projections,  by 


THE  WHEEL    AmMALCUI.ES    (ROTATORTA)  577 

which  the  animals  attach  themselves;  it  bears  also  a  pair  of  ''spurs " 
on  its  dorsal  side,  a  short  distance  from  the  end.  These  spurs 
perhaps  represent  the  two  toes  of  other  rotifers. 

The  trophi  (Fig.  867)  present  perhaps  the  most  modified  type 
found  in  the  Rotifera;  they  show  clearly  that  this  group  is  not  a 
primitive  one.  In  most  species  the  trophi  are  represented  by  two 
pieces  shaped  like  a  quarter  of  a  sphere  and  placed  side  by  side 
(Fig.  867,  A).  Across  the  free  surface  of  these  pieces  extend  two  or 
more  ridges.  These  jaws  may  be  opened  and  closed  by  the  mus- 
cular mass  in  which  they  are  imbedded,  the  ridges  fitting  together 
in  such  a  way  as  to  serve  as  grinding  teeth.     The  two  halves  of  the 


Fig.  867.     Jaws  of  Bdelloida.    ^,  Jaws  of  P/n'Wina  Sryce/ Weber  (typical  ramate  jaws). 
Microdina  paradoxa  Murray.     (After  Murray.) 


B.  Jaws  of 


trophi  represent  the  two  rami  of  other  rotifers,  the  remainder  of 
the  apparatus  having  almost  completely  disappeared.  But  tran- 
sitional forms  (Fig.  867,  B)  show  clearly  how  these  trophi  are  de- 
rived from  the  typical  structure. 

The  point  in  which  the  Bdelloida  differ  most  from  other  rotifers 
is  in  the  fact  that  they  have  two  ovaries  in  place  of  one.  This 
pecuharity  is  shared  with  the  Bdelloida  only  by  a  bizarre  group  of 
parasitic  marine  rotifers,  the  Seisonacea  (Fig.  868)  which  live  at- 
tached to  the  marine  crustacean  Nehalia.  On  account  of  this  pecu- 
liarity the  Bdelloida  and  Seisonacea  are  commonl}'  classed  apart 
from  all  other  rotifers  as  the  Digononta,  the  others  being  called  the 
Monogononta. 

The  Bdelloida  include  an  immense  number  of  species,  the  greater 
part  of  them  belonging  to  the  genus  Callidina.  The  difference 
between  species  is  often  only  slight,  and  the  animals  change  form 
almost  continually,  so  that  their  systematic  study  is  perhaps  more 


578 


FRESH-WATER   BIOLOGY 


difficult  than  that  of  any  other  group  of  rotifers;  it  has  been  con- 
fined mainly  to  specialists  in  this  particular  group. 

Many  species  of  the  Bdelloida  possess 
a  remarkable  power  of  withstanding  dry- 
ing. Philodina  roseola  is  often  found  as 
Httle  pink  balls  in  the  dry  deposits  in 
the  bottoms  of  urns  and  eave-troughs. 
When  this  material  is  placed  in  water, 
the  pink  balls  quickly  swell,  take  the 
rotifer  form,  and  continue  their  inter- 
rupted life  activities  where  these  were 
stopped.  Many  species  may  be  ob- 
tained for  study  in  the  Hving  condition 
from  dried  moss  and  other  vegetation 
brought  from  a  distance.  No  males  are 
known  in  the  Bdelloida. 

26.  Tlie  Seisonacea  (Fig.  868)  are  ex- 
traordinary rotifers  parasitic  on  marine 
Crustacea.  Their  relationships  are  un- 
certain, but,  having  two  ovaries,  they 
are  usually  placed  near  the  Bdelloida. 
In  the  Seisonacea  male  and  female  are 
Since  they  are  exclusively  marine,  these 
forms  are  omitted  from  the  synoptic  key. 

The  studies  thus  far  made  of  the  rotifers  of  different  regions 
seem  to  indicate  that  in  general  these  animals  may  be  said  to  be 
potentially  cosmopolitan,  any  given  species  occurring  wherever  the 
conditions  necessary  to  its  existence  occur.  Whether  any  given 
rotifer  shall  be  found  in  a  given  body  of  water  depends  mainly, 
not  upon  the  locahty  of  this  body  of  water,  but  upon  the  precise 
conditions  there  found.  Studies  on  the  rotifers  of  Europe,  Asia, 
Africa,  America,  and  AustraHa  show,  not  different  faunas  in  these 
regions,  but  the  same  common  rotifers  found  everywhere,  with 
merely  a  new  form  here  and  there,  and  it  is  an  extraordinary 
fact  that  when  a  new  rotifer  is  described  from  Africa  or  Australia, 
its  next  occurrence  is  often  recorded  from  Europe  or  America.  In 
stagnant  swamps  all  over  the  world  appear  to  be  found  the  char- 


FiG.  868.  Seison  annulatus  Glaus,  female. 
(After  Claus.) 


similar  and  of  equal  size. 


THE   WHEEL   ANIMALCULES    (ROTATORLA)  579 

acteristic  rotifers  of  stagnant  water;  in  clear  lake  water  arc  found 
the  characteristic  Hmnetic  rotifers;  in  sphagnum  swamps  every- 
where, the  sphagnum  rotifers.  Variation  in  the  rotifer  fauna  of 
different  countries  is  probably  due  mainly  to  differences  in  the  con- 
ditions of  existence  in  the  waters  of  these  countries,  rather  than  to 
any  difficulty  in  passing  from  one  country  to  another.  The  num- 
ber of  different  sorts  of  Rotifera  to  be  found  in  any  given  region 
depends  upon  the  variety  of  conditions  to  be  found  in  the  waters 
of  this  region.  Two  bodies  of  water  half  a  mile  apart,  presenting 
entirely  different  conditions,  are  likely  to  vary  more  in  their  rotifer 
fauna  than  two  bodies  of  water  5000  miles  apart  that  present 
similar  conditions.  Of  course,  the  tropics  will  have  characteristic 
species  not  found  in  cooler  regions,  since  they  present  conditions  of 
existence  not  found  elsewhere,  and  the  same  may  be  true  of  Arctic 
regions.  The  problem  of  the  distribution  of  the  Rotifera  is  then 
mainly  a  problem  of  the  conditions  of  existence  rather  than  of  the 
means  of  distribution.  The  ability  of  the  eggs  to  live  in  dried 
mud,  which  may  be  carried  about  on  the  feet  of  birds  or  I)l()wn 
about  as  dust  by  the  winds,  seems  to  give  sufficient  opportunities 
for  any  species  to  multiply  wherever  occur  the  conditions  neces- 
sary for  existence.  Most  rotifers  seem  adapted  to  a  rather  nar- 
rowly limited  set  of  conditions. 

Many  species  of  rotifers  vary  extremely  in  the  external  details 
of  their  structure.  This  is  particularly  true  of  loricate  rotifers 
that  bear  teeth,  spines,  or  other  projections.  Extreme  examples 
of  such  variation  are  seen  in  Brachionus  bakeri  Ehr.  and  in  Anuraca 
cochlearis  Gosse  (Fig.  913).  Lauterborn  shows  that  the  variations 
of  Anuraea  cochlearis  are  by  no  means  haphazard,  but  depend  upon 
the  seasons  and  upon  changes  in  the  conditions  of  existence.  In 
the  course  of  a  year  this  species  undergoes  a  cycle  of  regular  changes 
from  month  to  month,  and  this  yearly  cycle  was  found  to  be  essen- 
tially the  same  during  a  period  of  study  of  twelve  years.  In  the 
colder  months  of  the  year  appear  individuals  of  greater  size,  with 
smooth  loricas  and  long  prominent  spines.  As  the  waters  become 
warmer,  in  spring  and  summer,  the  individuals  found  are  smaller 
in  size,  the  surface  of  the  lorica  becomes  roughened,  and  the  spines 
grow  shorter,  until  the  caudal  one  disappears  completely.     As  cold 


^8o  FRESH-WATER   BIOLOGY 

weather  approaches  there  is  a  return  to  the  stouter  forms.  There 
results  an  immense  number  of  different  forms,  many  of  which  have 
been  described  as  different  species.  Apparently  these  changes  are 
adaptive  in  character.  At  the  higher  temperatures  of  summer  the 
inner  friction  of  the  water  decreases  much  (as  Ostwald  has  shown) , 
so  that  swimming  animals  tend  to  sink  more  readily  than  be- 
fore. The  decrease  in  size  of  the  body,  with  the  roughening  of  its 
surface,  increases  greatly  the  proportion  of  body  surface  to  body 
weight,  so  that  the  animals  sink  less  readily;  the  tendency  to  sink 
due  to  the  warmth  of  the  water  is  compensated.  The  small,  rough 
forms  are  therefore  adapted  to  warm  ,weather.  But  the  decrease 
in  size  of  the  spines  cannot  be  accounted  for  in  this  way;  it  must 
depend  on  other  relations. 

In  the  Rotifera  the  males  are  usually  minute,  degenerate  crea- 
tures, —  the  race  being  represented  mainly  by  the  females !  The 
males  usually  have  no  alimentary  canal,  and  thus  during  their 
entire  life  they  never  take  food.  They  are,  of  course,  therefore, 
condemned  to  an  early  death.  They  usually  swim  about  rapidly, 
often  swarming  about  the  females.  Fecundation  takes  place  in 
some  cases  by  the  insertion  of  the  copulatory  organ  of  the  male 
into  the  cloaca  of  the  female;  this  has  been  seen  in  many  cases. 
In  other  cases  apparently  the  male  pierces  the  body  wall  of  the 
female,  injecting  the  spermatozoa  directly  into  the  body  cavity. 
This  takes  place  in  Hydatina. 

In  a  few  of  the  Rotifera  the  males  are  of  the  same  size  and  struc- 
ture as  the  females  (in  the  Seisonacea).  In  Proales  werneckii  the 
male  is  of  the  same  size  and  form  as  the  female,  but  the  aHmentary 
canal,  while  present,  is  simplified  and  reduced  in  size.  In  other 
species,  various  vestiges  of  the  alimentary  canal  may  be  present, 
but  they  are  not  functional.  In  certain  groups  no  male  is  known 
to  exist;  this  is  true  for  the  entire  suborder  of  the  Bdelloida.  In 
the  Rattulidae  likewise  no  males  have  as  yet  been  seen.  Much 
further  study  of  the  existence,  structure,  and  activities  of  the  males 
is  needed.  If  they  are  actually  non-existent  in  some  groups,  then 
of  course  the  reproduction  is  throughout  by  parthenogenesis,  — 
fertilization  of  the  egg  not  occurring  even  at  long  intervals. 
Most  rotifers  produce  several  different  sorts  of  eggs.    These  are 


THE   WHEEL   ANIMALCULES    (ROTATORL\)  581 

the  following:  (i)  large  eggs,  without  a  thick  shell,  from  which 
females  are  produced;  (2)  small  eggs,  similar  to  the  last  in  ap- 
pearance but  producing  males;  (3)  eggs  which  have  a  thick  shell, 
often  armed  with  spines  or  projections.  These  are  often  spoken 
of  as  ^'winter  eggs"  or  ''resting  eggs."  They  may  apparently 
live  a  long  time  under  all  sorts  of  unfavorable  conditions,  devel- 
oping when  favorable  conditions  are  restored.  The  relation  of 
these  different  sorts  of  eggs  to  the  appearance  of  the  males,  and  to 
fertiHzation,  has  been  much  discussed  and  investigated.  In  Ilyda- 
tina,  according  to  Maupas,  and  in  Asplanchna  priodonta,  according 
to  Lauterborn,  the  following  is  the  state  of  the  case.  There  are 
two  sorts  of  females,  not  distinguishable  externally,  but  one  pro- 
ducing large  eggs,  the  others  small  ones.  The  large  eggs  cannot  be 
fertilized,  and  they  always  develop  into  female  rotifers.  The  small 
eggs,  if  not  fertiHzed,  develop  into  male  rotifers,  but  they  may  be 
fertilized,  and  if  this  occurs  they  become  transformed  into  the 
*' resting  eggs,"  from  which  there  later  develop  female  rotifers. 
In  Hydatina,  according  to  Maupas,  fecundation  can  occur  only 
when  the  female  is  young,  before  any  of  the  eggs  develop,  and  the 
female  so  fecundated  produces  only  resting  eggs.  But  in  As- 
planchna and  in  various  other  rotifers  the  same  female  produces 
both  male  eggs  and  resting  eggs,  although  only  the  latter  are 
fertilized.  According  to  Mrazek,  in  Asplanchna  herrickii  the  same 
female  bears  at  the  same  time  ordinary  female  eggs,  male  eggs,  and 
resting  eggs.  There  is  apparently  much  variation  in  these  rela- 
tions among  different  rotifers. 

Males  and  resting  eggs  are  as  a  rule  not  found  at  all  times  of 
the  year,  but  appear  at  certain  periods,  —  the  resting  eggs  of 
course  following  the  appearance  of  males.  In  the  pelagic  Rotifera, 
Lauterborn  has  made  a  study  of  the  periodical  appearance  of  males 
and  of  resting  eggs.  He  finds  that  these  rotifers  may  be  divided 
into  three  classes:  (i)  perennial  rotifers,  which  occur  in  greater 
or  less  numbers  all  the  year  round;  (2)  summer  species,  found 
only  in  summer;  (3)  winter  species,  found  only  in  winter.  In  the 
perennial  species  parthenogenetic  reproduction  continues  through- 
out the  year;  but  males  appear  as  a  rule  only  twice  a  year,  in 
spring  and  fall.     In  the  summer  rotifers,  males  appear  in  the  fall, 


582 


FRESH-WATER  BIOLOGY 


and  the  species  is  carried  over  the  winter  in  the  resting  eggs  re- 
sulting from  fertilization  by  the  males.  In  the  winter  rotifers,  the 
males  appear  in  the  spring,  and  the  species  is  carried  over  the  sum- 
mer by  the  resting  eggs. 

By  the  greater  number  of  rotifers  the  eggs  are  laid  as  soon  as 
they  are  completely  formed,  development  taking  place  outside  the 
body  of  the  mother.  But  some  rotifers  are  viviparous,  the  egg 
being  retained  in  the  mother's  body  until  it  is  partly  or  completely 
developed.  It  is  remarkable  that  the  viviparous  condition  is  found 
in  several  different  groups  of  rotifers  that  are  not  closely  related, 
so  that  it  must  have  been  developed  independently  several  times 
within  the  Rotifera.  Asplanchna  and  Rotifer  are  among  the  best- 
known  viviparous  genera.  Philodina  and  Callidina,  closely  related 
to  Rotifer,  as  a  rule  deposit  the  eggs  undeveloped,  though  certain 
species  in  both   these  genera  produce  living  young.     Thus  ovi- 

parity  and  viviparity,  which  in 
some  higher  animals  distinguish 
grand  classes,  are  among  the 
rotifers  both  found  in  the  limits 
of  a  single  genus. 

It  is  a  rather  remarkable  fact 
that  the  cleavage  and  early  de- 
velopment of  the  rotifer  egg  does 
not  resemble  that  of  the  animals 
to  which  the  rotifers  have  often 
been  considered  the  nearest  rela- 
tives. In  annelids  and  lower 
mollusks  the  early  development 
shows   a   remarkable   similarity 

Fig.  869.    Developing  egg  of  a  rotifer  Asplanchna  eVCn  in  thc  dctails    of    tllC    Spiral 

herrickii  de  Guerne.     a.  Single  cell  stage;   b,  four  _                                            .           .                  . - 

cells;  c,  twenty  cells;  d,  ninety -four  cells;  e,  optical  clcaVagC.         But     m     thC     rOtllCrS 
section   through    embryo   formed   of   many   cells. 

(After  Jennings.)  the  clcavage  f ollows  a  Completely 

different  type  (Fig.  869).  The  developing  rotifer  forms  a  soKd  mass, 
which  contains  no  cavity  until  the  organs  formed  within  this  mass 
begin  to  separate,  just  before  the  rotifer  takes  its  final  form  and 
becomes  active. 

When  living  the  body  of  the  Rotifera  is  usually  transparent  and 


THE   WHEEL   ANIMALCULES   (ROTATORIA)  583 

all  the  organs  are  sharply  defined,  so  that  they  are  readily  seen. 
After  death,  the  transparency  and  sharpness  are  as  a  rule  lost,  and 
most  methods  of  killing  the  rotifers  cause  them  to  become  strongly 
contracted,  so  that  the  structure  is  no  longer  clear.  Direct  obser\'a- 
tion  of  the  hving  animal  will  therefore  always  remain  one  of  the  most 
important  methods  of  studying  these  forms,  for  whatever  purpose. 
By  Rousselet's  method,  however,  it  is  now  as  easy  to  pre- 
serve most  of  the  Rotifera  in  natural  form  as  any  other  lower 
animals.  This  method  is  essentially  as  follows:  The  animals 
are  killed  uncontracted  by  the  aid  of  a  narcotizing  fluid,  the  essen- 
tial feature  of  which  is  a  |  to  i  per  cent  solution  of  hydrochlorate 
of  cocaine.  The  cocaine  may  be  used  in  a  simple  watery  solution, 
but  better  results  are  reached  by  using  the  following  mixture: 

Hydrochlorate  of  cocaine  (2  per  cent  solution) .  .     3  parts 

Methyl  alcohol i  part 

Water 6  parts 

The  rotifers  are  brought  into  a  small  volume  of  water,  and  a 
little  of  this  narcotizing  fluid  is  mixed  with  it.  The  proper  amount 
must  be  learned  by  trial,  but  it  is  always  best  to  begin  with  a  very 
small  proportion  of  the  fluid,  ^o  or  less,  and  to  add  more  as  required. 
This  fluid  causes  the  rotifers  to  swim  slowly  and  gradually  to  sink 
to  the  bottom.  They  will  soon  die,  and  if  allowed  to  die  unfixed 
will  be  quite  worthless  for  study,  destructive  changes  taking  place 
in  the  tissues  at  the  moment  of  death.  As  soon  therefore  as  the 
ciliary  movement  has  nearly  ceased,  as  much  as  possible  of  the 
water  should  be  drawn  off,  and  a  small  amount  of  0.25  per  cent 
osmic  acid  introduced,  which  kills  and  fixes  the  rotifers  at  once. 
Now  the  osmic  acid  should  be  drawn  off  at  once  and  water  added 
or  the  rotifers  removed  with  a  capillary  pipette  to  fresh  water; 
they  should  be  washed  several  times  in  distilled  water.  If  the 
osmic  acid  is  allowed  to  act  too  long  the  rotifers  will  be  blackened. 
The  blackening  may,  however,  be  later  removed,  if  necessary,  with 
hydrogen  peroxide.  After  washing,  the  rotifers  should  be  pre- 
served in  3  to  6  per  cent  formahn.  They  cannot  as  a  rule  be  pre- 
served in  alcohol  without  extensive  shrinkage,  rendering  them  use- 
less for  further  study. 


584  FRESH-WATER    BIOLOGY 

If  desired,  the  specimens  may  be  permanently  mounted  in  hollow 
ground  slides.  The  slides  should  be  thin  and  the  concavities  shal- 
low, so  that  high  powers  of  the  microscope  may  be  used.  The 
specimens  are  transferred  to  the  concavities  along  with  some  of  the 
formalin  and  covered  with  a  circular  cover-glass.  It  is  best  not  to 
leave  any  bubbles  of  air  beneath  the  cover.  The  superfluous  for- 
malin may  be  withdrawn  from  the  edge  of  the  cover  with  a  bit  of 
filter  paper,  and  the  cover  is  then  sealed  by  the  aid  of  a  revolving 
stage.  It  is,  of  course,  necessary  to  use  some  sealing  material  that 
will  not  allow  water  to  evaporate  through  it.  Rousselet  recommends 
the  following  for  seahng  the  mounts:  After  fixing  the  cover  with  a 
layer  composed  of  a  mixture  of  two-thirds  gum  damar  with  one- 
third  gold  size,  there  are  added  two  coats  of  pure  shellac,  followed 
by  three  or  four  coats  of  gold  size,  allowing  twenty-four  hours  for 
each  coat  to  dry  before  another  is  added. 

Extensive  collections  containing  many  species  of  Rotifera  may 
be  made  by  travelers  and  others  by  the  use  of  the  method  given 
above.  The  rotifers,  taken  with  a  net  or  otherwise,  are  brought 
into  as  small  an  amount  of  water  as  possible,  in  a  watch-glass. 
Then  a  considerable  quantity  of  the  narcotizing  fluid  is  introduced 
and  the  rotifers  are  watched  till  most  of  them  have  sunk  to  the 
bottom.  Thereupon  the  water  is  removed,  so  far  as  possible,  and 
the  J  per  cent  osmic  acid  added.  This  is  removed  as  quickly  as 
can  be  done  without  taking  up  too  many  of  the  rotifers;  they  are 
then  washed  and  preserved  in  formalin.  It  is  very  desirable  to  kill 
a  certain  proportion  of  every  collection  in  osmic  acid  without  previ- 
ous narcotization,  as  some  of  the  loricate  rotifers  are  more  easily 
determined  from  contracted  specimens  than  from  extended  ones. 

A  method  of  mounting  Rotifera  in  the  ordinary  mounting  media, 
such  as  Canada  balsam,  has  been  given  by  Zograf.  It  does  not  give 
such  perfect  results,  in  most  cases,  as  does  Rousselet's  method,  but 
it  is  useful  for  some  species.  The  rotifers  are  stupefied  and  killed 
in  the  way  given  above.  After  they  have  been  in  the  osmic  acid 
from  two  to  four  minutes,  this  is  removed  as  far  as  possible,  and  a 
considerable  quantity  of  10  per  cent  pyroHgneous  acid  is  added. 
This  is  allowed  to  act  five  or  ten  minutes;  then  the  rotifers  are 
washed  several  times  in  distilled  water.     As  a  result  of  the  harden- 


THE   WHEEL   ANIMALCULES    (R0TAT0RL\)  585 

ing  action  of  the  pyroligneous  acid,  they  may  now  be  passed,  like 
other  objects,  through  successively  stronger  grades  of  alcohol  till 
absolute  alcohol  is  reached.  They  may  then  be  cleared  in  clove  or 
cedar  oil,  in  the  usual  way,  and  mounted  in  Canada  balsam,  or 
gum  damar,  or  they  may  be  mounted  in  glycerine. 

In  America  the  systematic  work  on  the  Rotifera  has  consisted 
largely  in  the  publication  of  lists  of  species  found  in  certain  regions. 
While  this  work  undoubtedly  has  its  uses,  there  are  other  lines  of 
study  which  would  at  the  present  time  be  of  much  greater  value 
even  for  purely  systematic  purposes.  On  account  of  the  very 
large  number  of  species  of  Rotifera,  their  minuteness,  and  the 
unsatisfactory  work  that  has  been  done  upon  them,  it  is  often 
almost  impossible  to  determine  with  certainty  even  common  spe- 
cies. This  can  best  be  remedied  by  studying  carefulh'  circum- 
scribed groups,  such  as  single  genera  and  families,  collecting  them 
extensively,  describing  and  figuring  all  the  species,  and  going  criti- 
cally over  the  literature  of  the  group  in  such  a  way  as  to  set  the 
synonymy  in  order. 

Careful  comparative  studies  of  certain  organs  or  sets  of  organs, 
such  as  the  corona,  the  trophi,  etc.,  throughout  varied  groups, 
would  help  much  in  understanding  the  interrelationships  of  the 
Rotifera.  If  possible  a  study  of  the  habits  should  be  made  in  their 
relation  with  the  structures,  since  these  matters  are  closely  con- 
nected. Monographic  anatomical  studies  of  certain  species  are 
always  of  value.  They  would  be  especially  useful  if  a  thorough 
study  of  the  habit  and  physiology  could  be  made  at  the  same  time. 

A  most  important  field,  and  one  little  cultivated,  lies  in  the 
study  of  the  activities  by  which  the  rotifers  respond  to  their  en- 
vironment. Thorough  studies  of  the  movements  and  habits,  the 
reactions  to  stimuh,  ''tropisms,"  and  the  like,  would  be  of  great 
interest.  Disconnected  observations  on  these  matters  are  of  com- 
paratively Httle  value;  definite  problems  should  be  taken  up  and 
followed  to  the  end. 

The  variations  induced  in  a  single  species,  and  in  an  entire 
fauna,  by  changes  in  seasons,  temperatures,  and  in  other  features, 
have  received  some  study  and  deserve  much  more.  One  of  the 
most  interesting  lines  of  work  for  which  the  rotifers  present  oppor- 


586  FRESH-WATER   BIOLOGY 

tunity  lies  in  the  study  of  the  various  problems  connected  with 
reproduction  and  the  diversity  of  the  sexes.  Few  groups  of  organ- 
isms present  conditions  so  favorable  for  the  study  of  these  funda- 
mental matters. 

The  relationships  of  the  Rotifera  to  other  groups,  and  their 
interrelationships  among  themselves  are  subjects  which  have  been 
much  discussed  and  on  which  there  is  wide  divergence  of  opinion. 
As  a  result,  the  classification  of  the  group  differs  greatly  with 
different  authors.  The  classification  perhaps  most  commonly 
employed  is  that  given  in  Hudson  and  Gosse's  Monograph  of  the 
Rotifera.  Wesenberg-Lund's  classification,  based  on  that  view  of 
the  interrelationships  of  the  Rotifera  set  forth  in  the  foregoing 
paper,  has  been  Httle  used;  yet  it  appears  to  be  that  to  which  a 
careful  and  unprejudiced  study  of  the  members  of  the  group  leads. 
Most  earlier  classifications  have  found  their  guiding  principles  in 
matters  quite  extraneous  to  the  Rotifera  as  such.  Led  by  theo- 
retical considerations,  the  primitive  rotifers  have  been  looked  for 
among  highly  specialized  species.  Huxley  compared  the  two  ciliary 
wreaths  of  Lacinularia  to  the  two  wreaths  of  certain  larvae  of  other 
groups,  —  of  echinoderms,  annelids,  and  the  Hke,  —  thus  indicating 
a  possible  close  relationship  between  them.  This  suggestion  was 
eagerly  followed  up,  and  the  primitive  organization  of  the  Rotifera 
has  been  sought  in  such  highly  differentiated,  untypical  forms  as 
the  Melicertidae,  the  Philodinidae,  and  the  Hke.  Even  that  bizarre 
side-shoot  of  one  of  the  most  highly  specialized  families,  Trocho- 
sphaera  (Fig.  947) ,  has  been  considered  a  primitive  rotifer  of  special 
significance,  from  its  superficial  resemblance  to  the  trochophore 
larvae  of  annehds,  etc.  Less  popular,  but  still  enjoying  consider- 
able repute,  have  been  the  theories  which  held  that  such  forms  as 
Pedalion  (Fig.  946)  show  a  close  relationship  of  the  Rotifera  with  the 
larvae  of  Crustacea.  Careful  comparative  study  of  the  Rotifera 
themselves  seems  to  show  clearly  that  Lacinularia  and  the  Meli- 
certidae,. Trochosphaera  and  Pedalion  are  alike  terminal  twigs  of 
the  rotatorian  tree  —  highly  speciaHzed  forms,  whose  origin  is  to 
be  sought  in  such  rotifers  as  the  primitive  Notommatidae. 

Note.  —  For  recent  changes  in  the  names  of  many  rotifers,  in  accordance  with  the 
strict  rules  of  priority,  the  paper  of  Harring  ('13)  should  be  consulted. 


THE   WHEEL  ANIMALCULES    (ROTATORL\)  587 

KEY  TO   NORTH  AMERICAN   FRESH-WATER   ROTATORIA 

I  (138)     One  ovary.     Do  not  creep  like  a  leech. 

Subclass  Monogononta   .    .      2 

This  subclass  includes  all  the  rotifers  commonly  met,  save  the  Bdelluida  (q.v.),  which  are 
distinguishable  by  their  habit  of  creeping  Uke  leeches. 


2  (109)     Corona  of  various  types.     Where  there  are  two  wreaths  of  cilia,  those 
of  outer  wreath  never  shorter  than  those  of  inner.    ...     3 


3  (97)     Mouth  not  near  center  of  corona.    .    .    .    Order  Notommatida  .    .     4 

Free-swimming  or  creeping  rotifers,  but  never  creeping  like  a  leech;  corona  ventral  or  ter- 
minal, consisting  of  a  disk  which  is  either  uniformly  ciliate  or  has  a  wreath  of  cilia  about  its 
circumference  with  usually  two  or  more  groups  of  cilia  close  to  the  mouth,  or  shows  some  inter- 
mediate condition.  Where  there  are  two  wreaths  of  cilia,  the  outer  is  never  shorter  than  the 
inner.  Mouth  not  in  the  center  of  the  disk.  Jaws  never  ramate  (Fig.  867,  .4)  nor  malleo- 
ramate  (Fig.  866).  Foot  usually  ending  in  two  toes  placed  side  by  side;  rarely  ending  in  one; 
sometimes  absent;  never  forming  a  disk  for  attachment  nor  ending  in  a  bunch  of  dlia.  Lorica 
present  or  absent. 


4  (90)     Jaws  not  incudate.     Intestine  and  anus  present 5 


5  (31,  64)  Without  lorica.  Corona  when  as  broad  as  other  parts  of  the  body, 
not  consisting  of  an  outer  wreath,  a  partial  wreath  about 
the  mouth  and  styligerous  prominences  between. 

Suborder  Notommatina   .    ,     6 

Body  usually  soft  and  somewhat  segmented.     (See  also  family  Hyd.\tinidae,  66.) 


6  (26)     Corona  without  long  antenna-like  bristles  and  setigerous  prominences. 
Foot  present Family  NoTOJiiiATiD.\K     .    .     7 

Soft-bodied  rotifers,  usually  elongated,  cuticula  more  or  less  distinctly  segmentetl;  ioot  not 
distinctly  marked  ofif  from  the  remainder  of  the  body,  usually  short  and  endmg  m  two  toes 
placed  side  by  side,  or  rarely  but  one  toe.  Corona  usually  not  so  wide  as  the  remamder  ot  the 
body.     Living  mainly  amid  vegetation  of  the  shores  and  bottom.    ,,,__,..,         t,. 

This  family  cannot  be  sharply  marked  oflf  from  others;  see  particularly  Hydatmidae.  Ihc 
genera  of  the  Notommatidae  are  likewise  not  sharply  definable;  they  are  merely  more  or  less 
convenient  subdivisions  of  a  group  that  would  be  too  unwieldy  if  taken  as  a  unit. 


7  (19)     Without  auricles 

N.B.     Auricles  are  often  contracted  and  are  then  invisible. 

8  (16)     With  one  or  more  eyes ^ 

9  (r2,  15)     With  a  single  eye  only ^° 


S88 


FRESH-WATER   BIOLOGY 


Fig.  870.  Furcularia  Fig.  871.  Furcularia 
Jorficula  Ehr.  X  300.  longiseta  Ehr.  X  400. 
(After  Weber.)  (After  Dixon-Nuttall.) 


Fig.  872.  Diglena  ros- 
trata  Dixon  -  Nuttall. 
X  320.  (After  Dixon- 
Nuttall.) 


Fig.  873.  Distemma  set- 
igerum  Ehrenberg. 
X  166.  (After  Ehren- 
berg.) 


Fig.  874.  Triophthalmus  Fig.  875.    Alhertia  iw  Fig.   876.     Pleurotrocha  Fig.  877.  Taphrocampa 

dorsualis   Ehrenberg.  trusor  Gosse.      X  13S.  grandw  Western.  X  125.  annulosa  Gosse.   X  I4» 

X80.    (After  Ehren-  (After  Gosse.)  (After  Dixon-Nuttall.)  (After  Weber.) 
berg.) 


THE   WHEEL   ANIMALCULES   (ROTATORL\)  589 

10(11)     Eye  in  neck  region Proalcs  Gosse 

Small,  slow-moving,  soft-bodied  species,  with  partly  ventral  corona.     Many  species. 

Representative  species(  Fig.  856,  page  555) .  Proaleswerneckii  Ehrcnberg. 
(Fig.  858,  page  557).  .  .  .  P.  sonlida  Coasc. 
(Fig.  859,  page  558).     .    .    .      P.  tigrida  Gossc. 

11(10)     Eye  near  front Furcularia  EhrcnhcTg. 

Cuticula  a  little  stiffer,  so  that  the  form  is  retained;    shape  at  times  a  little  prismatic;    toes 
longer  and  stiflfer  than  in  Proales;  active.     Species  numerous. 

Representative  species  (Fig.  870).    .     Furcularia  jorficida  Y.\\mi\\)<:rg. 
(Fig.  871) F.  longiscta  Ehrcnberg. 

12  (9,  15)     With  two  eyes 13 

13(14)     Eyes  near  front Digloia  Ehrcnhcvg. 

Strong  predacious  species  with  forcipate  jaws;   toes  usually  large.     One  or  two  species. 

Representative  species  (Fig.  872).    .  Diglena  rostrata  Dixon-Nuilail. 
(Fig.  860,  B,  page  559).  .  D.forcipata  Ehrcnberg. 

14  (13)     Eyes  in  neck Dlstemma  Ehrcnberg. 

Representative  species  (Fig.  873).    .   Distemma  setigeriim  Ehrcnberg. 

15  (9,  12)     With  three  eyes  in  a  transverse  row.    .    Triophthalmiis  Ehrcnberg. 

One  species  only  (Fig.  874) Triophthalmiis  dorsualis. 


16  (8)      Without  eyes. 


17(18)     Internal  parasites ^/6er/w  Dujardin. 

Few  species. 

Representative  species  (Fig.  875) ilbertia  intrusor  Gossc. 

18  (17)     Free,  or  external  parasites Pleurotrodm  Ehrcnberg. 

Few  species. 

Representative  species  (Fig.  876).   .    .  Pleurotrocha  grandis  Western. 

19  (7)     With  auricles ■^o 

N.B.    Auricles  invisible  when  contracted. 

20  (25)     With  one  eye - ^^ 

21  (24)     Smaller,  soft-bodied  forms 22 

22  (23)     Cuticula  with  many  transverse  folds Taphrocampa  Gosse. 

Representative  species  (Fig.  877).    .      Taphrocampa  annulosa  Ciossc. 


590 


FRESH-WATER  BIOLOGY 


Fig.  878.  A,  Notommata  aurita 
Ehr.  X200.  (After  Weber.) 
B,  corona.  (After  Wesen- 
berg-Lund.) 


Fig.  878.^. 


Fig.  880.     Male  of  Synchaeta  tremula   Ehr. 
X300.     (After  Rousselet.) 


Fig.  879.  Eosphora  dtgitata 
Ehrenberg.  X  78-  (After 
Weber.) 


Fig.  881.     Notommata      Fig.  882.     Polyarthra  platyptera 
torulosia  Duj.  X  200.        Ehr.     X  200.     (After  Weber.) 
(After  Cohn.) 


Fig.  883.     Female  of  5y»cAa6/a     Fig.  884.     Corona  of  5ynctoe/a  6a//tca  Ehr.     ^^f;  885.;4 «ar/Ara  a ^ 
styla^  Witrz.    X225.     (After  seen  from  above.    (After  Rousselet.)  ^6ra    Hood       X  220. 

Rousselet.)  ^^^^^  ^'^'^•^ 


THE   WHEEL   ANIM.\LCULES    (ROTATORIA)  591 

23  (22)     Cuticula  without  many  transverse  folds.      .     Notoinmata  Ehrenberg. 
Many  species. 

Representative  species  (Fig.  878).   .   .   Notommata  auritaEhrnnhQr^. 

(Fig.  881) N.  torulosia  Dujanlin 

(Fig.  857,  A  and  5,  page  556). 

N.  truncata  Jennings. 

24(21)     Very  large,  thick-bodied  forms Co/>ew5  Gosse. 

Corona  extending  far  on  ventral  surface.     Few  spedes. 

Representative  species  (Fig.  857,  C,  page  556,  and  Fig.  864,  page  565). 

C opens  pachyurns  Gossc. 

25  (20)     With  three  eyes Eosphora  Ehrenberg. 

One  large  eye  on  brain;   others  small,  in  front.     Few  species. 

Representative  species  (Fig.  879).    .    .    Eosphora  digitata  Ehrcnhcrg. 

26  (6)     Two  or  four  long  bristle-like  antennae  on  corona.     Foot  present  or 

absent Family  Synchaetidae  .    .     27 

Open- water  rotifers;  bodies  short;   foot  short  or  absent;   corona  as  broad  as  the  broadest 
part  of  the  body,  consisting  mainly  of  a  row  of  large  cilia  about  the  circumference. 

27  (28)     Auricles  present Synchaeta  Ehrenberg. 

Body  usually  conical,  largest  at  the  head;  foot  short,  rarely  absent.     About  a  dozen  spedes. 

Representative  species  (Fig.  883).     .    .  Synchaeta  stylata  Wierzcjski. 

(Fig.  880) S.  tremuhi  Ehr(.Til)crg. 

(Fig.  884) S.  baltica  Ehrenberg. 

28  (27)     Auricles  absent.     No  foot 29 


29  (30)     With  lateral  oar-like  swimming  appendages.  .    Polyarthra  Ehrenberg. 
One  species  only  (Fig.  882).    .    .    .     Polyarthra  platyptera  Ehrenberg. 


30(29)     Appendages  lacking \narthr a  Hood. 

One  species  only  (Fig.  885) Anarthra  aptcra  Hootl. 


31  (5,  64)     Lorica  always  present.     Corona  small,  not  so  broad,  as  a  rule,  as 

the  broadest  part  of  the  lorica.    Suborder  Loricatina   .    .     32 

Foot  present,  short,  not  ringed;   ending  in  two  toes,  or  rarely  one. 

32  (47)     Lorica  divided  into  plates  by  longitudinal  furrows ^i 


592 


FRESH-WATER   BIOLOGY 


Fig.  886.     Salpina  spinigera  Ehr.     X  200. 
(After  Weber.) 


Fig.  888.  Diplois  daviesiae  Fig.  889.  Diplax  mdens 
Gosse.  X87.  (After  Levander.  X  267.  (After 
Weber.)  Lucks.) 


Fig.  887.  Diaschiza  hoodii  Gosse. 
/I,  Female.  B.Male.  X  300. 
(After  Dizon-Nuttall  and  Free- 
man.) 


Fig.  890.     Distylainermis  Bryce.     A,  Dorsal  view;  5,  con- 
tracted; C,  side  view.     X  225.     (After  Dixon-NuttaU.) 


Fig.  89 1 .  Distyla  ohioensis  Herrick . 
X  420.     (After  Jennings.) 


THE   WHEEL  ANIMALCULES    (ROTATORLV)  593 

33  (40)     Lorica  of  three  or  four  plates.     Furrows  arc  one  mid-dorsal,  two 
lateral;  sometimes  one  mid- ventral. 

Family  Salpinidae  .    ,  34 


34  (35)     Lorica  with  teeth  or  spines  in  front,  or  behind,  or  both. 

Salphia  Ehrcnbcrg. 
Representative  species  (Fig.  886).   .    .   Salpina  spinigcra  Ehrcnbcrg. 


35  (34)     Lorica  without  teeth  or  spines 36 

36  (39)     One  eye  present 37 


37  (38)     Lorica  not  strongly  marked,  the  furrows  and  plates  noticeable  only 

on  close  examination Diaschizn  Gosse. 

Representative  species  (Fig.  887) Diaschiza  Iwodii  Gosse. 


38  (37)     Lorica  distinct  and  strong Diplois  Gosse. 

Two  species. 

Representative  species  (Fig.  888) Diplois  davi^siae  Gosse. 


39  (36)     No  eye;  lorica  distinct Diplax  Gosse. 

Representative  species  (Fig.  889) Diplax  viiiens  Lii\'i\n{\{:r. 


40  (33)     Lorica  of  two  plates.     Furrows  lateral.    Family  Euchlanidae.    .     41 
One  plate  dorsal,  the  other  ventral. 

41  (46)     Two  toes 42 


42  (45)     The  two  plates  connected  by  a  membrane  which  folds  into  the  lateral 

furrow 43 

Small  species,  not  specially  clear,  lorica  often  marked  in  various  ways. 


43  (44)     Lorica  narrower Distyhi  Eckstein. 

Many  species. 

Representative  species  (Fig.  800) Distyla  imrmis  Br>'ce. 

Representative  species  (Fig.  891) D.  ohioaisis  Hcrnck. 


594 


FRESH-WATER    BIOLOGY 


Fig.  895.  Diurella  sulcata 
Jennings.  X  35o.  (After 
Dixon-Nuttall.) 


Fig.  897.  RaUulus  latus 
Jennings,  r,  right  toe; 
I,  left  toe.  X  225. 
(After  Jennings.) 


Fig.  898.  A,  RaUulus 
longiseta  Schrank.  X 
200.  B,  Trophi  of  same. 
(After  Jennings.) 


THE   WHEEL  ANIM.\LCULES    (ROTATORIA)  595 

44  (43)     Lorica  broader Cathypna  Gossc. 

Several  species. 

Representative  species  (Fig.  892).    .    .    .    Cathypna  liina  Ehrenberg. 

45  (42)     The  two  plates  not  connected  by  membrane.  .  Euchlanis  Ehrenberg. 

Large,  conspicuous,  clear  species;  lorica  not  sculptured  or  otherwise  markc*!.     Many  s|x.-Lifs. 
Representative  species  (Fig.  893).    .     Euchlanis  macrura  Khrcn\KTi:,. 

46  (41)     One  toe Monostyla  Ehrenberg. 

Many  species. 

Representative  species  (Fig.  894).     .     Monostyla  lunaris  Ehnjiiberg. 

47  (32)     Lorica  undivided,  of  a  single  piece 48 

48  (51)     Lorica  somewhat  pipe-shaped,  often  unsymmetrical. 

Family  Rattulidai:  .    .     49 

Lorica  closed  all  around,  cylindrical,  fusiform,  ovate,  or  conical,  with  an  opening  at  each  end 
for  head  and  foot;  often  unsymmetrical  and  with  oblique  ridges  or  furrows.  Toes  bristle- 
like; sometimes  equal,  then  short;  sometimes  very  unequal,  so  that  but  one  is  noticeable,  this 
then  very  long. 

49  (50)     Toes  equal,  or,  if  unequal,  the  shorter  one  more  than  one-third  the 

length  of  the  longer Diurdla  Bory. 

Many  species. 

Representative  species  (Fig.  895) Diurclla  sulcata  Jennings. 

(Fig.  862,  page  562) D.  tigris  Miiller. 

50  (49)     Toes  unequal.     The  smaller  less  than  one-third  length  of  longer. 

Rattulus  Lamarck. 

Many  species. 

Representative  species  (Fig.  896).  .    .    .    Rattulus  cylindricus  Imhof. 

(Fig.  897) i?. /(i/;<-v  Jennings. 

(Fig.  898) R-  longiscta  Schrank. 

51  (48)     Lorica  not  pipe-shaped.     Symmetrical 52 

K2  Uq)     Foot  and  toes  not  exceptionally  long.     No  spines. 

^    ^^^^  Family  Coluridae  .    .   53 

Lorica  of  a  single  piece,  either  covering  both  dorsal  and  ventral  surfaces,  or  only  the  dors;i!. 
53  (58)     Head  surmounted  by  a  chitinous  shield 54 


596 


FRESH-WATER   BIOLOGY 


Fig.  899.  Stephanops  in- 
termedius  Burn.  X  350. 
(After  Weber.) 


Fig.  900.     Colurus  grallator 
Gosse.  X37S.  (After  Weber. 


Fig.  902.  Cochlearet  urbo  Gosse. 
X  200.     (After  Gosse.) 


Fig.  901.  Metopidia  ehren- 
hergii  Perty.  X  400-  (After 
Jennings.) 


Fig.  903.  Scaridium  longi- 
caudutn  Ehr.  X  200. 
(After  Dixon-Nuttall.) 


Fig.  904.    Dinocharis  pocillum  Ehr.    A,  Female.   B,  Male. 
X  300.     (After  Weber.) 


THE   WHEEL   ANIMALCULES    (ROTATORIA)  597 

54  (55)     Head  shield  broad,  flat,  appearing  from  above  like  a  halo. 

Skplianops  Ehrenberg. 
Several  species. 

Representative  species  (Fig.  899).  .    .  Skplianops  intermedins  Burn. 

55  (54)     Head  shield  arched,  in  side  view  appearing  like  a  hook 56 


56  (57)     Lorica  arched  and  laterally  compressed Colurus  Ehrenberg. 

Many  species. 

Representative  species  (Fig.  900) Colurus  grallator  Gossc. 


57  (56)     Lorica  flattened,  wider  than  high Metopidia  Ehrenberg. 

Representative  species  (Fig.  901),   .    .    .  Metopidia  clircnbergii  Wny. 


58  (53)     No  head  shield Cochleare  Gosse. 

Lorica  shaped  like  a  coat,  covering  only  the  anterior  half  or  less  of  the  dorsal  surface.     One 
or  two  species. 

Representative  species  (Fig.  902) CocJilcare  turbo  Gossc. 


59  (52)     Foot  and  toes  usually  long;   if  not,  upper  surface  of  lorica  with  long 

spines Family  Dixochakidak   .    .     60 

Lorica  entire,  covering  head  as  well  as  body.     Movements  often  of  a  leaping  character. 


60  (63)     Lorica  without  spines  on  dorsal  surface 61 

61  (62)     Lorica  weak,  hardly  noticeable Scaridium  Ehrenberg. 

No  sculpturing  of  any  sort;  toes  very  long.    Two  species. 

Representative  species  (Fig.  903). 

Scaridium  longicaudum  EhrenlK-rg. 


62  (61)     Lorica  rough Dinocharis  Ehrenberg 

Two  species. 

Representative  species  (Fig.  904).    .    Dinocharis  pocillum  EhrenJKTg. 


598 


FRESH-WATER  BIOLOGY 


Fig.  905.  Polychaetus  collinsii 
Gosse.  X  250.  (After 
Jennings.) 


B 


Fig  906.  Hydatina  senla  Ehr.  A,  Dorsal  view  of  female. 
X  150.  (After  Weber.)  B,  Corona.  (After  Wesenberg- 
Lund.)     CTrophi.     (After  Weber.) 


Fig.  907.  Cyrtonia  tuba 
Ehrenberg.  X  200. 
(After  Rousselet.) 


Fig.  908.    Triphylus  lacustris  Ehrenberg.     X  134.     (After  Western.) 


THE  WHEEL  ANIMALCULES   (ROTATORL\)  5Q9 

63  (60)     Lorica  bearing  long  spines  on  dorsal  surface.      .      Polychadus  IV-rty. 
Lorica  turtle-shaped.     Two  species. 

Representative  species  (Fig.  905).    .    .    .    Polychactiis  collinsii  Gossc. 


64  (5,  31)  With  or  without  lorica.  Corona  usually  as  broad  as  broadest 
part  of  body  and  consisting  of  an  outer  wreath  of  cilia  and 
an  inner  interrupted  wreath  about  the  mouth,  with  sty- 
ligerous  processes  between  them. 

Suborder  Hydatinina   .    .     65 

A  heterogeneous  group  in  external  characters  but  showing  eviflcncc  (jf  dost-  rtlation-ship 
throughout.  Corona  never  a  perfect  circle  of  two  wreaths,  with  mouth  in  center.  .Ml  loricate 
forms  without  foot  belong  here.  In  all  non-loricate  forms  foot  present  and  ending  in  two  U)C%, 
side  by  side.  In  loricate  forms  foot  when  present  ends  in  two  toes,  side  by  side,  .save  in  one 
species,  Gastropus  stylifer,  where  there  is  but  one  toe.  The  families  of  this  order  are  greatly 
in  need  of  a  revision  based  on  thorough  comparative  study  of  all  the  species. 


65  (73)     Without  lorica 66 

66  (70)     Foot  not  sharply  separated  from  body. 

Family  Hydatinidae  .    .     67 

Large  rotifers,  body  soft  and  segmented,  of  notommatoid  characteristics,  not  greatly  swollen 
dorsally,  nor  compressed  sidewise.  Corona  of  typical  form  of  suborder,  or  having  a  large 
dorsal  proboscis  that  bears  two  eyes.  Foot  lying  in  the  body  axis,  not  ventral;  ending  in  two 
short  toes. 


67  (68,  69)     No  eye Hydatina  Ehrenbcrg. 

Only  one  species  (Fig.  906) Hydatina  scuta  Ehrenberg. 


68  (67,  69)     One  eye Cyrtonia  Rousselet. 

Only  one  species  (Fig,  907) Cyrtonia  tuba  Ehrenberg. 


69  (67,  68)     Two  eyes;  corona  with  dorsal  proboscis.  .    .    .   Rhino ps  Hudson. 
Only  one  species  (Fig.  863,  page  565).    .    Rhinops  vitrca  Hudson. 


70  (66)     Foot  decidedly  set  off  from  remainder  of  body. 

Family  NoTOPsroAE  .    .     71 

Body  much  swollen  dorsally,  flatter  ventrally;  cuticula  slightly  stitTer  .st)  that  the  Ixxly  holds 
its  shape,  or  sometimes  forming  a  weak  but  evident  lorica.  Foot  forming  a  prolongation  oi' 
the  ventral  surface  or  extending  ventrally;  two  small  toes. 


71  (72)     Two  eyes Triphylus  Hudson. 

Only  one  species  (Fig.  908) Triphylus  lacustris  Ehrenberg. 


6oo 


FRESH-WATER  BIOLOGY 


Fig     909.     Notops  brachionus 
Ehr.  Xioo.  (After  Weber.) 


Fig.  910.  Notops  pelagicus  Jennings.  A,  side 
view;  B,  Corona.  X  400.  (After  Jen- 
nings.) 


B 


FlG.gii. Anapusovalis 
Bergendal.  X  240. 
(After  Weber.) 


Fig.  912.  A,  Notops  clavulatus  Ehr.  X  100. 
(After  Hudson  and  Gosse.)  B,  Corona. 
(After  Jennings .) 


Fig.  913.  A  and  B,  Forms  of  Anuraea  cochlearis  Gosse. 
A,  variety  macracantha.  B,  Variety  tecta.  X  300. 
(After  Lauterborn.)  C  Male  of  Anuraea  brevts- 
pina  Gosse. 


THE   WHEEL  ANIMALCULES    (ROTATORL\)  6oi 

72  (71)     One  eye Notops  Hudson. 

Slight  indication  of  lorica  sometimes.     Several  species. 

Representative  species  (Fig.  909).   .    .  Notops  hrachionus  Ehrcnlx^rg. 

(Fig.  912) N .  clavulatus  V.hritnXmrg. 

(Fig.  910) N.  pelagkus  Jennings. 


73  (65)     Lorica  present ^^ 


74  (81)     No  foot 7 


75  (76)     Lorica  of  two  convex  plates,  placed  together  at  their  edges. 

Family  ANAPOoroAE. 
Lorica  ovoid  or  oval. 

Only  one  genus ^na/»«5  Bergendal. 

One  or  two  species. 

Representative  species  (Fig.  911) ^«a/>w5  ora//^  Bergendal. 


76  (75)     Lorica  of  a  convex  dorsal  and  a  flat  ventral  plate,  or  sometimes 
irregular Family  Anuraeidae  .    .     77 

Open  in  front  for  head  and  behind  for  cloaca;  usually  armed  with  spines  or  teeth. 


77  (80)     Spines  or  teeth  at  the  anterior  or  posterior  edges  of  the  lorica,  or 
none 7^ 


78  (79)     Lorica  not  longitudinally  striated Anuraea  Ehrcnberg. 

Representative  species  (Fig.  913,  A  and  B).  Atturaea  coc/dairis  Closse. 
Many  species.    Lorica  of  convex  dorsal  and  flat  ventral  plate. 

(Fig.  913,  C) ■{.  brr.'is pi tui  Gossc. 


6o2 


FRESH-WATER   BIOLOGY 


Fig.  914.     Eretmia  trithrix  Gosse. 
CAfter  Gosse.) 


Fig.  916.  Nothol- 
ca  longispina 
Kellicott.  X 
170.  (After 
Weber.) 


Fig.  917.  Gastropus  stylifer 
Imhof.  X  200.  (After 
Weber.) 


Fig.  915.     Gastropus  hyptopus  Ehr. 
X  170.  (After  Hudson  and  Gosse.) 


Fig.  918.  Ploesomalenticulare 
Herrick.  X  300.  (After 
Wierzejski  and  Zacharias.) 


Fig.  919.  Ploesoma  hudsoni  Imhof.     X  150.   (After 
Wierzejski  and  Zacharias.) 


Fig.  920.  Ploesoma  truncatum  Le- 
vander.    X  160.    (After  Weber.) 


THE  WHEEL  ANIMALCULES   (ROTATORIA)  603 

79  (78)     Lorica  longitudinally  striated Notholca  Gosse. 

Sometimes  very  long  and  slender.    Three  or  four  species. 

Representative  species  (Fig.  916).    .   .  Notholca  longispina  KcWkuw. 


80  (77)     Lorica  with  long  bristle-like  outgrowths  from  its  surface  but  not 
from  anterior  or  posterior  borders Erctmia  Gossc. 

Few  species,  all  more  or  less  doubtful. 

Representative  species  (Fig.  914) Eretmia  irithrix  Gossc. 


81  (74)     Foot  present 83 


82  (85)     Foot  projects  from  ventral  surface 83 


83  (84)     Lorica  entire,  not  wrinkled Family  Gastropodidae. 

Lorica  flask-shaped  with  small  foot  projecting  from  ventral  surface.     Foot  ringed,  ending 
in  one  or  two  toes. 

One  genus  only Gastropiis  Imhof. 

Several  species. 

Representative  species  (Fig.  915).   .    Gastropus  hyptopits  Ehrcnbcrg. 
(Fig.  917) G.  stylijcr  Imhof. 


84  (83)     Lorica  open  along  mid-ventral  line;   marked  with  wrinkles  or  vesi- 
cles       Family  Ploesomidae. 

Lorica  stout,  widely  open  in  front  for  the  large  head,  and  open  ventrally  for  the  foot.     Foot 
strong,  ringed,  ending  in  two  toes.     Strong,  active  rotifers. 

Only  one  genus Plocsomu  \\<:n\c^. 

Three  or  four  species. 

Representative  species  (Fig.  Q2o).   .      Plocsoma  trumatum  Levandcr. 

(Fig.  918) P-  Icfiticuhirc  Hcrrick. 

(Fig*  919) ^^-  ^'n^^-'^oni  Imhof. 


6o4 


FRESH-WATER   BIOLOGY 

A 


Fig.  921.  A,  Brackionus  punctatus'Hempel.  X  400.  (After 
Dixon-Nuttall.)  B,  Male  of  Brachionus  quadratus  Rousselet. 
(After  Marks  and  Wesche.) 


Fig.  922.     Brachionus  pala  Ehr. 
X  160.     (After  Weber.) 


Fig.  923.  Corona  of  Brachionus 
annularis  Gosse.  (After  Wesen- 
berg-Lund.) 


^v^_ 


Fig.  924.  Schizocerca  dkersicornis 
Daday.  X300.  (After  Wier- 
zejski.) 


Fig.  925.     Brachionus  mollis  Hempcl. 
X  280.     (After  Hempel.) 


FlG.  926.  Noteus  quadricornis 
Ehrenberg.  X 144.  (After 
Hudson  and  Gosse.) 


THE   WHEEL  ANIMALCULES   (ROTATORIA)  605 

85  (82)     Foot  projects  from  posterior  end.    .    Family  Brachiontoae  .    .      86 

Lorica  consisting  of  a  convex  dorsal  plate  and  a  flat  ventral  one;  usually  stout  and  armed 
with  spines,  though  not  always.  Lorica  opened  behind  for  the  long,  strong  f(X)t  which  is  often 
covered  with  close  rings.     Foot  either  ending  in  two  toes  or  forked  at  its  free  end 


86  (89)     Foot  not  forked 87 


87  (88)     Lorica  very  convex  dorsally Brachionus  Ehrenberg. 

Many  species. 

Representative  species  (Fig.  922).     .    .    Brachionus  pala  EhrcnlKTR. 

(Fig.  921,. 4) B.  piimtatiis  WiimpuX. 

(Fig.  921, -B).    .    .    .    B.  qiuuiratus  KousscXtii. 

(Fig.  923) B.  annularis  iiossQ. 

(Fig.  925) B.  mollis  Hempcl. 


88  (87)     Lorica  flat ^otciis  Ehrenberg. 

Foot  not  ringed. 

Representative  species  (Fig.  926).   .    Noteus  quadricornis  Ehrenberg. 


89  (86)     Foot  forked  at  its  end Schizoccrca  Dadny. 

Only  one  species  (Fig.  924).   .    .    .      Schizoccrca  diver sicornis  Daday. 


6o6 


FRESH-WATER   BIOLOGY 


Fig.  927.  Asplanchnopxis  myrmeleo  Ehr.  A,  side 
view.  X  80.  (After  Weber.)  B,  jaws.  (After 
Wierzejski.) 


Fig.  928.  Harringia  eupoda  Gosse.  ^,  side  view. 
X 100.  (After  Western.)  B,  jaws.  (After 
Wierzejski.) 


Fig.  929.    Asplanchna  priodonta  Gosse.     A,  Dorsal  view. 
J<  100.    (After  Weber.)    B,  jaws.    (After  Wierzejski.) 


Fig.  930.  Ascomorpha  ecaudis  Perty. 
X  200.  (After  Hudson  and  Gosse.) 


THE   WHEEL  ANIMALCULES   (R0TAT0RL\)  607 

90  (4)     Jaws  incudate,  save  in  Ascomorpha.     Intestine  and  anus  lacking   save 

^^  ^''''P' Suborder  Asplanchnina. 

Sac-shaped  rotifers,  usually  without  a  foot,  though  in  some  cases  a  sm-ill  f.w.f  Jc  r.r».  ^. 
the  posterior  part  of  the  ventral  surface.  '  "^'^  '^  P*^^"^  "° 

One  family  only Family  Asplanchmdal  .    .     91 


91  (94)     Foot  present 


92  (93)     Intestine  absent Asplanchnopus  de  Guerne. 

Two  or  three  species. 

Representative  species  (Fig.  927) 

Asplanchnopus  myrmcico  Ehrenlx-rg. 


93  (92)     Intestine  present Harringia  Bcauchamp. 

Only  one  species  (Fig.  928) Harringia  eupoJa  Gosse. 


94  (91)     Foot  absent q5 


95  (96)     Large  clear  rotifers  w^ith  incudate  jaws Asplanchna  Gosse. 

Many  species. 

Representative  species  (Fig.  929).    .    .   Asplamhna  priodonUi  Ciosse. 
(Fig.  869,  page  583).    .    .1.  hcrrickii  de  Gucrnc. 


96  (95)     Very  small  rotifers,  usually  colored  or  opaque;  jaws  not  incudate. 

Ascomorpha  I'erty, 

,  One  or  two  species. 

Representative  species  (Fig.  930) [scovwrpha  ccaudi<  V^^^^^' 


6o8 


FRESH-WATER    BIOLOGY 


Fig.    931.      Microcodon 

clavus    Ehr.,    ventral  Fig.  932.      Microcodides  robustus 

view.     X  260.    (After  Glasscott,  with  corona  (c).     X 

Weber.)  300.     (After  Rousselet.) 


Fig.  933.  A .  Floscularia  proboscidea 
Ehr.  Female.  X  100.  (After 
Weber.)  B,  Male  of  the  same. 
D,  Side  view  of  jaws  of  Floscu- 
lariidae.      (After  Wierzejski.) 


Fig.  934.  Alimentary  canal  of  Floscu- 
laria campanulata  Dobie.  (Modified 
from  Montgomery.)  d,  diaphragm; 
i,infundibulum;  w,  mouth;  mx,  mastax; 
0,  esophagus;  pr,  proventriculus; 
V,  vestibulum. 


Fig.  935.  Floscularia  uni- 
loba  Wierz.  X  125. 
(After  Wierzejski.) 


Fig.  936.      Floscularia  edentata 
Collins.  X  150.  (After  Weber.) 


THE  WHEEL  ANIMALCULES    (ROTATORL\)  609 

97  (3)     Mouth  nearly  in  center  of  large  corona.   .     Order  Floscularida  .    .   98 

Corona  circular  or  drawn  out  into  lobes,  points,  or  arms.  Foot  never  ending  in  two  toes 
placed  side  by  side.  Mostly  attached  or  tube-bearing  rotifers,  the  foot  formins  a  disk  for 
attachment;  a  few  free-swimming  species  in  which  the  foot  ends  in  a  single  toe,  sometimes 
accompanied  by  a  dorsal  spur. 


98  (loi)     Free  swimming;  foot  ending  in  a  single  toe. 

Family  IVIicrodonid.\e  .    .     99 

Corona  circular,  with  mouth  in  center,  an  outer  wreath  of  active  cilia;  cilia  about  the  mouth 
larger  and  bristle-like.    One  eye. 


99  (100)     Foot  as  long  as  body Microcodon  Ehrenberg. 

Body  slender,  corona  with  raised  borders,  slightly  bilobed;  foot  slender,  straight,  ending  in 
a  single  toe;  no  dorsal  spur. 

Only  one  species  (Fig.  931) Microcodon  claims  Ehrenberg. 


100  (99)     Foot  not  more  than  half  as  long  as  body.  .  Microcodides  Bergendal. 

Body  not  so  slender;   foot  ending  in  one  toe  which  is  sometimes  accompanied  by  a  dorsal 
spur. 

Representative  species  (Fig.  932).  .  Microcodides  robust  us  Gkisscolt. 


10 1  (98)     Attached,  or  bearing  tubes  if  free  swimming 102 


102  (105)     Cilia  around  corona Family  Floscularhdae  .    .     103 

Corona  large,  forming  a  net  for  the  capture  of  prey.  Cilia  about  its  edge  usually  forming 
long  threads  or  bristles  which  do  not  beat  Hke  those  of  other  rotifers,  though  they  may  move 
rather  slowly.    Jaws  uncinate  (Fig.  933,  D). 


103  (104)     Corona  circular,  or  drawn  into  lobes,  or  pointed;    its  cilia  not  in 
whorls  or  regular  groups Flosculana  Okcn 

Many  species. 

Representative  species  (Fig.  933,  A  and  B). 

Floscularia  prohoscidca  EhrcnhtTg. 
(Fig.  934  and  861,  B,  page  561). 

F.  campanuhita  Dohic. 

(Fig.  935) F.;/;//A;/>c;\yier/.cjski. 

(Fig.  936) P'  cdcnldtd  i  oUin^. 


6io 


FRESH-WATER   BIOLOGY 


1-iG.  938.    Apsilus  bucinedax  Forbes. 
Ventral  view.   X65.  (After  Stokes.) 


Fig.  937.  Stephanoceros  eich- 
hornii  Ehr.  X  60.  (Alter 
Weber.) 


Fig  939-  Alrochus  tenlaculatus 
Wierz.  X35-  ( After  Wierzejski.) 


Fig.  941.  Acyclus  in- 
quietus  Leidy.  X  12. 
(After  Leidy,  from  Hud- 
son and  Gosse.) 


Fig.  940.  Pompholyx 
complanata  Gosse. 
X24S-  (After  Hud- 
son and  Gosse.) 


Fig  942.  Pterodvna  pattna  Ehr.  ,^- .I^^^f  .u^mak  ^(Aft'r 
V  o«  (After  Weber)  B,  Dorsal  view  of  the  male,  ^mier 
Sarki  and  w'eschS  C\  Corona,  showing  the  two  wreaths  of 
cilia.     (After  Wesenberg-Lund.) 


THE   WHEEL   ANIMALCULES   (ROTATORLK)  6ll 

104  (103)     Corona  drawn  out  into  long  pointed  arms,  which  bear  cilia  arranged 

in  whorls Stephanoceros  Ehrenberg 

One  species  only  (Fig.  937).   .  Stephanoceros  eichhornii  Ehrcnbcrg 


105  (102)     No  cilia  on  corona Family  Apsilidae 


106 


106  (107,  108)     Body  short,  sac-like Apsiliis  MetschnikofT. 

Corona  a  large  sac  or  chamber;  no  foot;  attached  by  an  adhesive  disk.     Two  or  three  spedes. 

Representative  species  (Fig.  938).   .    .    .     Apsiliis  hucincdax  Forbes. 

107  (106,  108)     Body   longer,    fusiform,   a   narrowed    neck   separating  off  a 

conical  anterior  part Atroclnis  Wicrzcjski. 

Corona  a  membranous  ring  with  five  short  lobes  bearing  tentacles. 

Only  one  species  (Fig.  939).  .  Atrochus  tentaculatus  VVierzejski. 

108  (106,  107)     Body  long,  with  a  long,  slender,  tapering  stalk. 

Acyclus  Leidy. 
Corona  with  but  one  large  dorsal  lobe.     Living  in  colonies  of  Megalotrocha  dboflavicans . 

Representative  species  (Fig.  941) Acyclus  inquictus  Leidy. 

109  (2)     Corona  surrounded  by  two  parallel  wreaths  of  cilia  with  a  furrow  be- 

tween.    CiUa  of  outer  wreath  always  shorter  than  those  of 
inner. 

Order  Melicertida   .    .      no 

The  furrow  between  the  wreaths  of  cilia  sometimes  clothed  with  short  cilia.  Jaws  malleo- 
ramate  (Fig.  866).  Foot  never  ending  in  two  toes  side  by  side;  sometimes  lacking.  Eyes  two, 
rarely  absent.  Fixed  or  free  swimming;  the  free-swimming  species  often  without  foot  and 
frequently  bearing  appendages  on  the  body. 

no  (121)     Free  swimming  and  not  in  tubes  or  in  colonies.    ....      n  i 

111  (120)     Not  spherical .    .     iii 

112  (115)     With  a  lorica.     Without  appendages. 

Family  Pterodinid.\e  .    .     nj 

113  (114)     Foot  present,  long,  ringed,  ending  in  a  bunch  of  cilia. 

Pkrodina  Ehrcnbcrg. 

Lorica  more  or  less  flattened  dorso-ventrally.     Many  species. 

Representative  species  (Fig.  942).    .    •   Pterodina  pal i mi  EhrenUTc 
(Fig.  866,  B,  page  575)-    •     ^'  <''^'<'''  Parson.v 

n4  (n3)     No  foot Pompholyx  Gosse. 

Lorica  not  flat.     Two  or  three  species 

Representative  species  (Fig.  940).    .    .      Pompholyx  com pUfUa  i.)o6&c. 


Fig.  943.  Pedetes  sal- 
tator  Gosse.  X  290. 
(After  Hudson  and 
Gosse.) 


Fig.  944.  Triarthna.  A.Triarthralongisela 
Ehr.,  side  view.  X  190.  (After  Weber.)  B, 
Triarlhra  brachiata  Rousselet.  X  200. 
(After  Rousselet.) 


Fig.  945.  Tetra- 
mastix  opoli- 
ensis  Zach. 
X  ISO.  (After 
Rousselet.) 


Fig.  946.    Pedalion  mirum  Hudson.     A,  Ventral  view  of  female,  ch, 
B,  Male.     (After  Wesenberg-Lund.) 


'chin."  X  70.     (After  Weber.) 


6X3 


Fig.  94^.     Trochosphaera  solstilialis  Thorpe.     X  80.     (After  Rousselet.) 


THE   WHEEL   ANIMALCULES   (R0TA'1XJRL\)  613 

115  (112)     Without  lorica.     With  spinc-Ukc  or  limlj-like  appendages.     No 
foot Family  rEDALioNiD/VE  .    .      116 


116  (117,  118,  119)     Appendages,  two,  very  long Pcddcs  Gosse. 

Representative  species  (Fig.  943) Pcddcs  sallalor  Ciossc. 


117(116,118,119)     Appendages,  three,  spine-like.     .      rr/flr/Aro  Ehrenberg. 

Two  or  three  species. 

Representative  species  (Fig.  944,  A).  .  Triarthra  lon^iscta  Ehrcnberg. 
(Fig.  944,  5) T.brachiata  RoxxssiiXci. 


118(116,117,119)     Appendages,  four;  spines  or  bristles. 

Tctramastix  Zacharias. 

One  species  only  (Fig.  945).   •    •   Tctramastix  opolicnsis  Zacharias. 


19  (116,  117,  118)     Appendages,  six,  branching,  somewhat  crustaccan-like. 
^  ^       '       "  Pcdalum  Hud.son. 

Two  species. 

Representative  species  (Fig.  946).  .    .    .     Pedalwn  mirum  WuiX^Vi. 


Representative  species  (Fig. 947).  •   Tmhosphacra  sol sti I tohs  Thorpe 


Fig.  948.  Melicerta  ringens  Schrank.  A,  Animal  in 
its  tube.  X  60.  (After  Hudson  and  Gosse.)  B, 
Side  view  of  animal  removed  from  its  tube.  (After 
Weber.)  C,  Male.  X  45-  (After  Joliet,  from  Weber.) 


S' 


Fig.  949.  Limnias 
ceratophylli  Schrank, 
X87.  (After Hlava.) 


Fig.  9SO.  Octotrocha  sPeciosa  Thorpe.    X  40. 
(After  Thorpe.) 

614 


Fig.  951.    Oecistes  brevis  Hood. 
X  300.     (After  Rousselet.) 


THE  WHEEL  ANIMALCULES   (ROTATORL\)  615 

121  (no)  Fixed  by  the  tip  of  the  stalk-Uke  foot,  or  with  tubes,  or  in  colonies 
Secondarily  free  in  a  few  cases,  then  distinguishable  by  the 
soft  elongated  body,  without  lorica  or  appendages. 

Family  Melicertidae  .    .     122 


122  (130,  133)     Individuals  attached,  separate,  or  in  branching,  non-spherical 
colonies  of  few  specimens  (1-30) 123 


123(124,125)     Corona  four  lobed Melicerla  Schmnk. 

Two  lobes  in  one  species.     Living  in  tubes.     Several  species. 

Representative  species  (Fig.  948  and  Fig.  866,  .1,  page  575). 

Melicerta  ringcus  Schrank. 


124  (123,  125)     Corona  eight  lobed Octotrocha  Thorpe. 

Representative  species  (Fig.  950).  .    .    .     Octotrocha  spcciosa  Thorpe. 


125(123,124)     Corona  more  or  less  two  lobed 126 


126(129)     Dorsal  antenna  minute  or  absent 127 


127  (128)     Corona  broad,  of  two  lobes,  with  a  wide  dorsal  gap. 

Limn'uis  Schrank. 

Dorsal  antenna  minute,  ventral  antennae  long;  living  in  tubes  not  made  with  ix-llots.     Sev- 
eral species. 

Representative  species  (Fig.  949)-    •    •    Limnias  ccratophylli  Schrank. 


128  (127)     Corona  a  wide  oval  or  nearly  circular,  indistincUy  t^yo  lobed. 
Dorsal  gap  minute Occistes  YMvQnhcig. 

Dorsal  antenna  inconspicuous  or  absent.     Ventral  antennae  obvious.     Living  attached  in 
tubes.    Many  species. 

Representative  species  (Fig.  951) Occistcs  brcAs  Wood. 


Fig.  9 < 2.  Conochilus  unicornis  Rousselet.    ^, Colony.   X40 
5,  Single  animal  isolated.     X  150.    (After  Weber.) 


Fig.    953.    Conochiloides  nutans 
SeUgo.    X87.    (After  fflava.) 


Fig.  956.     Cephalosiphon 

Fig.  954.  Pseudoecistes  rotifer  Sten-        Fig.  955-  Megalotrocha  alboflavkans        ^l^^f^^^^^'Ji^f^' 
toos.     X150.     (After  Stenroos.)  Ehrenberg.        Single    individual.         (After  Dixon  Wultau.; 

^  X87.     (After  Hlava.) 


616 


THE  WHEEL  ANIMALCULES   (ROTATORIA)  617 

129  (126)     Dorsal  antenna  very  large,  with  two  projections  or  hooks  :ii  its 

side Ccphalosiphon  Ehrcnbcrg. 

Corona  nearly  circular  with  a  distinct  dorsal  gap.     Ventral  antennae  small  or  absent. 

Representative  species  (Fig.  956).  .  Ccphalosiphon  limnias  EhrcnherK. 


130  (122,  133)     Not  attached  nor  forming  colonics,  save  that  one  adult  may 
be  grouped  with  its  young 131 


131  (132)     Not  forming  tubes Psciidoccistcs  Stcnroos. 

In  other  respects  like  Cephalosiphon.     One  or  two  species. 

Representative  species  (Fig.  954).   .    .   Psciulocc isles  rotifer  Sicnroos. 


132(131)     Inhabiting  a  tube Cojiochiloides  Uhva.. 

Individuals  separate  or  one  grouped  with  its  young.     One  or  two  species. 

Representative  species  (Fig.  953).  .    .    .   Conochiloides  nalans  Seligo, 


133  (122,  130)     In  clusters  of  many  individuals,  forming  usually  a  spherical 
~~  colony  appearing  to  the  naked  eye  as  a  yellowish  ball.   .     134 


134  (137)     Clusters  attached US 


135  (136)     No  tubes Mcgalotrocha  Ehrcnbcrg. 

Colonies  often  several  millimeters  in  diameter,  attached  to  plants  Individuals  not  imbedded 
in  a  gelatinous  mass;  corona  broad,  kidney  shaped.  Body  usually  with  two  or  four  opaque 
warts.    Several  species. 

Representative  species  (Fig.  955).  .,1 

Megalolrocha  albojlavieans  Ehrcnbcrg. 


136  (135)     Dwelling  in  transparent  gelatinous  tubes.  .  Laciuidarui  Schwcigger. 

Colony,  a  mass  of  some  mm.  in  diameter,  often  appears  to  1)C  imbeddeii  in  a  mass  of  jelly. 
Corona  heart  shaped  (Figs.  861,  A,  and  865).    Several  species. 

Representative  species  (Fig.  86i,.4,  page  561.  and  Fig.  865.  page  575). 

Lacinularui  socuilis  Ehrcnbcrg. 


137(134)     Clusters  or  colonies  free  swimming.    .    .    .     C(7wor//;7w;y  Ehrcnbcrg. 
Two  or  three  species. 

Representative  species  (Fig.  952).    •  ConochUus  unuornis  Roussclet. 


Fig,    958.  Rotifer 

citrinus  Ehr. 

X  170.  (After 
Weber.) 


Fig.    962.     Microdina  paradoxa 
Murray.  X  400.  (After  Murray.) 


Fig.  060,    Rotifer  neptunius  Ehr.     X  100. 
(After  Weber.) 

6x8 


Fig.  961.  Callidina  angustt- 
collis  Murray.  X  325- 
(After  Murray.) 


THE   WHEEL  ANIMALCULES    (ROTATOR L\)  619 

138  (i)     Two  ovaries Subclass  Digononta, 

In  fresh  water;  only  one  group Order  Bdelloida  .    .      139 

Free-living.  Swimming  with  the  corona  or  creeping  hke  a  leech,  or  Ixjth.  Bo^ly  without 
lorica,  usually  nearly  cyHndrical,  dorsal  and  ventral  surfaces  not  being  conspicuously  differ- 
entiated, and  composed  of  rings  which  may  be  drawn  one  within  the  other  in  telescopic 
fashion.    A  dorsal  proboscis  behind  the  corona;  jaws  ramate  (Fig.  867). 


139  (146)     Corona  present i 


40 


140  (145)     Corona  of  two  nearly  circular  disks  raised  on  short  stalks,  present- 
ing the  appearance  of  two  wheels. 

Family  Philodinid.vk  .    .      141 


141  (144)     Eyes,  two 142 

142  (143)     Eyes  in  the  dorsal  proboscis Rotifer  Schrank. 

Several  species. 

Representative  species  (Fig.  958).     .    .      Rotifer  citriniis  KhrcnbcrK. 
(Fig.  960).     .    .    .     R.  neptunius  Ehrcnberg. 


143  (142)     Eyes  in  the  neck,  directly  over  the  brain,  just  above  the  jaws. 

Philodina  Ehrenberg. 

Several  species. 

Representative  species  (Fig.  959).    .    .     Philodina  roseola  Ehrenberg. 
(Fig.  867,  A,  page  577).    .    .     P-  brya-i  Weber. 


144  (141)     Eyes,  none CaUidina  Ehrenberg. 

The  genus  CalUdina  when  revised  will  be  broken  into  several  genera.     Many  species. 

Representative  species  (Fig.  961).   •     CaUidina  angusticollis  Murray. 

I4<  (140)     Corona  a  flat  surface  covered  with  cilia  on  the  ventral  side  of  the 

anterior  end Family  Vdinktidak. 

One  genus  only IJ/m/.i  Hudson. 

Representative  species  (Fig.  957) Ulmeta  vaga  \hxy\,^. 

146  (139)     No  corona Family  MICRODIMD.^K. 

The  mouth  has  a  group  of  cilia  about  it. 

One  genus  only ;  ^.  '  «  '   „  "•''"""'{  ■""'">■• 

Representative  species  (Fig.  <,6.  and  ^^^^^^Jj^Jii;^^,^,^, 


620  FRESH-WATER   BIOLOGY 


IMPORTANT   REFERENCES   ON   FRESH-WATER  ROTATORIA 

DixoN-NuTTALL,  F.  R.,  and  Freeman,  R.     1903.     The  Rotatorian  Genus 

Diaschiza;  a  Monographic  Study.    Jour.  Roy.  Micr.  Soc,  1903:    1-14, 

129-141. 
Harring,  H.  K.     1913.     Synopsis  of  the  Rotatoria.     U.  S.  Natl.  Museum, 

Bull.  81.     226  pp.     (Changes  some  of  the  generic  names  here  employed.) 
Hudson,  C.  T.,  and  Gosse,  P.  H.     1889.     The  Rotifera  or  Wheel  Animalcules. 

2  vols.    London. 
Jennings,  H.  S.     1900.     Rotatoria  of  the  United  States  with  especial  reference 

to  those  of  the  Great  Lakes:  Bull.  U.  S.  Fish  Com.,  1899:  67-104. 
1901.     Synopsis  of  North  American  Invertebrates  XVII.     The  Rotatoria. 

Amer.  Nat.,  35:  725-777;  171  figures. 

1903.  Rotatoria  of  the  United  States,  II.     A   monograph  of  the  Rat- 
tulidae.     Bull.  U.  S.  Fish  Com.,  1902:  273-352. 

1904.  Reactions   to   Stimuli  in   certain  Rotifera.     Carnegie  Institution, 
Publ.  i6:  73-88. 

Montgomery,  T.  H.     1903.     On  the  Morphology  of  the  Rotatorian  Family 

Flosculariidae.     Proc.  Acad.  Nat.  Sci.,  Phila.,  1903:363-385. 
RoussELET,   C.  F.     1902.     The   Genus  Synchaeta;   a   Monographic  Study. 

Jour.  Roy.  Micr.  Soc,  1902:  269-290. 
Surface,  F.  M.     1906.     The  Formation  of  New  Colonies  of  the  Rotifer  Mega- 

lotr ocha  alboflavicans  Ehr.     Biol.  Bull.,  11:  182-192. 
Wesenberg-Lund,  C.    1899.    Danmarks  Rotifera  I.    Grundtraekkene  i  Roti- 

ferernes  Okologi,  Morfologi  og  Systematik.    Kobenhavn. 


I 


CHAPTER   XVIII 
GASTROTRICHA 

By  henry  B.  ward 

Professor  of  Zoology,  University  of  Illinois 

Among  the  microscopic  animals  common  in  fresh  water  and 
limited  in  distribution  to  that  environment  are  certain  minute 
organisms  known  as  the  Gastrotricha.  Though  limited  in  variety 
of  species  they  are  so  abundant,  so  widely  distributed,  and  so  strik- 
ing in  appearance  as  to  command  the  attention  of  every  student 
of  aquatic  Hfe.  They  live  in  numbers  among  algae  and  debris  and 
in  almost  every  bottom  collection  appear  in 
company  with  the  rotifers  and  protozoans.  In 
movements  and  habits  they  resemble  closely 
the  ciliate  Protozoa,  and  are  easily  confused 
with  them.  Ehrenberg,  who  first  described  in 
detail  the  structure  of  these  organisms,  placed 
them  among  the  Rotifera  and  many  later 
investigators  have  followed  this  suggestion. 
Others  incline  to  regard  them  as  Nematoda 
Irom  which  they  differ  most  strikingly  in  pos- 
sessing ciHa  which  are  not  known  in  other 
worms  of  that  group.  In  size  they  are  strictly 
microscopic,  varying  from  0.54  mm.  in  maxi- 
mum length  to  only  one-eighth  of  that.  They 
constitute  a  distinctly  uniform  group  not 
closely  related  to  any  other  existing  t^-pes  of 
animal  life.  Our  knowledge  of  the  anatomy 
of  these  organisms  is  due  principally  to  the 
investigations  of  Stokes  in  this  country  2ind^'V^i^s£:!''E:rS:^. 

ry    ^•    ^         •       rx.  ^l/,  muscles; /J,  brain; /-^crk. 

Z-elmka  m   Germany.  O.  esophagus;    /.   intestine; 

Ine  general  structure  of  the  group  is  well    zeiinka.) 
illustrated  in  the  figure  of  Chaetonotus  maximus  taken  from  Zeiinka 's 
monograph  (Fig.  963).     While  the  form  of  the  body  api)roachcs  a 
cylinder,  there  is  usually  an  expanded  area  in  front  known  as  the 

621 


62  2  FRESH-WATER   BIOLOGY 

''head,"  a  narrower  part  just  behind  it  called  the  ''neck"  and  the 
larger  "rump,"  or  body  proper,  which  constitutes  the  major  portion 
of  the  animal.  These  regions  are  not  sharply  limited  and  sometimes 
can  not  be  distinguished  at  all.  They  do  not  correspond  to  any 
internal  structures.  The  ventral  surface  is  more  or  less  flattened 
and  the  dorsal  surface  arched  as  is  conspicuously  seen  in  side  view. 

The  head  bears  at  its  tip  an  opening,  the  mouth,  surrounded  by 
a  row  of  deUcate  oral  bristles  which  point  forward.  The  sides  of 
the  head  are  often  lobed  and  carry  two  circles  or  series  of  groups 
of  fine  sense  hairs;  those  of  the  anterior  series  point  outward  and 
forward  while  the  others  are  usually  directed  backward.  Some- 
times the  entire  body  is  smooth,  or  it  may  be  partly  or  entirely 
covered  with  plates,  spines,  or  hooked  bristles.  These  furnish 
the  criteria  for  the  distinction  of  species  and  are  carefully  described 
in  the  key. 

The  posterior  end  of  the  body  may  be  bluntly  rounded,  pointed, 
or  forked.  The  caudal  processes,  often  spoken  of  as  "toes,"  carry 
special  bristles  and  contain  cement  glands,  the  secretion  of  which 
is  expressed  through  terminal  pores  and  enables  the  animal  to 
attach  itself  temporarily  to  objects  in  the  water. 

On  the  ventral  surface  are  two  bands  of  ciHa  near  the  median 
line,  extending  nearly  the  entire  length  of  the  body.  These  con- 
stitute the  chief  organs  of  locomotion.  The  movements  of  the 
Gastrotricha  are  so  graceful  as  to  eUcit  admiration  from  every 
observer.  In  motion  they  recall  the  long-necked  infusoria,  though 
excelhng  the  latter  in  speed  and  variety  of  movement.  By  bend- 
ing the  body  sharply  on  itself  the  animal  may  instantly  reverse  its 
course.  Those  species  possessed  of  long  bristles  utilize  them  in 
moving  by  leaps  like  jumping  rotifers.  Other  species  employ  the 
caudal  processes  in  movement,  looping  the  body  and  attaching  the 
tips  of  these  toes  successively  in  different  places. 

The  internal  anatomy  is  simple.  From  the  mouth  (Fig.  964,  A), 
a  straight  ahmentary  canal  traverses  the  length  of  the  animal 
terminating  in  a  simple  anal  orifice  just  above  the  posterior  end  of 
the  body.  One  can  distinguish  an  anterior  muscular  region,  the 
esophagus  and  a  posterior  portion,  the  intestine  (Fig.  964,  C),  which 
is  lined  by  large  digestive  cells,  rich  in  protoplasm.     Small  gland 


GASTROTRrCHA  627 

cells  on  the  esophagus  are  designated  as  salivary  in  character 
and  other  gland  cells  in  a  fringe  at  the  beginning  of  the  intestine 
have  been  regarded  as  hepatic  or  liver  cells.  The  food  of  the 
Gastrotricha  consists  mainly  of  unicellular  algae,  the  tests  of  wliich 
can  often  be  recognized  in  the  intestine. 

Six  pairs  of  delicate  longitudinal  strands  constitute  the  entire 
muscular  system  as  there  are  neither  circular  nor  oblique  muscles. 


the   body;  ^  c: 


One  pair  of  muscles  extends  nearly 
the  entire  length  of 
the  others  occupy  only  the  ante- 
rior or  the  posterior  region  meeting 
near  the  center.  They  He  in  the 
body  cavity  which  is  devoid  of 
any  special  lining  epithelium.  The 
head  region  of  the  body  cavity 
is  almost  completely  filled  by  a 
saddle-shaped  mass  (Fig.  964,^)  of 
nerve  cells  dorsal  and  lateral  to 
the  esophagus  which  constitutes 
the  brain.  From  it  nerve  fibers 
go  out  to  the  anterior  sense  hairs 
and  lateral  strands  follow  the 
alimentary  canal  to  the  posterior 
end  of  the  body.  Minute  pigment 
spots  which  may  be  designated  as  eyes  certainly  occur  in  some 
species  despite  the  doubts  expressed  by  Zelinka. 

Excretory  organs  are  present  in  the  form  of  a  pair  of  lateral 
much  coiled  tubes  near  the  center  of  the  body.  The  inner  end  of 
each  tube  is  closed  by  a  long  flame  cell  and  the  outer  end  opens 
on  the  ventral  surface  near  the  median  fine  and  just  behind  the 
center  of  the  body.  Just  behind  these  coils,  in  the  mature  females, 
lie  the  large  eggs  that  mark  the  anterior  limit  of  the  simple  ovary. 
These  eggs  become  so  large  that  they  extend  over  one-third  to 
one-half  the  length  of  the  entire  body  and  increase  its  normal 
transverse  diameter  noticeably  so  as  to  modify  greatly  the  form  of 
the  gravid  female.  The  large,  oval  eggs  are  laid  on  algal  threads 
or  empty  shells  of  other  animals.     When  deposited  they  ha\e  a 


Fig.  964.  Chaetonotus  maximus.  i4,  optical  longitu- 
dinal section  through  anterior  tip  of  the  body 
showing  mouth,  oral  bristles,  frontal  plate,  and 
esophagus.  X  535-  B,  cross  section  through 
posterior  extremity  of  A,  showing  tripartite 
esophagus  and  above  it  the  saddle-shai>eti  brain 
while  below  are  the  two  ventral  cilian  bands. 
X  690.  C,  longitudinal  section  through  the  pos- 
terior region  of  the  body  showing  below  the  in- 
testine, rectum,  and  anus;  above  in  the  ovary  a 
single  ripe  egg;  on  the  up[)er  surface  fine 
bristles,  and  at  the  pxisterior  tip  one  of  the  toes 
with  its  adhesive  gland.    X  430.      (.\fter  Zelinka.) 


624  FRESH-WATER   BIOLOGY 

tough  thick  shell,  often  covered  with  hooks  and  knobs,  that  seem 
to  anchor  them  in  place.  When  the  embryo  has  reached  its  full 
development  its  vigorous  movements  burst  the  shell  and  a  full- 
grown  animal  emerges. 

No  one  has  yet  described  a  male  and  it  is  uncertain  that  any 
other  t^pe  than  the  female  exists.  This  form  may  have  a  sperm- 
producing  organ  yet  undiscovered  and  thus  be  in  reality  hermaph- 
roditic or  may  reproduce  exclusively  by  parthenogenesis. 

The  Gastrotricha  have  been  studied  but  Httle  in  North  America. 
Of  the  seventy-five  species  thus  far  described  only  sixteen  have 
been  recorded  from  the  United  States.  Most  of  these  were  found 
and  described  by  Stokes  at  Trenton,  New  Jersey.  While  this  dis- 
tribution appears  highly  local  there  is  no  doubt  that  search  in 
other  places  will  demonstrate  for  American  species  the  same  wide 
general  distribution  that  has  been  shown  for  European  forms. 
Further  study  will  doubtless  result  also  in  the  discovery  of  many 
other  species  on  this  continent,  since  the  evidence  thus  far  secured 
indicates  that,  like  most  minute  aquatic  organisms,  these  forms,  too, 
are  cosmopolitan  in  distribution. 

KEY  TO   NORTH  AMERICAN   FRESH-WATER   GASTROTRICHA 

1  (31)     Caudal  end  prolonged  into  two  prominent  lateral  processes. 

Suborder  Euichthydina  .    .      2 
Each  caudal  process  encloses  a  glandular  apparatus  and  bears  a  pore  at  the  tip. 

2  (11)     Body  naked,  scaled,  or  covered  with  rugosities  or  papillae,  but  never 

bearing  spines Family  Ichthydidae  .    .     3 

s(6)     Body  without  scales;  cuticula  smooth. 

Ichthydium  Ehrenberg  1830  .    .     4 
Seven  or  eight  species  described;   only  two  reported  from  North  America. 

4  (5)     Surface  of  body  entirely  smooth,  no  constant  furrows  or  ridges. 

Ichthydium  podura  O.  F.  Miiller  1786. 

Total  length  0.075  mm.;  esophagus  0.0188  mm.,  caudal  process  0.00875  mm. 
long.  Breadth  of  anterior  region  0.0163  mm.  The  cuticula  is  thin  and  is 
often  laid  in  deep  wrinkles,  but  these  are  entirely  inconstant.  The  lateral 
margins  show  no  trace  of  being  flattened.  The  caudal  processes  are  sharply 
set  off  from  the  body.     Eggs  smooth. 

Fig.  965.    Ichthydium  podura  in  dorsal  view.     X  360.     (After  Zelinka.) 


GASTROTRICHA 


625 


5  (4)     Dorsal  and  lateral  surface  with  deep  transverse  furrows.     Posterior 
region  of  body  narrow  and  elongated. 

Ichthydium  sulcatum  Slokes  1.S87. 

Total  length  0.107  to  0.187  mm.;  esophagus  not  more  than  one-si.xlh  the 
entire  length.  The  body  is  unusually  soft  and  flexible.  The  lateral  mar^in-s 
are  so  flattened  that  they  impart  to  the  body  the  effect  of  wings.  The  i)os- 
terior  region  is  narrow  and  very  much  longer  than  in  other  species. 


Fig.  966.     Posterior  region  of  Ichthydium  sulcatum  in  dorsal  :isi>ect. 

(After  Stokes.) 


X  alxjul  600. 


6  (3)     Body  covered  with  smooth  scales  or  with  rounded  papilhu-,  hut  wit  hout 

spines Lepidodcrma  Zelinka  iSSc,   .    .      7 

Six  species  described;   three  reported  from  North  America. 

7  (10)     Minute  soft  scales  present 8 


8  (9)     Scales  shield-shaped. 


Lepidoderma  squamatum  (Dujardin)  1841, 


Length  of  body  from  0.119  to  0.2  mm.,  of  esophagus  0.042  to  0.044  mm.;  breadth  of  anterior 
region  0.033  mm.,  of  posterior  body  also  0.033  mm.  Large  smooth  scales  near  the  posterior 
end  seen  in  profile  simulate  curved  bristles  or  spines.  Scales  on  body  and  neck  in  seven  alter- 
nating longitudinal  rows;   on  posterior  region  eight  rows  present.     New  Jersey. 


(05DD 


Fig.  967.     Lepidoderma  squamatum  in  dorsal  aspect  with  characteristic  dorsal  scales  of  head.  neck,  and 
trunk.     X  375-      (After  Zelinka.) 


9  (8)     Scales  rhombic,  pointed. 


Lepidoderma  rlwmlwidcs  (Stokes)  18S7. 


Fig.  968.  Lepidoderma  rhomboides.  A,  ventral 
view  of  head.  B,  caudal  branch.  C,  portion  of  the 
scale  pattern.     X  350-     (After  Stokes.) 

Length  0.295  mm.;  breadth  of  anterior  region 
0.036  mm.  Body  long,  slender.  Esophagus 
short,  "  not  over  one-sixth  total  length."  Scales 
0.00506  mm.  long,  thickened  along  the  margins. 

Posterior  margin  of  each  scale  appears  to  carry  ,    ,  ,    1  111,  .i...,.f  -,« 

a  small  triangular  supplementary  scale.     Caudal  process  remarkably  long,  markeil  b>  aln.ut  ao 
delicate  rings.     New  Jersey. 


626 


FRESH-WATER   BIOLOGY 


lo  (7)     Body  covered  with  hemispherical  papillae. 

Lepidoderma  concinnum  (Stokes)  1887. 


Length  0.096.  Body  cylindrical.  Back  and  sides  covered  with 
small  half-round  papillae  arranged  in  thick -set  oblique  rows.  Egg 
smooth,  0.055  mm.  long.     New  Jersey. 


Fig.  969. 


Posterior  region  of  Lepidoderma  concinnum  in  dorsal  view. 
X  about  525.     (After  Stokes.) 


11  (2)     Body  provided  with  spines  either  attached  to  the  dermal  scales  or 

springing  directly  from  the  surface. 

Family  Chaetonotidae  .    .     12 

12  (30)     Caudal  process  simple;  spines  attached  to  dermal  scales. 

Chaetonotus  Ehrenberg  1830  .    .     13 
A  large  and  complicated  group;   more  than  forty  species  already  described;   ten  species  re- 
ported from  North  America  by  Stokes. 

13  (20)     Dorsal  spines  nearly  uniform  in  length,  at  most  twice  as  long  on 

posterior  region  as  on  anterior  region,   and  without  any 
marked  transition  from  one  size  to  another 14 

14  (15)     Dorsal    spines    with    accessory   barbs   or   points.     Anterior   region 

sharply  set  off  from  so-called  "neck." 

Chaetonotus  similis  Zelinka  1889. 

Length  of  body  0.12  to  0.22  mm.,  of  esophagus  0.05  mm.  Body 
covered  dorsally  and  laterally  with  triangular  scales  carrying  spines 
with  accessory  point.  Oral  funnel  plicate.  Originally  described 
from  Trenton,  New  Jersey,  as  Ch.  maximus  which  it  closely 
resembles  in  head  and  body.  Under  a  high  magnification  differ- 
ences in  the  spines  appear.  All  of  them  are  forked  and  have 
a  fine  lateral  point  near  the  tip. 


ml 


Fig.  970.     Chaetonotus  similis  in  dorsal  view.     X  375-     A,  body  spine 
from  the  side,     X  1600.     (After  Zelinka.) 


GASTROTRICHA 
15  (14)     Dorsal  spines  simple;  i.e.,  without  lateral  barbs 


627 


or  pointb. 


16  (17)     Anterior  region  sharply  set  off  from  narrow  "neck"  region. 

Chaetonotiis  Jormosus  Stokes  1887. 

Length  0.169  mm.  Oral  ring  minutely  beaded.  Head  thn-e  l<,l,cd.  I)„rsal  and  lateral 
aspects  of  body  covered  with  short  tine  recurved  spines  with  slight  basal  cnlarRcmcnls  -but 
without  scales.^.     Spines  all  subequal,  in  length  0.0292  mm.,  or  less.     Trenton.  New  Jcr«v 

No  figure  pubhshed.  j  ■  ^>  • 


17  (16)     Transition  from  anterior  region  to  body  gradual,  not  sharply  market! 
at  any  point '  ,^ 


18(19)     Head  rounded Chaetonolus  brcvispi)wsus  ZcV\n\i-d  iHH(}. 


Length  of  body  0.095  to  0.149  mm.,  of  esophagus  0.0223  mm- 
Spines  somewhat  curved,  remarkably  short,  slightly  larger  poste- 
riorly, arranged  in  eleven  rows  Head  circular  in  front,  with  four 
eye-spots.  The  only  American  species  reported  ni(jrc  than  ontc. 
Orono,  Me.,  and  Trenton,  New  Jersey.  It  is  the  C.  larus  of  Stoke-, 
also  of  Fernald. 


Fig.  971. 


Chaetonolus  brevispinosus  in  dorsal  view,  X  a^K),  with  spioiMC 
scale  more  highly  magnified,     (.\fter  Zelinka.) 


19(18)     Head  five  lobed Chaetonof us  ncdnt/iodes  Siokcs  i^S-;. 


Length  0.1411  mm.  Body  covered  with  scali-s  which  In-ar  eaih  a 
small  supplementary  scale;  the  latter  in  the  anterior  region  iios-st-s-^t-i 
a  short,  curved  spine;  just  behind  the  middle  of  the  IhkIv  these  trrnu- 
nate  in  a  cross  row  of  larger  spines.  t)n  each  side  near  the  laudal 
processes  are  two  larger  curved  spines.     Trenton,  New  Jer>cy. 

Fig.  972.     Posterior  end  of  Charlonotus  acanlht>dfs  in  dor^;d  virw. 
X  about  570.     (After  Stokes.) 


628  FRESH-WATER    BIOLOGY 

20  (13)     Certain  dorsal  spines  of  much  greater  length  than  others.    ...     21 

All  species  in  this  group  thus  far  reported  from  North  America  have  large  bifurcate  spines. 
A  number  of  European  species  have  simple  spines  without  a  lateral  point  near  the  tip.  Griin- 
spann  classes  the  ne.xt  species  among  the  latter  despite  Stokes'  positive  statement  that  the 
spines  are  bifurcate. 


21  (26)     Head  and  neck  free  from  covering  of  small  spines.     Large  spines  on 
body  proper 22 


22  (23)     Large  dorsal  spines  in  longitudinal  rows  and  of  approximately  equal 
length Chaetonotus  octonarius  Stokes  1887. 


Length  0.0862  to  0.1034  nun.  Breadth  of  distinctly  five-lobed  head 
0.0206  mm.  Large  spines  unequally  furcate  arranged  in  two  lateral 
rows  of  three  spines  each  and  a  median  row  with  one  anterior  and  one 
posterior  spine.  The  figures  and  descriptions  given  by  Stokes  and 
Griinspann  do  not  agree  fully  and  may  belong  to  separate  species. 
Rare;   Trenton,  New  Jersey. 


Fig.  973.     Chaetonotus  octonarius  mdorsaXw'xtwi.     X  about  580.     (After  Stokes.) 


23  (22)     Large  dorsal  spines  in  two  distinct  transverse  row^s,  with  spines  in 

one  row  clearly  longer  than  those  of  the  other 24 

24  (25)     Eight  (rarely  fewer)  large  spines  in  two  transverse  rows  set  close 

together Chaetonotus  longispinosus  Stokes  1887. 


Length  0.0736  mm.  Large  spines  usually  eight,  four  in  each  row,  or 
five  in  one  and  three  in  the  other;  sometimes  only  four  spines  in  all 
(the  others  lost?);  longer  spines  in  posterior  row.  The  figure  in 
Griinspann  is  really  the  next  species.  The  European  form  identified 
as  this  species  is  twice  as  large.     Trenton,  New  Jersey. 

Fig.  974.     Chaetonotus  longispinosus  in  dorsal  view.    X  6io.    (After  Stokes.) 


GASTROTRKI 


()2Q 


25  (24)     Seven  (rarely  fewer)  large  spines  in  tuo  ui.idy  sq>aratc.l  irahsvcrse 
^^^^ C/iaclunolus  spinulosus  Slokc:,  iHii?. 


Length  0.0675  to  o  089  mm.  I'sually  four  larRc  spine  in  antcri.r 
row  and  three  m  posterior.  Some  may  Iw  supprcsswl  („r  l.,Ht'>  Icav- 
ing  three  m  front  and  only  one  in  the  center  U-huM  <ui-,ns  o( 
anterior   row   distinctly   longer.      ICgg  o.o.i.}«;   mm.    1,,.  '      .,n 

one  side  with  short  hairs.      The  embryo  esta|>e>  in  11  .,»d 

thirty  hours  later  the  young  individual  shows  an  ovan  1  „  h 

the  nucleus  becomes  conspicuous  si.\  hours  later. 


Fig.  975.     C/iaetonolus  spinulosus  IthIots^A  view.     X  665.     (After  Stokes.) 


26  (21)     Spines 


present   on 
body.   .    . 


head   and    neck   much    smaller   than    those 


on 
27 


27  (28,  29)  Four  transverse  rows  of  large  dorsal  spines  on  posterior  region 
of  body.  Also  one  large  lateral  spine  on  each  side  at  caudal 
process Chaetonotus  acanthophorus  Stokes  1887. 


Length  0.108  mm.  Head  and  neck  covered  with  short  spin«. 
Large  spines  on  body  in  four  cross  rows  of  five  each,  not  altrrnalinjt 
so  that  they  appear  also  as  five  longitudinal  rows  of  four  spines  each. 
The  last  lateral  spine  at  the  base  of  the  caudal  process  is  large  and  much 
like  those  in  the  dorsal  rows.     Trenton,  New  Jersey. 


Fig.  976.     Chaetonotus  acanthomorphus '\n  dors>a.\  \'\cy; ■     X  415-     \Suhdork*i 
spine.     X  about  1165.     (After  Stokes.) 


28  (27,  29)     One  transverse  row  of  large  spines  just  in  front  of  the  caudal  end 
of  the  body C/iai'io)iolus  spinifcr  Siokcs  iSS-;. 

Length  0.1954  mm.  Back  and  sides  covered  by 
rounded  imbricated  scales,  each  with  stout  n-oirved 
spine  minutely  furcate  at  tip.     The  f'  -^  » 

smgle  series  immediately  in  front  of  tlu  nw 

are  much  larger  and  stouter  than  tho-  '  ol 

the  body.  Egg  ornamentetl  with  provc.-v<-.s  \Aiyu\K 
in  length  and  sha|)e  in  dilTerenl  s|>et-imcns.  Stoke* 
distinguishes  eggs  with  three  se|wirate  i>attcrn»  rrM»ri-- 
tively,  0.0705.  o.o7,i5.  and  o  0793  mm.  lon^.  Trenton. 
New  jersey. 

Fig.  977.     CItaelotuUus  spinifrr.     A  •'J^ 

tion  of  egg.  showing  tnfi.l  .in.l  -i  ■ 
and  surface  asi^ecls.     Highly  ma>;i. 


630 


FRESH-WATER   BIOLOGY 


29  (27,  28)     Five  transverse  rows  with  thirteen  large  spines.     Also  two  con- 
spicuous lateral  spines  on  each  side  near  the  end. 

Chaetonotus  enormis  Stokes  1887. 


Length  0.0846  mm.  Of  the  thirteen  large  spines  three  stand  in  the  ante- 
rior row,  four  in  the  next,  one  at  the  extreme  on  each  side  in  the  next,  three 
in  the  fourth  row,  and  one  at  the  center  in  the  fifth  row.  On  each  side 
near  the  caudal  process  are  two  forked  spines  easily  confused  with  those  of 
the  five  rows  which  they  much  resemble.     Trenton,  New  Jersey. 


Fig.  978.    Chaetonotus  enormis  in  dorsal  view.     X  530.     (After  Stokes.) 


30  (12)     Caudal  process  branching  or  notched.    A  transverse  row  of  large 

spines  near  its  base.     Body  surface  rough. 

Chaeturina  Ward. 
Only  one  species  known. 

Chaeturina  capricornia  (Metchinkoff)  1864. 

A  swamp  animal  not  yet  reported  from  North  America. 

31  (i)     No  caudal  processes.     Posterior  end  simply  rounded  or  lobed,  in  the 

latter  case  provided  with  long  fine  spines. 

Suborder  Apodina. 

Reported  from  North  America Family  Dasydytidae. 

'Iwo  genera  described  for  Europe. 

Single  North  American  genus Dasydytes  Gosse  185 1. 

Several  species  listed  from  Europe. 

Only  species  reported  from  North  America. 

Dasydytes  saltitans  Stokes  1887. 


Length  0.085  mm.  Head  three  lobed,  distinctly  separated  from  body  by 
slender  neck,  provided  with  two  rows  of  cilia  which  vibrate  alternately. 
Four  long  heavy  spines  arise  on  each  side  near  the  neck  and  cross  the  back 
obliquely.  Two  long  straight  spines,  and  two  others  long  and  curved, 
project  from  the  posterior  end.  This  species  swims  rapidly  but  also  moves 
by  sudden  leaps  to  one  side  or  the  other,  covering  a  distance  equal  to 
double  its  length  or  more  in  a  single  jump.     Trenton,  New  Jersey. 


Fig.  979.    Dasydytes  saltitans  in  dorsal  view.     X  4iO'     (After  Stokes.) 


GASTROTRICHA  6^, 

IMPORTANT   PAPERS    ON    NORTH    AxMERICAX    GASTROTRICHA 

Fernald,  C.  H.     1883.     Notes  on  the  Chactonolus  larus.     Amcr.  Nat.,  17: 

12 17-1220;  2  figs. 

Interesting  biological  study  on  Ch.  breiispiitosus. 
Grunspann,  Th.     1910.     Die  Susswasser-Gastrotrichen  Europas      Ann.  Biol. 

Lacustre,  4:  211-365;  61  figs. 
Stokes,  A.   C.     1887.     Observations   on   ClnidonotHs     The    MicroscoiH?,   7: 

1-9,  33-43;    2  pi.  Translated  in  Jour.  Microg.,  11:    77-85,  150-153,  560- 

565;  2  pi. 
1887a.     Observations  on  a  New  Dasydyles  and  a  New  Chaetomtus.    T!ic 

Microscope,  7:    261-265;    i  pi.     Translated  in  Jour.  Microg.,  12:  19-22. 

49-51;  I  pi. 
1896.     Aquatic  Microscopy  for  Beginners.     Third  edition  (Gastrotricha,  pp. 

178-193). 
Zelinka,  C.     1889.    Die  Gastrotrichen.    Zeit.  f.  wiss.  Zool.,  49:    209-3S4: 

5P1. 


CHAPTER   XIX 

AQUATIC    EARTHWORMS   AND    OTHER 
BRISTLE-BEARING   WORMS 
(CHAETOPODA) 

By  frank  smith 

Professor  of  Systematic  Zoology  and  Curator  of  the  Museum  of  Natural  History,  University  of  Illinois 

Earthworms,  with  their  flexible  segmented  bodies  and  four 
double  rows  of  bristles,  or  setae,  are  objects  familiar  to  all  students 
of  animal  hfe.  Although  most  species  are  terrestrial  there  are  also 
aquatic  ones  and  these  are  abundantly  represented  in  our  fresh 
waters.  Closely  related  to  the  earthworms  and  similar  in  structure 
are  numerous  other  worms  which  are  essentially  aquatic.  These 
also,  with  certain  exceptions,  are  provided  with  setae  and  are 
included  with  earthworms  in  the  group  Oligochaeta.  The  setae- 
bearing  worms  of  the  sea  (Polychaeta)  commonly  bear  the  setae  on 
lateral  muscular  outgrowths  of  the  body  wall,  the  parapodia.  The 
Oligochaeta  and  Polychaeta  collectively  are  often  referred  to  as  the 
Chaetopoda. 

The  Chaetopoda,  Hirudinea  (leeches),  and  certain  strictly  marine 
worms  which  are  not  under  consideration  here,  are  included  in  the 
phylum  Annelida. 

Fresh-water  Polychaeta 

Although  the  Polychaeta  are  essentially  marine  in  habit,  a  few 
species  in  various  parts  of  the  world  have  become  adapted  to 
fresh-water  conditions.  Manayunkia  speciosa  Leidy  is  found  in 
the  Schuylkill  River  and  in  other  fresh-water  situations  near  Phila- 
delphia, and  Johnson  has  described  two  fresh-water  species  from 
the  western  coast  region,  —  Nereis  limnicola  Johnson  from  Lake 
Merced,  near  San  Francisco,  and  Lycastoides  alticola  Johnson  from 
Lower  California. 

These  are  stray  intruders  from  the  rich,  marine  fauna  of  this 
group  in  adjacent  salt  water,  and  none  have  yet  been  discovered 

632 


AQUATIC    EARTHWORMS  6^3 

at  any  great  distance  from  the  sea.  Further,  more  careful  study 
of  the  Hfe  in  brackish  water  estuaries  and  fresh-water  bodies  in 
close  contiguity  with  the  ocean  is  Hkely  to  reveal  the  presence  of 
such  forms  in  other  locahties. 

Fresh-water  Oligochaeta 

The  Oligochaeta,  including  the  earthworms  and  related  aquatic 
forms,  are  segmented  worms  which  have  a  somewhat  extensive 
and  well-defined  body  cavity  separating  the  alimentary  tract  from 
the  body  wall.  They  are  hermaphroditic,  with  the  reproductive 
organs  limited  to  a  few  definite  segments  or  somites.  The  bristle- 
Hke  setae  in  the  body  wall  aid  in  locomotion,  but  such  setae  are 
absent  in  the  family  Discodrilidae  which  are  parasitic  on  the  ex- 
ternal surfaces  of  crayfishes.  The  majority  of  the  species  are 
terrestrial,  and  the  aquatic  forms  are  nearly  all  confined  to  fresh 
water.  Seven  families  of  aquatic  Oligochaeta  are  found  in  the 
northern  hemisphere  and  are  all  abundantly  represented  in  the 
United  States. 

Morphological  Relations.  The  general  plan  of  structure  of  the 
aquatic  forms  agrees  essentially  with  that  of  the  earthworm. 
External  metamerism  is  indicated  by  the  transverse  grooves  and 
by  the  segmentally  arranged  setae,  and  the  corresponding  internal 
metamerism  is  recognizable  in  the  septa,  nephridia,  transverse 
blood  vessels,  and  in  the  ganglia  of  the  ventral  nerve  chain.  The 
prostomium  —  the  dorsal  part  of  the  anterior  somite  extending 
anterior  to  the  mouth  —  is  very  flexible  and  sensitive,  and  is  an 
important  tactile  organ  which  in  some  species  is  prolonged  into  a 
proboscis  (Fig.  984.)  The  somites  are  numbered  consecutively  from 
the  anterior  end,  and  are  designated  in  these  pages  by  Roman  nu- 
merals in  accordance  with  a  common  practice.  The  boundary 
between  two  somites  is  indicated  thus:  X/XI. 

The  setae  are  usually  conspicuous  and  are  of  taxonomic  impor- 
tance. They  are  commonly  grouped  into  dorsal  and  ventral  bundles, 
the  most  anterior  ventral  pairs  being  always  on  the  second  somite. 
Figure  991  illustrates  some  of  the  more  usual  types  of  setae. 

The  nephridia  are  the  segmental  excretory  organs,  which  t>iM- 
cally  are  paired  and  are  usually  present  in  all  somites  of  the  body 


634  FRESH-WATER   BIOLOGY 

except  a  few  anterior  ones  and  one  at  the  posterior  end.  Not  infre- 
quently some  of  the  nephridia  may  fail  to  develop,  when  a  more  or 
less  irregular  and  asymmetrical  distribution  results. 

The  reproductive  organs  of  the  fresh-water  OHgochaeta  are  simi- 
lar to  those  of  the  terrestrial  earthworms.     One  or  two  pairs  of 
male  gonads  (spermaries  or  testes)  are  attached  to  the  anterior 
septa  of  certain  somites  and  extend  freely  posteriad  into  the  cavities 
of  the  somites.     One  or  two  pairs  of  ovaries  are  correspondingly 
situated  in  somites  posterior  to  those  which  contain  the  spermaries. 
The  sperm,  ducts  of  most  species  have  their  internal  openings  or 
spermiducal  funnels  in  the  somites  which  contain  the  spermaries, 
and  the  external  openings,  or  spermiducal  pores,  on  some  somite 
posteriad;  but  in  a  few  species  both  openings  may  be  in  the  same 
somite.     In  many  species  the  sperm  ducts  are  modified  in  various 
ways,  giving  rise  to  prostates,  atria  and  storage  chambers  (Fig. 
990).     The  internal  openings  of  the  oviducts,  the  oviducal  funnels, 
are  in  the  ovarian  somite,  and  the  oviducal  pores  are  either  at  the 
posterior  boundary  of  the  same  somite  or,  more  commonly,  on 
the  following  one.     Accessory  reproductive  organs  are  commonly 
present.     Evaginations  of  the  septa  of  the  somites  which  contain 
spermaries  form  sperm  sacs  in  which  the  sperm  cells  may  complete 
their  development  and  be  temporarily  stored  before  they  pass  out 
through  the  sperm  ducts  during  copulation.     Evaginations  of  the 
posterior  septa  of  the  ovarian  somite  form  ovisacs.     Invaginations 
of  the  body  wall  of  certain  somites  produce  spermathecae,  usually 
paired,  which  serve  for  storage  of  the  sperm  cells  received  during 
copulation,  from  another  individual. 

Sexual  reproduction  occurs  in  all  famihes  of  fresh-water  OHgo- 
chaeta at  more  or  less  definite  seasons  of  the  year.  In  the  two 
famines  Naididae  and  Aeolosomatidae,  asexual  reproduction  by 
budding  is  the  mode  by  which  the  majority  of  new  individuals 
are  produced.  Figure  980  exhibits  the  main  features  of  the  process 
and  renders  an  extended  description  unnecessary.  The  body  wall 
thickens  anterior  to  the  middle  of  the  budding  somite  and  forms  a 
budding  zone,  the  anterior  half  of  which  gives  rise  to  an  indefinite 
number  of  new  somites  which  form  the  posterior  part  of  the  ante- 
rior daughter-worm.      The   posterior  half  of   the  budding   zone 


AQUATIC    EARTHWORMS 


635 


gives  rise  to  a  definite  number  of  new  somites  (five  in  most  species 
of  Naididae),  which  form  the  anterior  part  of  the  posterior  daughter- 
worm.  The  daughter-worms,  before  separation,  may  in  turn  de- 
velop budding  zones,  and  in  some  cases  even  a  third  series  oi  these 
zones  may  appear  and 
thus  give  rise  to  chains 
of  incipient  individuals, 
or  zooids.  In  some  spe- 
cies ehains  of  eight  zooids 
are  of  ordinary  occur- 
rence. In  the  genus 
Chaetogaster  the  plane 
of  division  is  in  a  septum 
between  two  somites. 
Although  many  aquat- 

\r    Olicrnrhaptn    Vin\7-p    tViP     ^^^-  9^°-     Development  of  budding  zones  in  Stylaria  lacuslris. 
IL    WilgUeildeLcl    nave    Uie  ^,  An  early  stage.    5.  A  later  stage.    C.  Still  later  sI;,kc  with 

power      to      regenerate  a  second  budding  zone  weU  started.   X. 5.    (.-Vfter  UuckarU 

missing  parts,  greatly  developed,  there  is  lack  of  evidence  that  it  is 
of  much  importance  in  normal  reproduction. 

Environmental  Relations.  The  well-known  investigations  of 
Darwin  and  others,  on  the  action  of  terrestrial  earth worm.s  on  the 
soil  and  its  organic  contents,  have  led  to  a  general  ai)preciation  of 
the  importance  of  the  relations  of  these  animals  to  their  surround- 
ings. It  is  less  generally  understood  that  their  aquatic  relatives 
play  a  very  important  part  in  reducing  the  great  masses  of  aquatic 
vegetation  to  a  finely-comminuted  condition.  Oligochaeta  of 
various  species  abound  in  the  mud  at  the  bottom  and  along  the 
shores  of  most  bodies  of  fresh  water,  and  an  almost  continuous 
stream  of  this  mud  with  its  decaying  organic  contents  is  passing 
through  their  bodies  and  being  still  further  subdivided  and  de- 
prived of  organic  material  and  its  available  energy.  Numerous 
other  species  swarm  in  the  decaying  leaves  and  stems  of  coarse 
vegetation  of  swampy  areas  and  materially  aid  in  their  disintegra- 
tion, while  still  other  kinds  populate  the  floating  masses  of  algae, 
which  they  rapidly  devour  as  decay  progresses.  Since  under 
favorable  conditions  it  requires  but  two  or  three  days  for  Xauh- 
form  worms  to  reproduce  by  budding,  they  multiply  with  such 


636  FRESH-WATER  BIOLOGY 

rapidity  that  they  can  extensively  populate  large  masses  of  mori- 
bund algae  in  a  very  short  time,  and  their  activity  accounts  in 
part  for  the  speedy  disappearance  of  such  masses  in  the  autumn. 
Although  many  of  these  worms  will  not  thrive  in  polluted  water, 
others  are  adapted  to  foul  conditions  where  fermentation  is  rife, 
and,  in  fact,  multiply  most  rapidly  in  such  situations.  Some 
species  of  this  sort  feed  extensively  on  the  zoogloeic  masses  which 
abound  where  fermentation  is  active.  The  food  of  most  Oligo- 
chaeta  consists  chiefly  of  decaying  vegetable  matter,  but  worms  of 
a  common  Naid  species,  Chaetogaster  diaphanus,  have  a  marked 
preference  for  Chydorus  sphaericus,  a  Cladoceran  species  which  they 
capture  and  devour  in  large  numbers.  Worms  of  the  family  Dis- 
codrilidae  are  parasitic  on  crayfishes. 

Certain  of  the  Naididae  can  swim  effectively  in  open  water,  but 
a  great  majority  of  the  Oligochaeta  are  limited  to  crawling  move- 
ments for  locomotion. 

Striking  structural  adaptations  are  not  numerous  in  the  group, 
but  the  pecuHar  modification  of  the  posterior  end  in  Aulophorus 
and  Dero  for  purposes  of  respiration,  deserves  mention.  These 
worms  live  chiefly  in  tubes  of  their  own  making  or  with  their 
bodies  almost  wholly  buried  in  masses  of  vegetable  material,  and 
respiration  is  aided  by  well-developed  gill  structures  (Fig.  985). 
The  Discodrilidae  in  adaptation  to  their  peculiar  mode  of  life,  have 
become  so  leech-like  in  action  and  external  appearance  that  for- 
merly it  was  usual  to  treat  them  as  belonging  to  the  Hirudinea 
rather  than  to  the  Oligochaeta. 

Collection  and  Preservation.  The  larger  specimens  may  be  ob- 
tained by  carefully  screening  mud  from  bottoms  and  shores  and 
from  about  the  roots  of  coarse  plants  through  fine-meshed  nets  or 
sieves.  Others  may  be  obtained  by  carefully  pulling  to  pieces 
decaying  rushes  and  masses  of  algae.  Smaller  specimens  often 
may  be  obtained  from  the  sides  of  aquaria  in  which  mud  and  vege- 
table material  have  been  allowed  to  stand  for  a  few  days.  During 
the  fermentation  of  such  masses  large  numbers  of  small  worms 
appear  in  the  surface  layers  and  about  the  margins. 

The  most  successful  methods  of  preservation  vary  with  different 
species,  and  must  be  gained  by  experiment,  but  some  general  hints 


AQUATIC   EARTHWORMS  637 

may  be  given  here.  Specimens  intended  fur  secLloning  must  be 
kept  in  water  and  material  which  is  free  from  grit  until  the  alimen- 
tary tract  is  cleansed  from  mud  and  sand.  The  methods  necessary 
for  securing  straight  and  well-extended  specimens  for  fixation  vary 
greatly  with  the  species.  Dilute  solutions  of  the  fixing  agent 
when  of  the  right  strength  will  often  cause  the  worms  to  (h'e  in  a 
properly  extended  condition,  and  this  is  esi)ecially  true  of  some  (jf 
the  Tubificidae  when  corrosive  sublimate  is  used.  Commonly  some 
means  of  narcotization  is  required  to  secure  the  relaxation  neces- 
sary for  the  preparation  of  well-extended  specimens.  Oood  re- 
sults are  often  obtained  by  the  gradual  addition  of  a  solution  of 
chloretone  until  the  worms  no  longer  respond  to  stimuli  and  fail 
to  contract  excessively  when  placed  in  the  iixing  lluid.  Another 
common  expedient  used  with  success  for  some  species  is  to  inmierse 
the  worms  in  water  within  a  closed  vessel  and  there  subject  them 
to  the  action  of  the  vapor  of  chloroform,  which  is  put  into  the  same 
closed  vessel  but  in  a  separate  container.  Only  the  vapor  should 
be  allowed  to  reach  the  water  that  contains  the  worms. 

When  properly  narcotized  the  specimens  may  be  immersed  in 
the  fixing  agent  and  kept  straight  by  holding  them  against  any 
convenient  straight  edge  until  they  have  become  sutTicientl)'  rigid. 
A  rectangular  glass  candy-tray  is  a  convenient  vessel  for  fixation 
purposes  since  the  angles  formed  by  the  sides  and  the  bottom 
furnish  good  opportunities  for  keeping  the  worms  straight.  It  is 
often  advantageous  to  use  a  small  amount  of  hxing  lluid  at  lirst 
and  to  keep  the  worms  only  partially  submerged  until  the\-  have 
become  stiffened  and  then  completely  immerse  them.  Small  speci- 
mens like  tubificids  and  enchytraeids  may  be  con\'enientl\-  fixed  on 
a  glass  plate  with  the  aid  of  square-edged  toothpicks  which  have 
been  soaked  in  the  fixing  agent.  A  toothpick  with  the  adhering' 
fluid  is  placed  on  the  glass,  an  anesthetized  worm  stretched  along 
one  edge  of  the  toothpick,  another  toothpick  placed  against  the 
other  side  of  the  worm  and  a  second  worm  stretched  along  the  free 
edge  of  the  second  toothpick.  A  repetition  of  this  process  will 
enable  one  to  prepare  a  considerable  number  of  specimens  in  a 
brief  time.  Subsequent  treatment  is  like  that  for  other  material 
of  similar  nature. 


638 


FRESH-WATER   BIOLOGY 


KEY  TO  NORTH  AMERICAN  FRESH-WATER  OLIGOCHAETA 

1  (45)         Well-developed  setae  present  on  most  somites 2 

2  (24)         Reproduction   chiefly   asexual,   by   budding;   sexual   reproduction 

less  frequent.  Clitellum,  when  present,  on  some  somites  of 
V-VIII.     Length  less  than  25  mm.  in  most  species.       .     3 

3  (4)  Setae  of  ventral  bundles  as  well  as  dorsal  setae  capilliform;  septa 

imperfectly  developed;  prostomium  broad  and  ciliated  ven- 
trally;  integument  of  most  species  contains  conspicuous 
colored  bodies  of  some  shade  of  red,  green,  or  yellow.  Usu- 
ally 1-2  nmi.  long Family  Aeolosomatidae. 


A  eolosoma  Ehrenberg  is  the  only  North  American 
genus  and  the  species  of  the  U.  S.  have  not  been 
much  studied.  A .  tenehrarum  Vejdovsky  has  pale 
yellow  or  greenish  integumental  bodies.  One  or 
two  species  with  colorless  bodies  are  known.  A. 
hemprichi  Ehrenberg  has  salmon-colored  bodies. 
This  last  named  species  thrives  exceptionally  well 
in  hay  infusions  and  in  similar  cultures  from  wheat 
and  thus  large  numbers  are  readily  obtained  for 
experimental  purposes. 


Fig.  981.    Aeolosoma  hemprichi. 
Lankester.) 


X  20.    (After 


4(3) 


Ventral  setae  all  uncinate  (Fig.  991);   septa  well  developed;   no 
brightly  colored  integumental  bodies. 

Family  Naididae  .    .     5 

5  (8)  No  dorsal  setae 6 

6  (7)  Ventral  bundles  of  setae  on  III-V  as  on  other  somites. 

Schmardaella  Michaelsen  1900. 
The  South  American  species  5.  filiformis  (Schmarda)  has  recently  been  reported  from  Lake 
St.  Clair  (Moore,  1906). 

7  (6)  No  setae  on  III-V.     Somite  III  much  elongated. 

Chaetogaster  K.  von  Baer  1827. 


Several  species  are  known 
from  North  America,  of  which 
C.  limnaei  K.  von  Baer,  which 
lives  in  mollusks,  and  the  large 
transparent  C.  diaphanus 
(Gruithuisen),  10-15  mm.  long, 
are  easily  recognized. 


Chaetogaster  limnaei.     X  40. 
(After  Lankester.) 


8  (5)  Setae  in  both  dorsal  and  ventral  bundles 9 

0(12)         No  capilliform  setae  in  dorsal  bimdles.     ..........      ip 


AQUATIC   EARTHWORMS  639 

10  (11)         Setae  of  dorsal  bundles  all  uncinate.    .    Paratmis  Czerniavsky  1880. 
P.  litoralis  (Muller)  reported  as  abundant  on  the  New  England  coast  and  may  occur  in  adja- 
cent fresh  waters.     The  first  dorsal  setae  are  on  V. 

11  (10)         Dorsal  setae  nearly  straight,  slightly  toothed  or  simple-pointed. 

Ophidomiis  Gervai.s  1.H38. 

B«an^(ii<f.^!i'!JBrl"llL_Mi ^"  ^^>'P^"^^'^'^  (Miiller)  may  be  easily  rccoKnizcd  by  the 

^^^1^^^^"^'  ■W^^HtefcrK.  small  irregularly  distributed  dorsal  sctar;  by  the  four  larKC 

^P^^^I''l^^o''^o-^^^^^^  transverse  pigmented  areas  on  the  anterior  resion,  and 

-li^To-  '■  ''Wl  !    *?    ''  °o 0  J^  by  the  relatively  large  size.     Length  25-30  mm. 

'^j ^  ''^-,>;>.U^^>-W^.,^ sjf  Fig.  983.     AnterioT  tndolOphidonais  serpentina.    X  40.    (After 

""""T  ''  ^  Piguet.) 

12  (9)  CapiUiform  setae  present  in  dorsal  bundles 13 

13(21)         First  anterior  dorsal  setae  on  V  or  VI 14 

14  (18)         Posterior  end  not  modified  into  a  gill-bearing  respirator}-  organ; 

first  anterior  dorsal  setae  on  \'1 15 

15  (16,  17)  One  or  more  capilliform  setae  of  VI  much  longer  than  those  of 

other  somites  and  equal  to  three  or  four  times  the  diameter 
of  the  body Slavimi  Vejdovsky  1883. 

S.  appendiculata  (d'Udekem),  common  in  some  parts  of  the  United  States,  has  Ixidy  surface 
studded  with  sensory  papillae  and  with  foreign  bodies. 

16  (15,  17)  Prostomium  elongated  to  form  a  proboscis;  dorsal  setae  of  \'I  similar 

in  length  to  those  of  other  somites.     Stylaria  Lamarck  1816. 


S.  lacustris  (Linnaeus)  has  proboscis  flanked  by  promi- 
nent lateral  prostomial  lobes  (Figs.  980  and  9!^4);.  -*>•  foi- 
sidaris  Leidy  lacks  the  lateral  prostomial  lobes  (Fig.  984). 
The  former'  is  abundant  and  widely  distributed  in  the 
United  States  while  the  latter  is  reported  only  very  infre- 
quently. 


Fig.  984. 


Prostomium  and  proboscis,  Stylaria.    A,  S.  laeuitrii 

B.S./ossularis.     X40.     (Original) 


17  (iK,  16)  Without  proboscis;  dorsal  setae  of  VI  similar  in  length  to  those  of 

other  somites A'd/^  Muller  1774. 

Several  species  without  conspicuous  differences  are  reported  from  the  United  States.     A'. 
elinguis  Muller  is  one  of  the  best-known  species  and  A^.  communts  I>.guet  is  very  common. 

18  (14)         Posterior  end  modified  into  a  gill-bearing  respiratory  organ,  the 

branchial  area ^^ 

10  (20)         Ventral  margin  of  the  branchial  area  with  a  pair  of  long  processj-s. 
^^     ^  .l;</()/)//t;r//5  Schmarda  iSoi. 

A  Jurcatiis  (Okcn)  has  the  first  dorsal  setae  on  V  and 
has  two  pairs  of  well-develo,R'd  gills 

A  vagus  Leidv  crawls  or  tloats  about  m  a  tube  made 
;  ^i;:'^^-.  from  bryozoan  statoblasts  and  bits  .)f  vegetation      It  hw 

the  first  dorsal  setae  on  VI  and  has  only  slightly  devel- 
oped gills. 


Fig  q8s.    Posterior  end  of  .1  ulo Chorus  /urcaius. 
^  Bousflicld.) 


X  40.    (After 


640  FRESH-WATER   BIOLOGY 

20  (19)         Ventral  margin  of  the  branchial  area  without  long  processes. 

Dero  Oken  181 5. 

D.  limosa  Leidy  is  abundant  and  the  best  known  of  the  North 
American  species.  D.  obtusa  d'Udekem  and  a  species  which  prob- 
ably is  D.  perrieri  Bousefield  are  of  frequent  occurrence,  but  a  careful 
study  of  the  North  American  representatives  of  this  genus,  as  well 
as  of  Nais,  is  necessary  before  we  can  be  sure  of  their  exact  relation 
to  European  species. 

Fig.  986.    Posterior  end  of  Dero  limosa.     X  25.    (After  Bousefield.) 

21  (13)         First  anterior  dorsal  setae  on  II 22 

22  (23)         Dorsal  setae  of  two  kinds:  capilliform  and  shorter  needle-form  setae 

which  commonly  have  cleft  distal  ends, 

Naidium  O.  Schmidt  1847. 
N.  osborni  Walton  has  been  described  from  Lake  Erie  (Walton,  1906).    This  genus  is  united 
with  Pristina  by  some  writers. 

23  (22)        Dorsal  setae  all  capiUiform,  mostly  with  very  fine  teeth  on  convex 

side;  prostomium  commonly  elongated  into  a  proboscis. 

Pristina  Ehrenberg  1831. 

P.  longiseta  var.  leidyi  Frank  Smith  has  the  capiUiform  setae  of  III  greatly 
lengthened  (.700  mm.)  and  without  serrations.  The  typical  form  of  this 
species  as  found  in  Europe  has  extremely  minute  inconspicuous  serrations 
on  the  capilliform  setae  of  dorsal  bundles  of  somites  other  than  III.  In  the 
variety  P.  I.  leidyi,  which  is  found  in  the  United  States  and  certain  other 
parts  of  the  world,  the  serrations  are  coarser  and  more  easily  seen. 


d.s. 


Fig.  987.     Pristina  longiseta  ya-r.  leidyi.    r.  5.,  ventral  seta;   X  3oo-    (i.  5.,  part  of  seta 
from  dorsal  bundle.     X  450.     (After  Smith.) 


P.  flagellum  Leidy  has  a  very  characteristic  posterior  end.  Specimens  of 
this  species  have  been  met  with  by  the  writer  but  once  and  when  there  was 
no  opportunity  for  study  beyond  enough  to  convince  him  of  the  general  accu- 
racy of  Leidy's  description  and  that  the  species  really  belongs  to  Pristina. 

Representatives  are  sometimes  found  of  certain  species  in  which  the  dorsal 
setae  of  III  are  not  especially  elongated  but  their  exact  relationship  to  Eu- 
ropean species  is  uncertain. 

Fig.  988.    Posterior  end  of  Pm/ma^ageWMW.     X  16.    (After  Leidy.) 

24  (2)  Reproduction  sexual,  never  by  budding;  clitellum  ordinarily  poste- 

rior to  VIII 25 

25  (34i  35)  Ordinarily  more  than  two  well-developed  setae  in  each  of  some  or 

all  of  the  bundles;  ventral  setae  ordinarily  cleft  (exc.  Telma- 
todrilus:  see  below);  clitellum  ordinarily  on  X  or  XI  and 
one  or  more  adjacent  somites;  $  pores  ordinarily  on  XI,  ex- 
ceptionally on  XII;  spermathecal  pores  on  somite  anterior 
to  one  bearing  <?  pores  (in  North  American  species) ;  length 
commonly  more  than  25  mm.;  blood  vessels  usually  with  con- 
spicuous red  contents.    .    .    .    Family  Tubificidae  .    .     26 

^  Accurate  identification  of  species  in  this  family  usually  requires  the  aid  of  careful  dissec- 
tions or  of  serial  sections,  and  depends  largely  on  a  careful  study  of  the  reproductive  organs. 
(Fig.  990.) 


AQUATIC   EARTHWORMS 


641 


Sperm-ducts  without  definite  prostate  glands  and  opening  into  a 
common  median  chamber  with  single  ventral  median  <>|K-n- 
ing  on  XI;  spermathecal  pores  on  X;  setae  of  dorsal  bundles 
all  cleft RJiizodrilus  Frank  Smith  u/x). 

One  species  thus  far  known  in  North  America,  R.  latUus  Frank  Smith, 
found  in  roots  oi  Sagittaria  in  Illinois.  Has  two  kinds  of  jjcnital  setae 
on  IX  and  XI;  length  75-100  mm.;  whitish  in  ap[)carancc  (Smith,  lyoo). 
Michaelsen  includes  this  species  in  Monopylephorus  Levinscn. 


Fig.  989. 


Rhizodrilus  lacteus.    a,  ordinary  uncinate  seta;  b  and  c,  Kcniul  N<-ta. 
from  IX  and  XI.     X  150.     (After  Smith.) 


27  (26)         Sperm-ducts  with  definite  prostate  glands 28 

28  (29)         Ten  or  more  small  definite  prostates  on  each  sperm-duct;  no  capil- 

liform  setae;  setae  indistinctly  cleft  and  sometimes  simple- 
pointed Tclmalodrilus  Eisen  iHyg. 

Two  species,  T.  vejdovskyi  Eisen  and  T.  mcgregori  Eisen,  are  found  in  California. 

29  (28)         Sperm-ducts  each  with  one  definite  prostate  gland  (Fig.  990).    .    30 


30  (31)         Dorsal  setae  all  uncinate  and  similar  to  ventral  setae;  penis  with 
chitinous  sheath Limnodriliis  Clapartkie  1S62. 

Several  species  have  been  descrif>ed  from 
California  (Eisen,  1885). 

L.  gracilis  Moore  has  recently  been  described 
from  Lake  Erie  (Moore,  1906).  In  L.  clapare- 
dianiis  Ratzel,  an  abundant  si)ecies  of  wide 
distribution,  the  length  of  the  chitinous  penis 
sheath  is  8-50  times  its  diameter. 

Fig.  990.  Reproductive  organs  of  Limncdritus 
gracilis.  I,  spermary:  sp.  spermatheca;  /.  spenni- 
ducal  funnel;  r, :,  sperm-duct;  6.  prostate  kIuxI; 
r,  atrium;  at,  penis  and  jx-nis  sncath;  av,  ovary. 
X  20.     (.\fter  Moore.) 


31   (30) 


Dorsal  bundles  ordinarily  contain  capilliform  setae  and  also  jx-cti- 
nate  or  paknate  setae.    (Fig.  991.) 32 


Fig  991     a  and  fi,  uncinate  setae  from  7'M/>f7rx»»ik//i5r/<ir«»J,f  and 
d,  palmate  setae.  T.  tnultisrlosus;  e  and  /.  jKCtinatc  setae.  T. 

tubifex.    <i,  ft,  and  <,  X  150.     (DriKinal.) 


?2  (s3)         Length  of  atrium  and  penis  combined,  at  least  two-thirds  that  of 
the  remainder  of  the  sperm -duct.    .     Ilyodnlus  Eisen  iNTQ- 

Three  species  described  from  California  (Eisen,  1S85). 


642  FRESH-WATER   BIOLOGY 

^^  (32)        Atrium  and  penis  combined,  much  shorter  than  the  remainder  of 
the  sperm-duct Tubifex  Lamarck  1816. 

■^\\  v\i  ^\  ^\  Several  species  have  been  described  from  North  America. 

^ -^^^''^^JL^L^L^  T.  tubifex   (Muller)   is  a  widely  distributed   species  and 

^^^> — \      ■-  ^   \:    " "  "-  abundant  both  in  Europe  and   the   United   States.     An- 

^^  t_         ^      J'     ^--^"z  -ijji,  other  species,  T.  multisetosus  (Frank  Smith)  from  Illinois 

'^^^-^jM^M^W' ^^  ^^^  ^^^^^  integumental  papillae  and  conspicuous  clusters 

^"'  •^^^nn'^*Pp*?5p^;i^5-4^;  ^j  capilliform  setae  (Smith,  1900).     (Figs.  991  and  992.) 

Fig.  992.    Anterior  somites  oi  Tubijex  multisetosus.     X  i3-     (Original.) 

34  (25.  35)  Ordinarily  with  more  than  two  setae  in  each  of  some  or  all  the 

bundles;  setae  simple-pointed  and  usually  nearly  straight; 
clitellum  on  XII  and  on  more  or  less  of  adjacent  somites; 
Spores  ordinarily  on  XII;  spermathecal  pores  on  IV/V. 
Ordinarily  whitish  in  appearance  and  seldom  more  than 
25  mm.  in  length.  Both  terrestrial  and  aquatic  species 
abound Family  Enchytraeidae  .    .     35 

There  are  numerous  species  of  this  family  represented  in  the  fresh  waters  of  North  America, 
which  have  only  recently  received  attention  from  the  systematists  of  the  group.  Eisen 
(1905)  has  described  several  fresh-water  species  from  the  Pacific  Coast  states  belonging 
to  Mesenchytraeiis  Eisen,  Enchytraeus  Henle  and  Lumbricillus  Oersted.  Smith  and  Welch 
(1913)  have  described  Marionina  forbesae  from  Illinois  and  Welch  (1914)  has  described 
Luynbricillus  rutilus  from  IlUnois. 

35  (25.  34)  Ordinarily  with  not  more  than  two  well-developed  setae  per  bundle, 

or  eight  more  or  less  separated  setae  per  somite.   ...      36 

36  (37.42)  Setae  simple-pointed;  J  pores,  2  pairs  on  XI  and  XII  or  both 

pairs  on  XII;  spermaries  in  X  and  XL 

Family  Haplotaxidae. 

Haplotaxis  (Phreoryctes)  emissarius  (Forbes)  is  the  only  representative  of  this  family  thus  far 
known  in  North  America.  Has  two  large  isolated  ventral  setae  and  two  small  dorsal  setae 
oer  somite;  many  somites  without  dorsal  setae;  length  150-200  mm.;  diameter,  scarcely  i  mm.; 
subterranean  habit. 

37  (36,  42)  Setae  either  simple-pointed  or  cleft;  S  pores  on  one  or  more  somites 

anterior  to  XII,  with  spermiducal  funnels  in  same  somites; 
cecal  diverticula  of  the  dorsal  vessel  or  its  branches,  in  the 
mid-body  region Family  Lumbriculidae  .    .     38 

38  (39)         Setae  cleft  at  distal  extremities;   prostomium  without  distinct  pro- 

boscis; spermathecae  and  spermathecal  pores  paired  or 
asymmetrical  in  three  or  more  somites  posterior  to  somite 
bearing  ^  pores Lumbricillus  Grube  1844. 

L.  inconstans  (Frank  Smith),  common  in  the  Mississippi  Valley,  has  Z  pores  on  X  or  XI  and 
spermathecae  in  XI-XV  or  XII-XVI  (Smith,  1905) 

39  (38)         Setae  simple-pointed;  spermathecal  pores  on  but  one  somite  ante- 

rior to  $  pores 40 

40  (41)        Large  median  spermathecal  sac  with  numerous  tubular  diverticula 

in  VIII;  with  single  median  external  opening. 

Siitroa  Eisen  1888. 

Two  species.  5.  rostrata  Eisen  and  5.  alpestris  Eisen,  each  with  distinct  proboscis,  are 
found  west  of  the  Rocky  Mountains. 


AQUATIC   EARTHWORMS  6^^ 

41  (40)         Spermathecae  withoul  diverticula,  paired  or  two  unpaired  ones 

opening  separately;  long,  highly  muscular,  ejaculatorv 
chamber  forms  part  of  each  otherwise  highly  difrcrcntiatcd 
sperm-duct EclipiJrilus  Eisen  1881. 

A  genus  of  peculiar  North  American  Lumljriculida,-  which  includes  /•.  fnnJus  Fism 
from  Cahfornia,  with  paired  $  pores  on  X;  E.  asymmetricus  (I-rank  Smith/ from  IIIinST 
with  single  median  ^  pore  on  X;  and  t.  palustns  (Frank  Smith)  fr(.m  Florida  with  wirH  I 
pores  on  IX  (Smith,  igooa).  i^ucu  ,5 

42  (36,37)    Earthworms,  essentially  aquatic  in  habit.     Setae  simple-[M)intcd 

and  paired  in  each  of  four  bundles  per  somite;  i  jM^res  ex- 
ceptionally on  XII  or  XIII,  commonly  further  jxjsterior- 
spermaries  in  X  and  XI;  ovaries  in  XIII 43 

43  (44)         Clitellum  beginning  on  XIV  to  X\T  and  extending  over  10-12 

somites;  $  pores  on  XVHI/XIX  or  on  XIX.  recognizable 
only  in  sections;  few  or  no  dorsal  [)()res;  without  well- 
developed  gizzard Sparganophiliis  Benham  1892. 

Several  North  American  species,  of  which  S.  eiseni  Frank  Smith  is  found  in  the  Mi«isissinpi 
Valley,  Great  Lakes  region,  and  Florida;  S.  smithi  Eisen  and  subspecies  occur  in  Caiifomia 
6".  benhami  Eisen  and  subspecies  in  Mexicoand  Central  America  (Eisen,  i8g6). 

44  (43)         Clitellum  beginning  on  XVIII-XXIII   and    extending   over   4-6 

somites;  ^  pores  on  XII,  XIII,  or  X\',  conspicuous;  gizzard 
limited  to  XVII;  first  dorsal  pores  on  I\'/\'. 

Hdodrilus  Subgenus  Eiscnidla  Michaelsen  kjoo. 

The  highly  variable  species,  H.  (E.)  tetraedriis  (Savigny),  is  represented  in  North  A  merit  a 
by  several  of  the  subspecies  indicated  in  the  diagram  from  Michaelsen  (Fig.  9^3). 

12    13    14    15    16    17    18     19   20    21    22    23    24    25    26    27    2S 


furm    tjfica 

furm     hcrcynxa 
form     tura/x^itiina 
furm     .\'iHnii 

fulin     ylv/ii 

Fig.  993.     Different  forms  of  Heloirilus  {Ehenidla)  tctraedrus  (SaviRny).     The  diaKram  shows 
the  positions  for  the  spermiducal  pores  and  the  tubercula  pubertalis.     (.\ftcr  Michaclicn.) 


A  specimen  which  is  presumably  the  type  of  Ilclodrilus  tclrarJrus  forma  pupj  (Eis<-n) 
was  deposited  in  the  United  States  National  Museum  and  has  been  studittl  by  the  writer 
It  is  almost  certainly  a  regenerated  individual  and  is  hii^hly  abnormal  and  hence  the  form 
presumably  has  no  systematic  status  except  in  synonomy.  References  in  |>ara>iraphs  42  and 
44  of  the  above  key  and  in  Fig.  993,  to  spermiducal  pores  on  XII,  have  therefore  lost  their 
significance. 

Beside  these  essentially  aquatic  forms,  several  species  ji  Diplocardia  and  HciodrUus  live 
in  bottomlands  and  low-lying  banks  of  streams  which  are  subject  to  overflow  for  prolonged 
mtervals 


— • ^^ 

^^ f~ 

— ;• ^ 

-p* ^  ^^  — 

-y        II  — 


644 

45  (i) 


FRESH-WATER   BIOLOGY 


Without  setae;  pharynx  with  two  chitinous  jaws,  dorsal  and  ven- 
tral. Small  leech-like  worms,  parasitic  or  symbiotic,  on 
crayfishes Family  Discodrilidae  .    .     46 

The  family  name  Branchiobdellidae  is  preferred  by  some  writers. 


46  (49)         Two  pairs  of  spermaries  and  two  pairs  of  sperm-ducts  in  the  fifth 
.   and  sixth  post-cephaHc  somites 47 


47  (48)         Without  conspicuous  dorsal  appendages  on  post-cephalic  somites. 

Bdellodrilus  Moore  1895. 

B.  philadelphicus  (Leidy)  and  B.  illuminatus  (Moore) 
resemble  each  other  in  having  the  anterior  pair  of  nephridia 
open  to  the  exterior  through  a  common  pulsatile  vesicle  on 
the  mid-dorsal  line  of  the  third  post-cephalic  somite  and  in 
having  the  dorsal  and  ventral  jaws  quite  dissimilar.  The 
former  has  the  head  much  broader  than  the  anterior  body 
somite  and  enjoys  a  wide  distribution  in  the  eastern  half  of 
the  United  States.  The  latter  has  nine  pairs  of  conspicuous 
lateral  glands,  the  head  narrower  than  the  following  somite  and  is  less  common. 


Fig.  994.     Bdellodrilus  phiiadel- 
phicus.     X  9-     (After  Moore.) 


B.  pulcherrimiis  (Moore)  and  B.  instahilis  (Moore)  re- 
semble each  other  in  having  the  anterior  nephridia  open 
separately  and  in  having  the  dorsal  and  ventral  jaws  simi- 
lar. The  former  has  all  post-cephalic  somites  evidently 
biannulate;  ahmentary  canal  straight;  jaws  small,  each 
bearing  three  teeth.  The  latter  has  biannulation  con- 
spicuous on  only  anterior  four  post-cephalic  somites;  ali- 
mentary canal  with  transverse  loop  in  seventh  somite; 

and  dark-brown  jaws,  each  bearing  four  teeth.     They  have  been  described  from  North  CaroUna 

and  Pennsylvania  (Moore  1893). 

Under  the  name  Cambarincola  macrodonta,  Ellis  (191 2)  has  described  a  species  from  Colorado 

which  is  closely  allied  to  B.  philadelphicus  but  which  has  the  head  narrower  than  the  greatest 

width  of  the  body  and  different  shaped  jaws.     It  also  lacks  the  conspicuous  glands  of  B. 

illuminatus. 


Fig.  995.    Bdellodrilus  instahilis. 
X  9.      (After  Moore.) 


48  (47)         W'ith   conspicuous    dorsal   appendages  on  each  of   several   post- 
cephalic  somites Pterodrilus  Moore  1894. 

P  distichus  Moore,  with  simple  cylindrical  dorsal  append- 
ages on  each  of  post-cephaUc  somites  II  to  VIII,  and  P. 
alcicornus  Moore,  with  dorsal  appendages  of  complex  form 
on  post-cephalic  somites  III  and  VIII  and  simple  ones  on 
IV  and  V,  have  been  described  from  crayfishes  of  eastern 
United  States  (Moore  1894). 

Under  the  name  Ceratodrilus  thysanosomus.  Hall  (1914) 
has  described  a  species  from  Utah  which  resembles  the 
above  described  species  of  Pterodrilus  closely,  but  has  the 
antero-dorsal  border  of  the  head  furnished  with  a  membran- 
ous border  deeply  incised  to  form  four  tentacular  append- 
ages.    The  dorsal  appendages  are  transverse  bands  with  edges  bearing  six  to  eight  points. 


Fig.  996.    Pterodrilus  alcicornus. 
X  50.     (After  Moore.) 


49  (46)        But  one  pair  of  spermaries  and  one  pair  of  sperm-ducts  and  these 
in  the  fifth  post-cephalic  somite. 

Branchiobdella  Odier  1823. 

B.  americana  Pierantoni  has  the  prostomium  entire  and  the  jaws  dissimilar.  It  has  been 
collected  in  Texas  and  North  CaroUna.  B.  tetrodonta  Pierantoni  has  the  prostomium  divided 
into  dorsal  and  ventral  lobes  and  the  jaws  similar.     It  is  found  in  California  (Pierantoni  1912). 


AQUATIC   EARTHWORMS  645 

LITERATURE    ON    FRESH-WATER   OLIGOCHAITA 

EiSEN,  G.     1885.     Oligochactological  Researches.     Rcpt.  U.  S.  Fish  Com.  for 
1883,  11:  879-964;  19  pi. 
1896.     Pacific  Coast  Oligochaeta  II.     Alem.  CaHf.  Acad.  Sci.,  2:    123-198; 
12  pi. 

1905.  Enchytraeidae  of   the  West    Coast  of  North   America.     Harriman 
Alaska  Expedition,  12:    1-166;    20  pi.     New  York. 

Ellis,   M.    M.     1912.    A  New   Discodrilid   Worm   from    Colori.lo.      Proc. 

U.  S.  Nat'l  Mus.,  42:  481-486. 
Galloway,  T.  W.     191  i.     The  Common   Fresh- Water  Oligochada  of  the 

United  States.     Trans.  Amer.  Micr.  Soc,  30:  285-317;  14  figs. 
Hall,  M.   C.      1914.      Descriptions  of  a   New  Genus  and   Species  of   the 

Discodrilid  Worms.     Proc.  U.  S.  Nat'l  Mus.,  48:    187-193. 
Michaelsen,  W.    1900.    Oligochaeta.    Das  Tierreich.    No.  10.    Pp.  .x.xi.x  and 

575. 
Moore,  J.  P.     1893.     On  Some  Leech-like  Parasites  of  .American  Crayfishes. 
Proc.  Acad.  Nat.  Sci.  Phila.,  1893:  419-428;  i  pi. 
1894.     Pterodrilus,  a  Remarkable  Discodrilid.    Proc.  Acad.  Nat.  Sci.  Phila.. 
1894:  449-454;  I  Pl. 

1906.  Hirudinea  and  Oligochaeta  Collected  in  the  Great  Lakes  Region. 
Bull.  Bur.  Fish.,  21:  1 53-171;  i  pl. 

PiERANTONi,    U.     191 2.     Mouografia    dei    Discodrilidae.     Ann.    Mus.    Zool. 

Univ.  Napoli,  n.s.,  3,  No.  24,  28  pp.;   i  pl. 
Smith,  Frank.     1900.     Notes  on  Species  of  North  American  Oligochaeta  IH. 

Bull.  111.  State  Lab.  Nat.  Hist.,  5:  441-458;  2  pl. 
1900a.     Notes  on  Species  of  North  American  Oligochaeta  I\'.     Bull.  III. 

State  Lab.  Nat.  Hist.,  5:  459-478;  i  pl. 
1905.     Notes  on   Species  of   North  American  Oligochaeta   \'.      Bull.   111. 

State  Lab.  Nat.  Hist.,  7:  45-51- 
Smith,  F.,  and  Welch,  P.  S.     1913.     Some  New  Illinois  Enchytraeidae.     Bull. 

111.  State  Lab.  Nat.  Hist.,  9:  615-636;   5  pl. 
Walton,  L.B.   1906.  Naididae  of  Cedar  Point,  Ohio.  Amer.  Nat.,  40:  683-706. 
Welch,  P.  S.     1914.     Studies  on  the  Enchytraeidae  of  North  America.    Bull. 

111.  State  Lab.  Nat.  Hist.,  10:    123-212;   5  pl. 


CHAPTER   XX 
THE    LEECHES    (HIRUDINEA) 

By  J.  PERCY  MOORE 

Professor  of  Zoology  in  the  University  of  Pennsylvania 

The  Hirudinea  or  leeches  are  predatory  or  parasitic  annelids 
with  terminal  suckers  serving  for  attachment  and  locomotion. 
Quite  nearly  related  to  the  Oligochaeta  and  closely  resembled  by 
the  semi-parasitic  Discodrilidae  in  the  possession  of  suckers,  jaws, 
and  median  genital  orifices  and  in  the  absence  of  setae,  they  are 
characteristically  modified  for  procuring  and  digesting  their  pecul- 
iar food,  consisting  typically  of  blood  and  other  animal  juices. 

The  body  of  a  leech  is  generally  constituted  of  thirty-four  meta- 
meres  (designated  I  to  XXXIV),  each  represented  in  the  central 
nervous  system  by  a  ganglion  usually  consisting  of  six  capsules  or 
groups  of  nerve  cells.  Externally  superficial  furrows  divide  each 
fully  developed  somite  into  from  two  to  sixteen  rings  or  annuli. 
One  of  these,  lying  at  the  middle  of  the  somite,  contains  the  gangKon 
and  usually  bears  three  or  four  dorsal  pairs  and  three  ventral  pairs 
of  eye-like  sense  organs  or  sensillae  and  is  termed  the  neural  or 
sensory  ring.  Segments  having  the  full  number  of  annuli  charac- 
teristic of  the  genus  are  termed  complete,  and  are  always  found  in 
the  middle  region.  Incomplete  or  abbreviated  segments  occur  at 
the  ends  of  the  body  and  may  have  any  number  of  annuli  less 
tlian  the  complete  somites  into  which  they  grade.  Recognizing 
the  triannulate  somite  as  basic  for  most  leeches  and  considering 
that  more  complex  somites  may  be  derived  by  repeated  binary 
division  of  its  annuli  the  following  symbols  are  employed  for  the 
precise  designation  of  particular  rings.  Counting  from  the  head 
end  the  rings  of  the  triannulate  somite  are  A'^,  A"^,  and  A^,  where 
A^  is  the  neural  or  sensory  annulus.  These,  bisected,  give  col- 
lectively the  secondary  annuli  B^  to  B^.  Repeated  subdivisions 
give  tertiary  annuH  C^  to  O^  and  quaternary  annuh  D^  to  D^\ 
But  the  full   theoretical  number    of    the    fourth  order  is  never 

646 


THE  LEECHES    (HIRUDINEA)  647 

developed  and  the  neural  annulus  is  usually  less  divided  than  the 
others. 

Setae  are  always  absent,  except  in  AcantJiobdella,  and  suckers 
always  present,  except  in  a  few  exotic,  chiefly  burrowing,  genera. 
The  oral  sucker  surrounds  the  mouth,  sometimes  forming  mere 
lips-  and  being  widely  expanded  only  in  Ichthyobdellidae  and  a  few 
Glossiphonidae.  The  caudal  or  subanal  sucker  is  larger,  discoid  or, 
more  rarely,  deeply  cupped,  and  widely  expanded  beyond  its  con- 
stricted central  pedicle.  There  is  a  powerful  and  elaborate  muscu- 
lar system,  consisting  of  circular,  oblique,  and  thick,  longitudinal 
coats,  as  well  as  vertical  and  radial  sheets  and  fibers. 

The  digestive  tract  is  divided  into  buccal  chamber,  pharynx, 
esophagus,  stomach  or  crop,  intestine  and  rectum.  In  the  jawed 
leeches  the  mouth  is  large;  in  the  proboscis  leeches  a  mere  pore  in 
the  disk  of  the  sucker.  In  the  former  the  buccal  chamber  usually 
contains  three  compressed  muscular  jaws  bearing  serial  teeth  on 
the  ridge.  The  pharynx  is  a  muscular  bulb,  a  straight  tube,  or  a 
slender,  exertile  proboscis  moving  within  a  sheath.  Salivary  glands 
may  open  into  the  short  esophagus  or  on  the  jaws.  The  large 
stomach  or  crop  varies  with  the  nature  of  the  food  and  may  be  a 
straight  tube,  or  compHcated  by  from  one  to  twenty  pairs  of  simple 
or  branched  lateral  ceca,  of  which  the  posterior  pair  is  largest  and 
most  constant.  Generally  short  and  simple,  the  intestine  may 
bear  four  pairs  of  simple  ceca  (Glossiphonidae).  A  short,  narrow 
rectum  opens  by  a  small  dorsal  anus  usually  behind  XXVI  or 
XXVII,  but  rarely  behind  XXIII. 

Leeches  are  hermaphroditic.  The  genital  orifices  are  median,  with 
the  male  pore  preceding  the  female.  The  testes  (really  coelomic 
sacs  enclosing  the  testes)  vary  from  one  elongated  pair  in  Acafi- 
thobdella  to  usually  six  (five  to  nine)  pairs  in  the  Rhynchobdelhie, 
nine  or  ten  (five  to  nineteen)  pairs  in  the  Hirudinidae.  and  very 
numerous  small  ones  in  the  HerpobdcUidae.  A  vas  deferens  on 
each  side  continues  into  an  epididymis  and  an  ejaculatory  duct 
which  may  be  provided  with  a  sperm  sac  and  a  glandular  region 
for  forming  the  horny  spermatophores.  The  two  ejaculatory  ducts 
open  into  an  unpaired  genital  bursa  or  a  more  complex  atrium 
.  which  may  be  elongated  into  a  highly  muscular  sheath  cnclosmg  a 


648  FRESH-WATER   BIOLOGY 

penis  and  provided  with  a  prostate  gland.  The  ovaries,  also 
coelomic  sacs,  are  a  single  pair,  usually  elongated  and  folded  and 
opening  directly  into  a  small  median  bursa.  In  the  Hirudinidae 
they  have  special  ducts  provided  with  an  unpaired  albumen 
gland  and  a  muscular  vagina.  Accessory  copulatory  glands  may 
occur. 

A  most  striking  characteristic  of  leeches  is  the  great  reduction  of 
the  body  cavity  which,  besides  the  ovarian  and  testicular  coelom,  is 
represented  only  by  a  system  of  sinuses,  the  extent  and  arrange- 
ment of  which  vary  in  the  several  famiKes.  In  addition  there  is  a 
true  blood  vascular  system  consisting  of  dorsal  and  ventral  longi- 
tudinal trunks  and  a  peri-intestinal  sinus  united  by  transverse 
loops  and  in  the  caudal  sucker  by  a  circle  of  radiating  loops.  Ex- 
cept in  some  Ichthyobdellidae,  which  have  lateral  gills  or  pulsating 
vesicles,  leeches  respire  solely  by  virtue  of  the  capillary  network 
underlying  or  even  penetrating  the  hypodermis. 

The  nephridia  in  general  resemble  those  of  the  OHgochaeta,  but 
the  funnels  especially  are  more  complex  and  variable,  being  some- 
times branched  and  sometimes  having  the  opening  occluded.  Not 
more  than  seventeen  pairs  usually  occur,  they  being  absent  from 
both  ends  of  the  body  and  often  from  one  or  more  clitellar  segments. 

Pigment  occurs  in  the  form  of  excreted  matter  contained  in 
wandering  cells  and  reserve  cells  and  is  usually  deposited  along 
the  line  of  muscle  bundles  in  either  metameric  or  non-metameric 
spots  or  bands.  The  eyes  are  highly  developed  sensillae,  several 
of  which  are  sometimes  united  in  a  common  pigment  mass.  They 
occur  rarely  on  the  caudal  sucker  as  weh  as  on  the  head. 

Leeches  are  among  the  most  interesting  and  beautiful  of  the 
invertebrate  inhabitants  of  our  fresh  waters.  They  abound  in 
ditches,  pools,  ponds  and  lakes,  few  species  occurring  in  swift,  cold 
streams.  In  the  small  lakes  of  our  northern  borders  they  fairly 
swarm. 

They  are  predatory  hunters  or  scavengers,  temporary  or  nearly 
permanent  parasites,  or  they  may  change  from  one  mode  of  life 
to  another.  The  few  fresh-water  Ichthyobdellidae  attach  them- 
selves chiefly  to  the  fins  and  gills  of  fishes.  Several  Glossiphonidae 
have  similar  habits  and  one  remarkable  species  is  a  nearly  permanent 


THE   LEECHES    (HIRUDINEA)  649 

parasite  on  the  sheepshead  of  the  lakes  of  Minnesota,  its  sucker 
becoming  fixed  into  deep  pits  in  the  inflamed  tissues  of  the  isthmus. 
Many  of  this  family  are  temporary  parasites  on  turtles,  frogs, 
salamanders,  etc.,  but  also  Hve  free  and  subsist  upon  a([ualic 
worms,  mollusks,  etc.  Because  of  the  nature  of  their  food  the 
smaller  species  are  known  as  snail  leeches.  The  Herpobdellidac  are 
voracious  destroyers  of  aquatic  worms,  larvae,  insects,  and  even  of 
their  own  kind.  Many  of  the  Hirudinidae  have  similar  habits  but 
also  burrow  into  mud.  Some  even  habitually  leave  the  water  in 
quest  of  earthworms  and  one,  Haemopis  lateralis  tcrrcslris.  inhabits 
garden  soil  several  miles  from  water. 

While  most  species  will  partake  of  vertebrate  blood,  especially 
just  before  the  breeding  season,  Macrobdella  is  our  only  native  true 
sanguivorous  jawed  leech.  While  young  it  feeds  upon  larvae  and 
worms  and  attacks  vertebrates  only  when  mature,  and  even  then 
varies  the  blood  diet  with  an  occasional  meal  of  frogs'  eggs.  This 
and  other  jawed  leeches  painlessly  make  a  trifid  incision  in  the 
skin  and  quickly  extract  more  than  their  own  weight  of  blood,  the 
flow  of  which  is  faciUtated  by  a  ferment  which  prevents  coagula- 
tion. As  the  blood  fills  the  gastric  ceca  its  fluid  constituents  are 
drawn  off  through  the  walls  and  exude  in  droplets  from  the  ncph- 
ropores.  The  solid  parts  remain  and,  protected  from  decay  by  a 
preservative  secretion,  may  not  be  completely  digested  for  upwards 
of  a  year. 

The  short,  flat  triannulate  Glossiphonidae  are  poor  swimmers 
but  sometimes  active  creepers.  When  disturbed  they  roll  into  a 
ball,  pill-bug-like,  and  fall  to  the  bottom,  soon  to  creep  hastily  to 
shelter.  Species  with  longer,  more  complex  segments  are  better 
swimmers  and  the  elongated  and  muscular  HerpobdcUidae  and 
Hirudinidae  swim  powerfully,  moving  rapidl}'  with  graceful  undu- 
lations in  either  the  vertical  or  horizontal  plane.  Their  resting 
attitudes  are  varied  and  characteristic.  Probabl>-  in  order  to  facili- 
tate respiration  many  species  attach  one  or  both  suckers  and  wave 
the  body  with  an  undulatory  motion.  Most  leeches  are  nocturnal 
and  except  when  stimulated  by  hunger  and  the  proximity  of  food 
they  avoid  the  light  by  hiding  beneath  stones,  among  plants  or  in 
the  mud. 


650  FRESH-WATER   BIOLOGY 

Reproduction  takes  place  in  the  spring  and  summer,  some  species 
continuing  to  produce  batches  of  eggs  for  five  or  six  months.  In 
the  Rhynchobdellae  and  HerpobdelJidae  copulation  consists  in  the 
implanting  by  one  individual  of  a  horny,  usually  two-chambered 
spermatophore  on  the  skin  of  another.  From  this  the  spermatozoa 
issue  in  a  stream  and,  by  a  process  that  Professor  Whitman  has 
aptly  termed  hypodermic  injection,  penetrate  the  tissues  to  the 
ovarian  sac  where  impregnation  occurs.  Among  the  Hirudinidae 
a  more  definite  act  of  copulation  and  reciprocal  fertilization  takes 
place  during  which  the  filamentous  penis  of  one  individual 
deposits  a  spermatophore  within  the  vagina  or  at  the  genital 
orifice  of  the  other. 

The  Glossiphonidae  carry  their  eggs  in  several  membranous 
capsules  attached  to  the  venter,  maintaining  an  undulatory  move- 
ment for  their  aeration.  The  young  also  remain  for  a  time  fixed 
by  a  sort  of  byssus  thread  and  later  by  the  sucker,  and  are  said  to 
be  partly  nourished  by  an  albuminous  secretion  of  the  parent.  All 
other  leeches  form  chitinoid  cocoons  or  egg  capsules  from  the  secre- 
tion of  the  deeper  glands  of  the  clitellum  which  hardens  on  exposure 
to  the  water.  The  Ichthyobdellidae  deposit  a  single  ovum  in  a 
small  stalked  capsule,  the  Herpobdellidae  and  Hirudinidae  several 
in  an  albuminous  mass  within  a  larger  capsule,  which  in  the  case 
of  the  former  is  a  flat  pouch  attached  by  one  side  and  in  the 
latter  an  ellipsoidal  case  with  a  thick,  spongy,  vesicular  wall  buried 
in  wet  earth. 

Leeches  have  rather  dull  senses  which  arise  in  three  sets  of 
cutaneous  organs.  Numerous  goblet  cells  located  in  the  lips  are 
taste  organs  and  guide  the  leech  on  the  trail  of  its  prey.  Tactile 
organs  are  scattered  all  over  the  skin  but  are  especially  numerous 
on  the  lips.  Wave  movements  and  light  stimuli  appear  to  affect 
all  parts  of  the  body.  The  eyes  are  strongly  sensitive  and  the 
sensillae  much  less  so  to  changes  in  the  intensity  of  light. 

Leeches  may  readily  be  found  by  searching  in  the  situations  indi- 
cated above.  Sanguivorous  species  are  easily  collected  by  stirring 
the  mud  in  their  haunts  with  one's  bare  feet  and  removing  them 
from  the  skin  as  they  become  attached,  or  by  attracting  them  with 
fresh  blood  placed  in  the  water.     They  may  be  kept  and  studied 


THE   LEECHES    (HIRUDIXEA)  651 

indefinitely  in  aquaria.  For  examination  alive  under  a  microsa)pe 
they  should  be  stupefied  and  relaxed  by  placing  a  little  carbon 
dioxide  (as  soda  water),  chlorotone,  or  cocaine  in  the  water. 

For  preservation  they  should  always  be  tirst  relaxed  with  similar 
reagents  and  extended  before  fixing.  Chromic  acid  in  one-cjuarter 
to  one-half  per  cent  solutions,  picro-sulphuric  acid.  Gilson's  fluid, 
corrosive-sublimate-acetic  mixture  and  Fleming's  fluids  are  all 
good  fixatives,  but  great  care  should  be  taken  to  wash  out  the 
acids  in  order  to  prevent  sweUing  of  the  connective  tissues.  Forma- 
lin is  a  good  preservative  for  general  purposes. 


KEY   TO   NORTH  AMERICAN   FRESH-WATER   LEECHES 


I  (36)         Mouth  a  small  pore  in  oral  sucker  from  which  a  muscular  pro- 
boscis may  be  protruded;  no  jaws. 

Suborder  Rhynchobdellae   .    . 


2  iss)  Body  not  divided  into  two  regions;  usually  much  depressed;  eyes 
near  median  line;  stomach  usually  with  well  developed  lateral 
ceca Family  Glossiphonid.vk  .    .       3 


3  (28)         Complete  somites  essentially  triannulate 4 

4  (13)         Epididymis  and  ejaculatory  duct  forming  a  long.  open,  backward 

loop;  salivary  glands  diffuse;  eyes  simple;  size  small;  chiefly 
under  stones  and  on  plants  in  ponds  and  lakes. 

Glossip/ionia  Johnston  iSib   .    .       5 

5  (10)         Eyes  one  pair,  well  separated.     Genital  pores  separated  by  one 

annulus ^ 


6  (7)  A  brown  chitinoid  plate  and  underlying  nuchal  ghunl  on  dorsum 

of  VIII -.     Glossip/ionia  sldgHiilis  {LmnM-ns)  i-js^' 

7  (6)  No  nuchal  gland  or  plate ^^ 

8  (0)  Greatly   elongated,  slender  and  neariy  terete;    without  papiUae; 

very  transparent;  colorless;  gastric  ceca  one  pair. 

Glossiphonia  mphcloidca  (Graf)  1S99. 


FRESH-WATER  BIOLOGY 


12  (ll) 

13(4) 

14  (27) 

15  (16) 

16  (15) 


Relatively  short,  broad  and  flat;  cutaneous  papillae  absent  or  in 
I  to  5  series,  small  or  large,  often  double;  deeply  pigmented 
in  narrow  longitudinal  lines,  or  diffusely  with  metameric 

'°  white  spots  on  neural  annuli;  gastric  ceca  six  pairs,  simple. 

Glossiphonia  fusca  Castle  1900. 


This  species  is  very  variable,  especially  in  the  character  of 
the  dorsal  cutaneous  papillae  which  may  be  scarcely  evident 
and  limited  to  a  median  series  on  a  few  segments,  or  large  and 
conspicuous  and  arranged  in  five  series  extending  for  the  en- 
tire length,  or  in  any  intermediate  condition.  Those  of  the 
median  series  are  formed  of  a  pair  of  papillae  more  or  less 
completely  coalesced.  Usually  they  are  deeply  pigmented 
and  contrast  strongly  with  the  clear  white  spots  flanking 
them.  The  eyes  are  unusually  large  and  conspicuous.  It 
lives  in  ponds  but  also  in  colder  waters  than  most  species  of 
the  genus,  even  in  springs,  and  attaches  itself  to  the  larger 
water  snails  and  more  rarely  to  leeches.  The  eggs,  Hke 
those  of  Glossiphonia  complanata,  are  laid  in  a  few  large 
gelatinous  capsules  borne  on  the  venter  of  the  parent  leech 
and  breeding  is  continued  to  midsummer.  Glossiphonia  fusca 
is  much  less  active  than  Glossiphonia  complanata  and  feeds 
less  frequently  upon  worms  and  larvae,  preferring  snails. 


Fig.  997.  Glossiphonia  fusca.  General  anatomy  showing  external 
outline,  segmentation  and  annulation,  alimentary  canal,  re- 
productive organs,  etc.  I-XXVII  —  somites;  2-70,  annuli;  pro, 
proboscis;  Po  $  ,  male  orifice;  Po  9  ,  female  orifice;  ov,  ovary; 
oe,  esophagus;  iglv,  stomach  or  crop;  te,  testes;  ga  and  in,  in- 
testine; an,  anus;  dt.  ej,  ductus  ejactulatorius.  X  10.  (Modified 
from  Castle.) 


Eyes  three  pairs n 

Genital  pores  separated  by  one  annulus;  eyes  in  three  groups  of 
two,  in  a  triangular  figure;  body  transparent,  with  little 
pigment;  no  papillae;  gastric  ceca  six  pairs,  nearly  or  quite 
unbranched.     .    .     Glossiphonia  heteroclita  (Linnaeus)  1758. 

Genital  pores  separated  by  two  annuli;  eyes  in  two  nearly  parallel 
rows;  body  rather  thick  and  opaque,  usually  deeply  pig- 
mented, a  pair  of  dorsal  and  ventral  dark,  narrow  lines  run- 
ning for  nearly  entire  length;  gastric  ceca  seven  pairs, 
slightly  branched.  .  Glossiphonia  complanata  (Linna-eus)  ij  $8. 

Epididymis  more  or  less  complexly  and  compactly  folded  in  vi- 
cinity of  atrium ;   salivary  glands  usually  compact.    .    .      14 

One  pair  of  anterior  compound  eyes;  gastric  ceca  seven  pairs, 
usually  much  branched;  saUvary  glands  compact;  size  mod- 
erate to  large.  Temporary  parasites  on  water  turtles,  frogs 
and  fishes;  most  species  also  free-living. 

Placobdella  R.  Blanchard  1893  .         15 

Somites  I-V  distinctly  widened  to  form  a  discoid  "head."  Somites 
I  and  II  biannulate;  dorsum  with  three  strong  papillated 
keels.  On  fishes  and  frogs.  .  Placobdella  monHferaMooieigi  2. 

Somites  I-V  not  especially  widened 17 


THE   LEECHES    (HIRUDI.VEA) 


17  (18) 


18  (17) 

19  (22) 

20  (21) 


I 


653 

I'lacobdelh  pediculata  I  k-miiiKway  1008 
Anus  behind  XXVII;  posterior  segments  normal. 

Placobddla  is.  sir.).    .  ,g 

Cutaneous  papillae  smooth  and  round. 

Integuments  opaque,  deeply  niemonfr.rl  ."n  ..  ^ 

leii  ^  ^     '         ^y  pigmcnicd  m  a  conspicuous  pattern 

ol  ohvc  green  and  yellow;  annulus 
^     without    trace  of   a  secondary 
furrovv;   size  large.      Common  on 
Lnelydra,  etc. 
Placobddla  parasitica  (Say)  1824. 

One  of  the  best  known  of  our  leeches 
most  often  found  clinKinK  in  lanrc 
numbers  to  the  naked  skin  at  the  base 
of  the  hind  leRs  of  the  .snapping  turtle 
whose  I)lood  they  suck.  LarRe  in.li- 
yiduals  measure  fn.m  ,  to  4  inches 
ong  in  partial  e.xtension  and  arc  very 
broad,  thm,  and  fohaceous.  When 
bearing  eK«s  or  young  the>'  often  leave 
the  host  and  for  a  time  lead  a  free  li/e 
m  ponds  and  streams,  feeding  ofj 
worms  and  lar\ae.  Eggs  and  youn« 
are  borne  m  large  numbers  and  it  is 
an  mterestmg  sight  to  obser\-e  the 
crowded  family  of  youngsters  actively 
bending  and  turning  on  the  venter  of 
the  parent,  the  thin  margins  of  whose 
body  are  mrollefi  to  form  a  i)rotccting 
fold.  The  color  patti-rn  is  rich  and 
striking,  theground  color  of  dull  green 
or  ohve  green  standing  in  sharj)  con- 
trast to  the  bold  and  characteristic 
markings  of  yellow  by  which  it  is  re- 
placed to  a  varjing  degree. 

Fig.  998.  PlacobdrUd  parasitica.  Kxtemai 
metamerism,  central  lunous system,  re- 
productive organs,  etc.  l-.VXVII  — 
somites;  mg,  ol.  I.  m.  marjiinal.  outer 
lateral,  lateral  and  median  srasill.ic  re- 
spectively; pkg.^  \  i.h.ir>n>:c.il  kLiwIs; 
0€,  esophagus;  v,  atrium  or  s|irrma(o- 
phore  sac;  d,  ductus  eiaculatorius;  ri, 
vesicula  seminalis;  <J  and  9.  male 
and  female  jwrcs;  tdc.  vas  deferens.  /. 
testes;  ov,  ovary.  X  J.  (Redrawn 
from  Whitman.) 


,     'XAIV 
t   •   '      XXV 

XXVI 
XXVII 


21   (20) 


22  (19) 

23  (26) 


Integuments  translucent,  brightly  but  not  deeply  pigmented  with 
green,  orange,  and  white;  a^  of  complete  somites  with  a 
distinct  secondary  cross-furrow;  size  medium. 

Placohdclla  picta  (\'crrill)  1S7J 

Cutaneous  papillae  prominent  and  rough  or  pointed :: 

No  marginal  papillae  on  caudal  sucker 


654  FRESH-WATER  BIOLOGY 

24  (25)         Much  depressed;  papillae  numerous;  no  accessory  eyes;  size  large. 

Placohdella  riigosa  (Verrill)  1874. 

25  (24)         Moderately  depressed;  papillae  less  numerous;  neural  annulus  with 

much  dark  pigment;  several  pairs  of  simple  accessory  eyes 
succeeding  compound  eyes;  size  medium. 

Placohdella  hollensis  (Whitman)  1892. 

26  (23)         Numerous  minute  papillae  around  margin  of  caudal  sucker.     Mod- 

erately depressed;  dorsal  papillae  usually  in  a  median  and 
two  paired  series,  small,  acute  and  pale  yellow  or  brown;  a 
very  conspicuous  and  constant  pale  band  across  somite  VI; 
size  small Placohdella  phalera  (Graf)  1899. 

27  (14)         Eyes  four  pairs,  all  simple;  gastric  ceca  nine  or  ten  pairs;   salivary 

glands  diffuse;  body  very  soft  and  almost  oedemous ;  genital 
pores  at  XI-XII  and  XII  a^/a^;  color  green  with  three  series 
of  pale  yellow  spots.     On  fishes  and  free  in  streams. 

Protoclepsis  occidentalis  (Verrill)  1874. 

This  leech  and  others  of  the  genus  are  noteworthy 
among  the  members  of  their  family  for  their  transparency 
and  activity.  No  other  glossiphonids  creep  with  any 
approach  to  the  same  speed  and  none  swim  so  well.  So 
far  as  has  been  observed  the  eastern  species  is  exclusively 
sanguivorous,  pursuing  and  attacking  frogs  and  fishes. 
Nothing  is  known  of  the  breeding  habits  beyond  the  fact 
that  spermatophores  are  formed  and  attached  to  the  skin. 

Fig.  999.  Protoclepsis  occidentalis.  Dorsal  view  of  anterior 
seven  segments,  showing  annuli,  eyes,  and  sensillae.  X  20. 
(Original.) 


^"CC 

^ 

>'/^-~— . 

__ — "-K 

I'v^;/--,^ 

—'9     9;^- 

2jA 

"^'■7°    ~ 

■    9        ©_^ 

■~\ 

vi('^^ 

. .  ' 

» 

0    i\ 

J 

-"^ 

'^II;'  •      . 

0 

•    -_J 

-J 

Complete  somites  not  triannulate 29 

Complete  somites  of  two  annuli,  the  anterior  much  the  larger. 
Salivary  glands  compact;  gastric  ceca  seven  pairs;  epidid- 
ymis a  short,  wide,  U-shaped  sperm-sac;  eyes  one  pair, 
united;  genital  pores  separated  by  the  large  annulus  of 
XII;  size  small.     On  salamanders,  North  Carolina. 

*  Oligohdella  hiannulata  (Moore)  1900. 

(*  Oligohdella  nom.  nov.  for  Microbdella  Moore  preoccupied.) 


An  interesting  and  Httle  known  leech  taken  on  only  one 
occasion  in  a  cold  mountain  stream.  Nothing  known  of 
breeding  habits.     Color  green. 


Fig.  1000.  Oligohdella  hiannulata.  General  anatomy:  boundaries  of 
middle  somites  indicated;  g,  salivary  gland;  at,  atrium;  pg, 
spermatophore  sac;  55,  sperm  sac;  $  male  and  9  female  orifices; 
Ci  to  cv,  gastric  ceca;  ov,  ovar\';  vd,  vas  deferens;  /i  to  to,  testes;  i, 
intestine;  a,  anus.     X  10.     (After  Moore.) 


THE   LEECHES    (mRUDIXEA) 


655 


30  (29)         Complete  somites  of  six  unequal  annuli;    salivary  glands  difluse- 

gastric  ceca  seven  pairs;  caudal  sucker  wiih  marginal  circle' 
of  glands  and  papillae;   eyes  one  pair,  united;   size  small 
Probably  fish  parasites.   .    ActinobdellaMvvTi:  u)Oi    .    .     31 

31  (32)         Sucker  papillae  and  glands  about  60;  five  series  of  dorsal  i)apillae. 

Actinohdrllti  anucclens  Moore  i<;oi. 

32  (31)         Sucker  papillae  and  glands  about  30;    median  dcjrsal  series  of  t)a- 
pillae  alone  developed. 

Actinobddla  inajuiannuluta  Moore  i.^Os. 


Fig.  iooi.  Actinohdclla  inequian- 
nulata.  Annulation,  s^-nsilUc 
and  (lursal  cutaneous  ^lapilUc  of 
anterior  twelve  Mimites.  Pov 
terior  en(l  with  sucker  from  the 
side.     X  20.     (After  Moore.) 


33  (2)  Body  divided  into  a  narrow  anterior  and  a  wider  posterior  region; 

little  depressed;  eyes  when  present  usually  well  separated; 
stomach  usually  with  only  a  posterior  pair  of  more  or  less 
coalesced  ceca.     .    .    ,    Family  Ichthyobdellidak  .    .     34 

34  (35)         Complete  somites  of  12-14  very  short  annuli;  no  distinct  lateral 

vesicles;  eyes  one  or  two  pairs;  size  small.  Parasitic  on 
small  fishes Piscicola  punctatii  iW'TnU)  iS-ji. 

35  (34)  Complete  somites  of  six  annuli;  strongly  divided  into  two  regions; 
lateral  pulsating  vesicles  in  somites  XII  to  XXIII;  eyes 
two  pairs;  size  medium.  Parasitic  on  Fundulus  in  fresh  and 
saltwater Trachclobdelld  viviJa  {\crTill)  iS-j  2. 


The  anterior  region  is  formed  of  eleven  somites  of  which  the  first 
five  comprise  the  head  and  the  last  three  the  clitellum.  which  is 
somewhat  sunken  into  the  widened  jxisterior  rcRioii.  .X  little  known 
leech  which  has  been  taken  only  in  southern  New  Kn^land. 


Fig.  1002.  Trachelobdellavivida.  Annulation  from  dorsum.  Somites  al  the 
ends  of  the  body  are  numbered  and  the  annuli  l)et\vecn  which  the  male 
and  female  orifices  lie  are  indicated.     X  j.     (After  M.x.n-  > 


656  FRESH-WATER   BIOLOGY 

36  (i)  Mouth   large,    occupying   entire   cavity   of   sucker;   pharynx   not 

forming  a  proboscis;  jaws  often  present. 

Suborder  Gnathobdellae    .    .     37 


37  (54)  Eyes  typically  five  pairs  on  somites  II- VI,  arranged  in  a  regular  sub- 
marginal  arch;  complete  somites  five-ringed;  toothed  jaws 
usually  present;  genital  ducts  complex,  usually  with  a  pro- 
trusible  penis  and  muscular  sheath  (atrium)  and  a  vagina 
of  corresponding  length;  testes  strictly  paired,  usually  nine  or 
ten  pairs;  stomach  with  at  least  one  pair  of  spacious  ccca; 
size  generally  large Family  Hirudinidae  .    .     38 


38  (43)         Jaws  prominent,  teeth  numerous,  in  one  series;    ceca  along  entire 
length  of  stomach.      True  blood-suckers 39 


39  (42)         Copulatory  gland  pores  on  somites  XIII  and  XIV;  penis  conical; 

dorsum  with  metameric  median  red  and  lateral  black  spots. 

M acrobdella  \'Gr rill  18^2   .    .      40 


40  (41)         Genital  orifices  separated  by  five  annuli. 

Macrobdella  decora  (Say)  1824. 

The  species  of  Macrobdella  are  the  nearest  approach  in  our 
fauna  to  the  medicinal  leech  of  Europe  but  at  times  vary  the 
diet  of  blood  with  frogs'  eggs  and  worms.  M.  decora  is  well- 
known  as  a  voracious  infester  of  swimming  holes  and  of  drinking 
places  for  cattle  and  has  received  the  name  of  "blood-sucker." 
After  coitus,  during  which  the  copulatory  glands  function, 
spongy  cocoons  are  formed  and  deposited  to  hatch  in  the  mud 
by  the  side  of  ponds  and  streams.  Widely  distributed;  reported 
from  ]\Iaine  to  Minnesota  and  from  Pennsylvania  to  Kansas, 
northward  into  Canada.  Frequently  used  by  physicians  instead 
of  imported  leeches  for  blood-letting.  Said  to  be  equally  eflBca- 
cious  of  the  smaller  capacity,  about  5  gm.  It  is  so  powerful  that 
serious  results  have  followed  its  attacks  on  legs  of  children  wading 
in  ite  haunts. 

Fig.  1003.  Macrobdella  decora.  Reproductive  organs  (in  part)  dissected. 
at,  atrium;  cgl,  copulatorj'  gLnds;  de,  ductus  ejaculatorius;  ep,  epidi- 
dymis; gXI-XIV,  ganglia  XI  to  XIV;  os,  ovisac;  od  and  ode,  oviduct; 
ov,  ovary;  ij  and  ^,  first  and  second  pairs  of  testes;  vd,  vas  deferens. 
X  3.     (After  Moore.) 


41  (4c) 


Genital  orifices  separated  by  two  and  one-half  annuli. 

Macrobdella  sestertia  Whitman  1886. 


THE   LEECHES    (HU^UDINEA) 


657 

42  (39)  No  copulatory  glands;  penis  lilamcntous;  colors  variable,  dorsum 
usually  green  with  six  or  four  brown  stripes,  sometimes 
broken.     European  medicinal  leech;  introduced. 

lliriidu  medUinalis  Linnaeus  17 58. 


Fig.  1004.  Htrudo  medicinalts.  External  morphology  from  the  dorsum.  The  numerals  on  the  rishl 
indicate  the  annuli,  those  on  the  left  the  somites,  the  index  lines  running  to  the  ncuml  annul!- 
1st  P.  and  17th  P.,  first  and  last  nephridiopores.     Natural  size.     (After  Whitman.) 

43  (38)         Jaws    variable,    sometimes    rudimentary    or   absent;    teeth    when 

present  all  or  partly  in  double  series;  gastric  ceca  one  large 
posterior  pair  only.     Chiefly  predaceous 44 

44  (47)         Jaws  short  and  high;  teeth  small,  only  partly  in  two  scries;  no  penis; 

genital  orifices  separated  by  three  or  four  rings,  surrounded 
by  systems  of  gland  pores.  .    Philobdella  W-rriW  iS-j 4.    .     45 


45  (46)         Denticles  about  35;  narrow  median  dorsal  and  broader  marginal 
yellow  stripes  and  a  few  brown  spots. 

Philobdella  gracUe  Moore  igoi. 

Philohdclla  takes  the  place  of  Macro- 
bdella  in  the  Gulf  States  and  has 
singular  habits.  It  is  the  native 
"blood-sucker  "  of  that  ri-gion. 

Fig.  1005.  Philobdflla  gracile.  A ,  external 
genital  orifices  {  $  ,  9  )  wi'h  their  re- 
spective svstems  of  pland  (K)rcs  icj;p  J 
and  cppy);  np,  ncphridit>pt>rrs;  tbrn. 
vl,  vm,  submargmal,  lateral,  and  mnlian 
sensillae.  X  .^}.  (After  M.iorc.)  /». 
outlineof  a  jaw  with  te«lh.  X  .?S-  <.\ftcr 
Moore.) 


46  (45)         Denticles  about  20;  no  median  dorsal  stripe  and  no  spots;  two 

faint  stripes  of  reddish  brown  separated  b\-  a  narrow  line  of 
blackish  on  each  side  of  dorsum. 

Philohdelhi  jloridana  X'errill  1S74. 

47  (44)         Jaws  rather  small  and  retractile  into  pits  or  absent;  teeth  when 

present  coarse  and  all  in  double  series;  penis  filamentous; 

genital  orifices  separated  by  live  rings;  no  copulatory  glands. 

IJiumopis  Savigny  1S20  .    .      48 


48  (51)        Jaws  and  teeth  present. 


49 


658 


FRESH-WATER   BIOLOGY 


49  (50) 


Teeth  12-16  pairs;  annuli  VII  a*  and  VIII  a'  enlarged,  but  only 
slightly  subdivided;  color  variable,  usually  blotched. 

Haemopis  marmoratis  (Say)  1824. 


Fig.  1006.  Eaemopis  marmoratis.  External  morphology, 
showing  sensillae,  annulation,  and  limits  of  somites. 
c,  clitellum;  V-XXVII,  somites;  61,  62,  <h,  h,  h,  the  five 
annuli  of  somite  XV.     X  ij.     (Original.) 


Fig.  1007.  Haemopis  marmoratis.  Reproductive  organs, 
dissected,  al,  atrium  or  penis  sheath;  de,  ductus  ejacula^ 
torius;  ep,  epididymis;  gXI-XVI,  ganglia  XI-XVI 
ga,  albumin  gland;  gp,  prostate  gland  ;  os,  ovisac;  ode, 
common  oviduct;  ffv,  ovary;  ss,  sperm  sac;  /1-3,  testes 
va,  vagina;  vd,  vas  deferens;  $  male  orifice;  9  female 
orifice.     X  2.     (After  Moore.) 


50  (49)        Teeth  20-25  pairs;  annuH  VII  a^  and  VIII  a',  completely  subdivided; 

color  gray  or  plumbeus  with  no  or  few  spots,  usually  a 
median  black  and  marginal  orange  stripes;  size  very  large. 
An  aquatic  and  a  terrestrial  variety. 

Haemopis  lateralis  (Say)  1824. 

51  (48)        Jaws  absent  or  rudimentary;  no  teeth 52 

52  (53)        Upper  Hp  relatively  narrow  and  arched;    ^    orifice  XI  ftV^S   9 

XII  h^/h^;  protruded  penis  very  slender  and  straight;  ven- 
tral ground  color  paler  than  dorsal;  dark  blotches  always 
present;  size  very  large.   .   Haemopis  grandis  (Verrill)  1874. 

53  (52)        Lip  relatively  broad  and  flat;  genital  pores  near  middle  of  XI  b^ 

and  XII  b^;  protruded  penis  very  long,  rather  thick  and 
twisted;  ground  color  nearly  uniform;  dark  blotches  fre- 
quently absent  or  few;  size  moderate. 

Haemopis  plumbeus  Moore  191 2. 


THE    LEECHES     (HIRUDIXKA) 


^59 


54  (37)  Eyes  three  or  four  pairs  (rarely  absent),  usually  one  or  two  pairs 
on  II  and  two  pairs  at  sides  of  mouth  on  I\';  no  jaws,  no 
gastric  ceca;  genital  ducts  relatively  simple,  with  small 
atrium  produced  into  a  pair  of  dorsal  cornua  and  no  jK-nis; 
testes  numerous,  not  paired.     Predaceous. 

Family  Merpoudlli.idai:  .    .      55 


55  (56)         Som 


gxu. 


ites  strictly  five-ringed,  none  of  the  annuli  obviously  enlarged 
or  subdivided.  Eyes  three  pairs,  the  first  largest;  genital 
pores  separated  by  two  annuli;  atrial  cornua  simply  cur\'ed; 
vasa  deferentia  reaching  forward  to  ganglion  XI. 

Ilcrpohdclla  punctata  (Leidy)  iSyc. 

The  largest,  bi-st  known  and  most  widely  di^^tributcd 
member  of  the  family  in  North  America.  The  color  variw 
considerably  according  to  the  amount  of  black  i)i>s'mfni 
present.  A  very  active  leech  which  feeds  voraciously  on 
small  worms,  other  leeches,  and  aquatic  insect  laivae.  It 
will  take  human  blood  when  opiKjrt unity  offers.  Kgg 
capsules  found  abundantly  attached  to  stones,  etc. 

Fig.  1008.  Eerpobdella  Punctata.  Atrium  and  nciRhborinK  parts 
of  reproductive  organs.  at,  atrium;  df.  ductus  cjacuiatoriur; 
iXI,  ganglion  XI;  9  .  female  orifice;  of,  fundus  of  ovary; 
ov,  ovary;  p,  atrial  horn.     X  7 J.     (After  Moore.) 


56  (55)         Annulus  b  obviously  enlarged  and  subdivided 57 

57  (58)  Atrial  cornua  spirally  coiled,  vasa  deferentia  with  anterior  l{X)ps 
reaching  to  ganglion  XI;  eyes  four  pairs;  genital  orifices 
separated  by  two  annuli;  colors  plain  or  irregularly  blotched. 

Nephelopsis  obscura  \'errill  1.S27. 


Fig.  1009. 


Nephelopsis  obscura.     Dorsal  and  lateral  aspects  of  atrial 
region.     X  3-     (Ori^'inal.) 


58  (57)         Atrial  cornua  not  spirally  coiled,  l)ut  short  and  merely  curved. 

Dina  R.  liianchard  iSc):    .    .      50 

59  (62)         Vasa  deferentia  with  anterior  loops  reaching  to  ganglion  XI.  .     60 

60  (61)         No  pigmented  eyes;  genital  pores  separated  by  two  annuli;   longi- 

tudinally striped.     California.   .    Dina  atioculata'SlooTC  i^S>. 

61  (60)         Eyes  four  pairs;  genital  pores  separated  by  three  to  three  and  one- 

half  annuli;  nearly  pigmcntless.    .     Dina  parva  Moore  1Q12. 


62  (59)         Vasa  deferentia  not  extending  anterior  to  atrium 6j 

63  (64)         Eyes,  three  pairs;  genital  pores  separated  by  three  annuli;  atrial 

cornua  very  small;  pigment  nearly  absent. 

Dina  microstoma  Moore  looi. 


66o  FRESH-WATER   BIOLOGY 

64  (63)         Eyes,  three  or  four  pairs;  genital  pores  separated  by  two  annuli; 
atrial  cornua  prominent;  pigment  absent  or  in  scattered  flecks. 

Dinafervida  (Verrill)  187 1. 


Fig.  ioio.  Dinafervida.  Reproductive  organs  except  testes,  at,  atrial  cornua;  de,  ductus  ejaculatorius; 
gXI-XVIII,  ganglia  XI  to  XVIII;  of,  closed  end  of  ovary;  ov,  ovary;  ss,  sperm  sac;  vd,  vas  deferens. 
X  .35.     (After  Moore.) 


IMPORTANT   PAPERS   ON  NORTH   AMERICAN  LEECHES 

Bristol,  C.  L.     1899.     The  Metamerism  of  Nephelis.      Journ.  Morph.,  15: 
17-72. 

Castle,  W.  E.     1900.     Some  North  American  Fresh-water  Rhynchobdellidae 
and  their  Parasites.     Bull.  Mus.  Comp.  Zool.  Harv.,  36:  18-64. 
1900.     The  Metamerism  of  the  Hirudinea.     Proc.  Amer.  Acad.,  Arts  and 
Sci.,  35:  285-303. 

Forbes,  S.  A.  1890.  An  American  Terrestrial  Leech.  Bull.  111.  State  Lab. 
Nat.  Hist.,  3:  1 19-122. 

Graf,  A.  1899.  Hirudineenstudien.  Nova  Acta  Leop.  Carol.  Akad.  Natw., 
72:  215-404. 

Hemingway,  Ernest  E.  1908.  Placobdella  pediculata  n.  sp.  Amer.  Nat., 
42:  527-532. 

Leidy,  Joseph.  1868.  Notice  of  Some  American  Leeches.  Proc.  Acad.  Nat. 
Sci.,  Phila.,  20:  229-230. 

Moore,  J.  Percy.     1901.     The  Hirudinea  of  Illinois.  Bull.  111.  State  Lab. 
Nat.  Hist.,  5:  479-546. 
1905.     Hirudinea  and  Oligochaeta  collected  in  the  Great  Lakes  Region. 
Bull.  U.  S.  Bur.  Fish.,  25:  153-171. 

Nachtrieb,  Hemingway,  and  Moore.  191 2.  Report  on  the  Leeches  of 
Minnesota.  Geological  and  Natural  History  Survey  of  Minnesota, 
Zoological  Series  No.  V.  Part  III.,  Classification  of  the  Leeches  of  Min- 
nesota, by  J.  Percy  Moore,  pp.  65-150.    Frontispiece  and  Plates  I-VI. 

Verrill,  A.  E.  1874.  Synopsis  of  the  North  American  Fresh-Water  Leeches. 
Report  U.  S.  Comm.  Fish.,  2:  666-689. 


I, 


CHAPTER  XXT 
THE    FAIRY    SHRIMPS    (PHYLLOPODA) 

By  a.  S.  PEARSE 

Associate  Professor  of  Zoology,  University  of  Wisconsin 

Phyllopod  crustaceans  are  among  the  most  graceful  and  attrac- 
tive of  the  inhabitants  of  fresh- water  pools.  A  familiar  example 
is  the  fairy  shrimp  {Euhranchipus)  that  is  a  harbinger  of  spring 
throughout  the  eastern  and  central  United  States.  No  ph}'llopods 
are  of  great  size,  the  largest  usually  not  exceeding  a  couple  of 
centimeters  in  length,  though  one  species  of  A  pus  reaches  seven. 
Certain  genera  of  this  group  ^  of  crustaceans  existed  in  Devonian 
times  but  recent  species  were  first  described  by  scientists  early  in 
the  eighteenth  century,  and  were,  with  the  cladoceran  Daplniia^ 
made  the  subject  of  a  series  of  remarkable  memoirs  by  J.  C.  SchatTer 
(1752-1756).  Up  to  the  present  time  forty-one  species  have  been 
described  from  North  America  and  a  large  number  from  other 
continents,  for  phyllopods  occur  in  every  part  of  the  world  and  are 
found  from  sea-level  to  altitudes  of  more  than  10,000  feet.  But 
the  animals  that  are  to  be  discussed  in  this  chapter  are  interest- 
ing not  only  on  account  of  their  ancient  lineage  and  wide  distribu- 
tion. Their  primitive  structure  has  been  much  studied  by  those 
who  sought  to  solve  the  riddle  of  the  origin  of  the  arthropods,  and 
their  remarkable  ability  to  withstand  striking  changes  in  temper- 
ature and  humidity,  as  well  as  the  various  forms  that  some  species 
assume  under  different  conditions,  have  made  them  equally  attrac- 
tive to  naturalists  and  those  interested  in  the  experimental  side  of 

zoology. 

The  different  suborders  of  phyllopods  present  considerable 
diversity  in  general  shape.  Such  diversity  is  due  largely  to  differ- 
ences in  the  development  of  the  carapace,  which  may  form  a  shell- 
fold,  and  these  differences  are  curiously  correlated  with  variations 

1  Caiman  rejects  the  suborder  Phyllopoda  and  divides  his  subcla,«vs  Rranchiopoda 
into  four  orders:  Anostraca,  Notostraca,  Conchostraca,  Cladocera.  Iherr  ,s  much  m 
favor  of  such  a  system. 

661 


662 


FRESH-WATER  BIOLOGY 


in  the  position  of  the  eyes.  In  the  Anostraca  (Fig.  loii)  there  is 
no  shell-fold  and  the  body,  composed  of  many  distinct  somites,  has 
an  almost  worm-like  aspect;  the  Notostraca  (Fig.  1012)  are  also 
elongated  and  composed  of  numerous  somites,  but  are  flattened,  and 
their  anterior  portion  is  covered  dorsally  by  a  broad  arched  carapace ; 
the  bodies  of  the  Conchostraca  (Fig.  1013)  tend  to  be  laterally  com- 
pressed and  are  enveloped  in  a  bivalve  shell  that  makes  them  look 
like  a  small  clam.  The  shell-fold  is  not  attached  to  the  trunk 
somites  which  it  envelops.  It  may  be  more  or  less  corneous  but 
is  never  calcified.  The  eyes  are  elevated  on  movable  peduncles  in 
the  Anostraca  but  are  sessile  in  all  other  phyllopods.     A  pecuhar 


ttJ  .. 


Fig.  loii.     Branchineda  paludosa,  ma-le  and  female,    ai,  first  antenna;   a2,  second  antenna;  d,  cerco- 
pods  or  furcal  rami;  p,  penis;  t,  telson.     X  3.     (After  Packard.) , 

structure,  the  frontal  (or  haft)  organ,  is  variously  developed  in 
the  different  groups;  in  some  it  is  only  a  sensory  area  and  in  others 
it  has  a  knob-Hke  pediculated  form. 

The  head  is  distinct  from  the  trunk  and  the  number  of  trunk- 
somites  is  variable.  Some  notostracans  have  as  many  as  forty-two 
trunk-somites;  the  Conchostraca  have  from  thirteen  to  twenty- 
eight,  and  the  number  in  the  Anostraca  ranges  from  nineteen  to 
twenty-three.  Apart  from  the  head,  the  trunk  of  phyllopods 
shows  no  differentiation  into  distinct  regions.  The  terms  "thorax" 
and  ''abdomen"  have  been  variously  used  to  designate  the  pre- 
or  post-genital,  or  the  limb-bearing  or  limbless,  regions  respectively. 
But  the  Hmits  of  these  regions  do  not  coincide,  even  approximately, 
except  in  the  Anostraca;  and  ''thoracic"  and  "abdominal"  are 
therefore  not  appHcable  to  the  group.  The  last  segment,  or  telson, 
usually  bears  a  pair  of  appendages,  the  furcal  rami  or  cercopods. 

The  appendages  are  fairly  uniform  in  character,  except  as  they 
are  modified  by  sexual  dimorphism.     The  first  antennae  are  always 


THE    FAIRY    SHRIMPS    (PHYLLOPODA) 


663 


small  and  often  unsegmented.  The  second  antennae  are  vestigial 
or  absent  in  the  Notostraca;  in  the  male  anostracans  they  form 
variously  modified  clasping  organs;  and  in  the  Conchostraca  they 
are  biramous  swimming  appendages.  Male  Anostraca  uften  bear 
frontal  organs  which  may  arise  from  the  bases  of  the  second  anten- 
nae or  from  the  front  of  the  head.  The  trunk-limbs  are  leaf-like 
in  form  (hence  the  name  Phyllopoda)  and  are  remarkable  for  ha\- 
ing  gnathobases,  or  '^ chewing  bases,"  far  removerl  from  the  mouth. 
The  first  or  the  first  and  second  pair  are  modified  in  male  Con- 
chostraca for  clasping  the  female.  In  female  Notostraca  the  limbs 
of  the  eleventh  trunk  somite  are 
modified  to  form  brood-pouches,  or 
''oostegopods,"  for  carrying  eggs.  The 
females  of  some  Conchostraca  have 
the  flabella  of  two  or  three  limbs  near 
the  genital  aperture  enlarged  and  the 
egg  masses  are  attached  to  these.  In 
the  Anostraca  the  appendages  of  the 
somites  on  either  side  of  the  genital 
opening  are  modified  for  reproduction 
in  both  sexes. 

In  addition  to  the  various  appendages 
which  serve  as  accessory  reproductive 
organs,  the  oviducts  unite  to  form  an 
external  uterine  chamber  in  the  Anos- 
traca, and  the  males  of  the  same  suborder  have  a  copulatory  organ 
formed  by  the  fusion  of  the  extremities  of  the  vasa  deferent ia. 
All  phyllopods  are  of  separate  sexes.  Males  are  much  less  conmion 
than  females,  in  fact  some  species  are  known  onl\-  from  female 
specimens,  and  the  development  of  several  is  believed  to  be  usu- 
ally parthenogenetic.  The  gonads  are  paired  and  have  a  simple 
tubular  structure,  except  in  the  Notostraca  where  the\'  are  much 
ramified.  In  the  Anostraca  the  eggs  are  carried  in  the  female's 
brood-pouch,  the  uterine  portion  of  the  oviduct,  sometimes  until 
they  hatch.  The  Notostraca  bear  the  eggs  in  the  special  receptacles 
formed  by  the  eleventh  pair  of  trunk-limbs,  and  the  Conchostraca 
carry  them  enclosed  in  the  valves  of  the  shell. 


Fio.  1012.  A  pus  aequaiis.  c,  caraf>acr: 
/,  telson;  d,  ccranxids  or  furcal  rami. 
X  3.     (After  Packard.) 


664 


FRESH-WATER   BIOLOGY 


Fig.  1013.  Estheria  morsei,  with  left  valve  of  shell  removed.  X  9- 
ai,  first  antenna;  02,  second  antenna;  c.  carapace;  d,  cercopods 
or  furcal  rami;  /,  flabella;  u,  umbone.     (After  Packard.) 


The  alimentary  canal  of  phyllopods  consists  of  a  large  mastica- 
tory and  glandular  atrium  produced  by  an  overhanging  labrum 

c  in  front  of  the  mouth; 

this  is  followed  by  a 
buccal  cavity,  a  ver- 
tical esophagus  and  a 
small  globular  stom- 
ach within  the  head; 
and,  behind  these,  is  a 
long  straight  intestine 
which  terminates  in  a 
short  rectum  at  the 
posterior  end  of  the 
body.  The  heart  is 
greatly  elongated  in 
the  Anostraca,  oc- 
cupying nearly  all  the  trunk-somites,  with  a  pair  of  ostia  opening 
in  each  somite.  In  the  Notostraca  and  Conchostraca  it  is  more 
restricted  —  and  extends  through  only  three  or  four  segments  in 
the  latter.  There  are  no  definite  blood  vessels.  A  maxillary  gland 
(consisting  of  an  end-sac,  glandular  coiled  tube,  and  short  terminal 
duct)  serves  as  an  excretory  organ  in  phyllopods.  The  ladder-like 
structure  of  the  ventral  nerve  chain  shows  the  primitive  character 
of  the  nervous  system. 

After  leaving  the  egg,  all  American 
phyllopods  begin  their  development  as  a 
free  swimming  nauphus  or  metanaupHus 
(Fig.  1014).  Some  differences  exist  even 
in  closely  allied  forms  in  regard  to  the 
stage  ot  development  reached  at  hatching. 
The  larvae  of  the  Notostraca  and  Anos-  ^'f;iformis,  ^sfh^Sd!^  ^MtRiaus, 

,  ,  1    •      ..   J.1       i.*  from  Lankester's  Treatise  on  Zoology.) 

traca  are  typical  metanauplei  at  the  time 

of  hatching,  with  an  oval  body  that  shows  the  beginning  of  several 
trunk-somites  posteriorly  and  sometimes  the  rudiments  of  their 
appendages.  The  first  antennae  are  well  developed  but  uniramous, 
the  second  antennae  have  a  movable  masticatory  process  and  the 
mandibles  are  but  feebly  developed.     The  earliest  conchostracan 


THE    FAIRY   SHRIMPS    (PHYLLOPODA)  665 

larva  has  no  trace  of  trunk-somites;  the  first  antennae  are  greatly 
reduced  and  the  labrum  is  very  large.  The  trunk-somites  and  thc-ir 
appendages  become  differentiated  in  regular  order  from  before 
backwards.  The  single  median  eye  of  the  larva  persists  in  adult 
phyllopods. 

All  Phyllopoda,  except  Artemia,  live  in  small  fresh-water  jxiols. 
especially  those  that  are  formed  during  spring  rains  and  dry  up 
during  the  summer.  In  such  situations  they  often  occur  in  enormous 
numbers.  The  writer  once  saw  in  Nebraska  nearly  half  a  bushel 
of  dead  Apus  bodies  on  the  bottom  of  a  shallow  dried-up  depression 
about  twenty  feet  in  diameter.  The  eggs  of  most  genera  can  re- 
sist prolonged  desiccation;  indeed  it  seems  necess:iry  for  the  develoi)- 
ment  of  many  species  that  eggs  should  first  be  dried  and  afterwards 
immersed  in  water.  Many  eggs  float  when  placed  in  water  and 
development  takes  place  at  the  surface.  The  mud  of  dried  pools 
often  contains  large  numbers  of  eggs  that  may  be  carried  long 
distances  by  winds,  birds,  or  by  other  means.  Many  exotic  species 
have  been  reared  from  dried  mud  brought  home  by  travelers. 

On  account  of  the  rapid  evaporation  of  the  pools  in  which  they 
live,  phyllopods  are  able  to  withstand  considerable  changes  in  the 
amount  of  mineral  salts  in  the  water.  It  is  remarkable  that, 
though  none  of  these  crustaceans  are  marine,  Artcmia  salina  lives 
in  salt  lakes  and  salt  evaporating  basins  where  the  salinity  far  ex- 
ceeds that  of  the  ocean.  One  instance  has  been  recorded  where 
the  salts  in  solution  were  271  grams  per  liter,  and  where  the  watrr 
was  of  the  color  and  consistency  of  beer.  Artcmia  salina  is  subject 
to  marked  form  variations  that  are  more  or  less  correlated  with 
sahnity,  and  both  Kellogg  and  Artrom  have  observed  that  this 
species  tends  to  assume  a  reddish  color  as  the  water  about  it  .^rows 
denser. 

Phyllopods  usually  swim  on  their  backs  with  the  ventral  surface 
uppermost.  Eubranchipus  swims  easily  about  when  it  is  not  rest- 
ing on  the  bottom;  Apus  is  a  graceful  swimmer  but  often  creeps  on 
its  ventral  surface  over  the  bottom  and  upon  vegetation;  Esthcria 
commonly  burrows  in  the  mud.  Food  is  collected  in  the  ventral 
food-groove  between  the  post-oral  limbs  whose  gnathobases  drive  it 
forward  to  the  mouth.     It  consists  of  suspended  organic  debris, 


666  FRESH-WATER   BIOLOGY 

together  with  diatoms,  other  algae,  and  Protozoa.  Large  species, 
however,  are  able  to  gnaw  objects,  and  Apus  is  said  to  nibble 
insect  larvae  and  tadpoles.     No  parasitic  phyllopods  are  known. 

The  distribution  of  all  species  is  apt  to  be  local  and  irregular. 
A  certain  pool  may  swarm  with  phyllopods,  while  others  near  at 
hand  will  not  possess  a  single  individual.  A  particular  species  may 
be  extremely  abundant  for  one  season  and  then  be  infrequent  or 
entirely  absent  for  several  years,  or  it  may  appear  regularly  in  a 
certain  spot  season  after  season.  No  Notostraca  have  been  found 
in  eastern  United  States  and  none  of  the  genus  Estheria  in  the 
Conchostraca  are  found  east  of  the  Mississippi  River.  The  greater 
part  of  the  North  American  species  are  found  on  the  great  plains. 

Collecting  phyllopods  is  usually  a  simple  matter.  They  are 
easily  captured  with  a  hand  net  or  picked  up  with  the  fingers. 
For  ordinary  purposes  70  per  cent  alcohol  is  a  satisfactory  preserv- 
ative; specimens  may  be  kept  for  future  reference  by  dropping 
them  into  it  and  keeping  them  in  a  tightly  stoppered  bottle.  Dilute 
formol  may  also  be  used,  but  is  not  as  satisfactory  as  alcohol  because 
it  often  makes  specimens  so  brittle  that  they  break  up  easily. 
These  crustaceans  are  admirable  aquarium  animals  and  make 
attractive  objects  for  a  school  room  or  private  study.  With  a 
few  water  plants  for  company  they  may  Hve  for  weeks.  They 
should  not  be  put  in  aquaria  with  predaceous  animals  for  usually 
they  will  be  quickly  devoured. 

ElEY  TO  NORTH  AMERICAN  FRESH-WATER  PHYLLOPODA 

1(36)     Body  elongated,  without  carapace  (Fig.  loii)  .   Suborder  Anostraca  .   2 

2  (5)     Seventeen  to  nineteen  pairs  of  pregenital  ambulatory  limbs. 

Family  Polyartemudae. 
Only  one  genus  in  America Polyartemiella.  .  .  3 

3  (4)     Male  frontal  appendage  tuberculiform ;   male  clasping  antenna  quadri- 

ramose Polyartemiella  hanseni  (Murdoch)  1874. 


Described  from  Alaska.  This  and  the  following  species  are  remarkable 
for  the  large  number  of  ambulatory  limbs  which  exceeds  that  of  any  other 
anostracan.  Apparently  common  in  portions  of  Alaska  and  Yukon 
Territory  that  border  on  the  Arctic  Ocean. 


Fig.  1015.    Polyartemiella  hanseni.    Side  view  of  head  of  male.     X  6. 
(After  Daday.) 


THE    FAIRY   SHRIMPS    (PHYLLOPODA)  067 

4  (3)     Male  frontal  appendage  wanting;    male  clasping  antenna  triramose. 
^  ^  Polyarttmidla  jmlayi  Daday  ic^oy. 

^      ;?\  The  copulatory  appendages  of  this  form  arc  thick,  spiny,  and  shapcti  like 

/^V.   \  ^  t^sh-hook;    the   female  has  a  long  median  fmKcr-Iike  apiK-nda«e  on  the 

dorsal  surface  above  the  egg  sac. 

PribylofT  Islands  and  Alaska.     The  genus  to  which  this  species  belonw  is 
entirely  arctic  in  its  distribution. 

Fig.  1016.    Polyartemiellajudayi.    Dorsal  view  of  head  of  male     X  S-    (After  Daday.) 

5  (2)     Eleven  pairs  of  pregenital  ambulatory  limbs 6 

6  {t,^)     Clasping  antenna  of  male  biarticulatc 


7  (16)     Head  of  male  unarmed  in  front,  basal  segment  of  clasping  antenna  with- 
out a  laminar  appendage.   .   Family  BKANcmNKCTiDAK  .    .   8 

8(15)     Post-genital  region  9-segmented,  apical  article  of  male  clasping  antenna 
triangular  and  falciform Bramliiiieclii  .    .   9 

9  (10)     Basal  segment  of  male  clasping  antenna  serrate  on  inner  margin. 

Branchinccta  paludosa  (O.  F.  Muller)  1788. 


The  egg  sac  of  the  female  is  very  long  and  slender.  The  c(ipulator>' 
appendage  of  the  male  is  thick  antl  arcuate. 

This  is  an  arctic  species  and  occurs  in  northern  Elurope  as  well  as  in 
Greenland,  Labrador,  and  Alaska,  in  North  America.     See  also  Fij?.  101 1 

Fig.  1017.     Branchinccta  paludosa.     Head  of  male,  dorsal  view      X  s- 
(After  Daday.) 


10  (9)     Basal  segment  of  male  clasping  antenna  not  serrate  on  inner  margin.   1 1 

11  (14)     Basal   segment   of   male   clasping  antenna   with   a   spiny   area    on 

inner  margin 12 

12  (13)     Inner  margin  of  basal  segment  of  male  clasping   antenna   with  a 

rounded    tubercle    near    base    and    a    swollen    spiny    area 
just  proximal  to  middle. 

Branchineda  coloradoisis  Packard  1S74. 

The  segmentation  and  early  development  take  place  under  the  ice  in 
Alpine  Lakes,  The  eggs  of  this  species  are  much  larger  than  those  of 
others  in  the  genus.  This  fact  may  account  for  the  ability  to  devdop 
so  early. 

Reported  from  Colorado  where  it  occurs  at  an  altitude  of  11.000  ft. 
The  larvae  appear  as  soon  as  the  ice  melts  in  the  spring. 


Fig. 


branchinccta  cnloradensis.     He.-id  of  male,  fro 
(After  Shantz.) 


13  (12)  Basal  segment  of  male  clasping  antenna  armed  with  a  large  spmy 
process,  one  third  as  long  as  the  segment,  which  arises  just 
distal  to  the  middle  of  the  inner  margin  and  projects  pro.xi- 
mally,  a  prominent  finger-like  process  with  a  tiiberculatol 
tip  near  inner  proximal  angle. 

Branchincdii  packanli  Pearse  ioi3- 

The  five  pregenital  segments  of  female  produce*!  laterally  into  strong 
spinous  processes;  these  grow  larger  posteriorly.  Colltvte<l  at  La  Junta, 
Colorado. 

Fig.  1019.    Branchinccta  packardi.  Basal  segment  of  iccond  ititconi  ol  mxle. 


FRESH-WATER  BIOLOGY 

Inner  margin  of  basal  segment  of  male  clasping  antenna  without  a 
tubercle  but  with  a  spiny  area  near  proximal  end. 

Branchinecta  lindahli  Packard  i88^. 


The  body  is  robust;  the  caudal  appendages  are  comparatively  long; 
the  eggs  are  small,  and  the  ovisac  usually  contains  about  fifty  of  them. 

A  plains  species  recorded  from  Kansas,  Nebraska,  Colorado,  and 
Wyoming.     It  is  known  to  occur  as  high  as  7500  ft.  above  sea  level. 

Fig.  1020.   Branchinecta  lindahli.    Headof  male,  front  view.  X  3.    (After  Shantz.) 


15  (8)     Post-genital  region  8-segmented,  apical  article  of  male  clasping  antenna 
compressed Artemia. 

Only  one  species.     .    .    .  Artemia  salina  (Linnaeus)  1851. 

Connecticut,  Utah,  California,  Lower  California.  This  species  is 
remarkable  for  its  ability  to  live  in  extremely  saline  water.  It  is 
frequently  found  in  salt  evaporating  basins.  The  form  is  variable, 
and  several  varieties  have  been  described. 

Fig.  1021.    Artemia  salina.    Head  of  male,  dorsal  view.     X  4.     (After  Daday.) 

16  (7)     Head  of  male  often  bearing  a  frontal  appendage  or  a  laminar  appendage 

on  the  basal  segment  of  the  clasping  antenna. 

Family  Chirocephalidae  .    .    17 

17  (30)     Frontal  appendage  of  male  variable,  rather  short;  terminal  segment 

of  copula tory  organ  smooth Euhranchipus  .    ,    18 

18  (25)     Body  segments  of  male  and  female  all  superficially  unarmed.   .    .    19 

19  (20)     Frontal  appendage  of  male  short,  about  as  long  as  basal  joint  of  sec- 

ond antenna;  lanceolate,  margin  denticulate. 

Euhranchipus  vernalis  Verrill  1869. 


Massachusetts,  New  Jersey,  Indiana,  Michigan.  This  species 
appears  in  small  quiet  pools  soon  after  the  snow  disappears  in  spring, 
or  even  in  mid-winter,  but  has  not  been  observed  during  the  summer 
months. 

Fig.  1022.    Euhranchipus  vernalis.     Head  of  male,  side  view.     X  4. 
(After  Packard.) 


Frontal  appendages  of  male  when  extended  longer  than  basal  joint 
of  second  antenna 21 

Frontal  appendages  of  male  attenuate,  middle  fourth  serrate. 

Euhranchipus  holmani  (Ryder)  1879. 


This  species  was  first  discovered  in 
New  Jersey  and  has  since  been  ob- 
served on  Long  Island,  New  York. 
Packard  ('83)  confused  this  species 
with  Branchinella  gissleri  Daday. 

Fig.  1023.  Euhranchipus  holmani.  Head 
of  male;  yi,  side  view;  5,  front  view. 
X  4.     (After  Daday.) 


22  (21)     Frontal  appendages  of  male  broad,  lanceolate,  lobate  on  margins.    23 


THE    FAIRY    SHRIMPS    (PHVLLOPODA)  ,...; 

23  (24)     Terminal  segment  of  male  clasping  antenna  with  a  small  process  near 

base  that  is  one-eighth  as  long  as  the  segment. 

Eiibninchipus  ornatus  Holmes  k^i. 

lliis  s  p  {_•  c  i  c  s  was  dc- 
stril>L«l  from  sixrcitncns 
taken  in  Wisconsin.  The 
frontal  apiK-ntla^t-s  are  re- 
markably l>roa«l.  In  the 
left-hand  fij^urc  the  male 
frontal  appendages  arc 
rolled  up. 

Fig.  1024.  Eubratuhipu\  or- 
nalus.  Male.  A.  i«»Ntcrior 
view  of  head;  B.  (r«»ntal 
orRan;  C,  second  antrnria. 
X  10      (AhcT  Hnlmr^., 

24  (2^)     Terminal  segment  of  male  clasping  antenna  armed  with  a  i)rocess 

near  its  base  that  is  half  as  long  as  itself. 

Euhranchipiis  dadayi  Pcarse  10 1.^. 


Recorded  from  eastern 
Nebraska  and  Missouri. 
Some  sfx-cimens  arc  re- 
markably transparent. 
This  sjxries  appears  in 
small  p<jols  durinc  April 
and  NIay.  The  females 
are  more  reddish  than  the 
translucent  male^. 


Fig.  1025.  Euhranchipui  da- 
dayi. Male.  A.  ix>sterior 
view  of  head;  fi,  frontal 
organ;  C,  second  antenna. 
X8. 

25  (18)     Some  body  segments  produced  into  lateral  processes 26 


26  (27)     Body  segments  9  and  10  of  female  produced  into  latcnil  processes; 
post-genital  segments  unarmed. 

Eiibrauchi  pus  gel  id  us  (Hay)  IvSSq. 


Records  from  New  York.  Massachusetts. 
Indiana,  Alaska,  and  Yukon  Territor>-.  Canaila 
Usually  abundant  where  it  is  found.  The  proc- 
esses on  the  .somites  just  in  front  of  the  epR  sac 
on  the  female  distinguish  this  six-cies  from  al! 
others  in  the  genus.  The  Hay's  (Syl  haliheil 
the  eggs  of  this  anostracan  from  driisl  mud. 
without  freezing,  and  describi^l  development.il 
stages.  The  wide  range  is  remarkable  for  a 
member  of  this  genus. 

Fig.    1026.     Eubrandtipus    grOdus.    A.   side    view    of 
head  of   male;    H,  side  view  of   posterior  jvirtion  ol 

female.     X  4- 


27  (26)     Body  segments  9  and  10  of  female  not  produced  laterally 
genital  segments  acutely  produced  on  both  sides.    . 


p<ist- 
.     28 


670  FRESH-WATER   BIOLOGY 

28  (29)     Post-genital  region  8-segmented;  cercopods  ensiform. 

Euhranchipus  serratus  Forbes  1876. 
Described  from  specimens  taken  in  Illinois. 

29  (28)     Post-genital    region    9-segmented;     cercopods    dilated   with   obtuse 

apices Euhranchipus  bundyi  Forbes  1876. 

Described  from  specimens  collected  in  Wisconsin. 

30  (17)     Frontal  appendage  of  male  either  vertical  or  extending  out  from  the 

middle  of  front  of  head;    terminal  segment  of  copula tory 
organ  spiny 31 

31  (32)     Post-genital  segments  distinct  in  both  sexes,  cyUndrical,  cercopods 

always  distinct Branchinella. 

Only  one  species  in  North  America.  .  Branchinella  gissleri  Dadsiy  1910. 

This  interesting  phyllopod  has  been  recently  described 
from  specimens  collected  in  New  York.  Packard  ('83) 
confused  it  with  Euhranchipus  holmanii  (Ryder).  The 
male  frontal  appendages  are  usually  twisted,  and  coiled 
together. 

Fig.  1027.     Branchinella  gissleri.     Dorsal  view  of  head  of  male. 
X  5-     (After  Daday.) 

32  (31)     Post-genital  segments  fused  in  both  sexes;  cercopods  confluent. 

Thamnocephalus . 
Only  one  species Thamnocephalus  platyurus  Packard  1879. 

A  peculiar  species  that  has  been  recorded  from  Ellis, 
Kansas,  where  it  frequented  temporary  pools  in  the 
bottoms  of  ravines,  and  from  La  Junta,  Colorado, 
where  it  w^as  found  in  a  "cattle  pool." 
Fig.  1028.  Thamnocephalus  platyurus.  Dorsal  view  of 
male.      X  i.     (After  Packard.) 

Z2>  (6)     Clasping  antenna  of  male  triarticulate.     Family  Streptocephalidae. 
Only  one  genus  in  America Streptocephalus  .    .   34 

34  (35)     Anterior  digit  of  male  clasping  antenna  broad,  undulate,  bifid  at  tip. 

Streptocephalus  texanus  Packard  187 1. 

The  second  antennae  of  the  female  scarcely  exceed  the  first  in  length; 
her  cercopods  are  stouter  than  those  of  the  male. 

The  appendages  beneath  the  head  of  the  male  are  root-like  and  give  the 
animal  a  very  pecuhar  appearance. 

Texas,  Kansas,  Colorado,  Nebraska.  This  species  occurs  in  the  spring  or 
fall  in  pools  on  the  open  prairie. 

Fig.  io2g.     Streptocephalus  texanus.     Head  of  male.     X  4-     (After  Packard.) 

35  (34)     Anterior  digit  of  male  clasping  antenna  nearly  straight,  hnear. 

Streptocephalus  sealii  Ryder  1879. 

New  Jersey.  This  species  has  been  known  to  appear  twice  in  the  same  pool 
during  a  summer,  in  June  and  August,  following  rains. 

Packard  described  another  species,  S.  floridanus,  but  the  description  was 
not  definite  enough  to  differentiate  it  from  other  American  species. 

Fig.  1030.    Streptocephalus  sealii.     Head  of  male.    X  3-     (After  Packard.) 


THE    FAIRY   SHRIMPS    (PHYLLOPODa)  671 

36(1)     Body  with  a  well-developed  carapace .^ 

37  (52)     Body  depressed,  covered  dorsally  by  a  depressed  shield. 

Suborder  Notostraca  38 

38(45)     Telson  ending  in  a  long,  paddle-shaped  outgrowth.  .  Lcpidurus  .       39 

39  (40)     Telson  short,  obtusely  pointed,  spiny  on  edge. 

Lepidurus  glacialis  Kroyer  1847. 

|?f~5J|  ^^  arctic  species  recorded  from  Greenland  and  Labrador.     The  larapace 

11^  nIS  ^^  ^^'^^  '^""^^  ^"^^  regularly  ovate;  twelve  segments  are  exposal  behind  it. 

^'ff  V.Wp  Fig.  1031.    Lepidurus  glacialis.    Telson.     X  6.     (After  Packard.) 

40  (39)     Telson  spatulate. ^  i 

41  (42)     Telson  carinate  dorsally;   carapace  large,  leaving  only  five  body  seg- 

ments and  telson  uncovered. 

Lepidurus  coucsii  Packard  1S75. 

This  species  occurs  in  Utah  where  it  frequents  prairie  p(x>ls  of 
various  sizes. 

Fig.  1052.    Lepidurus  couesii.    Telson.     X  6.     (After  Packard.) 

42  (41)     Telson  not  carinate  dorsally 43 

43  (44)     Telson  long  bilobed;   carapace  short,  without  spinous  crest. 

Lepidurus  bilobatus  Packard  1S77. 
This  species  has  not  been  recorded  since  the  Hayden  survey,  when  it  was  taken  in  Colorado. 

44  (43)     Telson  long,  not  carinate,  sometimes  bilobed;  carapace  with  a  median 

spinous  crest Lepidurus  lemmoni  llolmvs  iS(j4. 

California.     The  cercopods  are  very  long  in  this  species. 

45  (38)     Telson  short,  cyHndrical,  simple ipus   .    .    46 

46  (47)     Carapace  as  long  as  the  portion  of  the  abdomen  projecting  beyond 

it;    telson  short  with  two  median  and  two  lateral  spines  on 
its  dorsal  median  third.    .    .    .    A  pus  acqualis  FacksiTd  iSyi. 

V^    >l\  A  widely  distributed  species  occurring  in  Mexico.  Lower  California.  Texas, 

t^>  ,^\  Nebraska,  and  Kansas.     It  [has  23  segments  exposed  behind  the  carapace. 

^'^^^-■'^  Fig.  1012  shows  the  form  of  this  species. 

Fig.  1033.     Apusaequalis.     Telson.     X  6-     (After  Packard.) 

47  (46)     Carapace  shorter  than  the  portion  of  the  abdomen  exposed  behind 

it 48 

48  (49)     Telson  long,  with  three  median  and  two  lateral  spines  on  its  dorsal 

median  third;    29  segments  exposed  behind  carapace. 

Apus  nnvhcrryi  V:icka.Td  1S71. 

%  '^  "^  Recorded  from  Utah  and  Colorado.     The  hairs  along  the  cercopods  arc 

I  y  J>  ,     \  said  to  be  remarkably  fine. 

pr^^l  Fig.  1034.    A  pus  ncu'bcrryi.     Telson.     X  6.     (After  Packard.) 


49  (48)     More  than  30  segments  exposed  behind  carapace. 


^0 


672 


FRESH-WATER   BIOLOGY 


50  (51)     Carapace  short,  three-fifths  as  long  as  exposed  abdomen;  telson  with 

one  (or  two)  median  and  two  lateral  spines  on  its  dorsal 
median  third A  pus  lucasanus  Fs-cksnd  iSyi. 

An  abundant  and  widely  distributed  species;  reported  from  Lower  Cali- 
fornia and  Kansas. 

Fig.  1035.    Apus  lucasanus.     Telson.     X  6.     (After  Packard.) 

51  (50)     Carapace  even  shorter  than  in  A.  lucasanus;   telson  very  short  with 

one  median  and  four  lateral  spines  on  dorsal  median  third. 
Apus  longicaudatus  Leconte  1846. 

This  form  occurs  in  Colorado,  Nebraska,  Texas,  and  along  the  Yellowstone 
River. 

Fig.  1036.    Apus  longicaudatus.     Telson.     X  6.     (After  Packard.) 

52  (37)     Body  compressed,  carapace  forming  two  lateral  valves  which  enclose 

the  body Suborder  Conchostraca    .    ,   53 

53  (60)     Only  the  first  post-cephalic  Umbs  prehensile  in  the  male;    carapace 

spheroidal,   without   Knes   of   growth;    head   not   included 

within  carapace-chamber Family  Limnetidae. 

Only  one  genus Limnetis  .    .   54 

54  (57)     Shell  subspherical 55 

55  (56)     Length,  3  mm.;  front  of  male's  head  narrow;  second  antenna  i6-seg- 

^  ^    mented;  flabellum  very  large.  .  Limnetis  gouldii  Baird  1862. 

A  form  widely  distributed  through  Massachusetts,  Nevr 
Hampshire,  Rhode  Island,  New  York,  Illinois,  and  Canada. 
It  is  very  hardy  and  will  live  for  months  in  aquaria. 

Fig.  1037.    Limnetis  gouldii.    ^ ,  head  of  male,  dorsal  view.    X  21; 
B,  shape  of  shell.     X  7.     (After  Packard.) 

56  (55)     Length,  4.2  mm.;   front  of  male's  head  very  broad;   antenna  20-seg- 

mented Limnetis  gracilicornis  Packard  187 1. 

This  species  was  described  by  Packard  from  specimens  collected 
at  Waco,  Texas. 

Fig.  1038.    Limnetis  gracilicornis.      Head  of  male,  dorsal  view.      X  18. 
(After  Packard.) 

57  (54)     Shell  suboval 58 

58  (59)     Length,  4  nam.;  front  of  male's  head  broad  and  square;  second  an- 

A  B        tenna  14-  and    17-segmented;    flabellum  very  narrow. 

Limnetis  mucronatus  Packard  1875. 

This  species  has  been  reported  from  Montana  and  Kansas. 
It  is  easily  recognized  by  the  mucronate,  tridentate  front. 


^3 


Fig.  1039.    Limnetis  mucronatus.    ^ ,  head  of  male,  dorsal  view.    X  20; 
B,  shape  of  shell.    X  4.     (After  Packard.) 

59  (58)     Length,  4  (to  6)  mm.;    front  of  male's  head  rather  broad;   second 
A  B        antenna  29-segmented;  flabellum  short  and  broad. 

Limnetis  brevifrons  Packard  1877. 

This  is  the  largest  known  species  of  this  genus  in  North 
America.     It  has  been  observed  only  at  Ellis,  Kansas. 


Fig.  1040.    Limnetis  brevifrons.     A,  head  of  male.     X  8. 
of  shell.     X  3.     (After  Packard.) 


B,  shape 


THE    FAIRY    SHRIMPS    (PHYLLOPODA) 


673 


60  (53)  First  and  second  post-cephalic  limbs  prehensile  in  the  male;  carapace 
distinctly  bivalve,  enclosing  head,  with  concentric  growth 
lines  around  a  more  or  less  prominent  umbo. 

Family  Limnadhdai:  .61 

61(66)     With  pediculated  dorsal  organ  on  front  of  head 6i 

62  (63)  Shell  broad  oval,  much  flattened,  subtriangular,  with  about  18  lines 
of  growth;    fiagella  of  second  antenna  12-  to  is-segmente<l; 

18  to  22  pairs  of  limbs "     I^hmuuiia. 

Only  one  species Limmidia  iinuriccjna  Morse  iH-js. 


This  species  was  described  from  specimens  colIccte<l 
at  Lynn,  Massachusetts. 

Another  possible  species,  Limnadia  coriofea  lialdc- 
man,  was  collected  at  Cincinnati  and  in  ditches  ahing 
the  Susquehanna  river,  but  it  has  not  been  sufTuiently 
described  so  that  its  relati(jnships  can  be  determine*!. 
See  Packard  (1883,  pp.  .51.5,  ,}  14). 


Fig.  1041.     Limnadia  americana.     Side  view. 
(After  Packard.) 


X  \. 


63  (62)     Shell  narrow-ovate,  rather  prominent  behind  the  umboncs  with  4  to 

5  lines  of  growth;    fiagella  of  second  antennae  q-  to  lo-seg- 
mented;   18  pairs  of  limbs Eulimnadia   .    .   64 

64  (65)     Shell  narrow-ovate,  with  4  lines  of  growth;    telson  with  12  pairs  of 
•  ^      "*  dorsal  spinules  not  including  the  terminal  spine. 

Eulimnadia  agassizii  Packard  1S74. 


This  small  crustacean  has  only  been  o})ser\-e<l  on 
Penikese  Island,  Massachusetts.  The  fi^'ure  shows 
the  large  dorsal  organ  projecting  above  the  eye.  The 
valves  of  the  carapace  are  whitish  and  ver\-  trans- 
parent.    Their  shape  is  regularly  oval. 


Fig.  1042. 


Eulimtuidia  agassizii.     Side  view.     X  a. 
(Alter  Packard.) 


65  (64)     Shell  narrower  than  that  of  Eulimnadia  agassizii,  with  5  lines  01  growth ; 
telson  with  16  fine  teeth  above. 

Eulimnadia  tcxana  Packard  1S7.'. 


The  valves  of  the  carapace  are  whitish  and 
rounded  oval  in  shape. 

This  species  has  l)een  collectetl  in  Kansas, 
Nebraska,  and  Texas.  It  is  s;iid  to  be  com- 
mon in  the  last  locality  in  early  spring.  The 
figure  shows  only  the  shape  of  the  shell. 

Fig.  104,?.     Eulimruuiia   trxan^t.      Shape   of  shell, 
side  view.     X  7.     (.After  P.-tckard.) 


66  (61)  Shell  oval,  more  or  less  globose,  with  18  to  22  lines  of  growth,  amber 
colored;  no  pediculated  dors;il-organ  on  front  of  head; 
fiagella  of  second  antennae  11-  to  17-segmented;  24  to  28 
pairs  of  limbs Estluria   .    .   67 


674  FRESH-WATER   BIOLOGY 

67  (70)     Umbones  one-sixth  length  of  shell  from  anterior  end 68 

68  (69)     Shell  large  (16  mm.  long),  flat;  umbones  small;  flagella  of  second 

antenna  13-  and  15-segmented. 

Estheria  californica  Packard  1874. 


Thus  far  this  species  has  been  collected  at  two 
localities  in  Cahfornia.  The  small  size  of  the  umbones 
is  remarkable.  Length  of  shell,  i6  mm.;  height, 
10  mm  ;  breadth,  4  mm. 

Fig.  1044.    Estheria  californica.    Shell,  side  view.     X  3- 
(After  Packard.) 


69  (68)  Like  Estheria  californica  but  umbones  more  prominent  and  dorsal 
edge  of  shell  sloping  down  to  posterior  end. 

Estheria  newcomhii  Baird  1866, 

Possibly  the  same  as  the  last  species  but  as  Packard's  and 
Baird's  figures  appear  to  differ  somewhat  the  two  are  separated. 
It  is  found  only  in  California. 

Fig.  1045.    Estheria  newcombii.     Shell,  side  view.   X  2.     (After  Eaird.) 

70(67)     Umbones  more  than  one-sixth  length  of  shell  from  anterior  end.    .    71 

71  (72)  Shell  long  and  narrow;  umbones  small,  one-fifth  length  of  shell  from 
anterior  end;  telson  armed  with  small  fine  teeth;  hands  of 
male  short  and  thick;  flagella  of  second  antenna  15-  and 
14-segmented.  .    .    .  Estheria  compleximanus  Packard  1877. 

Packard  reported  this  species  from  two  localities  in 
Kansas  and  more  recently  Richard  discovered  it  in  a 
collection  from  Lower  California.  Length  of  shell, 
II  mm.;  height,  5.5  mm. 

Fig.    1046.    Estheria  compleximanus.     Shell,  side  view. 
X  3.     (After  Packard.) 


72  (71)     Shell  more  or  less  swollen  or  globose;  umbones  prominent. 


73 


73  (74)     Shell  globose,  wider  than  high;    umbones  prominent  and  oblique 

one-fourth  length  of  shell  from  anterior  end,  Hues  of  growth 

not  sharply  marked Esfheria  digiieti  Richard  1895. 

Described  from  Lower  California. 

74  (73)     Lines  of  growth  well  marked;  shell  not  wider  than  high 75 

75(78)     Flagellaof  second  antennae  15- and  14-segmented 76 

76  (77)     Shell  globose  with  24  lines  of  growth;  umbones  large  and  prominent, 
two-fifths  length  of  shell  from  anterior  end. 

Estheria  helfragei  Packard  187 1. 

This  fine  species  was  described  by  Packard  from  specimens  collected 
in  the  month  of  April  at  Waco,  Texas. 
Fig.  1047.    Estheria  helfragei.     Shell,  side  view.    X  4-     (After  Packard.) 


THE    FAIRY    SHRIMPS    (PHYLLOPODA) 


675 


77  (76)     Shell   globose  with  13  lines  of  growth;    umbones  prominent,  one- 
third  length  of  shell  from  anterior  end. 

Est  her  ia  sclosa  Pearse  igi3. 

This  species  resembles  Eslheria  bclfraRci  in  many  resiK-cts  hut  is  ca-sily 
distmguished  by  the  smaller  number  of  lines  of  growth  and  the  length  of 
the  dorsal  setae  at  the  anterior  edge  of  the  telson.  Collected  in  eastern 
Nebraska  from  small  pools. 

Fig.  1048.    Estheria  setosa.     Shell,  side  view.     X  .?. 

78(75)     Flagella  of  second  antenna  17- and  16-scgmented 79 

79  (80)     Shell  swollen;    umbones  rather  prominent,  one-fourth  length  of  shell 

from  anterior  end;  dorsal  margin  short,  sudtleniy  sloping  at 
posterior  end;  telson  with  larger  teeth  interpolated  l)etwecn 
the  smaller  ones Estheria  mexieana  Claus  1 860. 

A  species  of  very  wide  range  extending  from  Lake  Winnipeg 
through  Kansas,  Nebraska,  Kentucky,  Ohio,  and  New  Miticn 
into  Mexico.     It  is  rather  variable  in  its  structure. 

Fig.  1049,    Eslheria  mexieana.    Shell,  side  view.    X4.    (.After  i';iik:ir'l 

80  (79)     Shell  somewhat  globose;    umbones  more  prominent  than  in  Estheria 

mexieana,  slightly  nearer  the  anterior  end  than  in  Estheria 
heljragei Estheria  morsei  Packard  1S71. 

South  Dakota,  Nebraska.     Fig.  1049  shows  the  general  structure  of  this  species. 


IMPORTANT   PAPERS   ON   FRESH-WATER   PHYLLOPODA 

Calman,  W.  T.     1909.     Crustacea.     Lankester's  Treatise  on  Zoolog>',    Pt. 

VII,  Fasc.   3:  29-55.     London  and  New  York. 
Daday,  E.     1910,     Monographic  systematique  des  Phyllopodes  Anostraces. 

Ann.  Sci.  Natur.,  (9)  11:  91-492,  84  figs. 
Hay,  0.  P.,  and  W.  P.     1889.     A  contribution  to  the  knowledge  of  the  Genus 

Branchipus.    Amer.  Natur.,  23:  91-95. 
Packard,  A.  S.     1883.    A  Monograph  of  the  Phyllopod  Crustacea  of  North 

America,  with  Remarks  on  the  Order  Phyllocarida.     12  Ann.  Rept.  U.  S. 

Geol.  Surv.:  295-590,  39  pis.,  i  Map. 
Pearse,  A.  S.     1913.    Notes  on  Phyllopod  Crustacea.     14  R^'pt.  Michigan 

Acad.  Sci.:  191-197,  3  pis. 
Shantz,  H.  L.     1905.     Notes  on  North  American  Species  of  Branchinecla  and 

their  Habits.    Biol.  Bull.,  9:  249-264;  pis.  10-12. 


CHAPTER   XXII 
THE    WATER   FLEAS    (CLADOCERA) 

By  EDWARD  A.  BIRGE 

Dean,  University  of  Wisconsin 

When  men  began  to  study  nature  by  the  aid  of  the  microscope 
in  the  seventeenth  century  the  ''insects"  were  among  the  first  ob- 
jects to  be  examined.  In  1669,  the  Dutch  physician,  Swammerdam, 
described  in  his  history  of  insects  the  " pulex  aquaticus  arborescens^' 
—  the  water-flea  with  branching  arms.  This  was  one  of  the 
Cladocera,  still  called  Daphnia  pulex,  the  commonest  species  in 
shallow  pools.  These  creatures  he  described  and  figured,  giving  an 
account  of  their  structure  and  habits  and  speaking  of  their  sudden 
appearance  in  enormous  numbers,  and  their  equally  sudden  dis- 
appearance. So  the  Cladocera  made  their  debut  into  science  along 
with  the  microscope. 

For  nearly  a  century  Httle  was  added  to  the  knowledge  of  the 
group.  In  1755,  the  German,  Schaeffer,  gave  the  first  really  good 
account  of  their  structure.  In  1785,  0.  F.  Mueller,  the  Danish 
naturalist,  issued  the  first  general  systematic  work  upon  Entomo- 
straca.  This  described  many  of  the  species  as  we  now  know  them 
and  gave  a  firm  scientific  basis  for  further  knowledge  of  the  Clado- 
cera. In  the  rapid  advance  of  science  during  the  latter  half  of  the 
nineteenth  century  the  systematic  work  of  the  group  was  substan- 
tially done,  the  Norwegian,  G.  0.  Sars,  having  contributed  more 
than  any  other  one  man.  This  work  showed  that  the  Cladocera 
constitute  the  largest  group  of  fresh-water  Crustacea  in  number  of 
species;  the  most  diversified  in  size,  in  structure,  and  in  habits. 

During  the  opening  years  of  the  present  century  the  scientific 
study  of  fresh-water  life  has  advanced  rapidly  and  the  biology  of 
the  Cladocera  is  receiving  much  attention.  The  conditions  of 
variation  and  the  nature  of  the  variants  are  examined,  as  well  as 
the  conditions  of  sexual  reproduction,  the  centers  of  origin  and 
dispersal  of  species,  and  other  similar  matters. 

The  Cladocera  are  particularly  well  suited  for  study  by  those 
persons  who  are  interested  in  observing  animals  with  the  micro- 

676 


THE  WATER   FLEAS  (CLADOCERA) 


677 


-m^^ 


--  BO 


scope  and  who  cannot  command  the  resources  of  a  university  labo- 
ratory.    They  are  easily  collected  and  preserved  and  the  species 
may  be  readily  identified,  since  little  or  no  microscopic  dissection 
is  needed  to  make  out  the  specific  characters.     Many  of  the  Clado- 
cera  are  so  transparent  that  the  internal  or^^ans  can  be  studied  in 
detail  when  the  animal  is  viewed  from  the  side  under  the  microscope. 
Many  of  the  forms  can 
readily  be  kept  alive  in 
small  aquaria,  and  their 
habits  observed.     There 
is  still  a  great  amount  of 
work  to  be  done  in  this 
country  in  finding  out 
the    local    geographical 
distribution  of  the  spe- 
cies and  the  variation  of 
the  variable  forms. 
-    The    suborder    is   di- 
vided into  two  sections  so 
different  that  few  state- 
ments can  be  made  of 
them  in  common.     The 
first,  and  by  far  the  larger 
section,   the   Calypto- 
mera,  have  a  large,  bi- 
valve shell,  which  covers  the  body  and  legs.     The  second  section,  the 
Gymnomera,  includes  two  species  in  our  fresh  waters.     These  retain 
the  shell  only  as  a  brood  sac;  the  body  and  legs  being  free.      In  the 
account  which  follows,  the  Calyptomera  are  kept  in  mind.     The 
animals  belonging  to  this  group  range  in  size  from  about  0.2  mm. 
to  3.0  mm.,  or  even  more.     All  have  a  distinct  head,  and  a  body 
covered  by  a  fold  of  the  skin,  which  extends  backward  and  down- 
ward from  the  dorsal  side  of  the  head  and  constitutes  a  bivalve 
shell.     The  junction  of  head  and  body  is  sometimes  marked  by  a 
depression,  the  cervical  sinus  or  notch  (Figs.  105 1.  lOT.v  logi).' 

1  The  figures  referred  to  are  designed  to  give  the  specific  characters  raih.r  than 
the  anatomy,  which  is  shown  only  incidentally. 


Fig.  ioso.  Daplinia  Umgispina.  A',  ;intcnnulc;  A",  antenna: 
AP,  abdominal  processes;  .4.S',  abdominal  setae;  B,  brain  with 
optic  ganglion  and  ocellus;  BC,  brood  case  with  (Icvclopin^  ova; 
E,eye,  with  three  eye  muscles  of  left  side;  //.  heart  with  venous 
opening  on  side  and  exit  in  front;  HC.  hepatic  cecum;  /,  intes- 
tine; L,  legs;  MJ,  mandible;  O.  ovary;  PA.  jxist  alxlomen  with 
anal  spines  and  terminal  claw;  R,  rostrum  or  Ix-al;;  .SG.  >hcll 
gland.     (After  Sars.) 


678  FRESH-WATER  BIOLOGY 

In  the  head  is  the  large  compound  eye  (Fig.  1050).  This  has  nu- 
merous or  few  lenses  (Figs.  1059,  1076, 1169),  and  is  capable  of  being 
rotated  by  three  muscles  on  each  side.  It  is  a  most  conspicuous 
organ,  by  its  size,  its  dark  pigment,  and  its  constant  motion  during 
Hfe.  In  the  head  are  also  the  brain,  the  optic  gangUon,  with  its 
numerous  nerves  to  the  eye,  the  ocellus,  or  pigment  spot,  the  an- 
tennary  muscles,  and  the  anterior  part  of  the  digestive  tract.  The 
head  bears  two  pairs  of  appendages:  (i)  The  antennules  (Figs.  105 1, 
1079, 1114, 1152),  which  carry  sense-rods,  the  olfactory  setae,  usually 
placed  at  the  end,  and  have  also  ordinarily  one  or  more  lateral  sense 
hairs;  (2)  the  antennae,  the  main  organs  of  locomotion,  large  swim- 
ming appendages,  with  a  stout  basal  joint  bearing  two  branches  or 
rami,  which,  in  turn,  carry  long  plumose  setae.  The  number  of  the 
antennary  setae  may  be  expressed  by  a  formula  which  shows  the 
number  of  the  setae  on  each  joint  of  each  branch  of  the  antenna; 
the  numbers  for  the  dorsal  branch  occupying  the  place  of  the 
numerator  of  a  fraction.      The  formula  thus  constructed  reads 

Daphnia  (Fig.  1050),  ^^^~^  •  that  for  Sida  (Fig.  105 1),  5^^^. 

The  antennae  are  moved  by  powerful  muscles,  which  may  occupy 
a  great  part  of  the  interior  of  the  head  (Fig.  1050) .  On  the  size  of  the 
antennae,  the  length  and  number  of  the  setae,  and  on  the  size  of  the 
muscles  operating  them,  depends  the  type  of  locomotion.  Latona 
(Fig.  1052)  leaps  suddenly  from  point  to  point  by  single  powerful 
strokes  of  its  broad  antennae.  The  smaller  Daphnidae  (Fig.  1079) 
hop,  rather  than  leap,  by  more  numerous  and  less  vigorous  strokes. 
The  heavier  forms  of  this  family  (Fig.  1075),  with  smaller  anten- 
nae, have  a  rotating,  unsteady  motion,  produced  by  rapid  strokes. 
Drepanothrix  (Fig.  1104),  whose  antennae  bear  saber-like  setae, 
scrambles  and  pushes  itself  about,  and  the  mud-haiuntmg  Ilyocry plus 
(Fig.  1 1 10)  crawls  and  pulls  itself  about  among  the  weeds,  rather 
than  swims.  The  members  of  the  large  family  of  the  Chydoridae 
have  small  antennae  and  move  them  very  rapidly;  while  their 
progress  varies  from  a  rapid  whirling-motion,  as  in  Chydorus  (Fig. 
1 1 50),  to  a  slower  wavering  and  tottering  progress,  as  in  Acroperus 
(Fig.    1 1 21).     In  the  Macro thricidae   and   Chydoridae  the  post- 


THE  WATER   FLEAS  (CLADOCERA)  679 

abdomen  is  often  an  efficient  aid  to  locomotion.  It  ma\-  [)u.sh  tlu- 
animal  along,  as  in  Ilyocryptus  (Fig.  mo)  and  Camptoccrcus  (Fig. 
1119).  In  Dunhevedia  (Fig.  1134)  it  is  peculiarly  ciTectivc.  broad 
and  stout,  covered  with  numerous  small  spines  and  setae,  and  by  ii.s 
aid  the  animal  may  execute  sudden  and  vigorous  jumj)s. 

The  head  also  bears  the  mouth  parts:  (i)  The  mandibles  (Figs. 
1050,  1068,  1099,  and  others);  stout,  strongly  chitinizcd  organs. 
made  in  one  piece  and  without  a  palpus.  Their  op|)osing  faces  are 
toothed  and  ridged  and  they  grind  the  food  very  perfectly.  (2)  The 
maxillae,  a  pair  of  very  minute  organs,  lying  concealed  on  the  ven- 
tral surface  of  the  body,  just  behind  the  mandibles.  Each  is  a 
small,  pointed  structure,  bearing  several  curved  setae.  They  work 
like  a  pair  of  hands  to  push  the  food  between  the  mandibles.  (3) 
The  labrum,  an  unpaired  structure,  attached  to  the  rear  of  the 
head  and  closing  the  mouth  from  below.  In  many  of  the  Mac- 
rothricidae  and  Chydoridae  this  structure  bears  a  keel  or  projection 
which  is  of  systematic  value  (Figs.  1051,  1060,  1106,  1135). 

The  axis  of  the  head  may  continue  that  of  the  body  {extended,  Fig. 
1 100),  or  it  may  be  bent  downward  {depressed,  Fig.  1087).  That 
part  in  front  of  the  eye  is  known  as  the  vertex.  There  is  usually  a 
sort  of  beak  in  front  of,  or  between,  the  antennules,  which  is  known 
as  the  rostrum,  whose  size  and  shape  have  systematic  value.  There 
is  commonly  a  ridge  above  the  insertion  of  the  antenna,  which  helps 
to  stiffen  the  side  of  the  head  and  to  support  the  pull  of  the  antcn- 
nary  muscles.  This  is  the  fornix,  whose  shape  and  extent  may  form 
an  important  systematic  character  (Figs.  1063,  1083). 

The  shell,  though  called  bivalve,  is  really  in  one  piece,  bent  along 
the  back,  but  never  showing  a  division  or  joint  at  this  i)lace.  It 
has  very  different  forms,  as  seen  from  the  side,  nearly  square,  oval, 
or  round.  It  may  be  marked  in  the  most  various  fashions.  It 
may  bear  hairs,  or  spines,  along  the  ventral  edge.  There  may  be 
a  single  spine  on  the  dorsal  side,  prolonging  the  junction  of  the 
valves,  as  in  Daphnia,  or  each  valve  may  have  one  or  more  spines 
at  the  lower  posterior  part,  the  infero-posteal  angle  (Fig.  1076). 
This  angle  in  the  Chydoridae  may  be  acute  or  rounded,  smooth  or 
toothed,  and  its  characters  are  of  systematic  value.  The  shell  is 
always  a  duplicature  of  the  skin.      Its  inner  wall   is  far  more 


68o  FRESH-WATER   BIOLOGY 

delicate  than  the  outer,  and  between  the  walls  the  blood  circulates 
and  the  inner  surface  serves  as  a  respiratory  organ. 

Just  back  of  the  head,  on  the  dorsal  side,  lies  the  heart,  an  oval 
or  elongated  sac  (Figs.  1050,  105 1,  1089),  whose  rapid  pulsations  are 
easily  seen  in  the  living  animal.  It  receives  the  colorless  or  yellow 
blood  by  one  opening  on  each  side  and  expels  it  in  front.  There  are 
no  blood  vessels,  but  the  circulation  passes  along  definite  courses 
through  a  complex  series  of  passages  all  over  the  body.  The 
movements  of  the  blood  corpuscles  may  be  readily  seen  in  trans- 
parent Cladocera. 

Respiration  is  not  served  by  any  single  organ.  The  legs  and 
the  inside  of  the  valves  are  the  main  surfaces  for  the  exchange  of 
gases. 

In  the  anterior  part  of  the  valves  lies  an  organ  whose  structure 
is  not  readily  made  out.  This  is  the  shell  gland  (Figs.  1050,  105 1, 
1056),  a  flattened  glandular  tube  in  several  loops,  which  probably 
serves  the  function  of  a  kidney. 

The  body  lies  free  within  the  valves  and  is  divided  into  the  main 
portion,  bearing  the  feet,  which  is  not  plainly  segmented,  and  a 
single  unjointed  portion,  the  post-abdomen.  Through  it  runs  the 
intestine,  and  along  the  sides  of  the  body  lie  the  simple  reproduc- 
tive organs.  To  the  ventral  side  are  attached  the  feet,  ordinarily 
five  pairs,  sometimes  six.  These  are  mainly  leaf-like  structures, 
each  with  several  parts,  bearing  numerous  hairs  and  long  setae  (Figs. 
1050,  1 142).  Their  structure  is  too  complex  to  describe  here.  In 
the  first  two  famihes  all  the  feet  are  similar  and  foliaceous.  Their 
use  is  to  create  a  current  of  water  through  the  valves,  bringing 
in  oxygen  for  respiration  and  particles  of  food.  The  latter  consists 
chiefly  of  algae,  though  nothing  edible  is  rejected  that  the  current 
brings  in.  The  food  particles  collect  below  the  body  between  the 
bases  of  the  feet  and  are  fed  forward  into  the  mouth.  The  maxillae 
push  them  between  the  jaws  as  the  labrum  opens,  the  mandibles 
grind  them  up,  and  they  pass  on  into  the  esophagus.  Cladocera 
are  normally  eating  all  of  the  time. 

In  the  Daphnidae  and  remaining  famiHes  the  feet  differ  in  struc- 
ture ;  the  first  pairs  being  more  or  less  prehensile  and  having  other 
functions  besides  the  main  one  of  drawing  in  water.     These  animals 


THE   WATER    ELEAS   (CLADOCER.A)  68 1 

live  chiefly  among  the  weeds,  and  the  hooks  and  spines  of  the  first 
foot  aid  them  in  cUnging  to  plants  and  also  may  help  to  pull  off 
attached  algae,  etc.,  for  food. 

In  the  more  transparent  species  the  digestive  tract  may  be  seen 
throughout  its  full  extent.  The  narrow  csopha«,^us  ( Figs.  ^050, 105 1 , 
1096)  widens  suddenly  into  the  stomach,  wliich  lies  in  the  head  and 
whose  posterior  end  passes  insensibly  into  the  intestine.  Attached 
to  the  stomach  in  many  species  are  two  sacs,  often  long  and  curwd 
(Figs.  1050,  1053,  1060,  1064,  iico).  These  arc  the  hepatic  ccta. 
which  no  doubt  function  as  a  digestive  gland,  l^he  stomach  and 
intestine  have  a  muscular  wall  and  a  lining  of  dark-colored,  glandu- 
lar cells.  The  cavity  is  ordinarily  filled  with  food.  The  intestine 
has  a  direct  course  in  the  first  four  families.  In  the  Macrothricidae 
it  is  sometimes  direct  (Fig.  1106),  and  sometimes  convoluted  (Figs. 
1 100,  1 103).  In  the  Chydoridae  it  is  always  convoluted  and  there 
is  often  a  cecimi  attached  to  the  ventral  side  near  the  [)osterior  end 
(Figs.  1 1 21,  1 141).  The  terminal  part  of  the  intestine,  the  rectum, 
is  always  transparent  and  the  muscles  which  open  and  c  lose  it  can 
easily  be  seen.  The  anus  Hes  either  at  or  near  the  vnd  of  the  post- 
abdomen,  as  is  usually  the  case  in  the  first  live  families,  or  in  the 
Chydoridae  and  in  some  forms  of  the  other  families  (Figs.  1089. 
1091,  1 100,  11C9),  on  the  dorsal  side. 

The  post-abdomen  is  ordinarily  jointed  to  the  body  and  is  bent 
forward;  hence  its  dorsal  side  may  come  to  be  the  lower  one.  On 
the  dorsal  side  it  bears  two  sensory  hairs,  often  very  long  (Fig.  logo), 
the  abdominal  setae.  At  the  end  of  the  post-abdomen  are  two  ter- 
minal claws,  which,  in  turn,  may  have  spines  at  their  base,  the  basal 
spines  (Figs.  1123,  1144),  or,  when  numerous,  the  {K-ctcn  (Fig. 
1066),  and  the  concave  side  may  also  have  a  row  of  very  fine  spinules 
(denticulate).  The  post-abdomen  almost  always  has  more  or  fewer 
spines,  or  teeth,  the  anal  spines.  In  the  (liNcioridae  there  are  fre- 
quently two  rows  on  each  side  behind  the  anus,  the  marginal  and 
lateral  denticles  (Fig.  1147).  These  spines  and  teeth  may  have  the 
most  diverse  shape  and  structure  (squamae,  fascicles,  etc.).  and  fur 
nish  important  systematic  characters.  Their  main  use  seems  to  Ik» 
to  comb  the  legs  and  keep  them  clean  and  free  from  foreign  matters 
and  from  parasites  which  might  other^vise  readily  attach  them.selves. 


682  FRESH-WATER   BIOLOGY 

Little  study  has  been  given  to  the  senses  of  the  Cladocera,  except 
that  of  sight.  As  special  organs  of  touch  there  are  the  abdominal 
setae,  which  are  sometimes  very  long  (Fig.  1090) ;  sensory  hairs  on  the 
basal  joint  of  the  antenna  near  the  body  (Fig.  1075),  or  near  the  apex 
(Figs.  1051,  1053, 1089) ;  the  lateral  sense  hair  of  the  antennule  (Figs. 
1089,  1 1 17,  1 1 54);  the  flagellum  on  the  antennule  of  the  Sididae 
(Figs.  105 1- 1 05 7),  which  is  often  fringed  with  fine  hairs;  and  the 
frontal  sense  hair  of  Bosmma  (Fig.  1096).  Any  of  the  innumerable 
hairs  and  setae  may  also  serve  this  sense,  though  not  specially  modi- 
fied for  that  purpose.  There  is  no  auditory  organ.  Whether  the 
olfactory  setae  really  give  sensations  of  smell  and  taste  is  doubtful, 
although  the  structure  of  the  sense  rods  is  such  that  they  may  well 
serve  a  chemical  sense.  They  lie  at  the  entrance  of  the  valves  in 
the  current  of  water  which  is  coming  in  under  the  impulses  of  the 
feet,  and  may  take  cognizance  of  the  particles  of  food,  etc.,  which 
come  along  with  the  water.  The  Cladocera  are  certainly  able  to 
discriminate  between  different  kinds  of  particles  brought  in  by  the 
legs,  eating  some  and  rejecting  others.  They  have  decided  tastes 
in  the  matter  of  diet,  preferring  some  forms  of  algae  to  others.  In 
general,  the  diatoms  are  eaten  in  preference  to  the  blue-green  algae. 
In  the  selection  of  food,  the  Cladocera  are  aided  also  by  sensations 
which  arise  in  the  mouth,  since  they  may  reject  particles  which 
have  been  brought  into  the  mouth  and  partially  chewed. 

The  eye  is  obviously  the  visual  organ.  It  is  sensitive  to  light  and 
can  no  doubt  distinguish  objects  by  the  shadows  which  they  pro- 
duce, although  its  lenses  are  by  no  means  numerous  enough,  or 
perfect  enough,  to  give  sensations  of  form.  The  constant  motions 
of  the  eye  are  for  the  purpose  of  moving  the  lenses  so  that  they  will 
cover  the  entire  field  of  vision,  and  the  animal  no  doubt  directs  its 
movements  by  sensations  which  it  receives  through  the  eye.  The 
Cladocera  respond  differently  to  light  of  different  intensities  and 
various  colors.  Most  of  them  react  positively  to  a  weak  light  and 
negatively  to  a  strong  one.  There  is,  however,  much  difference  in 
this  respect.  Drepanothrix,  for  example,  is  vigorously  repelled  by 
the  light  of  a  lamp,  which  will  attract  all  the  other  Cladocera  in 
the  vessel  with  it.  Newly  hatched  Cladocera  are  attracted  by  Hght 
which  will  repel  older  forms.     On  a  bright,  calm  day  a  few  inches 


THE   WATER   FLEAS  (CLADOCERA)  683 

of  water  at  the  surface  of  a  lake  may  be  deserted  by  the  Clado- 
cera.  A  Httle  deeper  may  be  found  young  forms,  and  still  dcciK-r, 
perhaps  one  or  two  meters  below  the  surface,  the  aduh  animals. 
The  temperature  of  the  water  also  has  much  influence  on  the  reac- 
tion to  hght.  In  cold  water  Cladocera  are  attrac  ted  by  a  light 
which  will  repel  them  at  higher  temperatures.  The  linmetic  forms 
oi  Daphnia  pulex  ordinsinly  remain  durin<r  the  daytime  in  the  cool 
water  immediately  beneath  the  thermocline.  though  they  may  rise 
into  the  warm  water  during  the  night.  In  the  winter,  when  the  lake 
is  skimmed  with  ice,  the  same  animals  may  be  seen  in  the  bright 
sunshine  immediately  below  the  ice.  Practically  ail  of  the  (Madocera 
react  negatively  to  the  blue  rays  of  the  spectrum,  are  nearly  un- 
influenced by  the  rays  at  the  red  end,  and  iind  the  yellow  ra}s  the 
most  attractive. 

The  ocellus  is  rarely  absent  (Diaphanosoma.  Daplnda  rctrocuna, 
longiremis) ;  sometimes  rudimentary  (many  forms  of  D<iplmia)\ 
sometimes  larger  than  the  eye  {Leydigia,  Dadaya);  and  rarely  the 
sole  organ  sensitive  to  Hght  {Monospilus).  It  is  not  known  in  what 
respects  its  function  differs  from  that  of  the  e)'e. 

This  imperfect  sketch  shows  how  complex  the  structure  of  the 
Cladocera  is, — wonderfully  complex,  when  their  small  size  is  con- 
sidered. The  smallest  of  them  are  hardly  more  than  one  one- 
hundredth  of  an  inch  in  length.  Yet  these  have  ten  complicattxl 
legs,  besides  the  numerous  other  structures  named  and  many  which 
have  not  been  mentioned.  Probably  no  other  animals  of  so  small 
size  have  so  complex  a  structure,  yet  they  must  sulTer  the  disgrace 
of  being  eaten  by  Stentor  and  so  being  among  the  few  Metazoa 
which  are  swallowed  whole  by  one-celled  animals. 

The  reproduction  of  the  Cladocera  is  noteworthy.  During  the 
open  season  the  females  produce  eggs  which  develoj)  without  being 
fertihzed.  These  may  number  only  two,  the  usual  number  in  the 
Chydoridae,  or,  in  the  larger  Daphnidae,  there  may  be  more  than 
twenty.  These  eggs  are  deposited  in  the  cavity  bounded  by  the 
dorsal  part  of  the  valves  and  the  upper  side  of  the  body  -  the 
brood  case.  Here  they  develop  and  hatch  in  a  form  quite  like 
that  of  the  parent  and  are  well  grown  before  they  are  set  free. 
Hence  there  are  no  free-living  larval  forms  of  Cladocera.  such  as 


684  FRFSH-WATER    BIOLOGY 

are  so  abundant  in  the  Copepoda.  The  young  are  nourished  in  the 
brood-cavity,  not  only  by  the  yolk  of  the  egg,  but  also  by  a  secretion 
from  the  dorsal  wall  of  the  sac.  The  brood  case  may  be  closed 
behind  by  extensions  of  the  body  — ^the  abdominal  processes  — 
which  have  some  systematic  importance.  This  parthenogenesis 
goes  on  regularly  through  the  favorable  season  for  growth,  closing 
when  the  pools  begin  to  dry  or  other  unfavorable  conditions  arise. 
Several  successive  broods  of  females  are  ordinarily  produced  in  this 
way,  although  in  Moina,  which  lives  in  temporary  pools,  the  second 
generation  may  be  sexual.  Sooner  or  later  true  females  and  males 
are  hatched  from  the  eggs.  These  females  produce  one  or  two  eggs, 
large  and  opaque,  with  abundant  yolk  and  thick  shell,  and  which 
must  be  fertilized  by  the  male  before  developing.  These  eggs  pass 
into  the  brood  sac,  whose  walls  have  usually  acquired  a  peculiar 
structure.  In  the  Chydorinae  (Fig.  1159)  they  are  merely  thick- 
ened and  darkened.  In  the  Daphnidae  (Figs.  1073,  io79>  i093)> 
a  semi-elliptical  portion  of  the  dorsal  region  of  each  valve  becomes 
greatly  altered  to  form  the  ephippium,  so  called  from  its  resem- 
blance to  a  saddle.  In  the  Chydorinae  the  sexual  egg  is  deposited 
in  the  brood  sac  and  the  whole  shell  is  then  molted ;  the  egg  remain- 
ing enclosed  in  it.  Where  the  ephippium  is  developed,  this  separates 
during  the  molt  from  the  rest  of  the  shell  and  closes  about  the  one 
or  two  eggs  deposited  in  it.  In  either  case  the  eggs  lie  over  to  the 
next  favorable  season  before  they  develop. 

This  process  of  sexual  reproduction  occurs  at  different  times  in 
various  species.  Like  the  blossoming  of  flowers,  it  cannot  always 
be  directly  correlated  with  any  definite  conditions  of  food  or  tem- 
perature. In  those  species  which  live  in  the  open  waters  of  lakes, 
sexual  reproduction  is  often  greatly  reduced  or  wholly  absent  and 
the  species  is  carried  on  from  year  to  year  by  asexual  generations. 
In  many  species  the  males  are  very  rarely  seen  and  in  none  are  they 
abundant. 

The  males  are  smaller  than  the  females  and  usually  of  similar  form. 
They  are  distinguished  by  larger  antennules;  the  post-abdomen  is 
usually  somewhat  modified  (Fig.  1144);  the  first  foot  is  frequently 
armed  with  a  stout  hook  which  serves  to  clasp  the  females.  In  Moina 
this  function  is  performed  by  the  very  large  antennules  (Fig.  1092). 


THE    WATER    FLEAS   (CLADOCERA)  685 

Little  is  known  regarding  the  length  of  life  of  the  individual 
Cladocera.  It  doubtless  varies  from  a  few  weeks  to  several  moDihs 
Limnetic  forms  probably  have  a  longer  life  than  the  littoral,  as  the 
food  supply  and  other  conditions  of  life  are  more  constant.  Individ- 
uals from  the  broods  of  Daphnia  longispina  {liyalina)  which  arc  born 
late  in  October  and  in  November  may  sur\'ive  through  the  winter 
and  produce  one  or  more  broods  of  young  in  the  spring.  The  last 
survivors  die  in  June,  weakened  by  old  age  and  attacked  by  par- 
asitic fungi.  This  is  probably  about  the  maximum  length  uf 
life. 

The  Cladocera  are  found  in  all  sorts  of  fresh  waters.  Lakes  and 
ponds  contain  a  much  larger  number  of  forms  than  do  rivers.. 
The  shallow,  weedy  backwaters  of  a  lake  whose  level  is  fairly 
permanent  harbor  a  greater  variety  of  species  than  does  any  other 
kind  of  locality.  Here  are  found  almost  all  of  the  Chydoridae  and 
Macrothricidae,  as  well  as  most  of  the  representatives  of  the  other 
families.  In  such  localities  are  found  the  best  conditions  for  the 
life  of  these  animals:  warmth,  shelter  from  enemies,  and  abundant 
food.  It  must  not  be  supposed,  however,  that  each  square  rod  of 
such  waters  harbors  a  like  population.  On  the  contrar}-.  anyone 
who  collects  frequently  in  one  lake  will  come  to  know  certain  places 
as  especially  favorable  to  these  creatures,  which  are  }> resent  iri^ 
greater  number  and  variety  than  in  places  apparentl\-  (juite  simi- 
lar and  closely  adjacent.  While  by  far  the  greater  number  of 
species  belong  to  the  littoral  region,  living  among  the  weeds  and 
feeding  on  algae  and  similar  organisms,  a  few  species  live  near  the 
bottom.  Several  species  are  commonly  found  in  or  near  the  mud, 
although  not  specially  adapted  to  a  life  in  the  mud;  such  are 
Alona  quadrangularis  and  Drepanothrix.  The  genera  Ilyocryptus  and 
Monospilus  live  regularly  on  the  bottom;  their  structure  is  adjusted 
to  a  life  in  the  mud  and  their  shells  are  often  overgrown  by  algae. 
These  forms  may  and  do  swim,  but  more  often  scramble  about  on 
the  bottom,  pulling  with  their  antennae  and  pushing  with  the  post- 
abdomen.  In  both  forms  the  old  shell  is  not  cast  oil  in  molting, 
the  new  and  larger  shell  appearing  beneath  it  (Figs.  1 1 10.  nf)S). 

The  species  of  Moma  are  found  most  commonly  in  mudd\-  pools, 
such  as  those  in  brick-yards,  though  not  conlined  to  such  waters. 


'\ 


686  FRESH-WATER  BIOLOGY 

With  them  are  frequently  associated  members  of  the  Daphnia 
pulex  group.  These  last  are  also  found  in  temporary  pools  of  clear 
and  weedy  water,  and,  less  frequently,  in  lakes.  Daphnia  magna 
in  Europe  is  found  in  waters  which  are  slightly  brackish  and  very 
possibly  does  not  disdain  slightly  alkaline  waters  in  this  country. 

The  limnetic  region  of  the  inland  lakes  has  a  cladoceran  popula- 
tion, large  in  number  of  individuals  but  not  rich  in  species.  Chy- 
dorus  sphaericus  is  almost  the  only  Chydorid  which  is  ever  abun- 
dant here,  though  any  species  may  be  present  as  an  accidental 
visitor.  The  regularly  limnetic  species  belong  chiefly  to  the  genera 
Bosmina,  Diaphanosoma,  Daphnia,  and  Holopedium.  These  forms 
are  transparent  —  an  obviously  protective  character.  Chydorus 
is  an  exception  and  the  size  of  this  species  is  so  small  that  trans- 
parency mxay  be  unnecessary.  Apart  from  transparency  and  a 
general  lightness  of  build,  the  limnetic  forms  have  generally  no 
peculiar  characters.  Holopedium  forms  a  marked  exception  to 
this  statement,  as  its  globular  gelatinous  case  is  wholly  unique  in 
the  group  and  indeed  in  the  Crustacea. 

Certain  forms  are  intermediate  in  character  between  the  limnetic 
and  the  Httoral  forms.  Such  is  Ophryoxus  gracilis  (Fig.  iioo), 
which  paddles  about  in  the  open  waters  between  weeds,  and  such 
also  is  Sida  crystallina  (Fig.  105 1).  Both  of  these  forms  are  trans- 
parent, but  they  are  never  present  in  large  numbers  in  the  open 
water,  nor  are  they  likely  to  be  found  far  out  from  the  weedy 
margin. 

In  southern  waters,  where  are  found  masses  of  floating  plants 
such  as  the  water  hyacinth,  the  distinction  between  the  littora 
and  Umnetic  species  quite  disappears. 

The  Gymnomera  differ  widely  in  structure  and  habits  from  the 
Calyptomera.  The  section  includes  two  species  in  our  fresh 
waters:  Polyphemus  pediculus  (Fig.  1169),  and  Leptodora  kindtii 
(Fig.  1 1 70).  In  both  forms  the  shell  is  reduced  to  an  egg  case  and 
the  feet  are  free,  jointed,  and  provided  with  stout  spines  and  hairs. 
In  Leptodora  the  body  is  long  and  jointed,  while  in  Polyphemus  it 
is  very  short.  Both  animals  are  predacious,  feeding  on  protozoa, 
rotifers,  and  minute  Crustacea.  Polyphemus  lives  chiefly  in  marshes 
and  in  the  weedy  margins  of  ponds  and  lakes,  but  may  also  be 


THE  WATER   FLEAS  (CLADOCERA)  687 

found  in  the  limnetic  region  and  in  Ihc  Orcat  Lakes.  Uptodora 
is  always  limnetic  in  its  habits.  It  is  ahnost  perfectly  transi)arcnt; 
the  dark  eye  and  yellow  stomach  alone  bein<r  visible  when  the  animal 
is  viewed  by  transmitted  light.  It  is  by  far  the  lar^'cst  of  the 
Cladocera,  reaching  a  length  of  18  mm.  Its  winter  eggs  hatch  as 
nauplii  and  this  is  the  only  species  of  Cladoccra  in  which  thi-> 
characteristic  crustacean  larva  appears. 

The  Cladocera  have  great  economic  value.  Together  \sith  the 
Copepoda  they  constitute  the  chief  agency  for  converting  the 
smaller  algae  of  fresh  water  into  a  form  edible  by  the  carnivorous 
aquatic  animals.  They  are  the  prey  of  insect  larvae,  which  are  in 
turn  an  important  item  in  the  bill  of  fare  of  the  larger  fishes.  Clado- 
cera are  themselves  of  great  value  as  food  for  young  fishes  and  there 
is  a  period  in  the  life  of  almost  every  fish  when  it  feeds  exclusively 
on  Entomostraca.  Even  the  larger  fishes  do  not  disdain  these 
animals.  The  great  spoonbill  {Polyodon)  fills  its  stomach  with 
Bosminae,  or  other  tiny  inhabitants  of  the  water  from  which  it 
strains  its  food. 

The  geographical  distribution  of  Cladocera  ofTcrs  little  of  interest 
that  can  be  stated  in  a  brief  sketch,  chiefly  because  the  species  are 
so  widely  distributed.  Some  species,  like  Chydorus  sphacricus,  are 
cosmopolitan.  A  majority  of  the  species  found  in  this  country  are 
found  also  in  Europe.  Where  a  species  is  peculiar  to  this  region 
it  is  often  but  slightly  different  from  the  European  form.  The 
student  of  Cladocera  should  presume  that  any  species  is  probably 
intercontinental,  though  it  may  prove  to  be  more  restricted  in  its 
range.  The  study  of  our  forms  has  not  gone  far  enough  to  enable 
us  to  speak  of  the  local  distribution  of  each  species  within  the 
general  area  which  it  covers,  but  it  is  known  that  the  rare  s|x?cit^ 
are  very  irregularly  distributed.  On  the  whole,  the  fauna  of  the 
various  regions  of  the  country  is  strikingly  similar.  Init  with  some 
forms  peculiar  to  each  region.  The  southern  states  contain  numer- 
ous species  which  are  common  to  them  and  to  South  America. 
but  are  not  found  in  the  northern  states. 

The  student  of  Cladocera  will  fmd  the  cone  net  (p.  68)  the  l>est 
agent  for  collecting  the  Httoral  forms.  The  catc  h  should  be  put 
into  a  cup,  which  should  be  filled  with  water,  and  the  debris  allowed 


688  FRESH-WATER   BIOLOGY 

to  settle  before  pouring  off  the  water  and  the  Crustacea  through  the 
funnel.  As  little  as  possible  of  the  weed  and  debris  should  be  in- 
cluded in  the  catch,  since  it  is  a  wearisome  task  to  search  for  the 
various  species  in  a  catch  which  contains  great  masses  of  weed  with 
but  few  Crustacea.  It  is  well  to  retain  a  part  of  the  weed  in  a 
separate  bottle,  so  that  species  which  go  to  the  bottom  may  not 
be  overlooked.  It  is  also  well  to  cover  the  cup  with  one's  hat,  or 
otherwise,  while  the  debris  is  settling  so  that  species  which  fly  from 
the  light  may  not  go  into  the  weed  at  the  bottom.  Numerous  hauls 
of  the  net  should  be  made  and  concentrated  so  as  to  give  abundant 
material.  Considerable  experience  with  collections  sent  me  by 
students  of  Cladocera  has  shown  me  that  the  chief  faults  of  the 
collector  are  including  too  much  debris  in  the[^catch  and  taking 
too  few  hauls  of  the  dredge. 

The  best  preservative  I  have  found  to  be  strong,  95  per  cent, 
alcohol.  This  keeps  the  shape  of  the  species  as  well  as  or  better 
than  anything  else.  Certain  soft-bodied  forms  with  strong  muscles 
may  be  distorted  by  any  fluid  which  kills  and  hardens  quickly. 
Such  are  Pseudosida,  Latona,  and  Latonopsis,  and,  to  a  less  degree, 
Moina  and  Diaphanosoma.  For  these  also  we  have  nothing  better 
for  field  use  than  alcohol.  If  their  forms  are  to  be  well  preserved 
they  should  be  killed  individually  by  some  poison  like  osmic  acid, 
or  chloral  hydrate,  and  then  hardened  gradually,  according  to  regu- 
lar microscopic  methods.     Formalin  distorts  many  species. 

I  have  found  no  better  mounting  fluid  than  pure  glycerine.  I 
place  the  animal  with  a  small  drop  of  glycerine  in  the  center  of  the 
slide  and  support  the  cover  glass  by  three  bits  of  paper  thick  enough 
to  permit  the  cover  to  press  slightly  on  the  specimen.  The  cover 
glass  is  put  on  carefully  so  that  the  glycerine  occupies  its  center 
only.  A  bit  of  soft  paraffin  (melting  point  about  50°  C.)  is  placed  at 
the  edge  of  the  cover  glass,  and,  on  warming  the  sHde,  the  paraf- 
fin melts  and  runs  in,  sealing  the  mount.  The  cover  may  after- 
wards be  cemented  down  by  any  microscopic  cement,  and  this 
should  be  done  if  the  preparation  is  to  be  kept;  but  for  purposes 
of  study  it  is  well  not  to  do  so,  since  an  advantage  of  the  method  is 
the  ease  with  which  the  specimen  can  be  unmounted  for  study  or 
dissection. 


THE  WATER   FLEAS   (CLADOCERA)  68q 

KEY  TO  NORTH  AMERICAN  FRESH-WA  ri-R   CLADOCERA 

1  (248)     Body  and  feet  covered  by  a  bivalve  shell.     Feel  in  Kencral  f.iiiaccou^ 

not  plainly  jointed.     .    .    .      Section  A.  Calyptomera 

2  (21)     Six  pairs  of  feet,  all  similar,  except  the  last,  and  all  foliaccous. 

Tribe  L  Ctenopoda 

3  (18)     Shell  of  ordinary  type.     Antenna  biramous  in  female,  rami  llaiim..,, 

the  dorsal  with  numerous  setae,  both  lateral  and  terminal. 

Family  Sididak  Baird  4 

Head  large;  cervical  sinus  present.     Antennules  large,  movable,     .\nlcnn.ic  with  terminal 
setae  only  on  ventral  ramus.     Eye  large,  with  numerous  lenses;  ocellus  small  or  a?       ■       '   •    .. 
tine  simple,  usually  with  more  or  less  distinct  median  cecum  or  cnlargt-mcnt  at 
rarely  with  2  hepatic   ceca.      Heart   elongated.     Male  usually  with  charactcri-!  ' 

the  flagellum  united  with  the  base  into  one  structure,  long,  taix-ring.  with  a  row  of  hue  ^pmulcs 
toward  apex;   usually  with  grasping  organ  on  first  foot  and  copulatory  organs  on  ixfet -abdomen. 

4  (5)     Dorsal  ramus  of  antenna  3-jointed,  rostrum  present. 

Sida  Straus  1820. 

Head  with  large  gland  on  dorsal  side;  pointed  rostrum;  no  fomices.  .\ntennulcs  of  9 
attached  to  side  of  rostrum,  short,  truncate,  with  short  llagellum.  Ventral  ramus  of  antennae 
2-jointed.     Antennules  of  $  very  long;   no  copulatory  organ;   first  fcxjt  with  hook. 

Only  one  American  species.    .    .    Sida  crystallina  {0.  V. 'SiiiUcr)  i-j^s. 


■y^' 
^f^- 


A        **^^^*tit^<ii£ii:j 


I  MM.    I ' 

Fig.  105 1.     Sida  crystallina.     (Unless  otherwise  indicated  all  figures  were  dniwn  i-sjiccLUl)  for  this 

chapter.) 
Color  yellowish-hyaline,   sometimes  with  brilliant  blue  SF>ots.     Ungth.    9.  3.0-4.0  mm 
$ ,  1.5-2.0  mm. 
Common  in  lakes  and  ponds  among  weeds. 


5  (4)     Dorsal  ramus  of  antenna  2-jointed. 


6  (9)     With  lateral  expansion  on  basal  joint  of  dorsad  ramus  of  antenna. 

Liitofhi  Straus  1S20  .    .     7 

Large,  tongue-shaped  projection  on  ventral  side  of  head,  't^ventral  surface  coi^ca^.  Vcnilral 
ramus  of  antennae  3-Jointed.  Long  setae  on  posterior  marpn  of  valves.  h>c  dorsal,  far  Irum 
optic  ganglion.      $  with  copulatory  organ;  no  hook  on  lirbt  toot. 


690 


FRESH-WATER  BIOLOGY 


7  (8)     Antennary  expansion  very  large;  no  hepatic  ceca. 

Latona  setifera  (O.  F.  Miiller)  1785. 

Antennules  of  both  sexes  alike,  bent,  with  large,  hairy  flagellum  set  on  at  angle,  looking  like 

continuation  of  base.     Color  yellow;    not  transparent;    old    9   often  with  briUiant  colors  in 

late  autumn.    Length,  9  ,  2.0-3.0  mm. ;  ^  ,  ca.  i  .5  mm.    Widely  distributed,  but  never  abundant, 

among  weeds  in  ponds  and  lakes. 


'//nm- 


MM.    I. 


Fig.  1052.     Latona  setifera. 

8  (7)     Antennary  expansion  small;  hepatic  ceca  present. 

Latona  parviremis  Birge  1910. 

Antennule  of  9  with  basal  part  and  long  slender  flagellum,  like  Latonopsis;  of  ^  very  long, 
like  other  Sididae.  Color  yellow.  Length,  9'  to  2.5  mm.;  $  ,  0.8  mm.  Northern  Wisconsin, 
Michigan,  Maine;  in  weedy  waters  of  lake  . 


Fig.  1053.    Latona  parviremis. 

9  (6)     Without  lateral  expansion  of  antenna.    .    . 


10 


10(13)     No  spines  on  post-abdomen.   .     Diaphanosoma  Yi'^chei  i^s^  .    .     11 
No  rostrum,  fornix,  or  ocellus.     Antennule  small,  truncated;   olfactory  setae  terminal,  with 
slender  flagellimi.    Dorsal  ramus  of  antennae  2-jointed;  ventral  3-jointed.      Claws  with  3  basal 
spines.     $  with  long  antennule;  copulatory  organ;  hook  on  first  ''oot. 


THE   WATER    FLEAS   (CLADOCKRA) 


691 


II  (12)     Reflexed  antenna  not  reaching  posterior  margin  of  valves. 

„,„„,,:.  Diaplianosoma  brachyurum  (Lieven)  1848. 


Eye  pigment  large;  eye  filliuK  end  of  head.  Color  yd- 
lowish-transparent.  Length.  V  .  oS-o.g  mm.;  ^.ca.  04 
mm.  Common  in  marshes  ami  wec<ly  margins  of  Ukr^ 
Very  probably  the  next  s|K'cics  is  merely  a  limnetic  van 

ety  of  this. 


Fig.  1054.     Diaphanosoma  bra(hyurum. 


O.I  MM.    i 


12  (11)     Antenna  when  reflexed  reaches  or  exceeds  posterior  margin  of  valves. 

Diaphanosoma  Icuchtcnbcrgianum  I-'i.scher 

1850. 


J^-^ 


^  (f^m^^^- 


Eye  not  filling  end  of  head,  pigment  small. 
Color  hyaline.  Length.  V  ,  o.<>-i.i  mm.;  ^  .  to 
0.8  mm.     Common  in  open  waters  of  lakes 


Fig.  1055.     Diaphanosoma  Uucklrnbergu 


13  (10)    Spines  on  post-abdomen U 

14  (17)     Eye  dorsal,  far  from  insertion  of  antennule  and  optic  ganglion.     No 

rostrum Latonopsis  Sars  i^^i^   .    .      15 

No  tongue-shaped  process  on  ventral  side  of  head,  or  antennary  expansion.  Otherwise  much 
like  Latona  parviremis.  Posterior  margin  of  valves  with  ver>-  long  setae  (often  lost).  6  with 
long  antennule,  copulatory  organ,  and  hook  on  first  foot. 

15  (16)     Shell  gland  drawn  out  into  very  long  posterior  loop. 

Latonopsis  occidental  is  Hirge  kSqi. 

Post-abdomen  with  about  9  small  anal  spines.  Color  yellowirJi-trans- 
parent.  Length,  ? ,  to  i  .8  mm. ;  ^  ,  ca.  o.O  mm.  New  Lngbnd  lo  Colorado 
and  Texas;  in  weedy  pools  and  lakes. 


^^^^^.IbK^ ,  yV^ 


O^  MM 


^  1 '  \V '  ,    Figs  1056, 1057 .  h.   LaUmopns pctidtntHu 
\  /  ,  (Sec  alio  Fig  1057  J 

i 


692 


FRESH-WATER    BIOLOGY 


16  (15)     Shell  gland  of  ordinary  form.   .     .  Latonopsis  fasciculata  Daday  1905. 
Post-abdomen  with  projections  on  dorsal  (posterior)  margin  and  12-14  clusters  of  2-3  lancet- 
shaped  anal  spines.     Color  yellowish.     Length,   9-  to  2.0  mm.;     ^ ,  to  i.o  mm.     Louisiana, 
Texas;   in  weedy  pools  and  lakes. 


W 


I 


Fig.  1057.  a,  Latonopsis  fasciculata; 
b,  Latonopsis  occidentalis. 


Fig.  1058.    a,  Latonopsis  fasciculata;  b,  Pseudosida  bidentata. 


17  (14)     Eye  ventral  or  in  middle  of  head.     Rostrum  present. 

Pseudosida  Herri ck  1884. 
Only  one  American  species.     .    .     Pseudosida  bidentata  Herrick  1884. 

General  form  like  Sida  but  head  more  depressed  and  dorsum  more  arched.  Rostrum  present; 
no  fornix  or  cervical  glands.  Antennules  attached  as  in  Sida,  long  basal  part  with  olfactory 
setae  on  side,  and  long  flexible  fiagellum.  Dorsal  ramus  of  antennae  with  2,  ventral  with  3, 
joints;  setae  very  unequal  in  length.  Post-abdomen  with  about  14  clusters  of  spinules;  claws 
with  2  large 'basal  spines  and  a  very  small  spine  proximal  to  them. 

$  with  antennule  of  standard  form;  copulatory  organs.  Complex  grasping  apparatus  on 
first  foot. 

Color  yellowish,  semi-transparent.  Length,  9  .  to  1.8  or  2.0  mm.;  ^  ,  0.9  mm.  Southern 
states,  in  pools  and  lakes. 


0.5  MM.  I 


Figs.  1059,  1058,  b.    P.  bidentata.     (After  Foster. )     (.See  also  Fig.  1058.) 


THE   WATER    FLEAS   (CLADOCERA) 


693 


18(3)     Enclosed  in  gelatinous  mantle.     Antcnn; 
with  3  terminal  setae.    .    . 


simple  in  fi-malc,  cylimlrical, 
lamily  HoU)1'kuu>ak  Sars. 


fvl 


Animal  enclosed  in  a  large,  globular,  transparent,  (k-licatc  hut  U>uk\\.  Kfblinou>  lav   oum 
ventrally  and  forming  2  valves.     Body  much  compressed,  shell  of  lu-ati  and  lx..i\  s.  , ,  i'  I,, 
high,  as  seen  from  side,  leaving  uncovered  the  mouth  parts,  the  ends  of  the  I.    • 
part  of  body.     Antennule  small,  fixed;    with  5-0  olfactory  seta.-  and  lateral  s- 
flagellum.     Antennae  in  9  long;    basal  joint  curved,  annulated;  the  single  tatuvi.',  j  i.,,., 
antennae  of  $  biramous.    Post-abdomen  large, 
fleshy,   not  bent  forward;   with  rather  long, 
curved  anal  spines  and  clusters  of  very  fine 
spinules;  abdominal  setae  long,  set  on  single, 
long,  conical  projection.     Claws  large,  curved, 
denticulate,  not  set  ofT  from  body  by  distinct 
joint.  Eye  small,  with  numerous  len.ses;  ocellus 
small.     Intestine  simple  with  2  hepatic  ceca. 
Branchial  sac  on  second  to  fifth  feet.     Color 
transparent.     Swims  on  its  back. 


Sole  genus  with  characters  of  family. 
Holopedimn  Z3.dd3.ch.  iSss   ■       19 


19  (20)     Ventral   margins   of   valves 
with  fine  spines. 
Holopedium  gibberum  Zaddach  1855. 


Post-abdomen  elongated  (ca.  one-third 
length  of  body)  and  tapering;  anal  spines 
numerous,  up  to  20.  Claws  with  i 
basal  spine.  Length,  9.  1-5-2.2  mm.; 
$ ,  0.5-0.6  mm. 

This  remarkable  and  beautiful  species 
is  not  uncommon  in  open  water  in 
northern  lakes;  has  been  found  in  the 
Great  Lakes,  and  in  many  inland  waters, 
both  lakes  and  smaller  bodies  of  water. 

Figs.  1060,  1061,  a.  Holopedium  gibberum 
(gelatinous  case  not  shown).  (See  also 
Fig.  1061.) 


0.5  MM 


20  (19)     Ventral  margin  of  valves  smooth. 

Holopedium  anuizoniium  Stinpi-Im  looj- 


Post-ahdomcQ  sh«>rt.  I)lunt  («.a 
one-fourth  of  IkkIv  in  It-nKthl,  i»ilh 
7-S  anal  spines,  the  row  continued 
forward  by  .%  4  verv  •-'"  ■ 
Claws  without  has.1I 
inal  setae  ver>'  loni;  a 
unknown.  Ix-ngth.  V  '  >- 
Charles,  L»»uiMana. 


Fio.  ic/ii.    a  UMptJimm 
b    IlolofuJium  aHMiomU 


>ulr*. 

i 
i-ike 


694 


FRESH-WATER   BIOLOGY 


21  (2)     Five  or  six  pairs  of  feet.     First  and  second  pairs  more  or  less  prehen- 
sile, others  foliaceous.   .    .    .    Tribe  IT  Anomopoda   .    .      22 

Antennules  attached  to  ventral  side  of  head,  not  covered  by  for- 
nices 23 


22  (117) 

23  (76,  83) 


Antennules  of  female  usually  small,  sometimes  rudimentary;  if 
large,  never  inserted  at  anterior  end  of  ventral  surface  of 
head.  Dorsal  ramus  of  antenna  4-jointed,  ventral  ramus 
3-jointed.     Intestine  simple  with  2  hepatic  ceca. 

Family  Daphnidae  Straus   .    .     24 

Five  pairs  of  feet,  the  first  two  prehensile  and  without  branchial  lamella;  the  fifth  with  large 

recurved  seta,  extending  around  branchial  sac.     Antennules  in  general  small  or  rudimentary, 

and  when  large  not  at  the  anterior  extremity  of  the  head.     Antennae  long,  not  strong,  cyUndrical, 

setae  °~^^~^ .     Post-abdomen  distinctly  set  off  from  body,  usually  more  or  less  compressed, 

always  with  anal  spines.  Abdominal  setae  not  borne  on  distinct  projection  or  papilla.  Claws 
sometimes  pectinate;  always  denticulate,  unless  worn  by  use;  never  with  basal  spine.  Intes- 
tine not  convoluted,  with  2  hepatic  ceca.  Eye  large;  ocellus  usually  small,  sometimes  want- 
ing. Summer  eggs  ordinarily  numerous;  typical  ephippium  formed,  containing  i  or  2  eggs. 
$  usually  with  hook  on  first  foot. 

24  (48)     Rostrum  present 25 

25  (39)     No  cervical  sinus.    Valves  with  polygonal,  usually  rhomboidal,  mark- 

ing, and  with  a  posterior  spine.  Crest  on  dorsal  side  of  head. 
Daphnia  O.  F.  Miiller  1785   .    .     26 

Form  oval  or  elliptical,  except  as  modified  by  crest  of  head  (helmet)  in  some  species.  Body 
always  compressed,  often  greatly  so.  Valves  reticulated;  dorsal  and  ventral  margins  roundmg 
over  toward  each  other  and  provided  with  spinules  along  posterior  part.  Rostrum  well-marked 
in  9  and  pointed.  Antennules  small  or  rudimentary,  not  movable,  placed  behind  rostrum. 
Abdominal  processes  3-4,  all  ordinarily  developed;  the  anterior  especially  long,  tongue-shaped 
and  bent  forward.     Ephippium  with  2  eggs.     Summer  eggs  often  very  numerous. 

Head  of  $  without  rostrum;  antennules  large,  movable,  ordinarily  with  long,  stout,  anterior 
seta  or  flagellum;  first  foot  with  hook  and  long  flagellum. 


26  (34) 

27  (30) 

28  (29) 


Claws  with  pecten 27 

Heavy,  thick-bodied  forms.     Fornix  and  secondary  fornix  (Fig.  1063) 
well  developed.    Distal  pecten  with  more  than  1 2  teeth.    .    28 

Antennules   large   for   genus;     post-abdomen   with   deeply   sinuate 
\  margin Daphnia  magna  Straus  1820. 


Form  rounded  or  oval,  body  thick  and  heavy,  not  transparent. 
Post-abdomen  long,  with  deep  indentation  behind  anus,  breaking 
through  row  of  anal  spines.  These  are  about  1 2  in  proximal  and 
8-10  in  distal  set.  Claws  with  two  pectens  of  numerous  teeth. 
Ephippium  characteristic;  dorsal  margin  of  valves  separates  with 
it  both  behind  and  before;  2  eggs,  placed  obliquely.  Summer 
eggs  numerous.  Length,  9  ,  ^0  5.0  mm.;  $  ,  2.0  mm.  or  more.  The 
largest  of  the  family.  Maine,  Colorado,  Nebraska,  N.  Dakota, 
California. 


Fig.  1062.    Daphnia  magna,  post-abdomen. 


THE  WATER   FLEAS   (CLADOCERA) 


6<>> 


29  (28)     Rostrum   and   antcnnules   pulcx-Ukc;      p.^st-abdomen   tapered     not 
^^^^^^^ Ddpliniu  psitUirea  iH:iird)\hso. 


General  form  hke  D.  macui  hut  smaller  an.l  more  tmn*. 
parent.  1  ost-alxlonun  taiK-riiiK.  not  sinuate,  with  aU.ut  10 
anal  teeth  anc  many  Justtrs  <.f  sh..rt.  line  hair>.  Claws  »,ih 
two  pectens  the  <iistal  having  ahout  15  teeth.  Unicth.  9  to 
2.8  mm.  besides  spme  of  0.8  mm.;  ^  ,  to  1.8  mm.  NcbraJt*. 
m  pools.  ^^ 


Fig.  1063.     Daphnia  psittacca.  note  small  <*ci.i,.i... ,  ,.,i,u» 
lx;hin(l  |jrimary. 


0.5  MM 


30  (27)     Secondary  fornix  rudimentary  or  very  small.      Tcx-th  (.f  distal  (k-,  t.n 

rarely  exceeding  10,  usually  fewer : 

31  (32,  33)     Ocellus  present;   head  not  hclmeted. 

Daplinia  pulcx  (de  Gecr)  1778. 


I  MM.    1 


B<Kly   stout  and 

•  vn;    r.-ually  not 
.::    ;■..:...!         An- 
i.:.;.it  -  \in.-  small. 
the  apc.x  apiK.arinK  a.s  lupiliar  «»n  |k»- 
terior  surface   of   rostrum      iVist  ab- 
domen without  sinus;   anus  at  end; 
anal    spines     iJ-17.     Summer    ejacs 
numerous;   ephippium  with  two  cfocs 
plattd  nearly  vertically 

Color  red  to  yellow-brown,  vcr>'  variable. 
Length,  9.  to  2.5  mm.  In  pt>ols  and  bkcs  in 
all  regions;   numerous  varieties. 

Fig.  1064.    Daphnia  puUx. 

D.  pulex  includes  a  preat  number  of 
varieties,  many  of  which  havr  l>em  de- 
scribed as  distinct  sjx-iies  I'  '■  nl 
will  be  safe  in  assijcnins  to  / :.  .c. 
heavy-bodied  forms  with  I-  as. 
In  many  cases  the  identitn.ainjn  oi  the 
variety  is  more  imix)rtant  than  that  of  the 
species,  but  the  varieties  have  n«>t  l>ccn 
worked  out  for  this  country.  A  few  may 
be  noted: 


Figs. 1065.1066. 


Daphnia  puUx.  post-abdoiDCO 

ami  claw. 


Var.  pulicaria  Forbes.  A  semi-trans- 
parent limnetic  form.  vcr>-  close  to  pmUx^ 
but    more    sli>;htly    built.     Lon>:    Hiinc. 

Common  in  lakes. 

V'ar.  dathratii  Forbes.  Only  i;  anal 
spines.  IVcten  with  j-4  larpe  tcrlh. 
Yellowstone. 

\ar.  mitttirhaha   derrick      "^'"^  '     '    ■'- 
over  heart  in  adult  9  ^  '^'f' 
and  younK'-     Minnes.t.T  nv. 
Var.  ohtusii  Kurz 
absent.     9-10  anal  spines.     Rostrum  long  and  pointed.     Mainr.  W  im-mm 

Var.  curvirostris  Eylmann.     Rostrum  very   long  and 
valves.     Nebraska,  California. 


ontinutd   l).uk\\ 


696  FRESH-WATER   BIOLOGY 

32(31,33)     Ocellus  present;  head  helmeted.    .     Daphnia  arcuata  Forbes  iSg 3. 


Very  transparent.  Vertex  rounded,  rostrum  extending^  back- 
ward and  applied  to  margin  of  valves.  Slender  spine  projecting 
from  middle  of  valves.  Anal  spines  about  10-12;  claws  with 
distal  pecten  of  some  6  teeth.  Length  of  9  to  2  mm.,  besides 
spine  of  about  0.5  mm.  Wyoming,  Wisconsin;  in  open  waters  of 
lakes. 

This  species  forms  a  transition  to  the  retrocurva  forms. 


0.1  MM.    t— - 

33  (31,  32)     Ocellus  absent; 


Fig.  1067.     Daphnia  arcuala. 

head  helmeted.  .  Daphnia  retrocurva  Forbes  1SS2. 

Body  much  compressed,  pellucid.  Eye  small,  with 
numerous  projecting  lenses  and  Uttle  pigment;  no  ocellus. 
Spine  ordinarily  above  middle  of  valves,  directed  upward. 
Crest  very  variable,  often  enormous.  Claws  with  two 
pectens,  the  distal  of  7-9  teeth.  Anal  spines  7-12.  Sum- 
mer eggs  ordinarily  2;  sometimes  as  many  as  6.  Length, 
9,  to  2.0  mm.,  besides  spine,  which  may  reach  0.5  mm. 

Widely  distributed 
in  limnetic  region  of 
lakes.   Shape  of  head 
extremely     variable; 
all   forms  from  var. 
breiiceps        B  i  r g  e  , 
where    the    crest    is 
hardly  visible,  to  the 
exLieme  of  extension  shown  by  retro- 
curia   proper.     This  species  replaces 
in  the  United  States  the  European  D. 
cucullata,  which  is  related  to  D.  longi- 
spina,  much  as  this  form  is  to  D.  pulex. 
D.  retrocurva  never  has  the  extremely 
acuminate  form  of  head  whichcucullata 
sometimes  shows. 
Very  probably  study  will  show  that  all  the  pulex  forms  (31,  32,  33)  must  be  united  into  one 
polymorphic  species. 

34  (26)     Claws  without  pecten 35 

35  (38)     Ocellus  present,  though  small. 

Daphnia  longispina  (O.  F.  Miiller)  1785  .  .  36 
Spine  long;  claws  without  pecten.  Male  without  long  papilla  on  posterior  part  of  body. 
This  species  is  so  variable  that  almost  no  characters  can  be  given  for  it.  It  is  less  robust  than 
the  pulex  forms,  ordinarily  fairly  transparent;  often  hyaline.  This  part  of  the  species  divides 
at  once  into  2  sections  or  subspecies,  each  with  numerous  varieties  which  have  never  been 
thoroughly  studied  in  the  United  States. 


t).5  MM 


Fig.  1068.    Daphnia  retrocurva. 


f>^ 


Fig.  1069.     Daphnia  longispina.     (See  also  Fig.  1050,  p.  677.) 


THE  WATER   FLEAS  (CLADOCERA) 


36  (37)     Head  not  helmeted;  eye  close  to  margin.  .   Daplmii  longispina  profn-r 

There  are  numerous  varieties  of  D.  lon^ispina  pr()iH.T;  <lciR-n<linK  on  i.rot».>rtion  of  v  .1 
The  head  may  be  large  or  small,  its  ventral  marKin  struiKht,  com  ave.  or  •  onvcx      Th.-  ■ 
have  a  large  pigment  with  few  lenses  embedded  in  it,  or  it  may  be  small.r  with  nutn. 
jecting  lenses. 

Found  in  all  regions  of  the  United  States. 

37  (36)     Head  helmeted  and  eye  therefore  removed  from  margin.     lsu;illy 

more  dehcate  and  transparent  than  36. 

Daphnia  longispimi  var.  hyalina  Leydig  1H60. 
D.  longispina  var.  hyalina  varies  conspicuously  and  greatly  in  the  form  and  sizt-  of  the  irr»t 
and  of  the  ventral  and  dorsal  margins  of  the  head,  which  may  be  concave,  convex,  or  slraixhl 
with  any  form  of  crest.  The  crest  may  be  small  and  rounded  (var.  hyalina  lypica).  cxtcmlcil 
into  a  broad  semi-elliptical  form  (form  mendotac);  more  or  les.s  triangular,  with  an  acute  |Mjint 
in  front  (form  galeata);  which  may  be  extended  into  a  short  spine.  .\n  indehnitc  numljcr  ol 
other  forms  are  present,  some  of  which  have  been  studied  and  describe<l.  but  not  namc«l  by 
Entemann.  The  form  of  the  crest  in  specimens  from  any  one  lake  is  fairly  uniform  'ihouxh 
2  varieties  may  be  present),  changing  with  the  season,  being  larger  in  summer  than  in  s|>rinic. 
Adjacent  lakes  may  vary  greatly.  Deep  water  forms  usually  have  ^mailer  (rests  than  ihine 
from  the  shallow  surface  water.  All  varieties  found  in  open  water  of  lakes,  in  all  parts  ol  ihe 
coimtry. 


Figs.  1070, 107 
38  (35)     Ocellus  absent 


Daphnia  longispina  var.  hyalina.    A  and  B.  form  typica. 
D,  form  galeata. 


0.2  MM    . 

C.  furni  mcndolac. 


head  helmeted. 

Daphnia  loni^ispiiia  var.  lougircmis  Sars  1S61. 
Valves  broadly  oval;  spine  long  and  slender.  Head  small  and  rounde<I  with  crest,  .\ntcnnac 
very  long,  reaching  well  toward  posterior  margin  of  valves  when  rellexed.  Lenut  h.  9  •  t"  •  ^  '"'p- 
This  is  the  only  representative  of  the  European  cuculUita  groui)  as  yet  sc-cn  in  this  count r>-.  No 
doubt  other  forms  will  be  discovered.  Indiana;  Wisconsin,  in  deep  water  of  lakes  in  soulhcro 
part  of  state;   in  surface  waters  in  northern  part. 


Fig.  1072.    Daphnia  loniircmis. 


698 


FRESH-WATER  BIOLOGY 


39  (25)     Cervical  sinus  present.     No  crest 40 

40  (45)     Valves   transversely  striated.     Post-abdomen  broad,  with  indenta- 

tion in  which  anus  opens. 

Siniocephalus  Schoedler  1858   .    ,     41 

Body  large  and  heavy;  shell  thick.  Head  and  rostrum  small.  Valves  large,  somewhat 
quadrate,  with  rounded  angles  and  sometimes  a  posterior  spine;  marked  with  oblique  striae, 
anastomosing  irregularly  and  with  cross-connections.  Two  abdominal  processes  developed, 
placed  far  apart.  Post-abdomen  large,  broad,  truncate,  posterior  end  emarginate  and  bear- 
ing the  anal  spines.  Claws  rather  straight,  always  denticulate,  sometimes  pectinate.  Summer 
eggs  numerous;  ephippium  large,  triangular,  with  one  egg.  Antennules  of  ^  like  9  but  with 
2  lateral  sense-hairs.  First  foot  without  flagellum  and  with  small  hook.  Poor  swimmer;  swims 
often  on  its  back.     Color  yellow  to  yellow  brown. 

41  (44)     Vertex  rounded,  smooth.     No  posterior  spine  on  valves 42 

42  (43)     Ocellus  elongated.     Vertex  rounded  over.     Claws  denticulate. 

Simocephalus  vetulus  (O.  F.  Miiller)  1776. 

Ocellus  large,  elongated,  rarely  rhom- 
boidal.  No  spine  on  valves,  though 
there  may  be  a  blunt  posterior  angle. 
Post-abdomen  very  broad,  deeply 
emarginate;  anal  spines  about  ten,  de- 
creasing from  the  claws;  the  larger 
bent  and  ciliate  at  the  base.  Claws 
long,  slender,  little  curved,  denticulate 
only.  Length,  9  >  to  3.0  mm.;  ^  ,  ca. 
i.o  mm. 

Not  very  abundant,  but  found  every- 
where in  weedy  water. 


Fig.  1073 • 


0.1  MM 


Simocephalus  vetulus,  with 
ephippium. 


43  (42)     Ocellus  rhomboidal  or  round.     Vertex  with  obtuse  or  rounded  angle. 
Claws  pectinate.   .    .     Simocephalus  exspinosus  (Koch)  1841. 


Valves  much  as  in  vetulus,  but  striae  do  not 
anastomose  so  freely.  Post-abdomen  slightly 
narrower  toward  apex;  anal  spines  up  to  12, 
evenly  curved,  not  bent;  claws  with  pecten  of 
8-12  teeth  and  denticulate.  Color  and  gen- 
eral appearance  much  as  preceding  species. 
Length,  9.t03.omm.;    ^,  to  1.3  mm. 

Not  common;  reported  from  Massachu- 
setts, Wisconsin,  and  the  southern  states. 


Fig.  1074.     Simocephalus  exspinosus. 


THE   WATER   FLEAS  (CLADOCERA) 


699 


44(41)  Vertex  angulated  spinous.  Blunt,  rounded  posterior  spine  on 
valves  in  old  individuals.  Ocellus  rhomlx)idal  or  tri'inRuiar 
rarely  elongated.   .    .    Simocephulus  scrnUaius  (KiKh}  iSjii' 


Anal  spines  8-12,  the  larser  l)cnt  and  ciliatr.     (laws  wnf,  „„c 
denticles.     Color  yellow  or  brownish.     I^cnKth.  9 ,  3.8- j  o  mm 
$  ,  to  0.8  mm. 

Common  everywhere  amonp  weeds;    the  most  abundant  m>c- 
cies.     Very  variable  in  outline  of  head. 


Fig.  1075.     Simoctphalus  icrruUtuu 


0.1  MM. 


45  (40)     Valves  obscurely  reticulated  and  with  some  striar.      Posterior  an<i 

ventral  margins  straight,  the  latter  extended  into  a  \yo\i\\  or 

spine Scapholcbcris  Schocdlcr  1S58   .    .     46 

Body  not  compressed;  shape  more  or  less  quadrate.  Cervical  sinus  deep.  F'omicrs  and 
rostrum  well  developed.  Head  small,  depressed.  Valves  almost  rectan^'ular.  the  infcro- 
posteal  angle  of  each  produced  into  a  longer  or  shorter  spine;  ventral  margin  with  short,  fmc 
setae.  Claws  denticulate,  not  pectinate.  One  abdominal  projection  devclopc*!.  .\ntcnnulc« 
small,  about  alike  in  both  sexes,  borne  behind  the  rostrum.  .Summer  eggs  numerous;  one 
ephippial  egg.      $  much  like  9  J  hook  on  first  foot. 

46  (47)     Color  usually  dark,  often  nearly  black. 

Scapholeberis  mucronata  (O.  Y.  MuUer)  1785. 

Valves  arched  dorsally  in  old 
specimens;  fK)sti-rior  and  ven- 
tral margins  straight;  at  their 
junction  a  spine  often  sh«jrt, 
but  often  very  long;  in  v«r. 
armata  Merrick  as  long  as  ven- 
tral margin  of  valve,  .\nten- 
nules  very  small.  almo!it  im- 
movable, set  iK'hintI  l>eak. 
Post -abdomen  short  and  broad. 
rounded  at  i)i)sterior  end;  $-ii 
anal  teeth.  U-ngth.  9 .  0.8-1 .0 
mm.;  $  .  ca.  0.5  mm. 

The  form  with  frontal  spine 
has  never  In-cn  foun<l  in  the 
United  .*>tates.  Common  ever)'- 
where  in  pools  and  lakes  in 
weedy  water,  or  swimming  on 
Fig.  1076.    Scapholeberis  mucronata.  its  back  near  or  at  the  surface. 

47  (46)     Color  whitish  or  greenish;  transparent  or  opaque,  not  black. 

Scaphohbcris  iiuritii  (Fischer)  1840. 


Head  larger  than  in  mucrouata,  rostrum  long,  lying  ag.tinst 
margin  of  valves,  .\ntennules l)ehind  rostrum,  conical,  large,  and 
movable;  sense-hair  about  middle.  Valves  with  blunt  pn.jr.  tion 
at  infero-posteal  angle,  ob.scurely  striate  and  n-ticulate  m  (rxrtit. 
and  with  small  elevations  elsewhere.     U-ngth.   9 .  ca    1  o  mm  ; 

Not^ common;  in  weedy  ix)ols  and  margins  of  lakes.  Northern 
states. 


Fig.  1077.    ScaphoUbcris  aurito. 


0.1  MM. 


700  FRESH-WATER  BIOLOGY 

48  (24)     No  rostrum.     Cervical  sinus  present.     .    .    . 


49 


49  (65)     Head    small    and    depressed.     Antennules    small.     Valves    oval    or 
round.     No  post-anal  extension  of  post-abdomen. 

Ceriodaphnia  Dana  1853   .    .     50 

General  form  rounded  or  oval;  size  small,  rarely  exceeding  i  mm.  Vertex  a  rounded  or  angu- 
lar projection,  usually  nearly  filled  by  eye.  Valves  oval  or  round  to  subquadrate,  usually 
ending  in  a  sharp  dorsal  angle  or  short  spine.  Antennules  not  very  freely  movable.  One 
abdominal  process  ordinarily  developed.  Post-abdomen  of  various  forms,  large.  Ephippium 
triangular,  with  one  egg  placed  longitudinally.  Antennules  of  ^  with  long,  stout  seta,  modi- 
fication of  flagellum;  first  foot  with  hook  and  long  flagellum.  Free  swimming;  motion 
saltatory. 


50  (51)     Head  with  a  short  spine  or  horn. 


Ceriodaphnia  rigaudi  Richard  1894. 


Valves  reticulated.  Head  produced  in  front  of  antennules  into  a 
short,  conical,  sharp-pointed,  hornlike  process.  Two  abdominal  proc- 
esses. Post-abdomen  with  5-6  anal  spines.  Claws  smooth  or  den- 
ticulate. Antennules  rather  slender;  lateral  sense-hair  somewhat 
distal  to  middle.  Length  of  9>  0.4-0.5  mm.;  d  (South  American), 
0.38  mm. 

Pools;  Louisiana,  Texas. 

The  form  with  horn  on  vertex  also  is  found  in  South  America, 
mingled  with  typical  C.  rigaudi.  Probably  both  forms  should  be  in- 
cluded in  C.  cornuta  Sars. 


Fig.  1078.     Ceriodaphnia  rigaudi. 


51  (50)     Head  without  horn 52 


52  (53)     Claws  pectinate Ceriodaphnia  reticulata  (Jurine)  1820. 


Head  obtusely,  or  not  at  all,  angu- 
lated  in  front  of  antennules.  Valves 
reticulated,  ending  in  spine  or  angle. 
Antennules  small,  with  sense-hair  near 
apex.  Anal  spines  7-10.  Claws  with 
pecten  of  6-10  teeth  and  denticulate. 
Color  variable,  shades  of  red  and  yel- 
low. Length  of  9.  0.6-1.4  mm.;  of 
$ ,  0.4-0.8  mm. 

Common,  widely  distributed. 


Fig.  1079. 


Ceriodaphnia  reticulata,  with 
ephippium. 


53  (52)     Claws  not  pectinate 54 


THE   WATER    FLEAS   (CLADOCFRA) 


701 


54  (55)     Head  and  valves  strongly  reticulated  and  covered   with  jk. 
short  spinules Ccriodaphnia  ncuuthin.i  R,, 

General  shape  rotund  with  well-developed  spine.     Head  much  dc-prrssc*!,  n.'  .„ 

front  of  antennules  or  at  vertex.    Antennules  short  and  thick  with  sc'iisc--hair'nr  {. 

abdomen  narrow,  much  like  quadrannula,  with  7-0  anal  spines.     Claws  dcnticulau  . ..,,,  ict 

in  the  proximal  two-fifths  of  the  claw  obviou.sly  longer  than  ihc  remainder.     CoJor  whjtith- 
transparent  to  very  dark.     Length,  9.  to  i.o  mm.,  $  unknown. 

Manitoba,  in  weedy  slough. 


.p-¥ 


Fig.  1080.     Ceriodaphnia  acanthina.  FiG.  1081.     Details  of  vilve.  much  enlwiceil. 

(54)     Valves  not  spinulated 56 

(57,  62)     Post-abdomen    abruptly    cut    into    near    apex,    serrate    alwvc, 
spines  below Ceriodaphnia  mcgalops  *><.v^  i>f>! 


Head  angulated  before  antennules;  valves  striatwl.  Anten- 
nules with  sense-hair  near  apex.  Post-alxlomcn  J)n»a<i.  with 
an  angle  near  apex,  cut  into  below  angle,  limly  x-rralr  al«)ve 
and  with  7-9  slender  anal  spines  be-low.  (Maws  not  pectinate. 
Length.  9.  io-i-5  mm.;  $  ,  0.6-0.8  mm. 

Widely  distributed  but  not  common. 


Fig.  1082.     Ceriodaphnia  ttugalcps. 


57  (56,  62) 

58  (59) 


Post-abdomen  not  cut  into;  of  ordinary  form. 


;8 


Fornices  projecting  into  spinous  processes.     F^yc  small. 

Ceriodaphnia  lamslris  Birgc  1803 

Head  angulati^l  in  front  <»f  an- 
tennule;  vertex  with  t'inc  spinulc*. 
lornices  very  briKid.  tri;ini:uUr; 
with  spines  at  tip.  Valxt-^  with 
stout,  short  pi»sterit»r  sj>inc.  Munr- 
times  divide*!,  but  ">i  .IK  «ith 
^-4  s|)inules.    Pt»st  ..'  '  • 

Quadrjiigult}.       '  U!  'f 

yellow.  trans|xircnl.  i.<n(.'tn.  V. 
o.S-o.(;  mm. 

Wisconsin,  Michigan;  limnetic 
in  lakes. 

Fig.  1083.     CmodapkmU  iauilni 


702 


FRESH-WATER   BIOLOGY 


59  (58)     Fornices  of  ordinary  form;  eye  large 60 

60  (61)     Head  inflated  in  front  of  antennules.     Small  form  not  exceeding 
0.7  mm Ceriodaphnia  pulchella  Sars  1862. 

Form  of  ordinary  type.  Head  rounded  in  front;  inflated  m 
region  behind  eye,  angulated  in  front  of  antennules  Valves  retic- 
ulated but  not  plainly  so.  Post-abdomen  not  sinuate  above  anal 
spines,  which  number  7-10.     Length,  ?  ,  0.4-0.7  mm.;    cf,  05  mm. 

Found  among  weeds  and  limnetic  in  lakes  and  in  pools;  reported 
from  all  regions.  Forms  agreeing  perfectly  with  this  description 
may  be  found,  as  also  qiiadrangula  forms,  but  other  varieties  occur 
which  are  difficult  to  assign  to  either  species,  but  which  so  closely 
agree  with  them  as  to  render  it  impossible  to  make  a  new  species 
Fig.  1084      Ceriodaphnia  for  them. 

pulchella. 

61  (60)     Head  angulated  but  not  inflated  in  front  of  antennules.      Length  to 

i.o  mm.    .    .  Ceriodaphnia  qiiadrangula  (O.  F.  Miiller)  1785. 

General  form  like  reticulata.  Valves  reticulated,  often  not  plainly  marked.  Antennules 
with  lateral  sense-hair  near  apex.  Post-abdomen  narrowing  toward  apex,  often,  but  not  always, 
sinuate  above  anal  spines;  these  number  7-9.  Claws  large,  denticulate.  $  antennules  with 
long  flagellum,  hook-Uke  at  tip.  Color  transparent  to  pinkish  opaque.  Length,  V ,  to  i.o 
mm  ;    ^  ,  to  0.6  mm. 

Common  in  all  regions;  found  both  among 
weeds  and  limnetic.  C  scitida  Herrick  seems 
to  be  a  large  variety  of  this  species,  0.1  MM. 


Figs.  1085,  1086.     Ceriodaphnia  quadrangula. 

62  (56,  57)     Post-abdomen  very  broad,  obliquely  truncate 63 

63  (64)     Vertex  evenly  rounded,  without  spines.     Antennules  moderate. 


Ceriodaphnia  laticaudata  P.  E.  Miiller  1867. 


General  form  round.  Valves  ventricose 
below.  Post-abdomen  large,  dilated  near 
middle,  obHquely  truncated  and  bearing 
8-1 1  spines  on  lower  margin.  Claws  long, 
denticulate.  Color  transparent  or  opaque, 
through  red  and  red-brown  to  nearly  black. 
Length,  9 .  to  1.0  mm.,  but  not  seen  larger 
than  0.7  mm.  in  United  States;  Z .  to  0.7 
mm. 

Wisconsin  and  Minnesota  to  Florida,  Lou- 
isiana, and  Texas. 

This  species  is  C.  consors  Birge. 

Fig.  1087.     Ceriodaphnia  laticaudata. 


aiMNT. 


THE   WATER    ELEAS    (CL ADOCKRa) 


703 


64  (63)     Vertex  angulated,  with  spines.     Antennulcs  long. 

Ccriodaplinia  rotunda  Sars  1867. 

General  form  much  like  prccedinR.     Head  anslcl  at  vcrtr. 
with   spmes       Antennulcs   lon^   and   slender.      I'ost  al-i.- •  ^ 
samewhat  enlarged,  hut  not  s(j  much  as  in  latuaudata   t 
toward  apex,  ohiKiuely  truncate,  with  7  o  slender  an.i 
Color  yellowish  or  brown,  not  transfiarent.      IxrnKth     ',      •  , 
i.o  mm.;    $  ,  to  0.6  mm.  •    ♦  • 

Rare,  Wisconsin.     Both  this  species  and  the  precetJinx  live 
among  weeds. 

Fig.  1088.     Ceriodaphnia  mlutula.     (After  Lilljcburjt  ) 

65  (49)     Head    large    and    usually    extended.      Antennulcs    larRc   and    fri-idy 

movable.     Post-abdomen  with  posl-anal  extension.    .         66 

66  (67)     Body    compressed.     Valves   elliptical,    crested    dor.siiilv.    C()mi)l»;ii-ly 

covering  body.  Ocellus  present.  Fornix  and  atxlominal 
process  well  developed.  .  .  .  Mohwdaplmia  Herrick  18S7. 
Cervical  sinus  present;  no  cervical  gland.  Valves  tumid  in  posfero-dorsiil  rrpion;  crcsJed: 
minute  spines  on  ventral  margin;  sharp  angle,  not  spine,  at  junction  of  durvil  an.|  venirai 
margins;  marked  with  oblique  striae,  usually  invisible  in  preserved  siH.-cimcn^  .\ntennulc» 
attached  on  ventral  surface  of  head,  sense-hair  about  middle:  olfactory  set.ic  small.  One  larjje 
abdominal  process,  broad,  concave  in  front,  somewhat  saddle-shajXHl,  forming  a  transition  to 
the  condition  in  Moina.  Post-abdomen  as  in  Moiua,  with  slender  j)ost-anal  projection  l>earinx 
about  10  finely  ciliate  spines  and  a  much  longer  distal  spine  with  2  unequal  pronKs.  the  biJrmi 
(Fig.  1094).  Claws  denticulate.  Summer  eggs  numerous.  Male  (.South  .\merica)  much  like 
Moina,  with  large  curved  antennules. 

Only  one  certain  species.  .  Moinodaphnia  madcdyii  (King)  1853. 

Color  yellowish,  transparmt. 
Length.   9.  ^^-  'o  ^^■ 

Louisiana.  In  weedy  pcx>l« 
and  lakes. 

Ilerrick's  M.  alabamrnsis  is  re 
ported  as  larger  (1.68  mm  )  ami 
may  possibly  be  a  different  *pe 
cies.  Herrick  had  only  Kinx's 
very  imperfect  tles^ription  for 
comparist)n  with  hi-;  form,  .ind 
his  own  description  '  .  1- 

ingly  imiK-rfect.     "  >( 

M .  mdiUayii  from  I  v  1 

form    identical   wiiii    ihai    irom 

0.1  MM.    •  ■      >-  '        '    ' "  -^  ^^"^  ^^'•^^"^ 


Fig.  io8g.    .\foimhiaphmj  madtiyii. 

67  (66)  Body  thick  and  heavy.  Valves  somewhat  rhomlH)idal.  not  wholly 
covering  body.  Fornix  small.  Ocellus  absent.  AMominal 
process  represented  by  horse-shoe  shaped  told. 

Moina  Haird  1S50   .    .     68 

Cervical  sinus  present.  Valves  thin,  obscurely  reticulated  or  striate<l;  no  ix.sterior  Vi^nt. 
Head  large,  thick,  rounded  in  front;  sometimes  with  (lee|)  depres.sion  alH)ve  eye;  no  r. .strum. 
Antennules  long,  spindle-shaped,  freely  movable;  lateral  sense-hair  al)«)ut  muldle  .No  regular 
abdominal  projection,  but  in  old  9  a  horse-shoe  shaFx-d  ridge  which  closes  the  briHMl-<aviiy. 
Post-abdomen  extended  into  conical  post-anal  part,  bearing  cihatol  si.ines  ami  Indent  i  uw» 
small;  abdominal  setae  very  long.  Summer  eggs  numerous;  ephippium  oval,  with  i  or  3  c«*. 
Antennule  of  $  very  long  and  stout,  modified  into  clasping  organ;  denticulate,  witti  Miiaii 
recurved  hooks  at  apex.     First  foot  with  hook.  ....        ,  -n,        ^  ^  t, 

The  species  of  Moina  ordinarily  inhabit  muddy  pools  and  similar  placw.  ITiey  arc  sclt- 
bodied,  weak  creatures;  liable  to  be  much  distorte.l  by  preserving  llui.ls.  I  he  spcoc*  arc  mucn 
alike  and  often  hard  to  distinguish  unless  $  and  ephippial  9  arc  present. 


704 


FRESH-WATER   BIOLOGY 


68  (69)     Post-anal  spines  fewer  than 


Animal  small,  about  0.5  mm.  long. 

Moina  micrura  Kurz  1874. 


Small,  transparent;  head  relatively  very 
large;  deep  cervical  sinus;  supra-ocular  de- 
pression small  or  absent.  Terminal  portion 
of  post-abdomen  small  with  4-6  spines  and  a 
much  longer  bident.  Claws  pectinate.  Male 
unknown.     Length,  9  >  0.5-0.6  mm. 

Illinois,  Arkansas,  Louisiana. 


Fig.  1090.     Moina  micrura. 


69  (68)     Post-anal  spines  8  or  more.  Animal  larger,  about  i  .0  mm.  or  more.  .     70 

70  (75)     Supra-ocular  depression  present;    claws  pectinate;    no  fiagelliun  on 

first  foot  of  male 71 

71  (72)     Two  ephippial  eggs;  antennules  of  male  with  sense  seta  in  middle. 

Moina  hrachiata  (Jurine)  1820. 

Body  stout,  heavy;  greenish,  not  transparent.  Head  ordinarily  much  depressed,  so  that 
vertex  often  lies  almost  on  level  of  ventral  margin  of  valves.  Deep  supra-ocular  depression. 
Valves  faintly  reticulated.  Post-anal  spines  7-1 1  besides  bident;  claws  pectinate.  Anten- 
nules of  $  with  4  hooks;  first  foot  without  flagellum.  Length,  9  ,  to  1.5  mm.;  ^  unknown  in 
United  States.  ,.     .,        ,      t  1 

Wisconsin,  Nebraska,  Missouri;  no  doubt  widely  distributed.     In  pools. 


0.2  MM.  L 


Fig.  1091.    Moina  hrachiata 


72  (71)    One  ephippial  egg. 


73 


THE   WATER   FLEAS  (CLADOCERA) 


73  (74) 


Valves   smooth; 
middle: 


ephippium   reticulated   around    edges,  smooth    in 
antennules  of  male  with  sense  sc-ta  near  middle. 

Moina  rcctirostris  (Loydig)  i860. 

Colorless,  or  with  bluish  cast.     Head  extended  or  liitic  depressed-   .!,.<.  .  .r. ;.  .1  1 

ocular   depressions.      Post-abdomen   with  long  '    ' 

projection    and    10-15    post-anal    spines    and     C 
bident.     Claws    pectinate.     Antennules   of    $      ' 
with  5-6  hooks  at  apex.     Length,  V,  1.0-2.0   /> 

Widely     distrih-  '         N^ 
muddy 


0.4-0.6  to  i.o  mm. 


uted; 


pools, 


Fig.  1092.    Male  antennule.    A,  Moina  rcctirostris.    B,  M.  affinis 
C,  M.  macrocopa. 


0.1  MM.    s—^ 
09^     Ephippium     A   \fmma 
H.U  jfimi,.    (  .  i/ 
{A  an<lt  .iflcT  ISI\)9- 


74  (73)     Valves  striate;    ephippium  reticulated  all  over;   antennules  of  male 
with  sense  seta  near  base.   .    .    .      Moitui  affinis  Birgc  iSq\. 


005  MM  L 


!7S3 


Much  like  .\f .  rcctirostris,  from  which  the 
young  9  ^re  hardly  distin>:uish;ihlf  .\ntm- 
nules  of  $  broad,  frin^ri-d  with  lint-  hair>  »jo 
inner  margin;  4-0  h(H)ks  at  end.  Ix-n^th.  9t 
0.8-1.0  mm.;    ^.o.s-o.Omm. 

Wisconsin  to  Louisiana. 

M.  rcctirostris,  affinis.  and  briukiiitii  ha\*e 
been  often  confused  in  faunal  list.«i. 

Fig.  1094.     Moina  affinis,  apex  «>f  pml-abdomen. 


75(70)  No  supra-ocular  depression;  claws  not  pectinate;  antennules  of  male 
with  sense  seta  in  middle  or  l)eK)\v;  hrsl  foot  of  male 
with  long  flagellum.     .    Moifui  ynacroiopii  Straus  i8.'o. 


Not  very  transparent;  yellowish  or  grernish.  J!  '  -•  ■  r.\. 
Terminal  part  of  post-abdomen   long,  with   10- 1:  <-* 

bident.     Two  ephippial  eggs.      ^  with  eK»ngatitl  h.  ^» 

on  antennule.     Length,  9,  to  1.8  mm:^  .  o.s-<).f>  mm. 

Pools,  Wisconsin,  Nebra.ska,  Colorado.  N.  Dakota:  doubtlcM 
widely  distributed.  ,   ,,    a      n  .    it 

This  species  is  M.  paraJoxa  Wcismann  anil  .1/.  fl<igciUi<i  liu- 

dendorf. 

Fig.  loys      Moina  macro<.vpi. 


0.2  MM. 


7o6 


FRESH-WATER    BIOLOGY 


76  (23,  83)     Six  pairs  of  feet.     Antennules  of  female  large,  fixed.     Intestine 
simple;  no  ceca Family  Bosminidae  Sars  .    .    77 

Body  short  and  high  often  oval  or  round.  Valves  cover  body  and  abdomen.  Antennules 
of  9  long,  immovably  fixed  to  head.  No  abdominal  process  or  ocellus.  Intestine  without 
convolutions  or  ceca.     Animals  small,  rarely  exceeding  0.5  mm. 


77  (82)  Antennules  of  female  approximately  parallel  to  each  other,  curving 
backward,  fixed  to  head;  olfactory  setae  on  side,  usually 
near  base Bosmina  Baird  1845   .    .    78 

Animal  usually  hyaline:  valves  thin;  infero-posteal  angle  with  spine  —  the  miicro.  Antennules 
of  9  immovably  fixed  to  head;  olfactory  setae  on  side,  with  small  triangular  plate  above  them; 
distal  position  of  antennules  looks  segmented.  Antennae  with  3-  and4-jointed  ramus.  Post- 
abdomen  somewhat  quadrate;  anus  terminal:  spin.es  small  and  inconspicuous;  claws  set  on  a 
cylindrical  process.  ^  smaller  than  9  >  with  short,  blunt  rostrum;  large  free  antennules;  hook 
and  long  flagellum  on  first  foot. 

Little  work  has  been  done  in  this  country  on  this  very  diflacult  genus;  but  it  is  certain  there 
are  not  so  many  species  nor  so  great  an  amount  of  variation  here  as  in  Europe. 


78  (79) 


Claws  with  two  series  of  spinules. 

Bosmina  longirostris  (O.  F.  Miiller)  1785. 

Two  series  of  spinules  on 
^ — :^--^— ^-.^  claws,  the  basal  increasing 

in  length  distally,  contin- 
ued by  very  fine  denticles 
to   tip  of   claw.     Frontal 
sense-hair   about   midway 
\      between  eye  and  junction 
of  antennules.    Antennules 
:%     moderate    or    short    (var. 
; .  j|     brevicornis) ;  sometimes  re- 
%     curved  at  apex  (var.  cor- 
I     nula).    Transparent  or 
^^^     clear  yellowish.  Length,  9  - 
■^^       0.3-0.5  mm.;   ^,  0.25-0.4 
mm. 

Very  common  and  very 
variable.  In  open  water 
of  lakes,  in  weedy  mar- 
gins, in  pools  and  marshes. 


^ 

:;,^ 

X 

< 

0.1  MM.    4 


Fig.  1096.     Bosmina  longirostris,  typical  specimen;  p,  post-abdomen  more  highly  magnified. 
Rostrum;  a,  var.  cornuta:  b,  var.  brevicornis. 


79  (78)     Claws  with  basal  series  of  spinules  only 80 


THE   WATER    FLEAS   U  J..\l )(  ki:r.\) 

80  (8i)     Mucro  shorter  than  claws  and  process  bearing  I  hem. 

Bosmina  uhlusiroslris  Sars  1861. 

Frontal  sense-hair  near  junction  of  antennules.     Antcnnuks  shorter  than  Icnclh  of  v«lv« 
bhell  reticulated  or  smooth.     Length,    y,  0.3-0.5  mm. 

In  pools  and  lakes;   not  rare;   very  variabie. 


U. 


ft  ^1 

0.1  MM.  , 

Figs.  1097,  1097,  a.     Bosmina  obtusiroslris. 

81  (80)     Mucro  longer  than  claws  and  process. 


Bosmina  loni^ispittii  Ix*ydig  i860. 


Frontal  scnsc-hair  nt-ar  juik  tion  of  anttnnulc*. 
Mucro  and  antennuks  long.  Shi-il  >triatn!.  marL* 
especially  plain  un  head.  Tran.sjKircnt.  lx-nx(h, 
9  ,  ca.  0.4  mm. 

Rare,  in  lakes. 


Fig.  1098.      Bosmirui  I'ttct  ptna. 


Sole  American  species. 


82  (77)     Antennules  united  at  base,  and  diverging  at  ape.\;  numerous  long 
olfactory  setae  on  their  ventral  side. 

Bostfiiuopsis  Richard  1895. 

Bosminopsis  deitcrsi  Richard  18Q5. 

In  K'lniTd!  muih  like  Bos- 
mina. Has.ii  jurt  of  anlm- 
niili-s  uniloi  v^ith  .  n.  h  .thrr 
and  ht-atl  to  •  fxiC 

rostrum;  diN>  ''y 

mar  a|x"X.  wi: r..      .-UC- 

pling.  olfai-tor>- srtac.  Anten- 
na with  ^joint«-«!  rnmi  IN»*I- 
alMl«)nun  tai-*  'at 

tiaws;     I    l.i:  '*r 

I  laws  and   x  '^^i' 

luitc  sninulfs  .ni{iii»ir  t>>  it. 
$  with  larpi-  mov.ihlc  an- 
tinnulcs;  sh.>r*  -><"•-  Mrrt 
fiH)t  with  hi>  '  "tu 

IxiiK'th.  9.  *•'  'i' 

o.JS  nim. 

Lake  Charlcsand  CalcMktt 
^-  .    ,  River,  La. 

Fig.  1099.     Bosminopsis  Jcilcrsi. 


7o8 


FRESH-WATER   BIOLOGY 


83  (23,  76)     Antennules  of  female  long,  freely  movable,  usually  inserted  at 

anterior  end  of  ventral  surface  of  head.  Rami  of  antennae 
3-  and  4-jointed.  Intestine  simple  or  convoluted.  Hepatic 
ceca  usuaDy  wanting.     Five  or  six  pairs  of  feet. 

Family  Maceothricidae  Norman  and  Brady  .   .     84 

Abdominal  process  usually  absent;  rarely  present  {Ilyocryptus).  Feet  5  or  6  pai'rs  the 
first  two  prehensile;  the  last,  if  present,  rudimentary.  Post-abdomen  marked  off  from  body, 
usually  large,  often  bilobed;  anus  terminal  or  lateral.  Labrura  usually  with  keel  or  marked 
projection.     Valves  often  crested.     Fornices  well  developed.  .    .    ,      , 

The  members  of  this  family  are  so  various  in  form  that  it  is  hard  to  find  many  common 
character"^-  yet  the  general  appearance  is  always  characteristic.  The  size  and  position  of  the 
antennules  will  show  the  membership  of  every  genus  except  Ilyocryptus;  and  there  is  no  trouble 
in  recognizing  that  genus  as  belonging  to  the  family. 

84  (95)     Intestine  convoluted 85 


85  (86)     Valves  with  spine  at  supero-posteal  angle. 


Small  hepatic  ceca. 

Ophryoxus  Sars  1861. 

Sole  species Ophryoxus  gracilis  Sars  1861. 

General  form  elongated,  some- 
what daphnid.  Antennules  long, 
slender,  fringed  with  numerous 
hairs  behind,  lateral  sense-hair 
near  base;  olfactory  setae  vmequal. 
Antennae  long,  weak.  Six  pairs  of 
feet.  Post-abdomen  long,  taper- 
ing at  apex,  anus  dorsal,  post-anal 
portion  large  with  numerous  short, 
blunt,  cihated  spines,  the  proximal 
mere  elevations  bearing  fine  spi- 
nules.  Claws  straight,  with  (usu- 
ally) two  stout  basal  spines.  In- 
testine with  convolution  in  middle 
of  body;  2  small  hepatic  ceca. 
Antennules  of  $  longer  than  9  I 
sense-hairs  longer.  Vasa  deferen- 
tia  open  on  ventral  (anterior)  side 
of  post-abdomen  about  middle. 
Strong  hook  on  first  foot.  Color  transparent,  last  foot  often  purple  in  old  9  •  Length,  9 .  to 
2.0  mm.;    ^,1.0  mm.  ,       r    i_i        jji- 

Widely  distributed  in  lakes  among  weeds.     Swims  with  constant  but  rather  feeble  paddhng 
motion.     Spine  longer  in  young  than  adult. 

86  (85)     No  such  spine 87 


0.1  MM.    w._4 

Fig.  1 100.     Ophryoxus  gracilis. 


87  (92)     Hepatic  ceca  present. 


88  (89)     Antennary  setae  9  , ;  ^ , 1  valves  narrowed  behmd  and 

•  0-0-3  1-1-3 

prolonged  into  short  tube.    .      Parophryoxus  Doolittle  1909. 
Sole  species Parophryoxus  tubulatus  Doolittle  1909. 

Form  elongated  oval;  narrow  crest  on  head  and  valves.  Head  rounded,  rostrum  well 
marked;  cervical  sinus  present.  Valves  thin,  transparent;  unmarked  or  faintly  reticulated; 
prolonged  behind  into  a  sort  of  tube,  best  seen  from  above;  ventral  margin  with  moderate 
setae.  Post-abdomen  elongated,  triangular;  post-anal  part  long  and  slender,  narrowed  toward 
apex  somewhat  as  in  Ophryoxus;  bearing  a  few  very  small  spines.  Claws  long,  rather  straight; 
with  2  basal  spines.  Antennules  cylindrical,  slender;  with  basal  sense-hair  and  three  conspicu- 
ously long  olfactory  setae.  Antennae  long,  slender;  basal  joint  annulated;  setae  not  conspicu- 
ously dissimilar.     Feet,  6  pairs;  the  last  rudimentary.     Eye  moderate,  with  few  lenses;  ocellus 


THE    WATER    FLEAS    (CLAUUC  ERA) 


lare;e,  some  distance  from  apex  of  rostrum.     Intestine  convolultfj    wiili  vtn.i,!  lup,' 
$  with  hook  on  first   foot;  vas  deferens  opens  near  claws       Length,  ^ .  \u  13  mm      f«.lor 

transparent-yellowish. 

Maine.  New  Hampshire;  among  weeds  in  lakes.     The  diflcrtntc  in  unlinnary  setae  o(  i  and 
9  holds  for  all  specimens  hitherto  seen. 


Q.2  MM. 

Fig.  iioi.     Parophryoxus  liibulatus.     (,.\flcr  lJ(.K)lililc.; 


0-0-1-3 


Strchloccrus  Sars  1862 


QO 


(88)     Setae  "^  ^  ^  ^^ ;  animal  small,  spherical. 

Body  round-oval,  not  compressed  or  crested.     Labrum  with  larse,  serrate,  acute  proco*. 

Antennules  large,  flat,  bent,  or  rather  twisted,  broadened  in  distal  jxirf:   with  l.itrml  vnsc- 

hair  near  base,  several  hairs  on  posterior  face,  rows  of  fine  hairs,  and  su!  ■  •  t.ir. 

Post-abdomen  bilobed;    the  pre-anal  part  compressed,  semi-circular:   ;  icd, 

with  fine  spines  or  hairs.     Claws  small,  curved,  with  several  equal  mii.  ,  u.n- 

cave  edge.     Five  pairs  of  feet.     Intestine  convoluted,  with  small  hepatic  tcva.  ^  ^Lurupean, 
of  5.  serricaudatus)  small,  triangular,  much  like  9  ;  tirst  foot  without  hook. 

90  (91)     Dorsal  margin  of  valves  smooth. 

Strchloccrus  scrriaiudalus  (Eischcr)  1849. 

0.1  MM.  '  Pre-anal  part  of  po5t  abtJo- 

nun  with  serrate  margin  and 
bearing  rows  of  fine  haira. 
Anterior  margin  of  anlennule 
somewhat  tiM»the<l  ('ol«»r 
whitish  ojaquc  to  yellowish. 
LitiKth,  9.  «^'i  05  nim  :  $, 
la.  0:5  mm. 

Rare  but  widely  distributol 
in  wetily  yiooU  .md  mnrrin^  ol 
lakes.       Kep..:  New 

England.  \Vi>  -ka, 

Louisiana     l  :  >r- 

nia. 


91  (90)     Valves  reticulated,  the  edges  of 
ridges,  which  give 
0.05  MMa 


Fir..    iio->. 


rfaiiu. 


the  reticulations  making  scalc-Ukc 

the  dorsal  margin  a  scrrale  apjH-arancc. 

Strchloccrus  pygnuuus  Sars  ux)i. 


Pre-anal  part  of  post -abdomen  not  serrate,  with  4-5  ro^j 
of  fine  hairs.  Color  grayish  white,  uixi.jue.  to  nearly  Mac* 
in  enhinnial  9 .      Z  unknown.  ,  /  .i„ 

Len''th    9    o.2^.-'S   mm.    The  smallest    member  of  the 

familv^and  one  of  the  smallest  of  the  group        -—    '" 

weedy  pools,  with  5.  icrruaudaiui. 


1-lG.  lioj.     atreUvccrui  p> 


yio 


FRESH-WATER  BIOLOGY 


92  (87)     No  hepatic  ceca;  setae — ^— ^ 93 

93  (94)     Convolution  of  intestine  in  middle  of  body.     Valves  crested,  with 

strong  tooth  on  crest Drepanothrix  Sars  1861. 

Sole  species Drepanothrix  dentata  (Euren)  1861. 

Valves  reticulated;  dorsal  margin  arched,  crested,  with  conspicuous,  short,  backward- 
pointing  tooth  about  middle.  Antennules  broad,  flat,  twisted,  though  not  so  much  as  in 
Streblocerus;  post-abdomen  compressed  but  not  extended  into  a  thin  edge;  almost  quadrate 
as  seen  from  side.  Margin  with  2  rows  of  small  spines,  about  20,  and  with  several  rows  of  hairs 
besides  scattered  groups;  apex  truncate,  emarginate,  with  anus  in  depression.  Claws  short, 
broad,  crescentic,  smooth,  or  denticulate;  5  pairs  of  feet.  $  much  like  young  9  ;  hook  on  first 
foot;  post-abdomen  without  spines;  vasa  deferentia  open  in  front  of  claws.  Color  whitish  to 
yellowish;  opaque  or  transparent.  Length,  9>  ca.  0.7  mm.;  ^,  ca.  0.4  mm.  Not  commonly 
collected  though  widely  distributed  and  probably  not  very  rare  in  shallow  waters  of  lakes,  on 
bottom  or  among  weeds.     Maine,  Michigan,  Wisconsin,  Minnesota,  Colorado. 


0.1  MM.    . I 

Fig.  1 104.     Drepanothrix  dentata. 


94  (93)     Convolution  of  intestine  in  hind  part  of  body  and  in  post-abdomen. 

No  dorsal  tooth Acantholeheris  Lilljeborg  1853. 

Sole  species Acantholeheris  curvirostris  {0.  F.MiiUer)  1776. 

Form  in  general  angu- 
lar-oval, not  compressed, 
without  crest.  Posterior 
margin  of  valves  rounded 
over  into  ventral,  both 
fringed  with  long,  close- 
set,  plumose  setae.  La- 
brum  with  long,  slender, 
conical  process.  Anten- 
nules large,  flat,  somewhat 
curved,  expanded  toward 
apex.  Post -abdomen  large, 
moderately  broad,  not 
compressed  or  divided, 
hairy,  with  20  or  more 
small  dorsal  spines  in  each 
row;  anus  terminal.  Claws 
short,  stout,  broad,  curved, 
denticulate,  and  with  2 
small  basal  spines  set  side 
by  side.  Six  pairs  of  feet  Intestine  without  ceca,  convoluted,  the  loops  lying  in  great  part  in 
post-abdomen,  $  resembling  young  9  .  antennules  with  2  proximal  sense-hairs;  first  foot 
with  small,  inconspicuous  hook,  post-abdomen  emarginate  dorsally,  vasa  deferentia  open 
behind  claws.     Color  yellow,  not  transparent.     Length,  9  ,  to  1.8  mm.;    $  ,  0.5-0.7  mm. 

In  pools  and  margins  of  lakes  among  weeds,   reported  especially  frequent  in  Sphagnum  bogs. 
Maine,  Wisconsin,  Louisiana;  probably  in  all  regions  of  the  United  States. 

95  (84)     Intestine  simple 96 


0.5-MM.  » 

Fig.  1105.     Acantholeheris  curvirostris. 


THE  WATER   FLEAS  (CLADOCERA) 
96  (99)     Hepatic    ceca   present;     post-abdomen    bilobed- 


0-0-1-3 
1-1-3 


antennary   scUi- 


97  (98)     Post-abdomen  very  large,  with  few  spines.   .   Grimaldina  Richard  ,89. 
^^^^  ^P^'^^^ GrimaUina  hn.zzai  Richard  i8g.. 


Fig.  1 106.     Grimaldina  brazzai. 


Body  comprcs.scd.  somewhat  /mad- 
ran^ular.   with  all  m.i':  '       Uc* 

slightly  convex.      I'om  .,„. 

mous.  much  (omprcsv ;  .^\. 

elliptical  in  form;  the  pre  aiul  i-^rtioo 
nivKJed  |jy  a  notch  into  two  jartv  ol 
which  the  anterior  is  the  smallrr"-  a 
lonK  spine  in  the  notch  which  maris 
junction  of  anal  and  pre  anal  (wrt*  on 
anal  part  two  lateral  rows  of  Miulj. 
slender  spines.  aU)ut  7  in  anterior.' 
and  5  in  rxjslerior  row.  Claws  wnaJI 
denticulate,  with  i  .small  hasal  spine! 
Ephippium  roundtnl  (j  u  a  d  r  a  n  r  u  I  a  r: 
CRR-chamhers  rcniform  with  concave 
sides  toward  each  other.  ^  (.South 
America)  small,  like  immature  9;  an- 
tennuleswith  2  ba.sal  sense  hairs;  small 
hook  on  first  foot.  Color  rcrfdish- 
brown.  Length,  9  to  og  mm  ;  ^J . 
0.5  mm.  Louisiana;  weedy  prwb  of 
dear  water. 


98  (97)     Post-abdomen  moderate;    numerous  small  spines  on  prc-anal  part. 

clusters  of  hairs  on  anal  part.    .    .      Whissicsid  Daday  iqov 

Sole  American  species Wlassicsia  kinistimnsis  Ww^i.-  \gio 

Form  ovaJ,  not  com- 
pressed. Valves  crrsled; 
with  spines  on  ventral  mar- 
gin; market!  by  vcr>-  deli- 
cate transverse  striae  which 
anastomose,  forminj:  hne 
vertical  meslies  Olfactory 
setae  subeijual.  Two 
rounde<|  projct  lions  at  base 
of  labrum  on  ventral  sur- 
face t>f  heati.  I^brum  with 
strong  tonical  projection 
l^ointin^'  backwanl  and  a 
second  f^rojcition  just  in 
front  of  small  terminal 
lolx.'.  I'ost  aUlomcn  with 
line  spines  and  hair>  .\b- 
dominal  set .le  ver>-  lon^.  not 
set  on  projection  Claws 
with  V  e  r  >'  small  basal 
spines  live  jwiirs  of  feet; 
branchial  sacs  on  all  le«r&> 

$  with  large  antennule;   small  keel  on  labrum;   hook  on  first  foot.     Color  yellow.     Ixnicih, 

9,  0.8  mm.;    ^,0.4  mm.     Marsh  at  Kinistino.  Manitoba. 


Fig.  1107.     Wlassicsia  kinistinemis. 


99  (96)     No  hepatic  ceca;  post -abdomen  various. 


712 


FRESH-WATER   BIOLOGY 


TOO  (107,   116) 

loi  (102) 


Antennary  setae 


0-0-0-s 


1-1-3 
Wide  crest  on  dorsal  margin  of  valves.     Antennules  at  apex  of 
head.     Post-abdomen  bilobed,  of  moderate  size. 

Bunops  Birge  1893. 
Sole  American  species Bunops  serricaudata  (Daday)  1888. 

General  form  rounded,  much  compressed; 
high  keel  on  dorsal  side.  Front  of  head  flat, 
somewhat  kite-shaped,  with  boss  or  umbo 
over  eye.  Strong  triangular  keel  on  la- 
brum.  Valves  faintly  reticulated,  produced 
behind  into  rounded  projection;  ventral 
margin  gaping  in  front,  inflexed  behind, 
fringed  with  rather  long  straggUng  hairs  or 
weak  setae.  Antennules  with  basal  sense- 
hair  and  two  pairs  of  sense  setae  near  apex; 
olfactory  setae  somewhat  unequal.  Post-ab- 
domen much  like  Strcblocerus;  bilobed,  pre- 
anal  portion  flattened,  semi-circular,  with  7-8 
notches  or  teeth  on  the  dorsal  margin  and 
3-4  rows  of  fine  hairs;  anal  portion  with  fine 
hairs  and  3-4  spines.  Color  transparent, 
tinged  with  yellow.  ^  unknown.  Length  of 
9  to  i.o  mm.  Maine,  Wisconsin;  very  local 
in  distribution,  but  not  rare  when  present. 


Fig.  1 108. 


o  \  MM.   « 

Bunops  serricaudata. 


102  (loi)     Vertex  of  head  forming  sharp  angle  in  front  of  insertion  of  anten- 

nules.    Dorsal  crest  of  valves  absent  or  small.     Post-abdo- 
men very  large,  with  numerous  long  spines. 

Ilyocryptus  Sars  1861  .  .  103 
'  General  form  oval-triangular,  the  head  forming  the  apex  of  the  triangle,  while  the  enorm.ously 
dilated  ventral  and  posterior  edges  of  the  valves  round  into  each  other;  these  have  long,  close- 
set  fixed  setae,  usually  branched  and  fringed.  Antennules  long,  free  y  movable,  2-jomted, 
basal  joint  very  small,  attached  to  ventral  side  of  head  behind  vertex;  olfactory  setae  unequal. 
Antennae  short,  powerful;  basal  joint  annulated  nearly  to  apex;  with  long  sense  setae;  motor 
setae  not  plumose,  smooth,  or  with  sparse  hairs.  Abdommal  process  long,  tongue-shaped, 
hairy  Post-abdomen  large,  broad,  compressed;  anus  on  side  or  near  apex;  many  spines  on 
dorsal  margin;  numerous,  long,  curved,  lateral  spines  and  setae;  fine  spmulesnear  base  of 
claws.  Claws  long,  straight,  denticulate,  and  with  2  slender  basal  spines.  Intestine  simple,  no 
ceca,  but  enlarged  near  rectum.  Six  pairs  of  feet.  ^  with  larger  antennules  than  9  ,  bearing 
2  sense-hairs;  no  hook  on  first  foot.  ,.       ,  ,.    ^,  ^-  _i 

In  most  species  the  old  shells  are  not  cast  off  in  molting  but  overlie  the  youngest  in  several 
layers  The  species  live  in  mud,  creep  about  among  weeds,  though  they  can  and  do  swim; 
are  often  greatly  loaded  with  mud  and  vegetable  growths,  neariy  concealing  structure. 

103  (106)     Anus  opening  on  dorsal  margin  of  post-abdomen;   molting  imper- 

fect  104 

104  (105)     Eight  or  more  pre-anal  spines;  antennary  setae  short.  _^ 

Ilyocryptus  sordidus  (Lieven)  1848. 
Post-abdomen  emarginate 


0.1  MM 


Ilyocryptus  sordidus. 


Fig.  1 1 09 
Not  very  common  but  widely  distributed  in  weeds  on  muddy  bottoms 


where  anus  opens;  8-14  pre- 
anal  marginal  spines;  lateral 
post-anal  spines  about  8-10; 
marginal  row  of  nvimerous 
smaller  spines.  Ocellus 
nearer  base  of  antennule  than 
eye.  Six  to  eight  summer 
eggs. 

Color  red,  but  often  so 
loaded  with  debris  as  to  be 
opaque.  Length,  9»  ca.  i.o 
mm.,    $ ,  0.42  mm. 


THE   WATER    FLEAS   (CLADOCKRA)  7,^ 

105  (104)     Five  to  seven  prc-anal  spines;  anlennary  setae  ordinarily  ver>'  long. 

Ilyocryptus  spin  if  cr  Il'errick  1884. 


:^'W 


Anus  (.|K>ns  in  (lrpre\>ion  oo 
florsal  margin  of  p(>%(  al4<iontm; 
<;  7  pre  anal  spinps;  4  8  |)i>s(  aiul 
lateral  spines  in  ..:■   -  -  \n 

tt-nnary  st-tar  us»i. 
timi's  cqualint'    Ir  •  ,  ^ 

in  s<inu-  sjxi  :  rt. 

apparently  \><  .-ht 

til  tt-n  siimrii'  :      _  ip. 

Ilium  fiitrnvil  ami  r^) 

$  unknown      Cot  ■.tl- 

(iish.     Length.  9.  • 

This  siK-rics  is  /  ir»; 

/.  halyi  Uraiiy.      N    •  .'.n; 

Maine  to  Lake  Suixriur  an«!  (.ulj 
of  Mexico  l'rol»alily  in  .ill  rriouns 
of  United  States. 

FiC.  1 1 10.     IlyocrypiHi  ipinifn. 


106  (103)     Anus  at  end  of  post-abdomen;  molting  complete. 

Ilyocryplus  cicNlifrons  SaTS  i86i. 


0.1  MM 


Fig.  nil.     Ilyocryptus  acutifrons. 


Post-abdomen    not     emar^i:  '8 

small  spines  near  claws,  shor'  iw; 

about  ()  lonp,  curved,  lateral     ;  f  8 

marginal  spines  corresponding  lo  pre  auaJ^  of 
other  species;  the  proximal  two  dirrttoJ  for- 
ward; from  distal  spine  of  this  st-t  a  <(cric»  of 
vcr>'  small  marginals  to  anus,  .\ntcnnulc  club- 
shaped,  hairy.  Ocellus  nearer  eye  than  inser- 
tion of  antennules.  ("laws  as  in  /.  JorJiJui 
Three  to  four  summer  eggs.  S  unknown 
Color  reddish  or  yellowish.  I.trik'th.  9  f^- 
0.7  mm. 

Rhode  Island,  Colorado 


107  (100,  116)     Antennary  setae 


0-0-1-3 
1-1-3 


basal  seta  of  3-jointed  ramus  slout 


and  stiff iU(/(-r(j///r/.v  Haird  1843 


108 

Shape  oval  or  rotund,  somewhat  compressed,  with  dorsal  crest.  Hca.l  large,  onlinarily  noC 
depressed;  vertex  evenly  or  abruptly  rounded;  rostrum  short.  \^'"!^^''  ."^•■»'^'"  "f.^; '^ 
ordinarily  with  long,  stout,  movable  spines,  which  project  in  sc-yeral  «i'rfvttons^  „"  ^^TT 
large;  lateral  sense  hair  near  base.  Antennae  large;  the  proxmial  sc-ta  of  .,  jo.n  cjl  n»mu.  onj. 
stiff,  and  spinous;  the  others  sparsely  plumose  or  partly  spmous.  Hvc  i;'"7;  \"<  "  •;;*''• 
dominal  process.  Post-abdomen  large;  often  bilobed.  (  laws  small.  InteMme  s„npl.  .>.. .  .xa 
$  with  large  antennules;  hook  on  first  foot. 


108  (115)     Dorsal  margin  of  head  evenly  roundeil. 


109  (114)     Head  extended;  rostrum  far  from  m 
enlarged  near  distal  end. 


irgin  of  valves,     .\nlcnnulc5 
110 


714 


FRESH-WATER  BIOLOGY 


no  (hi)     Post-abdomen  not  bilobed.      .    M acrothrix  laticornis  (Junne)  1S20. 


Fig. 


t2.     Macrothrix  laticornis. 


Form  round-ovate.  Valves  crested, 
the  dorsal  edge  serrate  with  fine  teeth. 
Head  evenly  rounded.  Labrum  with 
large  triangular  process.  Antennule 
broader  distally;  a  setiferous  projec- 
tion on  posterior  margin  near  apex; 
anterior  margin  with  several  fine  in- 
cisions and  clusters  or  rows  of  hairs; 
olfactory  setae  conspicuously  unequal. 
Post-abdomen  with  numerous  fine 
spines  and  hairs;  anus  terminal. 
Claws  small.  Color  grayish  white  or 
yellowish.  Length,  9.  0-5-o-7  mm.; 
$ ,  0.3-0.4  mm. 

Widely  distributed;  found  in  all 
parts  of  the  country  but  nowhere  very 
abundant. 


Ill  (iio)     Post-abdomen  bilobed ■.     112 


112  (113)     Conspicuous  fold  or  folds  of  shell  of  head  at  cervical  sinus. 

Macrothrix  montana  Birge  1904. 


Form  ovoid.  Head  large;  dorsal  margin  evenly  rounded; 
the  shell  extended  into  collar-like  folds  in  front  of  cervical 
sinus.  Antennules  stout,  large,  enlarged  near  apex,  about  6 
anterior  cross-rows  of  hairs,  and  3-4  stouter  posterior  setae; 
olfactory  setae  unequal.  Post-abdomen  bilobed.  Claws  hardly 
larger  than  spines.  Color  transparent,  in  preserved  speci- 
mens.     $  unknown.    Length,  9 .  ca.  0.55  mm. 

Colorado. 

Fig.  1 1 13.     Macrothrix  montana. 


113  (112)     No  such  folds.     Macrothrix  hirsuticornis  Norman  and  Brady  1867. 


Form  broadly  ovate,  not  very  different  from  M.  laticornis. 
Antennules  broad,  flat,  bent,  varying  in  form  but  always  enlarged 
distally;  with  6-8  rows  of  stiff  hairs  on  anterior  side;  sometimes 
stout  setae  on  posterior  side;  olfactory  setae  unequal.  Post-abdo- 
men large,  broad,  bilobed;  pre-anal  part  not  flattened  nor  with 
projection  for  abdominal  setae;  numerous  small  spines  and  hairs 
on  both  anal  and  pre-anal  parts.  $  unknown.  Length,  9  .  o-55 
mm. 

New  England,  Colorado. 


Fig.  1 1 14.     Macrothrix  hirsuticornis. 


THE   WATER   FLEAS   (CLADOCERA) 


Antcn- 


114(109)     Head  much  depressed;   rostrum  close  to  margin  of  valves, 
nules  slender,  not  enlarged  near  distal  end. 

Macrotltrix  borysthcnica  Malilc  1890 


Dorsal  marKin  of  heafi  evenly  roun<ic*l  o\<r  int..  »V...f     • 
valves  without  sinus.     Front  of  lu-a<l  rem r  -.^ 

trum  is  very  close  to  valves.      Antennule^  .  xl 

tered  tine  hairs;  olfactory  setae  small.  e<jual     ;    .  .wjcn 

elongated,  bilobed;  with  numerous  fjne  spinulcn  an<l  hain 
on  both  lobes.  Claws  .small.  Kye  m«»<lcratc;  o<rllu»  at 
rostrum.     Color  transparent      Length.  9.  '"  «  «  mm. 

Albuquerque,  New  Mexico  (Herrick; 


Fig. 


Macrothrix  horystheniiii.     (.\fter  Matile.) 


115  (108)     Dorsal  margin  of  head  curved  abruptly  in  front  of  eye.     .Antennuk-s 
slender Macrothrix  rosea  (Jurinc)  i8io. 

Form  broadly  ovate.  Valves  reticulated,  crested,  not  serrate.  Head  large;  its  (lorsal  mar- 
gin rounding  over  abruptly  into  anterior  margin.  Antennulcs  long,  slender,  not  enlarRnl  near 
apex;  lateral  sense-hair  near  base  on  small  elevation;  olfactor\'  setae  une(|ual.  ro>t-aU)iimm 
extended  into  blunt  process,  on  which  abdominal  setae  are  borne;  pre-anal  jurt  >*-mi  clli(»tical. 
with  numerous  spinules  along  convex  edge  and  many  fine  hairs:  anal  jKirt  with  st- veral  sfnall 
spines.  Claws  small,  smooth.  Summer  eggs  numerous;  ephippium  well  <level()|)e<l.  with  ;  ciar»- 
Antennules  of  $  long,  curved.  Post-abdomen  terminating  in  long,  lleshy  pri>jtvti<>n  oq 
which  the  vasa  deferentia  open.  Hook  of  first  foot  serrate  at  tip  Color  tran>i»rrnl  to 
yellowish  or  sometimes  a  ruddy  tinge.  Length,  9.  ca.  0.7  mm.;  $,  0.4  mm.  Common 
everywhere  in  marshy  pools  and  margins  of  lakes. 

M.  tenuicornis  Kurz  is  a  variety  of  this  species  All  ^  $  found  in  .\merica  a^rcc  with  M. 
elegans  Sars. 


0.1  MM     I 

Fig.  1 1 16.     Macrothrix  rosea. 


7i6 


FRESH-WATER  BIOLOGY 


ii6  (loo,  107)     Antennary  setae ;   all  similar  and  plumose. 

^  1-1-3 

Lathonura  Lilljeborg  1853. 

Sole  species Lathonura  rectirostris  (0.  F.  Mliller)  1785. 

General  form  long-oval,  not  com- 
pressed. Valves  unmarked;  the 
ventral  margin  with  short,  close-set, 
smooth,  lancet-shaped,  or  spatulate 
spines.  Antennules  straight,  with 
sense-hair  near  base;  2  pairs  of  sense 
setae  in  distal  half.  Post-abdomen 
very  small,  extended  behind  into  a 
long  conical  process,  which  bears  the 
very  long  abdominal  setae;  covered 
with  fine  spines  and  setae.  Claws 
small,  smooth,  or  denticulate.  Sum- 
mer eggs,  2  to  10;  I  ephippial  egg. 
$  like  young  9 .  with  larger  anten- 
nules; 2  lateral  sense-hairs,  the  addi- 
tional one  —  the  distal  —  the  larger; 
olfactory  setae  longer.  First  foot 
with  hook.  Vas  deferens  opens  at 
claws.  Color  transparent  to  clear 
yellow  or  greenish.  Length,  9  >  to 
i.o  mm.;  $ ,  ca.  0.5  mm. 

Widely  distributed  in  weedy  mar- 
gins of  lakes  but  nowhere  common. 


Fig.  1 1 17.     Lathonura  rectirostris. 


117  (22)  Fornices  extended  so  as  to  cover  antennules  in  whole  or  in  part,  and 
uniting  with  the  rostrum  into  a  beak,  projecting  ventrally  in 
front  of  antennules.  .  Family  Chydoridae  Stebbing  .    .    118 


0-1-3 


Antennae  small,  rami  3- jointed;  setae =^  or  ^  .     Labrum  with  large  keel.     Five  or  six 

0-0-3        0-0-3  J    .  .       , 

pairs  of  feet.  No  true  abdominal  process  or  ephippium.  Post-abdomen  compressed,  jointed  to 
body.  Intestine  convoluted.  Ocellus  always  present.  $  with  hook  on  first  foot;  large  anten- 
nule;  short  rostrum. 


118  (119)     Anus   terminal.     2   hepatic   ceca.      Summer  and   ephippial   eggs 
numerous Subfamily  Eurycercinae  Kurz. 

Sole  genus Eurycercus  Baird  1843. 


THE   WATER   FLEAS   (CLADOCKR 


\) 


»7 


Only  one  American  species. 


Euryccrcus  lanidlatus  (U.  V.  Muilcr;  1-81 


Body  stout,  heavy.  i'oM  alxlomm  vit>-  Urir«. 
flattened,  general  form  (|ua<lraiiK'ular;  aruis  t«-nnin*l. 
in  depression;  (l<)rs.il  niarK'in.  with  \.r\  :  .:;i.r<>u» 
—  over  100  —  saw  like  ti-fth.    C'lav.  •  m* 

projection,  with  2  basal  spines  and  <:  Sit 

pairs  of  feet.  Inte.stine  with  hejxaii.  .  • .  .1  ....  1  ii^j- 
volution.  $  Uke  yoiuiK  9  ;  h.x.k  on  tir>t  fcit;  v%% 
deferens  opens  at  base  of  tlaw  on  ventral  (anterior) 
side.  Color  yeliowish-hrown.  oia(iue.  Ix-nKth,  9. 
to  3.0  mm.  or  more;  ^  .  to  1.4  mm.  '1'he  Luxcst 
member  of  the  family.  Found  ever>-where;  in  ijcr- 
manent  pools  or  margins  of  lakes  among  weeds. 


Fig.  1 1 18.     Eurycercus  lameUdJiu.     Poa-.M^iumrn. 


119  (118)  Anus  on  dorsal  side  of  post-abdomen,  whose  post-anal  portion  l)cars 
denticles.  No  hepatic  ceca.  Two  siminiiT  eggs;  one 
ephippial  egg.     $  with  strong  hook  on  first  fixjt. 

Subfamily  Chydorin.\e  .    .     120 

120(247)     Eye  present i.'« 

121  (246)     Eye  and  ocellus  of  ordinary  size;  antennulcs  do  not  [)rojccl  Ix^yond 

rostrum,  though  olfactory  setae  may 122 

122  (171)     Posterior  margin  of  valves  not  greatly  less  than  ma.ximum  height,  i:^ 

No  species  of  Pleuroxus  belong  in  this  section,  though  s«)me  individuals  of  lys  and  iw  m.»y 
seem  to  do  so. 

123  (135)     Body  compressed;  claws  with  secondary  tooth  in  middle. 

124(129,132)     Crested;    post-abdomen  narrow,'   with  marginal  and  Liicral 

denticles '^S 

1  Terms  denoting  relative  size  are  to  be  unclcrstcHHJ  with  reference  to  llic  s*-clit)n  in 
which  they  occur. 


7i8 


FRESH-WATER  BIOLOGY 


125(128)  Crest  on  head  and  valves.  .  Camptocercus  Baird  i&A3  •  •  126 
Form  oval-  greatly  compressed,  with  crest  on  head  and  back.  Valves  with  angles  rounded; 
small  teeth  at  infero-po steal  angle;  longitudinally  striated.  Post-abdomen  very  long,  slender, 
with  numerous  marginal  denticles  and  lateral  squamae.  Claws  long,_  straight,  with  i  basal 
spine;  a  series  of  small  denticles,  terminating  in  a  larger  one  about  the  middle  of  claw;  extremely 
fine  teeth  thence  to  apex.     Five  pairs  of  feet. 

126  (127)     Post-abdomen  with  15-17  marginal  denticles. 

Camptocercus  rectirostris  Schoedler  1862. 

Head  extended  or  de- 
pressed. ^  without 
denticles  on  post-abdo- 
men. Color  yellow- 
transparent.  Length, 
9  ,  to  i.o  mm. 

Common  everywhere 
among  weeds  in  mar- 
gins of  lakes,  etc.  Most 
of  the  specimens  from 
the  United  States  are  of 
the  variety  biserratus. 

Fig.  1119.     Camptocercus 
0.1  MM.    h  '  rectirostris. 


127  (126)     Post-abdomen  with  20-30  marginal  denticles. 

Camptocercus  macrurus  (O.  F.  Miiller)  1785. 
Much  Uke  the  preceding.    Very  rare,  but  reported  from  most  regions  in  the  United  States. 
Undoubtedly  the  preceding  species  has  been  mistaken  for  this  by  some  observers. 

128  (125)     Crest  on  valves  only.    .     Kurzia  Dybowski  and  Grochowski  1894. 

This  genus  is  Alonopsis  (part)  of  older  authors;  Pseudalona  Sars. 
Sole  American  species Kurzia  latissima  (Kurz)  1874. 


General  form  subquadrate; 
greatly  compressed;  but  with  only 
slight  crest  on  back,  none  on  head. 
Head  small,  the  rostrum  reaching 
not  much  below  middle  of  valves, 
though  longer  than  antennules. 
Post-abdomen  long,  slender; 
lower  angle  usually  produced  into 
a  lobe;  10-12  marginal  denticles. 
Claws  of  Camptocercus  type.  J 
like  9 ;  rostrum  shorter;  post- 
abdomen  with  small  denticles;  vas 
deferens  opens  on  ventral  (upper) 
side;  strong  hook  on  first  foot. 
Color  yellowish,  transparent. 
Length,  9>  o-6  mni.;    $  ,  0.4  mm. 

Found  in  all  regions  among 
weeds  in  pools  or  lakes. 


Fig.  II 20.     Kurzia  latissima. 


129  (124,  132)  Crest  on  head  and  valves;  post-abdomen  broad,  without 
marginal  denticles.  .  .  .  Acroperus  Baird  1843  .  .  130 
Body  thin,  compressed;  crest  on  head  and  back.  Valves  subquadrate,  obliquely  striated; 
infero-posteal  angle  rounded  or  acute,  usually  with  teeth.  Post-abdomen  large  compressed; 
without  marginal  denticles  but  with  lateral  row  of  squamae.  Claws  long,  straight,  with  i  basal 
spine  and  secondary  denticles,  much  as  in  Camptocercus.  Intestine  with  large  intestinal  cecum. 
Eye  larger  than  ocellus.     Color  yellow-transparent. 


THE   WATER    FLEAS   (CLADOCI-RA)  jic, 

130(131)     Dorsal  margin  much  arched Irn'/>rra5 /wrp.;,  Baird  1H35 


Eye  anfl  ocellus  m-ar  niarKin  ko»- 
trum  acute.  Kleven  lo  twelve  fcruufn  o( 
fine  spinules  on  {tost-alMlomen.  l^m^h. 
9.  to  o.S  mm.;    ^  .  to  00  mm 

Common  ever>where.  amoni;  »c*t|», 
ill  relatively  oinrn  water;   not  in  muddy 

IKJOIS. 


u;.  1 121.     Acrop<rui  hjrpct. 


0.1  MM. 


131  (130)     Dorsal  and  ventral  margins  nearly  straight. 

Acropcriis  angiistiitus  Sars  1863. 


Crest  larger  than  in  A .  harpar;  eye  and 
ocellus  removed  from  margin  and  rostrum 
obtuse.  Length,  9.  to  o.g  mm;  ^.  0.6 
mm. 

Common  in  similar  situations  to  prctc*!- 
ing  species.  Transition  forms  l)etwem  these 
species  may  be  found  and  ver>"  prolxibly 
they  should  be  united. 


Fig.  1 1 22.     Acroprrui  jnKuiliiJui 


0.1  MM.    I « 

r32  (124,  129)     No  crest 133 


^33  (134)     Valves  not  tumid;  post-abdomen  broad. 

Alonopsis  Sars  1S62 


/T'i 


tii^ 


General  form  resembling  Acroprrus  but  less  com- 
pressed and  without  crest.  Keel  of  InSnim  m^w'^mtr 
or  small,  almost  triangular.  Vahi  -  I 

but  striae  often  inconspicuous.     1 
broad;  with  well-develoix^i  mar,:  \ 

pairs  of  feet,  the  last  very  small.      S  **'ii'  "*"*' 
characters.      Color  yellow. 


Fig    1123.     a,   Alonopsis  flonfala:  h.  AUfmoptii 

(MU'T  n.v.littic 


0.1  MM. 


J   0.1  MM. 


133^^(133^)      15-17  marginal  denticles [hmo psis  chn^ata  Surs  i^i. 

Minute  tooth  at  infero-posteal  angle  of  valves.     Post-abdomen  with  lateral  f.^.  i.  I-      Im.Mh. 
9 ,  ca.  0.8  mm. 
1336(133^0     About  II  marginal  denticles.    .    Alonopsis  aurcohi  IhKAiiiki.i:. 

No  lateral  fascicles  or  infero-posteal  tooth.     Ix-ngth,    9   ^■'^-  '/^  TI^.^MinT*"""     ^^ 
species  in  margins  of  lakes  and  ponds  among  weeds.    Rare;  rei)ortcd  only  from  Maine 


720 


FRESH-WATER   BIOLOGY 


134  (133)     Valves  tumid  in  anterior  part;  post-abdomen  narrow. 

Euryalona  Sars  1901. 
Sole  American  species Euryalona  occidentalis  Sars  1901. 


Euryalona  occidentalis  Sars. 


General  form  resem- 
bling Kurzia,  but  less 
compressed;  no  crest. 
Valves  gaping  in  front, 
tumid  in  infero-ante- 
rior  region;  marked 
obscurely  with  concen- 
tric lines;  dorsal  mar- 
gin arched.  Keel  of 
labrum  angled  behind 
but  not  prolonged. 
Post-abdomen  very 
long,  slender,  lobed  at 
apex;  with  about  20 
marginal  and  very  fine 
lateral  denticles. 
Claws  straight,  armed 
about  as  in  Campto- 
Z  with  strong  hook;  vas  deferens  opens  on 
Color  dark  brown-yellow.     Length,  9 .  to 


cercus.  Five  pairs  of  feet;  hook  on  first  foot  of  9  • 
upper  (ventral)  side  of  post-abdomen  about  middle, 
i.o  mm.;    '$  0.7  mm-  .  ,  ,         ,  ,  , 

Florida,  Louisiana,  Texas;  not  uncommon  m  weedy  pools  and  lakes. 

135  (123)     Body  not  greatly  compressed;   claws  with  i  basal  spine,  or  rarely 

none 13^ 

For  all  species  with  two  spines  on  terminal  claw,  see  171  Q. 

136  (168)     Rostrum  not  greatly  exceeding  antennnles i37 

137  (167)     Rostrum  pointed 138 

138  (150)     Infero-posteal  angle  rounded,  without  teeth 139 


139  (144,  147)     Post-abdomen  with  marginal  and  lateral  denticles. 


140 


140(143)     Post-abdomen   relatively   long   and   narrow;     marginal  .  denticles 
numerous,  longer  distally.     Basal  spine  stout  and  long. 

Oxyurella  Dybowski  and  Grochowski  1894  .    .     141 

In  general  like  Alona.  Post-abdomen  long,  slender;  with  marginal  and  lateral  denticles, 
the  former  numerous  and  ending  in  a  group  of  large  denticles  at  angle  of  post-abdomen.  Termi- 
nal claw  straight,  with  one  large  basal  spine,  attached  some  way  distal  to  base  of  claw.  Color 
yellow  or  yellow-brown.    This  genus  is  the  same  as  Odontalona  Birge. 


141  (142)     12-15  marginal  denticles. 


Oxyurella  tenuicaudis  (Sars)  1862. 

Marginal  denticles  very  small  near  anus; 
the  distal  4-5  much  larger;  the  penulti- 
mate largest.  Length,  9,  ca.  0.5  mm.; 
$ ,  0.4  mm. 

Widely  distributed  but  not  abundant 
anywhere.  New  England  and  Wisconsin 
to  Gulf  of  Mexico.  This  species  is  Alona 
tenuicaudis  Sars. 

Fig.    1 1 25.     Oxyurella    tenuicaudis.     Apex  of 
post-abdomen.     (See  also  Fig.  1129,  b.) 


THE   WATER    FLEAS   (CLADOCERA) 


721 


(141) 


About  16  marginal  denticles. 


Oxyurclla  longUaudis  (Birgc)  igio. 

Between  Alona  and  f  .'     ' 
Valves  with  conccntrii  : 
marginal  dentiiles.  lar^  • 
nullimate  much  larger,  an.: 
larKer  still  and   serrate  on 

Basal  spine  stout,  attai lutl  aL....; .,.,,  . 

way    from    base-    of    daw.      ^   unknown 
Length,  9  . 0.5-0.6  mm. 

Rather  rare  amon^  wec<ls.  Lake  CliArlcs. 
La. 

Fig.  1 1 26.     OxyurtlU  Umtuaitdn. 

143  (140)     Post-abdomen  not  noticeably  narrow;  distal  denticles  not  conspicu- 

ously larger.  Basal  spine  small.    Alomj{miJsis\H:ck-s) .    .    151 
Take  up  the  key  at  the  number  indicated  where  the  genus  is  discussed  a^  a  unit. 

144  (139,  147)     Post-abdomen  with  marginal  denticles  only.   ...  ; ; 

145(146)     Post-abdomen  large,  denticles  very  small.    Alondladiaphdr.i 
Turn  to  the  key  at  the  number  indicated  where  the  species  named  is  discu.sscd. 

146  (145)     Post-abdomen  of  moderate  size;   denticles  of  usual  size. 

Alona  guttuUi 
Turn  to  the  key  at  the  number  indicated  where  the  species  named  is  discussed. 

147  (139,  144)     Post-abdomen  with  numerous  clusters  of  large  spines. 

Lcydigia  Kurz  1874 
General  shape  oval,  much  compressed  but  not  crested.     Head  small,  extendcl;    V-'    •' 
labrum  rhomboidal  with  angles  blunt  or  rounded.     Post-abdomen  very  large,  com;  • 
semi-elliptical  in  form;    post-anal  part  much  expanded,  with  numerous  clusters  of 
spines  in  distal  clusters  very  long.     Claws  long  and  slender.     Kye  smaller  than  wcIIun       (J 
with  blunt  rostrum;    process  on  upper  (ventral)  side  of  post-abdomen  on  which  vas  deferens 
opens;   post-abdomen  with  spines.     Color  yellow. 

148  (149)     Valves  without  markings.     Leydigia  quadrangular  is  (Lcydig)  i860. 
Keel  of  labrum  with  minute  setae.     Claws  with  basal  spine.     Length.  9  •  to  0.9  mm  ;     ' 

0.7  mm. 

In  all  regions  of  the  country;  not  common;  found  singly  among  weeds. 

149  (148)     Valves  striated  longitudinally. 

Leydigia  acanthoccrcoidcs  (Fischer)  1854. 

Keel  of  labrum  with  long  cilia.   Claws  without  basal  spine.    Length.  9 1  to  10  dmu.  or  more; 

d  (European),  0.7  mm. 
Rare:   Louisiana. 


I^O 


148 


0.2  MM. 


Fig.  1 1 2  7     Leydigia  acatUkocercoides. 


722 


FRESH-WATER  BIOLOGY 


150  (138)     Infero-posteal  angle  rounded,  with  small  tooth  or  teeth. 


151 


151(166)  Valves  with  longitudinal  striae.  .  .  .  yl/awa  Baird  1850  .  .  152 
General  form  subquadrate;  compressed,  not  crested.  Valve  with  supero-posteal  angle 
rounded  or  well  marked;  infero-posteal  angle  rounded,  almost  always  without  teeth.  Fornices 
broad;  rostrum  short  and  blunt,  little  exceeding  the  apex  of  the  antennules.  Antennules 
short,  thick;  olfactory  setae  equal.  Keel  of  labrum  large,  ordinarily  rounded;  the  posterior 
angle  not  acuminate.  Feet,  5  pairs,  rarely  6;  the  6th,  if  present,  rudimentary.  Post-abdomen 
broad,  compressed,  with  various  armature.  Claws  with  i  basal  spine  and  denticulate.  Color 
yellow  in  some  shade,  varying  from  light  to  dark,  with  shade  of  brown  in  large  species.  All 
species  littoral. 

152  (153)     Infero-posteal  angle  with  1-3  small  teeth. 

Alona  monacantha  Sars  1901. 


In  general  form  and  appearance  not  unlike  A . 
intermedia.  Valves  distinctly  striated;  infero- 
posteal  angle  rounded  and  with  1-3  small  teeth. 
Post-abdomen  with  g-io  denticles;  claws  with 
very  long  basal  spine.  Keel  of  labrum  angled 
behind.     Length,   9  >  o-35~0-4  nirn. 

This  species  may  be  confused  with  Alonella 
karua  (232).  The  length  of  the  basal  spine  on 
terminal  claw  offers  a  ready  distinction. 

Louisiana;  in  weedy  pools. 

Fig.  1 1 28.     Alona  monacantha. 


0.1  MM 


153  (152)     Infero-posteal  angle  unarmed i54 

154  (155)     Post-abdomen  long,  narrow;    distal  marginal  denticles  very  long. 

See  Oxyurella  .    .     140 

155  (154)     Post-abdomen  not  notably  long 156 

156  (157)     Post-abdomen  with  marginal  denticles  only. 

Alona  guttata  Sars  1862. 

Form  much  hke  A.  costata,  but  usually  smaller  and  dorsal  margin  less  arched.  Valves 
smooth,  striate,  or  tuberculate  (var.  tuberciilata  Kurz).  Post-abdomen  short,  broad,  shghtly 
tapering  toward  apex;  truncate,  angled,  with  longest  marginal  denticles  at  angle;  denticles 
8-10,  pointed,  small;  no  squamae.  Claws  with  small  basal  spine.  Post-abdomen  of  d  without 
spines;  vas  deferens  opens  behind  claws,  without  any  projection.  Length,  ?,  ca.  0.4  mm.; 
^  ,  0.3-0.35  mm.     See  Fig.  11 29,  d. 

Not  uncommon  everywhere. 


Fig.  1 1 29.    a,  Alona  quadrangularis;  b,  Oxyurella  ienuicaudis;  c,  Alona  costata;  d,  Alona  guttata;  e,  Alona 
rectangula;  f,  Alona  rectangula  var.  pulchra;  g,  Alona  intermedia. 
These  figures  are  not  drawn  to  the  same  scale. 


THE  WATER    FLEAS   (CLADOCERA) 

157  (156)     With  marginal  and  lateral  denticles 

158  (161)     Size  large;   14  or  more  marginal  (kninK:-. 

159  (160)     Cluster  of  fine  spinules  at  base  of  claw. 


723 


^■S\^<. 


■•^^.-,'r^'C-^-J 


0.1  MM. 


Mouii  ajjinis  (U-ydig)  i860. 


Greatest    hi-i^ht    usually    near    ti.i.lflr 
valves.     \'alvcs  IcmKituMinally    • 
ticulatod,  often  not  plainly  miir. 
with  rhomboidal  keel;  its  torn.  • 
lated,    sometimes    n)un(lc<J.       i 
large,  not  widened  behind  ant; 
serrate  marginal  dentitl«-s  an' I 
of  small   S(iuamaf.    Claws  Ion, 
with  long  ba.sal  spine  and  45    ; 


r; 


mentary.     Length,  9.  t"  «  o  mm.;   ^  .  to  0.7 
mm. 

The  largest  species  of  the  gcnuA;  very  abun- 
dant  in  all  regions,  in  maririn  of  jinnd*  and 
lakes,  among  weeds. 

Fig    1130.     Alotui  r-,nf 


160  (159)     No  spinules  at  base  of  claws. 

Alona  quddrangularis  {O.  V .  Miiilcr)  1785. 

Greatest  height  usually  posterior  to  middle  of  valves.  Valves  usually  plainly  striated. 
sometimes  conspicuously  so,  with  a  reticulated  area  in  infero-anterior  region  (var. /<-/>iJu  Hirifr). 
Labrum  with  large  keel  of  variable  form;  often  quadrate  or  with  rounder!  angles.  Post  aWo- 
men  large,  flattened,  dorsal  margin  dilated;  with  15-18  serrate  marginal  denticles  and  row  o( 
lateral  squamae.  Claws  large,  with  long  basal  spine;  no  spinules  on  inside  of  basal  ^%T^e. 
Length,  9.  to  0.9  mm.;  <? ,  to  0.6  mm.  See  Fig.  1129,  a.  In  similar  KKalitii's  to  prrcnlinjc 
species;  also  on  bottom  of  open  water. 

161(158)     Size  moderate  or  small.     Fewer  than  14  denticles. 

This  section  of  the  genus  needs  much  additional  study.  There  are  s|K'iics  .md  numerous 
varieties  beside  those  listed. 

162  (163)     Lateral  fascicles  or  squamae  do  not  extend  beyond  dorsal  marpin 
of  post-abdomen ^loun  costatu  Sars  iSO:. 

Evenly  arched  or  greatest  height  behind  middle;  posterior  margin  ranvcx.  Valve*  «ri*ted 
or  smooth.  Post-abdomen  short,  broad;  with  straight  dorsiil  (lower)  manan  tapenng  toward 
apex;  with  about  12  subequal  denticles  and  a  row  of  fine  squamae.  rost-alMl.>mcn  of  J  taper- 
ing; no  marginal  denticles;  very  fme  squamae;  vas  deferens  ojK-ns  at 
extending  out  ventral  to  (above)  claws;  claws  without  basal  spme.  I 
more;    ^  ,  0.4  mm.     See  Fig.  11 29,  c. 

Found  everywhere  and  very  abundant. 

163(162)     Lateral  fascicles  long,  extending  beyond  dorsal  ma r^nn.  if*; 

164  (165)     Post-abdomen  not  broadened  toward  ape.\. 

AloHii  rcctiin'^-M.i  : 

Body  evenly  arched;   general  form  like  A.  guttata.     Valves  striate*!,  rrtin.l.ntcl. 
rarely  tuberculate;    ventral  margin  usually  somewhat  a'"vex      1' ■; 
enlarged  toward  apex,  angle  rounded;  with  8-0  marginal  (  enticles  or 
as  many  fascicles,  the  distal  long  enough  to  project  beyond  margin  *''  i 
without   cecum,  enlarged   at  junction  of  intestine  and  rectum.  s*.incwh.ti  a-s  .» 
Length,   9,  0.35  to  0.42  mm.     See  Fig.  1129,  c.  /.  x  ;  t.  .  ii..ii:rK 

Common  everywhere.    Most  specimens  found  belong  to  var.  puUHra  nciuai. 


\\itx   of   pfucrsa 
ngth.   9.05  nim  or 


'     '-ly 

it 

■  uc 


724 


FRESH-WATER   BIOLOGY 


165  (164)     Post-abdomen  broader  toward  apex.     Alona  intermedia  Sars  1862. 

Body  evenly  arched  but  not  very  high.     Post-abdomen 
.  long,  broad,  enlarged  toward  apex,  with  rounded  angle;  the 

^  ^^  8-9  marginal  denticles  rather  small  and  thick;    the  lateral 

denticles  or  fascicles  much  more  conspicuous,  consisting  of 
bundles  of  fine  setae.  The  distal  seta  in  each  bundle  is  the 
largest  and  the  size  of  setae  increases  toward  apex  of  post- 
abdomen.  The  distal  bundles  {project  beyond  margin  of 
post-abdomen.  Length,  9-  ca.  0.4  mm.  See  Fig.  11 29,  g. 
Rare;  specimens  closely  agreeing  with  Lilljeborg's  descrip- 
O I  MM     I  tion  and  figures  found  in  Wisconsin.    Possibly  not  Sars'  inter- 

'  media,  as  his  figure  of  that  species  resembles  some  varieties 

Fig.  1 13 1.    Alona  intermedia.         of  Lilljeborg's  rectangula. 

166(151)     With  oblique  striae Alonella  karua   .    .     232 

Turn  to  the  key  at  the  number  indicated  where  the  species  named  is  discussed. 

167  (137)     Rostrum  broad,  semicircular Graptoleberis  Sars  1863. 

Sole  species Graptoleberis  testudinaria  (Fischer)  1848. 

__^^^^>.jytu.-anm.<uB tim,,^,^,^^  Posterior  margin  with  2  strong  teeth  at 

^^^  ^  '  ^^.7^-^^^**^%^  infero-posteal  angle;  valves  and  head  with 

y'"^                "~  <*"       '^         ^^^Ssv  conspicuous    reticulation.      Head    large; 

j^          "           j::^                      \^bv  fornix  very  broad,  forming  a  semicircular 

M^,  . ,                        -          •■            '^^^  rostrum,  covering  antennules  and  extend- 

y^'   '      "                 •     "                  ^  ^"-"^-^  ^^^  down   as   far   as  ventral   margin   of 

£/^ .                           ,^«=^j,                   "^4  valves.     Post-abdomen  bent  at  the  sharp 

ff^^       K                ■^-»s?^?l'^^-^W                       \  pre-anal  angle;  tapered  toward  claws,  so 

/'Q^^^j-'^                 '~  :.^ '  jz^~                     ^  that  form  is  nearly  triangular;  marginal 

^^^'^  y   *^                  ^                                  V^  spines  small;  lateral  fascicles  minute,  some- 

^       V^Ll    ,  -^    ^                ^               JJ,^'-^  times  wanting.     Claws  small,  with  i  mi- 

TS^\r\™\^\tHWN\rTn^\^^^'^      ^n  ^"^^  ^^s^'  SP'^^'  sometimes  wanting  (var. 

\WM\  ,m\i#W  \\  \^\^^\^  ^^  N.-^        ^-^^^^.^  Bjrgg).   ^  ^j^i^  iQj^g^  gignder  post- 

0.1  MM-  -  \  ii  abdomen,    without   spines;    vas   deferens 

Fig.  1 132.    Graptoleberis  testudinaria.  opens  on  ventral  side;   claws  very  minute; 

hook  of  first  foot  slender. 
Color  gray  to  yellow-white;  sometimes  opaque.     Length,   9-  o-5-o.7  mm.;   J,  0.5  mm.  or 
less. 

Common  among  weeds  or  on  bottom  of  pools  and  margin  of  lakes. 

168  (136)     Rostrum  considerably  exceeding  antennules 169 

169  (170)     Post-abdomen  with  marginal  denticles  only.     Alonella.   .  240,  241 
Turn  to  the  key  at  the  nimibers  indicated  where  two  species  are  discussed. 

170  (169)     Two  to  four  marginal  denticles;    long  series  of  lateral  denticles. 

Rostrum  very  long,  recurved.   .    .    Rhynchotalona  Norman  1903. 
Sole  species Rhynchotalona  falcata  (Sslts)  1861. 

General  form  of  body  like  Alona.     Ros- 

^     ^  trum  very   long,    slender,    and  recurved 

under    the    head.     Post-abdomen    stout, 

thick,   bent  at   anus,   truncate  at  apex; 

with   about   four   rather   stout   marginal 

tf#7  -/  -"  iV  ^\         denticles  near  apex,  and  a  lateral  series, 

^-^^'^'  '^       -  *\        continued  nearly   to    anus,    of   very   fine 

spinules  in  an  unbroken  row.  Intestine 
with  cecum.  $  (European)  with  long 
rostrum,  bilobed  at  apex;  post-abdomen 
tapering  and  armed  with  hairs  only;  ordi- 
nary hook  on  first  foot.  Color  yellow  or 
0.1  MM.    -  greenish.   Length,  9 ,  0.5  nmi.;  ^  ,0.4  mm. 

F1G.1133.    Rhynchotalona  falcata.  Maine,  Michigan. 


THE   WATER    FLEAS   (CLADOCKRA) 

171  (122)     Posterior  margin  of  valves  considerably  Kss  llian  maximum  height. 

All  species  of  Pleuroxus  belong  here;  also  AloncUa  excisa  an<l  <-.ri\'M<j. 

172  (204)     Body  elongated,  form  not  spherii  al. 

173  (174,  175)     Lower  part  of  posterior  margin  excised  or  crenulalwl. 

AloncUa  excisa,  A.  cxigwi  • ; ;    .  . 

Turn  to  the  key  at  the  numbers  indicated  where  two  species  are  discusv  ; 

174  (173,  175)     Posterior  margin  with  numerous  teeth  along  whole  length. 

Pleuroxus  procurvatus,  P.  trutUiitus  iK,s.  i,ji 

Turn  to  the  key  at  the  numbers  indicated  where  two  sik-cIcs  are  disrusM<i 

175  (173,  174)     Teeth  (if  any)  only  at  infero-jHjslcal  angle.  \-h 

176  (179)     Infero-posteal  angle  well  marked,  ordinarily  with  trcth  177 

177(178)     Rostrum  long /7<'//r<u;o- most  s{K'nes  186 

Take  up  the  key  at  the  number  indicated  where  the  genus  is  discussed  as  a  unit. 

178  (177)     Rostrum  short UoticUa  dctUiifra    .    . 

Take  up  the  key  at  the  number  indicated  where  the  genus  is  discussed  a.s  a  unit. 
N.B.     If  the  rostrum  is  broad,  semi-circular  at  vnd,  see  167. 

179  (176)     Infero-posteal  angle  rounded 180 

180  (185)     With  well-marked  tooth  or  teeth 181 

181  (182)     Rostrum  long,  recurved Pleuroxus  striatus   . 

Turn  to  the  key  at  the  number  indicated  where  the  species  named  is  di.scusse<i. 

182(181)     Rostrum  short D  u  )i /lanl  la  Kiuf;  iS-~,^  ..-, 

General  shape  rounded.  Valves  tumid,  gaping  below;  obscurely  reticulatc<!;  infcn>-i»i»Mc«l 
angle  rounded,  with  i  or  2  teeth  on  ventral  margin  in  front  of  angle.  I'ost-aiH!.  tm n  l-cnt 
abruptly  behind  anus;   post-anal  part  thick,  somewhat  foot-shajx'd  as  strn  from  d 

(lower)  margin  lying  parallel  to  ventral  margin  of  valves;  with  many  fine  dcnti' 
Claws  short,  curved,  with  i  basal  spine.      $  with  usual  characters;  ixjst-alxionuu  >-i. 
as  9  >  with  fine  hairs  only. 

183  (184)     Form  short  and  high,  as  dorsal  margin  is  much  arched. 

Dunhrccdi,!  srHi'cr,:  (Hirire)  1S77. 


^  ^  V";   '    ^    X,^  Keel  of  labrum  pro(iuce<i  into  a  stmicwhat  tm  . 

^^.^      I     '     '   ^       •  ^  v^^  form,  its  ventral  margin  sm(H)th.     Color  yellow.    1 

^:                               \  9,  to  0.5  mm.;    /,  ca.  o..^f)  mm. 

\  New  England  and  Wisconsin  to  Colorado,  l^ 

;  "         "        ^                 Jl,  and  Texas.    Not  common;  among  wcttls.    I'crhap 

.      ,                     ,  cal  with  D.  crassa  King. 

■''^■<-  .   ^ 

aiMMf.  . .  f- 


726 


FRESH-WATER   BIOLOGY 


^■--^^i 


184  (183)     Form  more  elongated,  as  dorsal  margin  is  little  arched. 

Dunhevedia  serrata  Daday  1898. 

,'^  ^._         „  ^  Usually    2    teeth   at    infero-posteal 

angle,  a  very  small  posterior  and  a 
larger  anterior  one.  Keel  of  labrum 
serrate  in  anterior  part,  smooth  be- 
hind; about  10-12  serrations,  pointing 
backward.  ^  unknown.  Color  yel- 
low.    Length,  9  .  ca.  0.7  mm. 

Louisiana,  Texas;  in  pools  and  lakes 
among  weeds;  not  abundant. 

Fig.  1 135.  Dunhevedia  serrata.  a,  labrum; 
h,  post -abdomen. 


0.1  MM. 


185  (180) 


Infero-posteal  angle  without  teeth,  or  tooth  very  small;  rostrum  long 
or  short 186 


186  (203)     Claws  with  2  basal  spines. 


Pleuroxus  Baird  1843 


187 


Rostrum  long  and  pointed,  rarely  bent  forward.  Dorsal  margin  much  arched;  posterior 
margin  short,  usually  less  than  one-half  height,  rarely  toothed  along  entire  length;  infero- 
posteal  angle  rarely  rounded,  usually  sharp  and  toothed.  Keel  of  labrum  large,  usually  tongue- 
shaped;  posterior  angle  prolonged.  Post-abdomen  with  marginal  denticles  only,  cf  smaller 
than  9 »  with  usual  characters;   post-abdomen  varies  in  different  species. 

Three  types  of  form  are  distinguishable  in  the  genus:  (i)  relatively  long  and  low  species: 
striatus  type  (P.  striatus,  hastaius,  hamulatus);  (2)  short,  high-arched  forms:  denticulatus 
type  (P.  denticulatus,  aduncus,  trigonellus,  truncatus);  (3)  the  second  form  with  rostrum  bent 
forward:   {P.  procurvatus,  uncinatus).     All  species  littoral. 

187  (190)     Rostrum  bent  up  in  front 188 


(189)     Rostrum  bent  sharply  into  hook;    teeth  along  whole  posterior 
margin  of  valves Pleuroxus  procurvatus  Birge  1878. 


General  form  and  markings  like  P.  denticulatus.  Posterior 
margin  of  valves  with  7-8  teeth  along  the  whole  length. 
Post-abdomen  like  P.  denticulatus  but  slightly  more  broad- 
ened behind  anus,  d  unknown.  Color  yellowish,  transpar- 
ent or  opaque.     Length,    9  >  ca.  0.5  mm. 

Northern  states,  common  in  weedy  waters. 


Fig.  113b.     Pleuroxus  procurvatus. 


0.2  MM.  1. 


189  (188) 


Rostrum  merely  curved  forward;  teeth  at  infero-posteal  angle  only. 

Pleuroxus  uncinatus  Baird  1850. 


Infero-posteal  angle  with  2-4  rather  long,  curved  teeth, 
sometimes  branched.  Rostrum  long,  acute,  bent  forward. 
Post-abdomen  like  P.  trigonellus,  broad,  somewhat  tapered 
toward  apex;  about  13  good-sized  marginal  denticles.  Color 
dirty  gray,  or  with  green  or  yellow  tinge.  Length,  9, 
0.7-0.9  mm.;   ^  (European),  0.56  mm. 

Nebraska  (Fordyce).  The  species  is  very  close  to  P. 
trigonellus,  separated  by  procurved  rostrum  and  large  teeth 
at  infero-posteal  angle. 


t>4MM. 


Fig.  ii37«    Pleuroxus  uncinatus.    European  specimens. 


THE    WATER    FLEAS   (CLADOCKKA) 

190  (187)     Rostrum  not  bent  forward. 

191  (192)     Numerous  teeth  along  whole  posterior  margin. 

Plcuroxiis  /run,. It  1,^  <( 


I-.  Mullcr 


Posterior  marKiii  unn  inm  , 
set  teeth;  valves  striate!   tli. 
nearly   longitudinal,   tlie  .,t)i, 
men  much  like  /'.  tri>-ondius.  >l,»{htiy'u- ■ 
apex,  an^le  mu.Klecl;   12-14  marginal  . Ic..'- 

Nebraska  (Fordyce). 


Fig.  1 138.      PUuroxus  Irunai 


I  F^urnj 


icati  ^I«xlm«■n 


192  (191)     Teeth  at  infero-posteal  angle  only 

193  (196)     Post-abdomen  long,  slender,  convex  on  ventral  (upiK-r;  side.        194 

194  (195)     Supero-posteal    angle    sharp    but    not    projecting-     infcro-posteaJ 
angle  a  sharp  point J'laaoxus /iaslatt4s  S^irs  1862. 


Infero-posteal  anple  a  sharp  point,  with  a  vcn-  snuill 
tooth;  valves  reticulated,  longitudinal  marks  oftrn  m.,rr 
distinct,  givmg  appearance  of  striation.     if. 
denticles.      Color   yellow,    transjKirent    ur 
black  unless  ephippial.     Length,  9.  ca.  o.f.  : 
0.45  mm. 

Rather   rare;     New    England.    Wisconsin.   NcbnuJtA, 
Caufornia. 


Fig.  1139.     PUuroxus  Auj/o/mj. 


0.1  MM 

195  (194)     Supero-posteal  angle  overhanging;   infero-po.^^teal  angle  rounded, 
with  small  tooth  in  front  of  it. 

Plcuroxiis  striiitHS  SchtK-dler  iS6j. 

General  shape  much  likr  T    '  .  • 

but  never  .so  high  archol  as  : 
Valves  obviously  striatal.     I'. 
long,  slender,  with  20.  or  nmrt-.  iiutrKiiiul 
denticles.     Color  dark.  rsjKHially  oiU(jvie 
on  dorsal  side,  often  nearly  bUik.    Length. 
9.  ca.  o.S  mm.;     '.  ca.  of*  mm. 

In  all  (Kirts  of  Cnitctl  States;  commoa 
among  weetls. 

This  sjK'cies  is  /'.  gradJis  Hutlcndorf; 
P.  unidctts  Birge. 


aiMM 


Fig,  1 1 40.     Plfur>fXMs  j/no/ni. 


728 


FRESH-WATER  BIOLOGY 


196  (193)     Post-abdomen  of  moderate  length;  ventral  (upper)  margin  straight, 

or  nearly  so;  greatest  width  behind  anus 197 

197  (200)     Angle  of  post-abdomen  sharp,  with  cluster  of  spines  at  apex.    .     198 


198  (199)     Teeth  at  infero-posteal  angle  of  valves;    no  hook  on  first  foot 
of  female Pleuroxus  denticulatus  Birge  1877. 


Infero-posteal  angle  with  small  tooth- 
like spines.  Post-abdomen  moderately 
long,  straight,  very  little  narrowed  toward 
apex;  length  of  post-anal  part  1.5  times, 
or  more,  that  of  anal  emargination;  apex 
truncate;  with  cluster  of  fine,  straight 
denticles  at  apex  and  8-12  anterior  to 
these.  Color  greenish  or  yellowish,  usu- 
ally transparent.  Length,  9  >  0.5-0.6 
mm.;    $  ,  0.36  mm. 

Common  everywhere  in  weedy  water. 


Fig.  1141.    Pleuroxus  denticulatus. 


199  (198)     Infero-posteal  angle  rounded;  first  foot  of  female  with  stout  hook. 

Pleuroxus  hamulatus  Birge  1910. 

Infero-p>osteal  angle  rounded,  without  teeth;   valves  reticulated;   also  marked  by  very  fine 


striae,  which  run   nearly  longitudinally. 


Rostrum  long,  recurved.  Keel  of  labrum  small, 
rounded,  prolonged.  Post-abdomen  much 
like  P.  denticulatus,  but  with  apex  more 
rounded  and  denticles  not  so  crowded  there. 
Denticles  about  12-14.  ^unknown.  Color 
horn-yellow,  often  dark  on  dorsal  side  like  P. 
striatus.     Length,  9  .  ca.  0.6  mm. 

New  England  and  southern  states;  prob- 
ably a  coastal  form;  not  reported  from  north 
central  region.  Common  in  pools  and 
weedy  waters. 


Pleuroxus  hamulatus. 
b,  post-abdomen. 


first  foot; 


1 143.     Pleuroxus  hamulatus. 


200  (197)     Angle  of  post-abdomen  rounded 201 


THE  WATER  FLEAS  (CLADOCERA)  729 

201  (202)  Series  of  marginal  denticles  longer  than  anal  emargination-  post- 
abdomen  of  male  broadened  in  middle  of  posl-amd  tiari 
with  crescentic  dorsal  margin. 

Pleuroxiis  trigoncllus  (O.  F.  MuUcr)  17S5 

Form  of   P.  dentUulatui   tvi>r      Infrro- 
postcal  anRlc  with  2  or  \  .small  trrth.  ..ftm 
minute,    sometimes    wantiriK      I'mt  aUlo- 
mcn  much  as  /'.  drntuulatut;  but  i\ui^\ 
mar^'in    slightly    convex.    I.roadcr    Jx-hind 
anus;  ai^x  rounde*!;   14-16  marKifwd  licn- 
tides,    longer   toward   apex,   hut    not    <liv 
tinctly  clustered  there.      ^  fxrt  aMnmm 
is  characteristic;    hroadene*!   ' 
into  a  semi-elliptical  plate,  t 
set  hairs,  no  spines;   jrreatly  ; 
ward  aiK'X.  forming'  a  slender  prolan. 
Color   yellowish,    transparent;    j*.-: 
men  often  dark.      Lcn^h.    9  .  o  <>  "im  . 
$ ,  0.4  mm. 

Not  common;    Maine,   \Vi.vx)n<un,   Ne- 
braska; doubtless  widely  dislribute<l. 


Fig.  1 144.  PUuroxus  lrif(meUus 


Pa8t-»l«.J<>m«j: 


202  (201)     Row  of  marginal  denticles  about  equals  anal  emargination;  male 
post-abdomen  not  crescentic. 

Pleuroxus  admicus  (Jurinc)  iSio. 


9  very  closely  resembling  P.  triionrUut. 
but  differing  as  follows:  valves  striatc<l;  in- 
fero-posteal  angle  usually  without  teeth.  iN^st- 
abdomen  shorter,  the  length  of  post -anal  p*rl 
hardly  e.xceeding  anal  emargination;  dors*! 
margin  slightly  arched,  with  0  u  manorul 
denticles;  ape.\  rounde<i.  <J  i>ost-alxlomen 
very  diflerent  from  P.  tri^ontUns:  narrower 
than  9.  tajx'red  toward  claws;  no  dorul  en- 
largement or  apical  prolongation.  Color  born- 
yellow,  sometimes  t)|)a(iue.  Length.  9.  ca. 
0.6  mm.;    ^  ,  ca.  0.45  mm. 

Colorado,  California.  Among  weeds  or  in 
pools. 


Fig.  11.(5.     Plfuroxus  aJumiiu. 


0.1  MM. 


203  (186)     Claws  with  i  basal  spine [lonilln  (most  six-cics)    .    .     230 

Take  up  the  key  at  the  number  indicated  where  one  sul)genus  is  discus.seii  as  a  irniL 

204(172)     Body  spherical  or  broadly  ellipsoidal 205 

205  (208)     Well  marked  or  small  spine  at  infero-posteal  angle 206 

206(207)     Valves  conspicuously  striated •     Monelhi  mimi   .    .      ^4-' 

Turn  to  the  key  at  the  number  indicated  where  the  species  is  discussed. 

207  (206)     Valves  reticulated  or  not  plainly  marked.     ChyJorus  barnyUi 

Chydorus  hyhruius  .    .     2 it,  337 
Turn  to  the  key  at  the  numbers  indicated  where  the  two  species  arc  discussed. 


730 


FRESH-WATER   BIOLOGY 


208  (205)     No  spine  at  infero-posteal  angle 209 

209  (210)     Valves  with  conspicuous  projection  on  antero-ventral  margin. 

Anchistropus  Sars  1862. 
Sole  American  species Anchistropus  minor  Birge  1893. 

Form  globular.  Ventral  region  tumid  anteriorly 
and  ventral  margin  of  valves  bent  sharply  away  from 
each  other  about  one-third  way  from  front  and  the 
valve  folded  out  into  a  hollow  groove  and  tooth, 
which  contains  the  strong  hook  of  the  first  foot. 
Head  large,  bulging  over  eye,  the  fornices  broad  and 
forming  a  sort  of  flap-like  rostrum,  which  can  be 
closely  pressed  to  the  valves.  Post-abdomen  broad 
at  base,  pre-anal  angle  overhanging;  rapidly  narrow- 
ing toward  apex,  which  is  prolonged  into  a  lobe;  a 
few  marginal  spines.  Claws  with  long,  slender  basal 
spine,  denticulate  or  smooth.  First  foot  of  9  with 
strong  hook,  toothed  on  concave  side,  which  lies  in 
groove  formed  by  folding  of  valves. 

In  A.  minor,  groove  for  hook  of  first  foot  near 
anterior  part  of  valves;  hook  not  large.  Color  brown- 
yellow.      ^  unknown.     Length,  9  >  ca.  0.35  mm. 

Maine,  Michigan,  Wisconsin,  Louisiana. 

Fig.  1 146.    Anchistropus  minor. 

210(209)     No  such  projection 211 

211  (229)     Post-abdomen  ordinarily  short  with  prominent  pre-anal  angle. 

Chydoriis  l^tdiCh.  i^^2>  ■  ■  212 
Shape  spherical  or  ovate.  Posterior  angles  little  marked;  infero-posteal  angle  usually  un- 
armed. Antennules  short  and  thick.  Rostrum  long  and  acute.  Post-abdomen  usually  short, 
broad,  rarely  long  and  narrow  (C.  globosus);  apex  rounded;  with  marginal  denticles  only  or 
(C.  globosus)  with  very  fine  lateral  fascicles.  Claws  with  2  basal  spines,  the  proximal  often  very 
minute,  rarely  absent.  ^  with  short  rostrum,  thick  antennule,  hook  on  first  foot,  post-abdomen 
often  very  narrow. 


212  (213)     Post-abdomen,  long,  narrow, 


Pleuroxus-\ik.t. 

Chydorus  globosus  Baird  1850. 


Almost  spherical;  valves  smooth  or  reticulated,  sometimes 
striated  in  front.  Post-abdomen  with  small  pre-anal  angle; 
numerous  marginal  denticles  and  very  fine  lateral  fascicles. 
Claws  with  2  basal  spines,  the  distal  very  long  and  slender. 
Color  bright  yellow  to  dark  brown,  usually  with  dark  spot  in 
center  of  valve.     Length,  9  -  to  0.8  mm.;    $  ,  0.6  mm. 

Everywhere;  in  lakes  and  ponds,  among  weeds,  but  never 
present  in  very  large  numbers. 

C.  globosus  might  well  be  type  of  a  separate  genus.  The  other 
species  fall  into  3  groups:  (i)  The  sphaericus  group  or  Chydorus 
proper  (C.  sphaericus,  gibbus,  piger,  lalus,  ovalis);  (2)  The 
faviformis  group,  similar  to  (i)  but  with  greatly  developed  cutic- 
ular  structures  (C.  faviformis,  bicornutus);  (3)  The  barroisi 
group,  with  toothed  labrum;  denticles  of  post-abdomen  shortest 
in  middle  of  row  (C.  barroisi,  hybridus,  poppei). 


Fig.  1147.    Chydorus  globosus. 


73J 


THE  WATER    FLEAS   (CLADOCERA) 

213  (212)     Post-abdomen  short,  broad;  prc-anal  an^lt-  markc<I. 

214  (215,  216)     Shell  covered  with  deep  polygonal  cx-Ils. 

C/iyilorus  fitviformis  Birgc  i8<;3 


Mmh  like  spharrifus  in  form  and  nizt     X 
unknown.     ('(.lor   yi-llow  to  lixht   bruwnith. 

Lt-nKth,   9.  0.5  -0.0  mm. 

New  Kn^'land,  Wistunsin,  Mkhiican.  Ijuuiti- 

ana;  nut  common. 


Fig.  ii4,S.     Chy<L,rus  /arifa 


cjukl  tixU 


0.1  MM. 


215  (214,  216) 


Shell  with  deep  polygonal  ceils  and  ciiticular  ridges. 

Clixdorus  hiiornulus  Doolilllc 


')Oi. 


0.1  MM. 


Like  faviformis  in  havinp  «lcfp  pulygonal 
cuticular  cells;  but  (listinRuishf*!  l»y  the  dr- 
velopment  of  an  extraonlinary  ami  fnmjJcJl 
system  of  thin  cuticular  ridges,  whiih  cxtcixl 
far  beyond  the  ordinary  cell>.  .\  lon^j  honi 
extends  laterally  from  the  mi«ldlc  dorsal  rcKtun 
of  each  valve,  from  which  radiate  v>mc  of  ihc 
ridges.  $  unknown.  Color  yellow.  Ixni^h. 
9.  to  0.7  mm. 

Maine,  New  Hampshire,  and  New  Jersey. 


I'IG.  1149.    Chydorns  buornutmi.    (..Mler  I>oQl*llr 


216  (214,  215)     Shell  of  ordinary  type -'' 

217(225)     Ventral  edge  of  keel  of  labrum  smooth -»S 

218  (219)     Antero-dorsal  surface  of  valves  and  head  flattened. 

Clivilorus  i^ihhiis  Ldljeborg  livS 


iVSo. 


The  cur\e  of  the  flor«il  surface  somewhat  ilat tend. 
both  in  front  and  behin.l.  making  a  M.rt  of  hump  in 
center  of  dorsal  margin.  X'alvi-s  reticulatcl.  \lr»d 
small;  rostrum  projects  from  valves  m  chara.len^tK 
wiv       I'ost-abdomen    with    S   10   mannnal   denUtic*. 


way 


Color  yellowish  to  brown.     I^-n>'th.  9  •  o  -S  '"'"• 
Lake  Superior.  WisconMM.  Michigan;   rare 
This  species  is  C  ruguiosui  lorl)e». 


Fig.  1150.    Lkydorus  cit^m. 


732 

219  (2i8) 


FRESH-WATER   BIOLOGY 


Dorsal  surface  not  flattened;  form  usually  spherical  or  broadly 
ovate 220 

220  (223,  224)     Small  forms  not  exceeding  0.5  mm.,  usually  less.    ...     221 

221  (222)     Fornices  gradually  narrowing  into  rostrum.    All  olfactory  setae  on 

end  of  antennule.     Chydorus  sphaericus  (0.  F.  MiUler)  1785. 


Spherical  or  broadly  elliptical.  Shell  usually  reticulated, 
sometimes  smooth  (var.  nitidus  Schoedler),  sometimes 
punctate  (var.  punctatus  Hellich),  or  with  elevations  (var. 
coelatus  Schoedler).  Post-abdomen  with  8-9  marginal 
denticles.  Claws  small;  proximal  basal  spine  very  minute. 
$  with  post-abdomen  much  emarginate.  Color  light 
yellow  to  dark  brown.  Length,  ^,0.5-0.5  mm.;  $, 
0.2  mm.  Small  limnetic  forms  constitute  var.  minor 
Lilljeborg. 

The  commonest  of  all  Cladocera;  found  all  over  the 
world. 


Fig.  1 151.     Chydorus  sphaericus. 


222  (221)     Fornices  abruptly  narrowed  into  rostrum.     Two  olfactory  setae 

on  side  of  antennule Chydorus  piger  Sars  1862. 

General  form  much  like  C.  sphaericus.  Ventral  margin  of  valves  densely  ciliated;  valves 
ordinarily  marked  by  oblique  striae,  sometimes  smooth.  Fornices  abruptly  narrowed  at  rostrum. 
Antennule  with  usual  lateral  sense  seta  and  two  olfactory  setae  on  side.  Post-abdomen  with 
8-g  rather  long  marginal  denticles.  Claws  with  2  basal  spines,  the  proximal  one  minute.  Z 
post-abdomen  narrow,  but  not  excavated.  Color  light  to  dark  yellow.  Length,  9 »  ca*  o-4 
mm.    Rare;  reported  only  from  Maine. 


/ 


0.1  MM 

Fig.  1152.    Chydorus  piger. 

223  (220,  224) 


Entire  specimen  and  lower  side  of  rostrum  with  antennules. 

Larger  forms,  to  0.8  mm.     Antennules  short  and  thick  with 
all  olfactory  setae  terminal.  .    .    .   Chydorus  latus  Sars  1862. 


Much  like  sphaericus,  but  larger.  Mandible  attached 
some  way  back  of  junction  of  head  and  valve.  Denti- 
cles of  post-abdomen  10-12.  Claws  sometimes  with 
only  I  basal  spine.  Color  dark  yellow-brown.  Length, 
9  ,  to  0.7-0.8  mm. 

Rare;   Canada,  near  Lake  Erie. 


Fig.  II 53.    Chydorus  latus. 


0.1  MM, 


THE   WATER    FLEAS    (CLADOC'KR A'l 

224  (220,  223)     About  0.5  mm.     Antcnnule  with  one  oli.ui..r%  ..  la  j.r,,\:-:  .,1 
to  cluster  at  end Chydorus  aialu  Kilrz  xs-^^. 


0.2  MM.  * 


Fig.  1 154.     Chydorus  ovalis.     Entire  specimen  and 
antennule. 


Form  roun»l  <.r  Port- 

alMlomt-n   with   r.  ij-i$ 

mar^'inal  ricnticlr       '  'hiKawl 

si)in(-^.    the    proximal  mmutc.     ('f>k)r 

yellow.  transjKirent  I-rnKth.  9.  to 
0.0  mm.;     '  <Kuro|K-ani,  05  mm. 

Rare;   Nebraska. 


225  (217)     Ventral  edge  of  keel  of  labrum  with  one  or  more  teeth. 


::6 


226  (227,  228)     With  several  teeth;  short  spine  at  infcro-postcal  angle  of  valves. 

Chydorus  barroisi  (^Richard)  iS<>4. 


Form  and  size  much  like  spkarruus.  thoujch 
ventral  margin  is  lexs  curved.  Keel  o(  la- 
brum acuminate  behind:  serrate,  with  (our  or 
more  teeth.  ro>t-alxlomen  with  well  dcvd- 
oped  pre  anal  an«le;  ia-12  marfrinal  drnticlo. 
shortest  in  middle  of  row.  (  olor  bruwnyd- 
low.     LenK'th,  9  .  ca-  °  4  nim. 

Rare;    Lake  Charles.  Ix)uisiana. 


Fig.  II ss.     Ckydorui  tnirraul. 


0.1  MM 


227  (226,  228)     With  one  tooth;  infero-postcal  spine  present. 

'  ^       '  Chydorus  hvhndus  Daday 


1005. 


Similar  to  barroisi  but  with  only  one  tcxuh  on  keel  o(  Ubrum. 
Rare;   Wisconsin.  .Micliican.  Ixmisiana,  FcxaA. 


Fic.  1 156.     ChyJortu  h)i>nJtu. 


734 


FRESH-WATER  BIOLOGY 


228  (226,  227)     With  one  tooth  on  labrum;  no  spine  on  valves. 

Chydorus  poppei  Richard  1897. 


Like  hyhridus  but  without  spine  at  infero-posteal 
angle.  Tooth  on  labrum  sometimes  small  or  obso- 
lescent. 

Louisiana,  California;    rare. 

Very  probably  the  last  two  species  should  be 
listed  as  varieties  of  barroisi.  These  species  were 
first  placed  in  Pleuroxus,  but  have  no  verj^  close 
afl&nity  with  either  Pleuroxus  or  Chydorus;  might 
well  be  made  a  separate  genus. 


Fig.  1157.    Chydorus  poppet. 


aiMM. 


229  (211) 


Post-abdomen  large,  pre-anal  angle  ordinarily  not  prominent. 

Alonella  Sars  1862    .    . 


230 


This  genus  consists  of  a  heterogeneous  assemblage  of  forms;  not  assignable  elsewhere  and  not 
easily  separable.     There  are  3  sections  which  might  well  constitute  separate  genera: 

(i)  y4/o?je//a  proper.  Rostrum  long,  slender,  recurved;  usually  conspicuously  so;  post- 
abdomen  with  marginal  denticles  only;  claws  with  i  basal  spine.  A.rostrata,  dadayi, 
nana.  (2)  Paralonella.  Rostrum  short,  hardly  exceeding  antennules;  post-abdomen  with 
very  small  marginal  denticles,  with  or  without  lateral  fascicles;  claws  with  i  basal  spine. 
A.  karua,  dentifera,  diaphana,  glohiilosa.  (3)  Pleuroxalonella.  Rostrum  moderate;  post- 
abdomen  with  marginal  denticles  only;  claws  with  2  basal  spines.  Pleuroxus-likt.  A. 
excisa,  exigua. 


230  (235)     Rostrum  short;  post-abdomen  with  marginal  and  lateral  denticles. 

231 


231  (234)     Valves  with  infero-posteal  angle  toothed.   . 232 


232  (233)     About  3  fine  teeth;  valves  striated.   .   Alonella  karua  (King)  1853. 


General  shape  like  Alona  and  easily 
taken  for  a  member  of  that  genus._  (See 
152.)  Valves  with  oblique  striae;  infero- 
posteal  angle  with  1-4  minute  teeth. 
Post-abdomen  broad,  expanded  behind 
anus;  apex  rovmded;  with  about  8  minute 
marginal  denticles  and  as  many  lateral 
fascicles,  much  larger.  Claws  with  i 
small  basal  spine.  Color  yellow,  trans- 
parent. Length,  9, 0.45  mm;  $  (South 
America),  0.23  mm. 

Louisiana,  Texas,  Arkansas;  not  rare, 
in  pools  and  lakes. 

Fig.  1158.    Alonella  karua. 


0.i  MM. 


THE    WATKR    FLEAS   (CEAOOCI.R  \)  73. 

233  (232)     One  to  three  rather  strong  teeth,  valves  reticulated. 

Aloiulla  dtntifcra  Sars  icxji. 


/A 


m<o:^ 


^fr^ 


0.1  MM. 


ft^^' 


v^^ 


Back  liiKh  arched;  iiifcr<>-iK>sl»-aI  .in^Ic  a.  uf.-   «iih 
1-5  fairly  strong  tL-clh.     Rostn;'     •  ,^ 

ventral   margin  of    valves.      ]■  ,. 

broad,    somewhat    exixindwl    Im,.,..  '.\ 

rounded;  with  alx^ut  12  minute  mar, 
and  as  many  very  minute  lateral  f.i  *, 

with  I  very  lon^  l)as;d  spine.     Color  y.  Iluw  l.ru*n 
Length.   5  ta.  o..}  mm.;   ^  ,  o  <s  mm. 

Louisiana  and  Te.xas;  not  rare  in  \*»A%  and  UJic^ 

Fig.  iisy.    Alonella  Jcnti/cra,  with  developing  cpbippium. 


234(231)     No  infero-posteal  teeth;  form  rotund 


O.I  MM,   i 


Uomild  glohulosa  Daday  1898. 

Small;  shafK-  oval  rotund;  head 
reachinK  alx)ut  to  miil.il.-  ..f  >.  .Kr^. 
Valves  striate<l;  all  ni  \ 

and  without  teeth.      I  n 

long,  narrow;    hr<)a<!.  »; 

about  \2  minute  m.i-  .^ 

and  as  many  slen<Ier  !  ■  •>. 

Keel  of  labrum  with  --  noulic*. 
Color  yellow-brown.  Lcn^h.  9. 
0.30-0.4  mm. 

Lake  Charles,  Louisiana, 
weeds. 

This  species  is  .! .  sctUpta  San. 

Fig.  1 1 60.    AlontUa  (lobmlos*. 


235  (230)     Post-abdomen  with  marginal  denticles  only ^36 


236  (237)     Denticles  minute;  post-abdomen  large,  bent  behind  anus;  no  in- 
fero-posteal tooth  on  valves.    Alouiila  diiiphaiia  (King)  1S53. 


0.1  MM 


Head  short,  n>strum  not  rracb- 
ing  more  than  two  thinls  distance 
toward  ventral  mrirdn.  Wilvc* 
striated.    M)nii  •  to 

reticulation.   .  ^: 

infero-ix).steal  i- 

out    teeth.       I 

slightly  enlar^'  h 

numerous  very  inuuitc  ir,.ii,.iiAJ 
denticles  anil  no  other  !*jnnri. 
Claws  long:  i  ba5al  sjMnc.  lycnitth. 
S  .  0.5  mm.;  S  <  o  4  rom.  Ci>lor 
yellow,  transjwrcnt. 

I^uisiana,  Texas;  in  pooU  and 
lakes;    rare. 

Fic.  1 161.     Aloneila  dui^ksm*. 


736  FRESH-WATER   BIOLOGY 

237  (236)  Denticles  of  ordinary  size;  infero-posteal  tooth  present.    .    .  238 

238  (243)  Claws  with  one  basal  spine 239 

239  (242)  Rostrum  long,  recurved 240 


240  (241)     Shape  elongated  oval;  valves  striated 


0.1  MM 

Fig.  1 162.     Alonella  rostrata. 


Alonella  rostrata  (Koch)  1841. 

General  form  not  unlike  a  Pletiroxus  of  the  striatus 
type.  Valves  striated  or  reticulated;  infero-posteal 
angle  rounded  and  with  minute  tooth,  sometimes  ab- 
sent. Rostrum  long,  slender,  recurved.  Post-ab- 
domen moderately  long,  somewhat  tapering  toward 
apex;  angle  rounded;  9-12  small  marginal  denticles. 
Claws  with  i  minute  basal  spine.  Color  yellow  or 
brown,  usually  rather  dark.  Length,  9' ca.  0.5  mm.; 
$ ,  ca.  0.4  mm. 

Rather  rare;  reported  from  New  England,  Michi- 
gan, Wisconsin,  Minnesota;  probably  to  be  found  in 
all  regions. 

This  species  is  Pleuroxus  acutirostris  Birge. 


241  (240)     Shape  short  oval; 


0.1  MM. 


valves  strongly  reticulated. 

Alonella  dadayi  Birge  1910. 

Shape  oval-rotund.  Valves  strongly  reticulated 
all  over;  infero-posteal  angle  rounded,  with  sev- 
eral minute  teeth.  Rostrum  long,  pointed,  re- 
curved. Keel  of  labrum  acuminate  behind  and 
its  margin  with  i  projection.  Post-abdomen 
short,  wide;  pre-anal  angle  strongly  marked,  as 
in  Chydorus;  with  numerous  small  denticles;  apex 
rounded.  Claws  with  i  basal  spine.  Color 
yellow  to  brown,  often  opaque.  Length,  9i 
0.25-0.3  mm.;  $  (South  America),  0.2  mm. 

Louisiana,  Texas;   not  rare  in  weedy  pools. 

This  species  is  Leptorhynchus  dentifer  Daday, 
whose  specific  name  has  to  be  changed  on  remov- 
ing to  Alonella,  as  Sars'  species  A.  dentifera  pre- 
occupies the  name. 

Fig.  II 63.     Alonella  dadayi. 


242  (239)     Rostrum  short  or  moderate;    shape  globose;  valves  conspicuously 
striated Alonella  nana  (Baird)  1850. 

Very  minute;  Chydorus-like.  Valves  coarsely  and  con- 
spicuously striated;  minute  tooth  in  infero-posteal  region. 
Rostrum  varies,  usually  rather  long,  recurved,  consider- 
ably exceeding  antennules.  Post-abdomen  short;  pre- 
anal  angle  strongly  projecting;  apex  rounded;  about  6 
marginal  denticles.  Claws  with  i  small  spine.  Color 
brownish,  usually  opaque.  Length,  9»  0.2-0.28  mm.; 
$ ,  0.25  mm. 

New  England,  Wisconsin,  Minnesota;  rare.  The  small- 
est member  of  the  family. 

Fig.  1164.    Alonella  nana. 


OJ  MM. 


THE  WATER   FLEAS  (CLADOCERA) 


737 


243  (238)     Claws  with  2  basal  spines;  posterior  mar^'in  of  valves  excised  near 
infero-posteal  angle 


244 


244  (245)     Post-abdomen  fairly  long;  angled  at  apex;    valves  reticulated  and 
with  fine  striae Honclla  excisa  (VischLT)  iSs.\. 


1165 


Alonella  excisa.     Entire  specimen  and  details  of 
markings  of  valve. 


Cicncral  apixrarancc  Pl/^u- 
rorM5  like.  Rostrum  moder- 
ate to  lon^,  never  as  pro- 
lonsed  as  in  A.  ro strata  nor 
recur\e<l;  longer  in  southern 
forms.  Infero-i>ostcal  angle 
marked,  sf>metimes  iinxiuce*! 
into  a  fxjint;  i)osterior  mar- 
gin al)ove  it  excisctl.  si>mc- 
times  crenulatefl.  Post  ab- 
domen long,  narrow,  not  nju'- 
rowing  much  toward  apci; 
apex  angled;  with  al)out  if- 
10  small  marginal  denticles. 
Color  yellow  to  bnjwn. 
Length.  9,  to  0.5  mm.;  ^, 
0.28  mm. 

Not  uncommon  in  all  lo- 
calities; in  weedy  pools  and 
lakes. 


245  (244)     Post-abdomen  short; 


rounded  at  apex;  valves  without  fine  striae. 
Alonella  exigua  (Lilljeborg;  1853. 


Much  like  preceding  sr>ecies  but  smaller.  About  6-8  small 
marginal  denticles.  Color  yellow,  not  ver>-  transparent. 
Length,    9.0-3Smm.;    ^,  0.28mm. 

Maine,  Wisconsin,  Michigan;    rare. 


Fig.  1 166.    Alonella  exigua. 


0.1  MM. 


■*4 


246  (121)     Eye  and  ocellus  very  large;  antennules  project  far  beyond  rostrum. 

Dadaya  Sars  1001. 
Sole  species Dadaya  nidcrops  {D^i.\:iy)  iSq8, 

Form  rounded-oval;  not  a)mpresseti.  Head 
small,  much  dcpres,se<l;  tumid  alxjve  eye;  ros- 
trum short  and  broad,  .\ntennules  long,  mtxl- 
erately  stout,  projecting  far  U-yond  rostnim. 
Post-abdomen  of  nKnlerate  si/^,  comprrw>l. 
somewhat  broadeni>d  l>ehind  anu.s  slightly 
narrowing  toward  ajx-x;  angle  roundcti;  al>out 
14-18  marginal  denticles.  Claws  small,  one 
small  basal  spine.  Kye  very  large,  with  few 
lenses;  ocellus  nearly  as  large,  crowtiixl  d»»wn 
into  rostrum.  X  unknown.  Color  dark 
brown.     Length.  9  . '■i*- 0-<  f""^- 

A  single  siK-cimen  of  this  s|»edes  was  found 
in  a  collection  from  a  wectly  ikx)I  at  Smilb- 
ville,  Texas. 

Fig.  1167.    Dadaya  m^ropi. 


738 


FRESH-WATER  BIOLOGY 


247  (120)     No  eye;    ocellus  only Monospilus  Sars  1861. 

Sole  species Monospilus  dispar  Sars  1861. 

Form  oval  or  round.  Shell  not  cast  in  molting,  as  in 
Ilyocryptus.  Valves  nearly  round  with  fine  setae  along 
ventral  edge.  Head  very  small,  depressed,  movable. 
Keel  of  labrum  with  about  4  scallops  on  ventral  edge. 
Post-abdomen  broad,  short,  with  about  5-7  marginal 
denticles  and  numerous  clusters  of  fine  hairs.  Eye  lack- 
ing; ocellus  large.  Antennules  short,  not  reaching  apex 
of  rostrum.  $  with  hook  on  first  foot;  post-abdomen 
tapering,  triangular,  somewhat  resembling  that  of  Grap- 
toleberis.  Color  brown-yellow.  Length,  J  ,  ca.  0.5  mm.; 
$  ,  ca.  0.4  mm. 

New  England,  Wisconsin,  Minnesota;  rare. 

Fig.  1 168.     Monospilus  dispar. 


0.1  MM. 


248  (i)     Body  and  feet  not  covered  by  shell.     Feet  subcylindrical  or  flattened, 
jointed,  prehensile.   .    .    .    Section  B.  Gymnomera  .    .     249 
No  fomices.    Rami  of  antennae  3-  to  4-jointed.    Feet,  4  to  6  pairs,  jointed,  prehensile. 


249  (250)     Four  pairs  of  feet,  stout,  compressed,  with  claw-like  spines  and 
branchial  appendages. 

Tribe  I.  Onychopoda. 
Sole  family Polyphemidae  Baird. 

Body  very  short.  Shell  converted  into  large  globular  brood-sac.  Caudal  process  long, 
slender,  with  2  long  caudal  stylets  or  setae.  Rami  of  antennae  with  3  and  4  joints.  Eye  very 
large;  no  ocellus.     Labrum  large.    Two  small  hepatic  ceca. 

One  genus Po/y/>/zeww5  0.  F.  Mtiller  1785. 

Sole  species Polyphemus  pediculus  (Linne)  1761. 


Brood-sac  globular,  with 
20-25  young  in  full  grown 
specimens.  Antennules 
very  small,  on  ventral  sur- 
face of  head.  Head  large, 
filled  in  front  by  huge 
movable  eye.  Antennae 
with  7  setae  on  each  ramus. 
Feet  stout,  with  strong 
claws,  and  branchial  ap- 
pendage; fourth  pair,  very 
small.  Length,  9  >  meas- 
ured to  back  of  brood-sac, 
to  1.5  mm.;    J  ,  0.8  mm. 

Common  in  northern 
United  States  in  lakes, 
pools,  and  marshes. 


Fig.  1 169 .    Polyphemus  pedic- 
ulus. 


THE  WATER  FLEAS  (CLADOCERA) 


739 


250  (249)     Six  pairs  of  feet,  cylindrical,  first  pair  vcrv  long;  without  branc  hial 

appendages '.      Tribe  II.  Haplopoda. 

Sole  family Lkptudoridai:  LilljcU>rg. 

Head  elongated  slender;  eye  filling  anterior  end.  Body  4-Jointc<l.  the  first  ivart  l>carir.K 
the  6  feet  and  dorsal  brood-sac;  the  3-jointed  abdomen  ends  in  2  .short  stylets  or  claws  \u\vn 
nules  small,  freely  movable.  Antennae  with  very  large  i)asal  joint;  rami  4-jointe<l  with  numer- 
ous setae.  Mandibles  long,  slender,  pointed,  with  3  spines  near  ai)ex.  Ksojihajcus  very  Ume 
stomach  in  last  abdominal  segment.  9  with  very  long  antennules.  The  young  from  winter 
eggs  hatch  as  a  naupHus. 

Sole  genus  with  characters  of  family Lcptodora  Lilljcborg. 

Sole  species Lcplodora  kindlii  (Vockt')  1H44. 

This  beautiful,  transparent  creature  is  the  largest  of  the  Cladocera.  the  9  reaching  a  length 
of  18  mm.  Rapacious,  though  its  weak  mandibles  prevent  it  from  being  formid.iMr  t.,  the 
harder  shelled  entomostraca;   nocturnal  in  coming  to  the  surface. 

Limnetic  in  Great  Lakes  and  small  lakes  in  northern  United  States;  not  rare. 


Fig.  1 1 70.     Leptodora  kindlii. 

IMPORTANT  REFERENCES  ON  NORTH  AMERICAN  CLADOCERA. 
BiRGE,  E.  A.     1891.     Notes  on  Cladocera  II.     List  of  Cladocera  from  >Li.li- 
son,  Wis.    Trans.  Wis.  Acad.,  8:  379-398;  i  pi. 
1893.     Notes  on   Cladocera  III.     Descriptions  of    new  and   rare  s|>ccic.s. 

Trans.  Wis.  Acad.,  9:  275-317;  i  pi- 
1910.     Notes  on  Cladocera  IV.     Descriptions  of  New  and   Rare  Spec  us 
Chiefly  Southern.     Trans.  Wis.  Acad.,  16:  10 18- 1066;  5  pi. 
Herrick,  C.  L.     1895.     Synopsis  of  the  Entomostraca  oi  Minnesota.     Second 
Report  of  State  Zoologist;  337  pp.,  81  pi. 
Contaia«  much  information  and  many  figures,  original  and  from  various  sourct-;;  hut  the 
material  is  not  very  carefully  or  critically  handled. 


740  FRESH-WATER   BIOLOGY 

Keilhack,  L.     1910.    Phyllopoda.     In  Brauer's  Siisswasserfauna  Deutsch- 

lands,  pt.  10;  112  pp.,  265  text  figs. 

An  admirable  account  of  the  Cladocera  of  Germany,  most  of  which  are  found  in  this  country 
also.    It  should  be  the  first  book  procured  by  any  one  who  can  read  German. 

LiLLjEBORG,  W.     1900.     Cladocera  Sueciae.     Upsala.     701  pp.,  87  pi. 

Latin  keys  and  diagnoses;   otherwise  German.      Indispensable  for  a  critical  study  of  the 
group. 

Richard,  J.     1894.    Revision  des  Cladoceres.    Part  I.     Sididae.    Ann.  Sci. 
Nat.,  Zool.,  (7)  18:  279-389,  2  pi. 
1896.     Part  II.    Daphnidae.    Ann.  Sci.  Nat.,  Zool.  (8)  2:  187-363;  6  pi. 
Invaluable  for  the  families  which  they  cover. 

Sars,  G.  O.     1901.     Contributions  to  the  Knowledge  of  the  Freshwater  Ento- 
mostraca  of  South  America.    Part  I.     Cladocera.    Arch.  Math.  Nat. 
Kristiana,  Bd.  23,  no.  3,  102  pp.,  12  pi. 
Necessary  for  the  study  of  southern  cladocera,  but  not  needed  for  the  northern  states. 

Note.  —  All  illustrations  for  this  chapter  have  been  drawn  especially  for  it,  and  all  are  made  from  the 
actual  specimens,  except  in  a  few  cases,  which  are  indicated. 


CHAPTER  XXIII 
COPEPODA 

By  C.  DWIGHT  MARSH 

United  States  Department  of  Agriculture 

Of  all  animals  encountered  in  fresh  water,  perhaps  none  are 
more  likely  to  arouse  interest  than  the  Copepoda.  Wliilc  many  of 
them  are  large  enough  to  be  seen  and  watched  with  the  naked 
eye,  yet  they  are  so  small  that  a  microscope  is  needed  to  get  a 
clear  understanding  of  their  form  and  structure.  In  company  with 
the  Cladocera,  they  are  almost  universally  distributed,  and  can  be 
collected  in  nearly  any  body  of  water.  Unlike  the  Cladocera, 
which  show  many  erratic  and  bizarre  species,  the  Copepoda  are 
graceful  and  symmetrical  in  their  forms,  with  a  beauty  of  structure 
that  is  very  attractive  to  the  amateur  student.  Some  are  wonder- 
fully transparent,  while  others  are  strikingl}'  and  in  some  cases 
gorgeously  colored. 

Copepoda  have  been  studied  ever  since  the  microscope  was  first 
used.  It  is  said  that  the  first  mention  of  these  animals  was  made 
by  Stephen  Blankaart  in  1688.  0.  F.  IMuller  in  1785  is  credited 
with  having  given  the  first  scientific  description  of  this  group. 
In  1820  Jurine  published  his  famous  ''Histoire  des  monocles  qui  se 
trouve  aux  environs  de  Geneve."  Some  of  the  species  which  he 
described  are  still  recognized  as  valid,  largely,  however.  b\-  the 
courtesy  of  succeeding  writers;  for  Jurine  made  his  distinctions  on 
insufficient  grounds  like  color,  and  it  is  only  through  his  figures 
that  one  can  conjecture  what  species  he  had  in  hand.  No  really 
serious  study  of  this  group  was  made  until  the  middle  of  the  nine- 
teenth century,  when  the  publication  of  Baird's  "Natural  IIistor>- 
of  the  British  Entomostraca "  in  1850  and  the  various  papers  ol 
Claus  a  few  years  later  were  the  beginning  of  exact  work  on  these 
forms.  The  work  of  Claus  was  of  first  importance.  In  Sorih 
America  articles  were  published  recrardin-  some  forms  in  the  early 
part  of  the  century,  but  nothing  recognizable  appeared  until  S.  A. 

74t 


742 


FRESH-WATER  BIOLOGY 


Forbes  commenced  his  series  of  papers.  Although  these  papers 
were  not  extensive,  they  were  exact  and  carefully  worked  out,  and 
to  Forbes  may  be  given  the  credit  of  laying  the  foundation  for  all 
subsequent  work  in  this  country. 

Though  attractive  in  form,  the  Copepoda  are  complex  in  their 
structure,  and  accurate  classification  can  only  be  attained  by  care- 
ful and  laborious  dissection,  so  that  study  of  the  order  has  been 
neglected. 

With  the  exception  of  the  Harpacticidae,  all  the  free-swimming 
Copepoda  are  characterized  by  a  distinct  division  of  the  body  into 
cephalothorax  and  abdomen,  the  former  being  composed  of  five  or 
six  segments  and  the  latter  of  from  three  to  five.  The  appendages 
are  as  follows,  commencing  with  the  front  of  the  animal: 


Frontalorgan 


Upper  Zip^TJ-^""^' 
Mandible     F 
Lower  Lip'jtzL', 


First  pair  of  antennae. 

Second  pair  of  antennae. 

Mandibles. 

First  maxillae. 

Second  maxillae. 

Maxillipedes. 

First  pair  of  swimming  feet. 

Second  pair  of  swimming  feet. 

Third  pair  of  swimming  feet. 

Fourth  pair  of  swimming  feet. 

Fifth  feet. 

Furcal  rami. 


Fig.    II 71.    Diagrammatic  figure  of  a  female 
Copepod.     (After  Giesbrecht  and  Schmeil.) 


Terminal  Setae 
Inner  orJ)ortal  Setae 


COPEPODA 

All  of  these  appendages  are  built  on  the  same  i)lan,  which  is 
typically  represented  in  the  swimming  feet  of  Cyclops  (Fig.  1221). 
Each  foot  consists  of  two  basal  segments,  and  attached  to  the  outer 
or  distal  of  these  are  two  branches  or  rami,  each  of  three  segments. 
The  outer  ramus  is  known  as  the  exopodite  and  the  inner  as  the 
endopodite.  This  typical  plan  may  be  very  much  modified  but. 
in  most  cases  the  fundamental  structure  can  be  recognized. 

Of  these  appendages,  the  first  antennae  are  ver\-  characteristic. 
They  are  so  modified  that  one  of  the  rami  has  entirely  disappeared, 
and  the  one  remaining  is  made  up  of  a  considerable  number  of 
segments,  varying  from  six  to  twenty-five.  In  the  same  species 
the  number  of  segments  in  the  antennae  is  ordinarih'  invariable. 
In  some  of  the  species  of  Cyclops  the  antennae  are  very  short,  in 
others  they  may  exceed  the  length  of  the  cephalothora.x,  while  in 
the  other  genera  they  may  equal  or  exceed  the  length  of  the  whole 
body.  The  segments  of  the  antennae  are  armed  with  hairs  which 
are  definite  in  number  and  location.  They  have  also  sensory 
structures  arranged  in  definite  places  on  the  segments.  The  club- 
shaped  sensory  appendage  of  the  twelfth  antenna  1  segment  of 
some  of  the  species  of  Cyclops  is  one  of  the  important  means  of 
identification.  Some  of  the  species  of  Cyclops  ha\e  circlets  or 
crowns  of  spines  on  certain  antennal  segments  which  give  them  a 
pecuUarly  ornate  appearance.  In  some  of  the  species  of  Cyclops 
there  is  a  thin  hyaline  lamella  extending  longitudinall\-  along  cer- 
tain of  the  segments,  being  especially  marked  on  the  last  two.  This 
is  particularly  noticeable  in  Cyclops  Juscus  (Fig.  1223). 

In  the  Cyclopidae  the  antennae  are  s^Tumetrical  and,  in  the  male, 
are  modified  to  form  grasping  organs.  In  the  C\'ntropagidae  it  is 
only  the  right  antenna  of  the  male  that  is  so  modilietl. 

In  many  of  the  species  of  Diaptomus  the  antepenultimate  seg- 
ment of  the  right  antenna  of  the  male  has  a  distinctive  form. 
This  may  be  a  hyaline  lamella  extending  the  length  of  the  segment, 
or  it  may  be  an  extension  of  one  side  of  the  segment  in  a  prt)cess 
which  varies  from  a  blunt  projection  to  a  hook  or,  in  some  cases, 
a  long,  slender  digitiform  extension.  The  armature  of  this  segment 
is  constant  and  is  one  of  the  important  characteristics  used  in 
distinguishing  species. 


744 


FRESH-WATER   BIOLOGY 


The  fifth  feet  in  Cyclops  are  very  rudimentary  structures. 

In  Diaptomus  the  fifth  feet  take  on  interesting  forms.  In  the 
female  they  are  symmetrical,  but  not  so  well  developed  as  the 
preceding  swimming  feet.  But  in  the  male,  the  right  fifth  foot 
differs  from  the  left,  and  is  modified  so  as  to  make  a  grasping 
organ.  The  figures  in  the  synoptical  key  show  the  form  of  these 
appendages.  The  modifications  are  constant  in  a  given  species, 
so  that  the  fifth  feet  in  this  genus  furnish  the  most  important 
means  of  specific  identification. 

In  Epischura  the  fifth  feet  are  modified  more  profoundly,  and 
this  modification  is  accompanied  by  a  pecuHar  development  of  the 
segments  of  the  abdomen,  which  also  serves  as  a  grasping  organ. 


Fig.  1172.  Nauplius  of  Cyc/o/)^.  The 
fourth  pair  of  appendages  are  repre- 
sented by  two  setae.    (After  Glaus.) 


Fig.  1173.  Second  Stage  of  Cydo/'^,  in 
which  are  seen  four  pairs  of  appen- 
dages.    (After  Claus.) 


In  their  growth  from  the  egg  up,  the  Copepoda  pass  through  a 
compHcated  series  of  forms.  On  issuing  from  the  egg  the  young 
animal  is  a  flat,  oval  creature,  without  any  division  of  the  body 
into  cephalothorax  and  abdomen,  and  with  only  three  pairs  of 
appendages,  the  first  three  of  the  mature  animal,  namely,  the  first 
and  second  antennae  and  the  mandibles.  These  are  all  used,  in 
this  stage  of  the  animal,  as  swimming  organs.  This  is  known  as 
the  nauplius  stage  (Fig.  11 72).     A  series  of  molts  follows.     In  the 


COPEPODA  -^- 

second  stage  (Fig.  1173)  a  fourth  pair  of  appendages  is  added, 
which  later  are  known  as  the  maxillae.  In  a  later  stage  three  more 
pairs  of  appendages  are  added,  —  the  maxillipcdcs,  and  ihc  first  two 
pairs  of  swimming  feet:  this  is  known  as  the  mclanauplius  stage. 
The  following  stage  is  the  first  Cyclops  stage;  in  this  there  is  a  dis- 
tinct division  of  the  body  into  cephaluthurax  and  abdomen,  and  the 
third  and  fourth  swimming  feet  are  present  in  a  rudimentary  form. 
In  this  stage,  too,  the  anterior  appendages  have  develoiK-d  into 
forms  more  similar  to  those  in  the  mature  animal. 

The  process  of  development  is  thus  accompanied  by  a  continued 
increase  in  the  number  of  appendages  beginning  at  the  anterior 
extremity,  in  the  number  of  segments  of  the  cephalothorax  and 
abdomen,  and  in  the  complexity  of  the  appendages,  until  the  mature 
forms  are  reached. 

Some  of  the  parasitic  forms  do  not  pass  through  all  these  stages. 
There  are  some  that  never  acquire  the  third  and  fourth  swimming 
feet;  in  others,  by  a  progress  of  regression,  the  first  and  second 
feet  may  disappear.  Some  parasitic  forms  jump  the  whole  scries 
of  nauplius  stages  and  almost  immediately  after  leaving  the  egg 
appear  in  the  first  Cyclops  stage. 

Hardly  any  body  of  water  is  without  its  copepod  inhabitants, 
although  running  waters  have  a  less  abundant  population  than 
lakes.  Frequently  standing  pools  swarm  with  the  individuals  of 
one  or  a  few  species  of  this  order.  Temporary  pools  in  the  spring, 
which  are  formed  in  the  same  place  in  successive  years,  will  some- 
times be  almost  literally  filled  with  Copepoda,  which  are  strictly 
seasonal  in  their  life  habits;  for,  as  the  pools  disappear,  the  cojw- 
pods  disappear,  their  eggs  sink  in  the  mud  of  the  bottom,  and 
remain  until  the  waters  of  the  next  season  bring  about  favorable 
conditions  for  their  generation. 

The  lakes  produce  an  exceedingly  abundant  coix-ix>d  fauna, 
which  has  an  important  practical  interest,  for  the  ultimate  focMJ  of 
fish  is  composed  almost  entirely  of  these  organisms;  that  is,  the 
small  fish  of  our  most  abundant  species  feed  entirely  ujKin  Knto- 
mostraca,  of  which  Copepoda  form  the  greater  part,  and,  in  many 
cases,  the  mature  fish  also  feed  entirely  on  these  same  minute 
creatures. 


746  FRESH-WATER  BIOLOGY 

Similar  conditions  prevail  in  the  ocean,  where  Copepoda  form  an 
essential  part  of  the  plankton,  which  there,  too,  is  an  important 
element  in  the  food,  not  only  of  fishes,  but  of  some  of  the  great 
ocean  mammals.  Our  fresh- water  Copepoda  are  descendants  of 
salt-water  forms,  and  the  elucidation  of  the  lines  of  descent  forms 
a  most  interesting  problem,  towards  the  solution  of  which  very 
little  has  been  done. 

The  distribution  of  the  Copepoda  in  our  lakes  is  a  matter  of 
great  interest.  Certain  species  are  characteristic  of  distinct  regions 
of  the  lakes.  For  example,  Cyclops  bicuspidatus,  Diaptomus  sicilis, 
Diaptomus  minutus,  and  Diaptomus  ashlandi  are  characteristic  of 
the  limnetic  regions  of  the  Great  Lakes.  Cyclops  prasinus  is  espe- 
cially characteristic  of  limnetic  regions,  Cyclops  albidus  and  Cyclops 
fuscus  are  more  commonly  littoral,  while  Cyclops  hicolor  and  Cyclops 
phaleratiis  are  more  usually  found  in  pools.  Others,  especially  at 
certain  seasons,  may  be  found  only  in  the  deeper  waters,  or  are 
''abyssal"  in  habitat.  This  is  true  of  Limnocalanus  macrurus, 
which  is  rarely  found  at  the  surface  in  the  summer  season,  but 
almost  entirely  in  the  region  below  the  thermocHne.  Generally 
speaking,  the  Diaptomi  in  lakes  are  characteristic  of  the  limnetic 
regions,  but  it  does  not  follow  that  all  Diaptomi  are  limnetic;  for 
there  are  many  species  that  confine  themselves  strictly  to  the 
extremely  shallow  waters  of  pools,  like  Diaptomus  sanguineus,  which 
occurs  widely  through  the  temperate  regions  in  the  temporary 
pools  of  spring.  It  should  not  be  inferred,  however,  that  these 
distinctions  between  littoral,  limnetic,  abyssal,  etc.,  are  absolute. 
In  many  cases,  species  commonly  Httoral  may  adapt  themselves  to 
a  limnetic  habitat,  or  those  commonly  found  in  limnetic  regions 
may  become  littoral,  and  flourish  in  those  regions,  thus  forming 
part  of  what  is  sometimes  known  as  the  tycholimnetic  or  tycholittoral 
fauna.  Cyclops  bicuspidatus,  for  example,  while  ordinarily  limnetic, 
may  become  a  part  of  the  littoral  fauna.  In  other  cases,  species 
like  Diaptomus  oregonensis  and  Diaptomus  minutus  may  seem  to  live 
equally  well  in  deep  or  shallow  waters.  Deep  lakes  and  shallow 
lakes  have  their  characteristic  copepod  faunas,  but  this  distinction 
does  not  always  hold  rigidly;  for  frequently  the  species  show  a 
great  deal  of  elasticity  in  adapting  themselves  to  changed  conditions. 


COPEPODA  y^y 

There  is  a  marked  difference  in  form  and  structure  fx-twcrn  the 
Copepoda  Hving  in  the  open  water  and  those  that  are  Hmnetic  in 
their  habit.  Those  that  Hve  among  the  weeds  alongshore,  or  in 
pools,  are  relatively  short  and  stout,  and  frequently  deeply  colored. 
A  good  example  of  this  is  Cyclops  akr,  which  has  recei\-ed  its  name 
because  of  its  dark  color.  It  is  to  be  presumed  that  Cyclops  viridis 
also  received  its  name  from  its  color,  for  man\'  of  iliese  shore  forms 
show  a  distinctly  green  coloration.  These  ccjjors.  doubtless,  are  i)r(>- 
tective,  for,  because  of  them,  the  animals  are  almost  invisible  when 
stationary  upon  a  background  of  bottom  mud  or  of  the  stems  of 
aquatic  plants. 

The  limnetic  species  have  long  and  slender  bodies,  Limuoca- 
lanus  macrurus  being  an  especially  good  type.  Some  species  of 
Cyclops  live  either  as  limnetic  or  as  littoral  inhabitants;  in  these 
cases  one  finds  the  same  differences  in  form,  the  littoral  variety 
being  short  and  stout,  and  the  limnetic  long  and  slender.  This  is 
especially  well  shown  in  the  varieties  of  Cyclops  viridis  and  Cyclops 
serrulatus.  The  figures  in  the  systematic  discussion  of  these  species 
show  these  differences  which  are  especially  well  marked  in  the  f ureal 
rami  (Figs.  12 14,  12 15).  The  littoral  species  have  short  and  stout 
furcal  rami,  whereas  in  the  limnetic  species  these  structures  are 
long  and  slender.  The  limnetic  species  are  ordinaril\-  colorless, 
their  transparent  bodies  making  beautiful  objects  for  examination 
under  low  magnifying  powers;  for  much  of  the  internal  anatomy 
of  the  animal  can  be  observed,  while  the  animal  is  still  alive:  the 
movements  of  the  alimentary  canal  can  be  followed,  and  the  beat- 
ings of  the  heart  observed.  This  lack  of  color  is  doubtless  an 
adaptation  to  the  environment,  for  in  open  waters  colorless  animals 
are  much  less  conspicuous. 

Occasionally  the  Copepoda  are  of  a  marked  red  color.  This  is 
sometimes  due  to  oil  globules,  and  is  especiall}-  marked  in  some  of 
the  species  appearing  in  the  early  spring,  or  li\ing  in  tlie  cold 
waters  of  lakes  at  great  altitudes.  In  other  cases,  and  this  is 
markedly  true  of  some  of  the  Diaptomi,  the  integument  may  l>e 
deeply  colored  in  reds,  blues,  and  purples.  Diaptomus  sJwshonc,  a 
large  species  found  in  the  mountain  regions  of  the  West,  is  an  esjje- 
cially  good  example  of  a  liiglily  colored  copepod. 


748  FRESH-WATER  BIOLOGY 

As  already  noted,  certain  species  appear  in  temporary  pools  only 
in  the  spring  season.  In  those  that  occur  in  lakes,  there  is  some- 
times a  pronounced  seasonal  distribution.  For  example,  in  Green 
Lake,  Wis.,  on  which  extended  studies  have  been  made,  Diaptomus 
sicilis  is  common  in  the  winter,  but  rarely  found  in  the  summer, 
while  most  forms,  as  would  be  expected  from  the  favorable  food 
conditions,  are  more  abundant  in  the  summer  months. 

Excepting  the  few  winter  forms,  the  maximum  numbers  of  any 
species  occur  in  the  months  from  May  to  September  or  early 
November.  Sometimes  there  are  two  maxima,  one  in  the  spring 
and  one  in  the  fall.  Generally  speaking,  the  maximum  develop- 
ment occurs  when  the  waters  reach  their  highest  temperature,  but 
other  factors  may  modify  the  time.  Generally  speaking,  also,  the 
maximum  development  in  numbers  is  somewhat  later  in  deep 
lakes  than  that  in  shallow  lakes,  corresponding  to  the  general  law 
for  the  development  of  the  total  plankton. 

The  great  controUing  factor  in  the  distribution  of  the  Copepoda 
is,  without  doubt,  temperature.  That  Diaptomus  sicilis  should  be 
found  in  Green  Lake  only  in  the  winter  is  a  matter  of  temperature, 
for  it  is  found  in  the  cold  waters  of  the  Great  Lakes  throughout  the 
summer.  Limnocalanus  macrurus,  which,  in  small,  deep  lakes,  is 
found  during  the  summer  only  below  the  thermocline,  comes  to 
the  surface  in  the  winter  months  when  the  surface  water  is  colder. 
In  Wisconsin,  Cyclops  bicuspidatus  is  a  common  limnetic  species  in 
the  deeper  lakes,  but  is  rarely  found  in  the  shallower  lakes  except 
in  the  winter  season.  It  is  evident  that  it  prefers  the  colder  waters. 
On  the  other  hand,  Epischura  lacustris  and  Diaptomus  oregonensis 
are  distinctly  summer  forms,  disappearing,  for  the  most  part,  in 
the  winter  months. 

Partial  studies  have  been  made  which  have  disclosed  some  very 
interesting  facts  in  regard  to  the  vertical  distribution  of  Copepoda 
in  our  lakes.  In  general  it  may  be  said  that  most  of  these  forms 
are  confined  to  the  upper  waters,  above  the  thermocline,  some 
having  very  distinct  vertical  migrations,  caused  by  changing  con- 
ditions of  light  and  temperature.  It  has  long  been  known  that 
not  only  are  the  open  waters  of  our  lakes  peopled  with  myriads 
of  these  minute  creatures,  which  can  readily  be  collected  by  a  tow- 


COPEPODA  y4Q 

net  dragged  behind  a  boat,  but  that  collections  made  in  the  night 
were  much  more  successful  than  those  in  the  (la>tinie.  It  \v;ls  at 
first  inferred  from  these  collections  that  the  animals  shunned  the 
light,  and  sank  beneath  the  surface  during  the  day,  to  rise  again 
at  night.  Careful  studies  of  the  subject,  however,  show  that  the 
migration  of  these  am'mals  is  by  no  means  so  simple  a  matter  as 
had  been  thought,  and  that  very  complex  forces  arc  at  work  con- 
trolling their  movements.  While  some  of  them  are  sensitive  to 
the  influence  of  light,  it  appears  that  temperature  is  much  the 
stronger  factor,  and  that,  generally  speaking,  they  mo\e  up  (jr  down 
as  the  result  of  changes  of  temperature  rather  than  because  they 
seek  or  avoid  the  light.  This,  without  doubt,  exj)lains  the  fact 
that  Limnocalanus  remains  in  the  deeper  waters  in  the  summer 
and  gradually  rises  higher  as  the  waters  cool  off  in  the  fall.  On 
the  other  hand,  Cyclops  prasinus  has  a  marked  preference  for 
warmer  waters.  During  the  summer  it  is  found  in  the  upper 
layers  of  water,  but  in  the  winter  it  is  inchned  to  a\oid  the  imme- 
diate surface  and  seek  the  deeper  and  warmer  waters. 

Epischura  lacustris  is  a  very  interesting  species  in  its  vertical 
distribution;  for  it  is  large  and  a  strong  swimmer,  and  changes 
its  location  from  hour  to  hour  during  the  day.  It  likes  warm 
water,  but  dislikes  the  Hght,  and  its  vertical  migrations  both  daily 
and  seasonal  are  the  resultant  of  these  two  forces,  so  Uiat  its  move- 
ments sometimes  seem  quite  erratic. 

It  is  a  curious  fact  that  the  Copepoda  differ  in  the  character  of 
the  habitat  they  like  best  at  different  times  of  their  lives.  Most 
of  the  larval  forms  are  found  close  to  the  surface  in  the  daytime, 
while  the  maturer  animals  are  found  at  a  greater  or  less  depth. 

It  seems  probable  that  the  movements  of  the  nauplii  and  larvd 
Copepoda  are  caused  by  comparatively  slight  changes  of  tempera- 
ture, and  that  a  somewhat  elaborate  determination  of  the  changes 
of  temperature  in  the  upper  layers  of  water  ma\'  explain  their 
movements,  which  now  seem  rather  strange. 

Through  the  study  of  the  geographical  distribution  one  may 
hope  to  get  some  knowledge  of  the  evolution  of  the  si>ecies  and 
genera  of  the  Copepoda,  and  it  is  on  this  account  that  this  phxse 
of  the  study  of  any  group  of  animals  is  especially  interesting  to 


750  FRESH-WATER   BIOLOGY 

the  zoologist.  Many  of  the  species  of  the  Cyclopidae  are  almost 
if  not  quite  cosmopolitan  in  their  distribution;  for  example,  Cyclops 
leuckarti  not  only  occurs  all  over  North  America,  but  in  Europe, 
Asia,  and  Africa,  and  without  any  variations  that  are  character- 
istic of  the  different  regions.  It  seems  very  remarkable  that  an 
animal  as  delicately  organized  as  Cyclops  should  not  show  the 
effect  of  change  of  location  in  its  structure.  Most  of  the  recog- 
nized American  species  of  Cyclops  are  identical  with  those  found 
in  other  continents;  and  it  is  even  possible  that,  when  the  genus 
is  known  more  thoroughly  than  at  present,  many  of  the  species 
which  are  now  considered  peculiar  to  our  continent  may  be  found 
to  be  either  identical  with  foreign  species  or  at  most  only  varia- 
tions of  those  forms.  So  our  common  species  of  LimnocalanuSj 
L.  macrurus,  is  identical  with  the  European  form.  On  the  other 
hand,  not  only  the  species  but  the  genera  of  Osphranticum  and 
Epischura  are  peculiar  to  North  America.  The  genera  of  the 
Harpacticidae  have  never  been  thoroughly  worked  over,  and,  while 
some  of  our  species  are  undoubtedly  European,  it  seems  probable, 
from  what  we  now  know,  that  many  of  them  are  peculiar  to  this 
continent.     Eurytemora  is  world-wide  in  its  distribution. 

Of  the  Diaptomi  there  are  now  recognized  thirty-nine  species 
in  North  America,  and  all  of  these  are  peculiar  to  this  continent. 
Not  only  are  they  peculiar  to  the  continent,  but  many  are  peculiar 
to  certain  regions.  In  a  broad  way,  they  illustrate  very  forcibly 
what  has  been  said  before,  — that  Copepoda  are  controlled  in  their 
distribution  by  temperature  conditions.  This  can  well  be  illus- 
trated by  a  brief  discussion  of  the  geographical  distribution  of  the 
more  common  species.  Diaptomus  minutus  is  found  from  Green- 
land and  Iceland  south  to  the  northern  tier  of  states  in  the  United 
States,  but  does  not  occur  south  of  42°  to  43°  N.  L.  Diaptomus 
sicilis  is  confined  to  the  northern  tier  of  states.  Diaptomus  sici- 
loides  is  found  in  a  band  farther  to  the  south,  being  limited  roughly 
to  the  region  between  the  thirty-sixth  and  forty-third  parallels. 
These  three  species  are  closely  related  to  each  other  in  structure, 
and  presumably  are  of  the  same  Hne  of  descent.  It  will  be  seen 
that  their  distribution,  taken  in  a  broad  way,  is  one  of  latitude. 

A  similar  relation  exists  between  Diaptomus  oregonensis,  Diapto- 


COPEPODA  -., 


mus  mississippiensis,  and  Diaplomus  paUidiis.  Diaptomus  orc^o- 
nensis  is  the  more  northern  species.  It  is  found  from  (jnc  sidc'.»l 
the  continent  to  the  other,  as  far  north  as  the  Saskatchewan  region, 
and  as  far  south  as  Ilhnois  and  Indiana.  Diaptomus  pallidus  is  a 
Mississippi  Valley  species,  having  been  found  from  Minnesota  to 
Louisiana,  and  as  far  west  as  Colorado.  Diaptomus  mississippiensis 
is  a  strictly  southern  species,  being  confined,  so  far  as  known,  to 
the  Gulf  States.  It  is  evident  that  this  distribution  again  is  con- 
trolled by  temperature  conditions. 

The  group  which  centers  around  Diaptomus  alhuqucrqucnsis  is 
confined  to  the  south,  the  most  southern  species  being  limited  to 
the  island  of  Cuba.  The  group  centering  about  Diaptomus  sit^fti- 
cauda  is  confined  to  the  mountain  regions  of  the  West,  where  a 
number  of  rather  closely  related  species  have  been  developed. 
Probably  the  greatest  number  of  species  is  found  in  this  mountain 
region  of  the  West,  where  the  lakes  are  separated  from  each  other, 
and  isolation  has  led  to  the  development  of  new  species.  It  will 
thus  be  seen  that  the  one  great  controlling  factor  in  the  distribu- 
tion of  the  Diaptomi  is  temperature. 

It  may  perhaps  be  assumed  that  most  of  our  North  .\mcrican 
species  are  descended  from  the  same  ancestors  as  those  of  the 
other  continents;  that  as  the  result  of  the  glacial  period  the  norths 
ern  forms  were  forced  far  to  the  south;  and  that,  on  the  retreat  of 
the  ice,  some  followed  after  the  ice,  while  others  remained  behind, 
but  changed  their  form  as  the  result  of  the  changed  environment. 
Thus  the  more  primitive  forms  would  be  found  tt)  the  north.  In 
the  south  we  would  find  specialized  forms  due  to  the  various  fac- 
tors which  have  come  into  play  in  the  evolution  of  these  animals. 
It  is  a  pecuHar  fact  that  in  this  change  of  conditions  the  Cyclo- 
pidae  should  have  succeeded  in  adapting  themselves  without  change 
of  structure,  while  the  Diaptomi  all  suffered  changes.  The  ditTer- 
ence  in  the  behavior  of  these  two  families  is  a  matter  that  is  not 
at  all  understood,  but  it  seems  possible  that  the  Cyclopidae  have 
more  efficient  means  of  distribution,  so  that  the  development  of 
new  species  from  isolation  would  not  be  as  probable  as  in  the  case 
of  the  Diaptomi.  As  a  matter  of  fact,  very  little  is  known  of  the 
life  histories  of  these  animals. 


752  FRJSH-WATER  BIOLOGY 

Mention  has  been  made  of  the  fact  that  new  species  may  arise 
because  of  isolation.  But  the  question  arises,  how  do  the  ancestors 
of  any  form  first  reach  a  given  body  of  water?  By  what  means 
are  these  animals  distributed  from  one  place  to  another?  Certain 
species  occur  in  bodies  of  water  from  one  side  of  the  continent  to 
the  other;  in  some  cases  the  same  forms  are  found  even  in  widely 
separated  continents.  How  have  they  reached  these  places?  Eggs 
are  formed  which  fall  into  the  mud  of  the  floor  of  the  lakes  and 
pools  and  retain  their  \itality,  sometimes  from  one  season  to 
another,  even  if  the  bodies  of  water  disappear  and  the  mud  becomes 
dry.  Many  species  have  been  seen  for  the  first  time  by  rearing 
them  from  eggs  found  in  dried  mud.  It  is  natural  to  infer  from 
this  that  anything  that  would  move  the  mud  would  also  move  the 
eggs  of  the  animals.  Dried  mud,  in  the  form  of  dust,  may  be 
widely  disseminated,  and  thus  the  eggs  might  be  carried  to  very 
distant  places.  Water  birds,  too,  carry  mud  on  their  feet  from 
one  body  of  water  to  another,  and  in  this  way  may  easily  transport 
the  eggs  of  Copepoda  and  possibly  the  living  animals.  Inasmuch 
as  these  birds  sometimes  make  long  flights,  it  is  clear  that  the 
species  of  Copepoda  may  be  planted  in  places  far  apart.  There  is 
no  doubt  that  in  both  these  ways  the  distribution  of  the  Copepoda 
has  been  effected,  but  these  are  not  the  principal  ways.  It  seems 
evident,  for  many  reasons,  that  they  go  from  one  place  to  another 
mainly  by  direct  water  carriage.  For  example,  Diaptomus  sici- 
loides  has  been  found  in  only  one  lake  in  Wisconsin.  If  it  were 
readily  carried  by  birds,  one  would  expect  to  find  it  in  other  bodies 
of  water  which  seem  to  have  the  same  kind  of  an  environment. 
On  the  other  hand,  in  Lake  St.  Clair,  although  it  is  a  very  shallow 
body  of  water,  occur  the  Copepoda  that  are  characteristic  of  the 
deeper  waters  of  the  Great  Lakes.  In  this  case  there  seems  to  be 
no  doubt  that  these  deep-lake  forms  have  been  carried  into  an  en- 
vironment where  one  would  not  expect  to  find  them.  It  is  notice- 
able that  in  connecting  bodies  of  water  we  find  the  same  forms  of 
Copepoda.  Irrigating  ditches  and  ponds  are  almost  entirely  with- 
out Copepoda.  They  are  pecuHarly  unprofitable  collecting  places 
although  the  environment  would  seem  to  be  favorable  for  the  propa- 
gation of  these  forms.     For  some  reason,  it  is  evident  that  the 


COPEPODA 


animals  are  not  planted  there.  If  the  eggs  of  Copci)oda  were  dis- 
seminated to  any  extent  with  the  dust  by  winds,  conditions  would 
seem  to  be  unusually  favorable;  for  such  [)()n(ls  arc  found  in  dry 
regions  subject  to  heavy  winds.  ''  Dust  storms  "  are  very  common, 
and  in  them  large  quantities  of  dust  are  moved  from  one  place  to 
another.  Ducks,  too,  frequent  these  ponds  in  enormous  numbers, 
and  are  continually  on  the  wing,  moving  from  one  place  to  another. 
It  would  seem,  then,  that  in  the  arid  and  semi-arid  regions  condi- 
tions were  as  favorable  as  possible  for  these  two  methods  of  trans- 
portation. Yet  the  fact  remains  that  the  ponds  are  frecjuently 
almost  entirely  devoid  of  copepod  life,  and  one  must  conclude 
that  these  methods  of  dissemination  are  of  minor  importance.  It 
apparently  follows  from  these  facts  that,  when  once  a  form  has 
reached  a  mountain  lake,  it  may  remain  in  undisturbed  possession 
for  a  long  time,  and  thus,  by  the  ordinary  processes  of  evolution, 
one  may  expect  to  find  in  mountain  regions  a  great  variety  of 
species.  As  a  matter  of  fact,  in  parts  of  the  country  where  water 
communication  is  easy,  as  in  the  Mississippi  Valley,  there  prevails 
great  uniformity  in  the  species,  while  in  the  mountain  regions  of 
the  West  one  finds  a  greater  variety  of  species. 

The  ordinary  means  of  collecting  other  forms  of  small  water 
animals  and  plants  will  serve  for  the  Copepoda.  The  Hirge  net  is 
the  most  useful  form  of  collecting  apparatus.  Inasmuch  as  Co- 
pepoda are  extremely  common  in  open  and  clean  waters,  the  wire- 
netting  cap  of  the  Birge  net  (p.  68)  can  frequently  be  disjx'nsed 
with,  and  the  apparatus  thus  simplified.  A  conical  net  of  fine  mus- 
lin with  the  opening  stiffened  by  a  wire  ring  will  serve  admirabl}-  for 
making  collections.  This  can  be  dragged  behind  a  boat.  or.  if 
weighted,  can  be  thrown  from  the  shore  to  a  distance  of  from  thirty 
to  forty  feet,  care  being  taken,  as  it  is  drawn  in,  to  collect  as  little 
as  possible  of  floating  debris  or  of  mud  if  it  strikes  the  bottom  near 
shore.  The  material  collected  in  the  end  of  the  net  can,  !)>•  in- 
verting the  net,  be  washed  into  a  wide-mouthed  bottle  or  tumbler 
or  tin  fruit  can,  and  then  transferred  to  the  homeopathic  vials  in 
which  it  is  stored.  An  easy  way  to  make  this  transfer  is  to  pour 
the  condensed  material  on  little  squares  or  circles  of  line  muslin. 
two  or  three  inches  in  diameter,  and  then  place  cloth  and  all  in 
the  preservative  fluid. 


754 


FRESH-WATER  BIOLOGY 


For  preservative  fluid  either  5  per  cent  formol  or  75  per  cent 
alcohol  can  be  used.  Alcohol  preserves  the  animals  in  a  little 
better  shape,  as  formol  is  apt  to  make  them  brittle.  Dissection  is 
best  performed  in  a  drop  of  glycerin  on  a  slide.  The  transfer 
from  alcohol  to  glycerin  should  be  made  gradually,  through  mix- 
tures of  alcohol  and  glycerin.  The  larger  forms  of  Copepoda  can 
be  dissected  under  lenses  magnifying  from  five  to  fifteen  diameters; 
but,  for  the  smaller  individuals,  powers  as  high  as  one  hundred 
diameters  must  be  used,  and  the  work  is  very  tedious.  The 
dissected  material  is  best  mounted  for  examination  in  Farrant's 
solution,  and  the  cover  must  be  ringed  with  a  good  cement,  — 
Brunswick  black,  for  instance. 

If  one  wishes  to  make  a  serious  study  of  the  animals,  the  struc- 
tures to  be  separated  and  studied  are  the  following:  the  antennae, 
male  and  female;  the  abdomens,  male  and  female;  the  fifth  feet, 
male  and  female.  In  addition,  the  general  form  of  the  cephalo- 
thorax  must  be  noted,  and,  in  some  cases,  the  structure  of  the  other 
appendages  of  the  cephalothorax.  The  Copepoda  are  so  widely 
distributed  and  their  forms  are  so  characteristic  of  biological  con- 
ditions that  it  is  very  desirable  that  every  student  of  water  forms, 
even  if  his  work  is  only  of  an  amateur  character,  should  be  able 
to  make  a  separation  into  genera,  and,  in  most  cases,  make  at  least 
a  provisional  specific  determination.  Fortunately,  the  generic  dis- 
tinctions of  our  American  forms  are  very  easily  made,  and  it  is  not 
difficult  to  recognize  some  of  the  more  common  species. 

Especially  confusing  to  the  beginner  is  the  large  number  of  im- 
mature forms.  Many  of  the  larval  stages  of  the  more  highly  de- 
veloped species  resemble  closely  the  mature  forms  of  the  simpler 
species,  so  that  the  tyro  is  apt  to  think  that  he  has  a  large  number 
of  species,  when  he  may  have  only  several  stages  of  one.  It  is 
safest  for  the  beginner  to  make  no  attempt  at  identification  except 
in  the  cases  of  evidently  mature  forms,  such  as  egg-bearing  females. 

The  Copepoda  are  an  order  of  Crustacea,  belonging  to  the  sub- 
class Entomostraca.  Tliis  subclass  cannot  be  easily  defined,  but 
it  is  sufficient  for  our  purposes  to  say  that  they  are  the  most  simply 
organized  Crustacea.  The  Copepoda  may  be  defined  as  those  En- 
tomostraca which  do  not  have  a  shell-Hke  covering  of  the  body 


COPEPODA 

(in  distinction  from  many  of  the  Phyllopoda).  wn,,  i..ur  or  iivc 
two-branched  swimming  feet  on  the  thorax  and  an  abdomen  with- 
out appendages.     The  Copepoda  are  divided  into  two  subor(ler>. 
the  Eucopepoda  and  the  Branchiura. 

The  Eucopepoda  do  not  have  compound  e>es,  and  the  Lg^s 
develop  in  one  or  two  brood  pouches  or  ovisacs  attached  to  the 
abdomen.  The  Branchiura  have  two  compound  eyes.  The  females 
do  not  have  ovisacs,  but  the  eggs  are  kud  on  stones  or  other  con- 
venient hard  surfaces.  The  body  is  flattened.  The  KucopejKida 
may  be  considered  in  two  divisions,  — Gnathosloniata.  and  Para,sita 
or  Siphonostomata.  The  Gnathostomata  inckide  the  free-swim- 
ming Copepoda;  they  have  appendages  about  the  mouth  adapted 
to  mastication  and  the  full  number  of  body  segments.  The  Si- 
phonostomata are  parasitic;  they  have  the  appendages  alxiut  the 
mouth  adapted  for  piercing  or  sucking,  and  generally  also  a  re- 
duced number  of  body  segments.  The  following  table  shows  this 
classification : 

Branch:  Arthropoda. 

Class:  Crustacea. 

Subclass:  Entomostraca. 
Order:  Copepoda. 

Suborder:  (a)  Eucopepoda. 
Group  I.    Gnathostomata. 
Group  2.    Siphonostomata. 
Suborder:  (b)  Branchiura. 

KEY  TO  NORTH  AMERICAN  FREE-SWIMMING  COPEI*ODA 
(GNATHOSTOMATA) 

I  (104)         Cephalothorax  and  abdomen  distinctly  separatL-d 


2  (76)  Antennae  long,  commonly  nearly  or  quite  as  Ioiir  as  the  whole 

animal,  and  composed  of  23,  24,  or  25  segments.  Antennae 
of  male  asymmetrical,  the  right  genicuhite  and  miMJilied  as 
a  grasping  organ.  The  fifth  feet  are  uiilikc  in  the  two  sexes, 
and  in  the  male  the  right  and  left  fifth  feet  arc  dissimiLir. 
Family  CENXROPAcroAi 

3(8,73)       Endopoditesof  first  swimming  feet  composed  of  one  segment.    .     .\ 

4  (7)  Endopodites  of  second,  third,  and  fourth  swimming  feet  compose<l 

of  one  segment.  Each  furcal  ramus  armed  with  three 
large  setae.  Abdomen  of  male  asymmetrical,  and  armed 
on  right  side  with  a  peculiar  grasi)ing  arrangement. 

Epischuru        .      5 


756  FRESH-WATER   BIOLOGY 

5  (6)  Abdomen  of  female  not  distinctly  flexed  to  the  right.     Terminal 

setae  of  furcae  equal. 

Epischura  nevadensis  Lilljeborg  1889. 


Found  in  the  mountain  lakes  of  the  western  United  States. 
Length  of  female,  2  mm. 
Length  of  male,  1.7  mm. 


Fig.  1 1 74.   Abdomen  oi  male  Epischura  nevadensis.     X  24.     (Original.) 


6  (5)  Abdomen  of  female  distinctly  flexed  to  the  right,  the  external 

furcal  setae  much  larger  than  the  others. 

Epischura  lacustris  Forbes  1882. 


Common  in  the  Great  Lakes  and  other  large  bodies  of  water  in 
the  central  and  eastern  United  States. 

Length  of  female,  1.78  mm. 
Length  of  male,  1.38  mm. 


Fig.  1 1 75.     Abdomen  of  male  Epischura  lacustris.      X  49.     (Original.) 


7  (4)  Endopodites  of  second,  third,  and  fourth  feet  composed  of  two 

segments.     Furcal  rami  elongated. 

Eurylemora  affinis  Poppe  1880. 

Really  a  salt-water  form,  and  commonly  found  in  fresh  water  only  when  it  is  more  or  less 
closely  connected  with  the  sea.  Only  one  species  is  known  in  America  in  fresh  waters  and  that 
has  been  found  in  waters  connected  with  the  Gulf  of  Mexico  and  the  Atlantic  Ocean. 

Length  of  female,  1.5  mm. 

Length  of  male,  1.5  mm. 

8  (3'  73)      Endopodites  of  first  swimming  feet  composed  of  two  segments,  of 

third  and  fourth  swimming  feet  composed  of  three  segments. 
Furcal  rami  short.  Right  fifth  foot  of  male  terminates  in 
a  more  or  less  sickle-shaped  hook.    .    .    .     Diaptomus.    .    9 


9  (22)        Antepenultimate  segment  of  the  male  right  antenna  without  dis- 
tinct appendage 10 


COPEPODA 


/  ^/ 


lo  (ii)         Right  and  left  fifth  feet  of  male  nearly  equal  in  length,  icrminal 
hook  of  right  foot  symmetrical. 

Diaptumiis  orcgomnsis  Lilljeborg  iSS«;. 


The  most  widily  <listril)Utc-«I  of  all  North  Amer- 
ican species,  and  the  one  most  likely  to  In-  collc<.1c<l 
in  the  northern  part  of  the  I'nite*!  Statt-%  It  is 
found  from  one  side  of  the  continent  to  the  other. 
The  most  noticeable  characteristic  is  the  equal 
length  of  the  fifth  feet  of  the  male 

Length  of  female,  1.5  mm. 

Length  of  male.  1.4  mm. 


Fig.   1176.    Diapinmus  orrgonemii. 
X  193.     B,  fifth  foot  of  female. 


.4.  fifth  fcrt  u(  Rulr. 
X  200.     (Uni'injl.i 


11  (10)         Left  fifth  foot  of  male  shorter  than  right 12 

12  (15)         Left  fifth  foot  reaching  beyond  first  segment  of  right  exopodile.  .    ij 

13  (14)         Terminal   hook  of  right  exopodite  uniangular,   right  endopotlilc 

equal  in  length  to  first  segment  of  e.xopodile. 

Diaptomus  rcigluirdi  Marsh  iSt}^. 


This  has  been  found  in  only  four  localities,  —  Intermcfliate 
Lake  and  Crooked  Lake  in  northern  Michigan,  a  lake  on  Beaver 
Island  in  Lake  Michigan,  and  Sodus  Bay,  N.  V 

Length  of  female.  1.14  mm. 

Length  of  male,  1.02  mm. 


Fig.   1177.     Fifth  feet  of  male  DiJ />/<'«««  rrKAurrfi.      X  US-     (Original.) 


14  (13)         Terminal  hook  biangular,  right  cndopodite  large,  longer  than  \n>\ 
segment  of  exopodite. 

Diaptomus  mississippicnsis  Marsh  i.S«>4- 


The  most  common  form  of  the  .Southern  .States;  it  is  abundant  all 
through  the  states  bordering  on  the  (iulf. 

Length  of  female,  i.-'  mm. 
Length  oi  male,  i.i  mm. 


Fig    1178      Fifth  feet  of  male  Diaptomm  misustippumis.      X  US 

(.Orits'inal.) 


758  FRESH-WATER   BIOLOGY 

15  (12)         Left  fifth  foot  of  male,  reaching  end  of  first  segment  of  right  exopo- 

dite,  or  only  slightly  exceeding  it 16 

16  (17)         Antepenultimate  segment  of  right  antenna  of  male  produced  at 

distal  end  into  a  blunt  point,  first  segment  of  right  exopo- 
dite  of  fifth  foot  with  marked  quadrangular  hyaHne  appen- 
dage  Diaptomus  hirgei  Marsh  1894. 


Fig.  1 1 79.     Diaptomus  birgei,ma.\e.     ^ ,  terminal  segment  of  right  antenna.     X  iQi* 
5,  fifth  feet.      X  109.     (Original.) 

Common  in  Indiana  and  has  been  found  in  Wisconsin  and  on  Long  Island. 
Length  of  female,  1.3  mm.         Length  of  male,  1.2  mm. 

17  (16)         Antepenultimate  segment  of  right  antenna  of  male  not  produced 

into  blunt  point  on  distal  end 18 

18  (19)         Inner  process  of  the  terminal  segment  of  exopodite  of  left  male 

fifth  foot  falciform,  no  hyaline  appendage  of  first  segment  of 
right  exopodite Diaptomus  pallidus  Herrick  1879, 


Occurs  in  Mississippi  Valley,  as  far  west  as  the  foothills  of  the  Rocky 
Moimtains,  but  is  comparatively  rare  north  of  Iowa  and  Illinois. 
Length  of  female,  1.2  mm. 
Length  of  male,  1.04  mm. 


Fig.  1 180.     Fiith  ieet  oi  male  Diaptomus  pallidus.     X  190-     (Original.) 


19  (i8) 

20  (21) 


COPEPODA 

759 

Inner  process  of  terminal  segment  of  left  exopcxlitc  of  male  i.fth 
foot  digitiform,  hyaline  appendage  on  internal  distal  angle 
of  first  segment  of  right  exo{)odite ,0 

Lateral  spine  of  second  segment  of  right  exopodite  nearly  straight 
no  blunt  spine  on  posterior  surLice  of  this  se-gmenl.  ' 

Diaptomui  tyrtlli  Vo\^\n:  iSMM. 


Widely  spread  in  the  mountain  lak.-s  of  the  West. 
Lenf^th  of  female.  1.2  mm. 
Length  of  male,  1.15  mm. 


Fig.  1181.     Fifth  feet  of  male  Diapiomui  tyrtlli      X  lya 
(Original.; 


21  (20)  A  second  hyaline  appendage  on  dorsal  side  of  distal  margin  of  tirst 

segment  of  right  exopodite,  lateral  spine  of  second  segment 
of  right  exopodite  strongly  curved,  and  a  blunt  spine  on 
posterior  surface  of  this  segment. 

Diaptomus  coloradoisis  Marsh  i()i  i. 


In  the  Rocky  Mountains  in  Colorado  D.  tyrclli  is  repiacctl  by  thi.s  cio?<-Iy 
allied  species  which  is,  apparently,  the  characteristic  species  of  the  moun- 
tain lakes  of  Colorado. 

Length  of  female,  1.38  mm. 

Length  of  male,  1.32  mm. 


Fig.  1182.     Vdlh  ieetol  male  Diaptomus  coloTodemis.     X  uo.     (.Original.) 


22  (9)  Antepenultimate  segment  of  male  riglu  antenna  with  lateral  lamella 

or  terminal  process ^ 

23  (26,  42)  Antepenultimate  segment  of  right  antenna  of  male  Nvith  h.Nalino 

lamella 


760 


FRESH-WATER   BIOLOGY 


24  (25)  Hyaline  lamella  broad,  extending  beyond  the  end  of  the  segment, 
second  basal  segment  of  right  exopodite  of  male  fifth  foot 
armed  on  the  posterior  surface  with  small  hook. 

Diaptomus  leplopus  Forbes  1882. 


Found  generally  distributed  through  the 
Mississippi  Valley,  and  extending  into  Canada. 
The  variety  piscinae  occurs  in  some  of  the 
more  northern  collections  and  as  far  west  as 
Flathead  Lake,  Montana.  This  dififers  from 
typical  leplopus  mainly  in  the  greater  length 
of  the  endopodites  of  the  male  fifth  feet  and 
in  the  fact  that  in  the  female  fifth  feet  the 
third  segment  of  the  exopodite  is  indistinctly 
separated  and  armed  with  two  spines  with  a 
third  one  present  on  the  second  segment. 
This  third  spine  is  absent  in  leplopus. 

Length  of  female,  1.5  to  1.89  mm. 

Length  of  male,  1.4  to  1.83  mm. 


Fig.  1 1 83.  Diaptomus  leplopus,  male.  A,  ter- 
minal segments  of  right  antenna.  X  185.  B, 
fifth  feet.     X  83.    (Original.) 


25  (24) 


Hyaline  lamella  narrow,  extending  beyond  the  end  of  the  segment 
slightly,  if  at  all;  first  basal  segment  of  right  fifth  foot  of 
male  armed  with  hook  equal  in  length  to  first  segment  of 
exopodite Diaptomus  clavipes  Schacht  1897. 


Has  been  found  in  three  locali- 
ties, in  West  Okoboji  Lake,  Iowa, 
near  Lincoln,  Nebraska,  and  at 
Greeley,  Colorado. 

Length  of  female  from  1.37 
to  2.5  mm. 


Fig.  1184.  Diaptomus  clavipes,  male. 
A,  fifth  feet.  X  83.  B,  terminal 
segments  of  right  antenna.  X  141. 
(Original.) 


26  (23,  42)   Antepenultimate  segment  of  right  antenna  of  male  bears  a  slender 
straight  process 27 


COPEPODA 


761 


27(32,35)    Process  much  shorter  than  penultimate  segment ,8 

28  (31)         Right  endopodite  of  male  fifth  foot  ru(hmentary [    ]      ,g 

29  (30)         Lateral  spine  of  second  segment  of  right  cx.,p«,.liic  of  male  fifih 

foot  terminal Diuplunnts  lintnn;  v>>r)>,..  ,s.. . 


Founri  in  Yellow- 
stone  I'ark  an«l  ui 
tin-  vallo'  of  the 
(iailalin    River, 

Mont.ui.i 


OiaUommt 

.-l.fiMhfr^ 


Flc..tiHy 
Union  i 

..Irn.ilr  .  M  f< 
t'  r:r,  :,  ;,  ■  .r..r-  ■ 
<>i  r:.(.t  .i;.;f  nr  ;  • 
nvalf  X  2  30  ( 
fifth  foot  of  female 
X  35&-    (Ohsiiul ) 


30  (29) 


Lateral  spine  of  second  segment  of  right  cxopodite  of  male  fifth  fool 
near  the  proximal  end.   .   Diaptomus  trybomi  Lilljclx>rg  1H89. 


Fig.  1186.    Diaptomus  trybomi.    ^,  abdomen  of  female.     X  70     '':/'f|^ ''^' ''^  Ti'-.K,^.','**^ 
C,  terminal  segments  of  right  antenna  of  male.     X  100.     (After  Dc  Oucnie  and  Kichanl  ) 

The  antenna!  process  is  dentate  on  the  outer  margin  and  the  alxiomcn  of  the  female  awi 
metrical.    Has  been  found  only  in  Oregon. 

Length  of  female,  1.5  mm. 
Length  of  male,  1.4  mm. 


762  FRESH-WATER   BIOLOGY 

31  (28)         Right  endopodite  of  male  fifth  foot  about  equal  in  length  to  first 
segment  of  exopodite.     .    .     Diapiomus  judayi  Marsh  1907. 


Fig.  1187.     Diaptomus  judayi.     A,  terminal  segments  of  right  antenna  of  male.     X  290.     B,  fifth  feet 
of  male.     X  i45-    C,  abdomen  of  female.     X  165.     (Original.) 
Lateral  spine  of  the  second  segment  of  the  right  exopodite  is  median,  first  segment  of  the 
female  abdomen  has  a  process  on  the  posterior  margin  on  the  right  side.     Has  been  found  only 
in  the  mountains  of  Colorado. 

Length  of  female,  0.93  mm. 
Length  of  male,  0.9  mm. 

32  (27.  35)  Process  nearly  or  fully  equals  penultimate  segment 33 

33  (^34;        Right  endopodite  of  male  fifth  foot  equals  in  length  first  segment 

of  exopodite,  spines  of  first  basal  segments  large. 

Diaptomus  tenuicaudatus  Marsh  1907. 


Found  in  Saskatchewan. 
Length  of  male,  1.195  mm. 


Fig.  1 188.  Diaptomus  tenuicaudatus,  male.  A ,  fifth  feet. 
X  145.  B,  terminal  segments  of  right  antenna. 
X  194-     (Original.) 


COPEPODA 


763 


34  (33)        Right  endopodite  of  male  fifth  f(X)t  exceeds  length  of  first  segment 
of  exopodite,  spines  of  first  bas^d  scgnu-nts  small. 

Diaptumus  siciiis  Forbes  i»8i. 


Found  in  the  GrcAt  XaktK  f»nnjt 
the  m<)st  abundant  form  laJccn  in 
limnetic  ( ollertions;  found  to  M>mr 
extent  in  other  lake*  in  the  vimc 
KeneraJ  ri^ion.  It  iv  a%  a  rule, 
confme*!  to  the  larger  and  flcrtwr 
lakes.  It  is  fre«iuently  founcl  a\m>- 
ciate<i  with  I)  miniUus  l»ut  i»  read- 
ily distinKuishe<l  by  the  sJefMlrr. 
symmetrical,  sitkleshaiirtl  hcmk 
terminating  the  cxofM^lite  trf  the 
riRhl  fifth  f<K»t  of  the  male;  thi*  it 
not  a  characteristic,  h«iwever,  that 
will  distinguish  it  frc)m  s{irc>cs 
found  in  other  Ifnalities. 

Lenjjth  of  fem;iJe.  1  js  mm 
Length  of  male,   i   i  <;  nun 

Fig.  1 189.    Diaptomus  siciiis,  male.    A,  terminal  segments  of 
right  antenna.     X  194.     B.  fifth  feet.     X  i94-     (Original.) 

35  (27,  32)  Process  exceeds  in  length  penultimate  segment 36 

36  (39)         Large.     Lateral  spine  of  second  segment  of  exopotlite  of  right  fifth 

foot  of  male  terminal  or  nearly  so 37 

37  (38)         Process  of  antepenultimate  segment  of  right  antenna  of  male  only 

slightly  longer  than  penultimate  segment,  antennae  equal  in 
length  to  cephalothorax. 

Diaptomus  slwshonc  Forbes  1803. 


Rocky  Mountains.  Not  so  wi<1«prr*d 
or  characteristic  of  the  mountain  lakes  ai 
D.  Tyrelli  Popix-,  althou>:h  this  K>ant  n|*^ 
cics  is  by  no  means  uncommon,  juul  i*  e>|^- 
ciaily  striking  because  commonly  colortd  • 
brigiit  red. 

IxMigth  of  fem.ile.  J  9  mm. 

Length  of  male,  i.5  mm. 


Fig.  1190.  Diaptomus  Shoshone,  ma\e.  i4,  fifth  feet. 
X  108.  B,  terminal  segments  of  right  antenna. 
X  180.     (Original.) 


764 


FRESH-WATER   BIOLOGY 


38  (37)         Antennal    process   of    male    exceeds    ultimate  segment,  antennae 
reach  furca Diaptomus  wardi  Pearse  1905. 


Washington. 

Length  of  female,  2.9  mm. 

Length  of  male,  1.6  mm. 


Fig.  1 191.  Diaptomus  wardi,  male.  A,  fifth  feet. 
X  173-  B,  terminal  segments  of  right  antenna. 
X  112.     (After  Pearse.) 


39  (36)  Small.  Lateral  spine  of  second  segment  of  right  exopodite  of 
male  on  proximal  half  of  segment,  antennae  reach  beyond 
furca 40 


40  (41)  Lateral  spine  of  second  segment  of  right  exopodite  of  male  fifth 
foot  short,  right  endopodite  rudimentary,  endopodites  of 
female  fifth  feet  rudimentary. 

Diaptomus  minutus  Lilljeborg  1889. 


Northern  United  States  and  north 
to  Greenland  and  Iceland.  It  is  one 
of  the  most  easily  recognized  species 
because  of  the  broad,  saber-like  hook 
on  the  right  fifth  foot  of  the  male  and 
the  rudimentary  endopodites  of  the 
fifth  feet  of  both  sexes.  It  is  common 
in  the  waters  of  the  Great  Lakes,  but 
that  is  as  far  south  as  one  may  expect 
to  find  it. 

Length  of  female,  i  to  i.i  mm. 

Length  of  male,  i  mm. 


Fig.  1192.  Diaptomus  minutus.  v4,  fifth  foot 
of  male.  X  154.  B,  fifth  feet  of  female. 
X  200.    (Original.) 


COPEPODA 


76s 


41  (40)  Lateral  spine  of  second  segment  of  right  cxopoditc  of  male  fifth 
foot  long,  right  endopodite  criuals  in  length  first  sfjcmcnl 
ofexopodite Oiaptomus  ashLnJt  SUr^h  iSi^s 


Foun<l  in  the  Grrat  Lakrs  and  v>ro« 
lakes  immt-diatcly  n »nnra r«l  wjlh  them 
and  west  to  thr  Slate  <»f  WashinKton. 

Length  of  frmale.  o.<>7  mm. 

Length  ^.>i  male,  o.tiy  mm. 


Fig.  1 193.  Dijptomus  ashlandi,  male.  .4,  fifth 
feet.  X  145-  B,  terminal  segments  of  right 
antenna.      X  145-     (Original.) 


42  (23,  26)    Antepenultimate  segment  of  right  antenna  of  male  l)cars  curved 
process 43 


43  (46)         Process  equals  or  exceeds  in  length  penultimate  segment. 


44  (45)  Process  about  equals  in  length  last  two  segments,  second  hasal 
segment  of  right  fifth  foot  of  male  dilated  on  inner  margin, 
endopodites  of  fifth  feet  in  both  sexes  indi.>itincily  two- 
segmented Diaptomus  cisoii  Lilljeborg   iSS<j. 


Has  been  found  only  in  CAlifomi* 
and  Nebraska. 

IxnKth  of  female.  4  nmi 
Length  of  male,  j.5  mm. 


Fig.  1194.  DiaMomus 
X  38.  B,  terminal 
X  133-     (Original.) 


eiseni,    male, 
segments    of 


A.    fifth    feet, 
right     antenna. 


766  FRESH-WATER   BIOLOGY 

45  (44)         Process  slightly  exceeds  in   length  penultimate  segment,   second 

basal  segment  of  right  fifth 
foot  of  male  not  dilated  on 
inner  margin,  endopodite 
of  left  fifth  foot  one-seg- 
mented. 

Diaptomus  franciscanus 
Lilljeborg  1889. 


Found  only  near   San   Fran- 
cisco. 

Length  of  female,  2.3  mm. 
Length  of  male,  2  mm. 


Fig.  1 195-  Diaptomus  Jranciscanus,  male  A,  terminal 
segments  of  right  antenna.  X  20c.  B,  fifth  feet. 
X  200.     (After  De  Guerne  and  Richard.) 

46  (43)         Process  shorter  than  penultimate  segment 47 

47  (66)         One  or  both  terminal  processes  of  last  segment  of  left  exopodite  of 

male  fifth  foot  distinctly  falciform 48 

48  (56,  63)  Right  endopodite  of  fifth  foot  of  male  small,  shorter  than  first 

segment  of  exopodite 49 

49  (53)        Terminal  segment  of  right  exopodite  of  fifth  foot  of  male  elon- 

gate       50 

50  (51,  52)  In  fifth  foot  of  male  right  endopodite  rudimentary,  left  endopodite 

two-segmented  and  spatulate  in  form. 

Diaptomus  spatulocrenatus  Pearse  1906. 


Found  in  New  England. 
Length  of  female,  1.52  mm. 
Length  of  male,  1.3 1. 


Fig.  1196.    Fifth  feet  of  male  Diaptomus  spatulocrenatus.    X  84. 
(After  Pearse.) 


COPEPODA 


767 


51  (50,  52)  Terminal  segment  of  right  cxopoditc  („  „nh  i.K.t  oi  niaU  iiiuch 
broader  at  distal  end.  lateral  spine  nearly  Icrminal  and 
straight,  left  endopoditc  elongate. 

Diaptomus  lonipfJatus  Marsh  1907. 


Founr!  in  I^ui^tana. 
lA-riKth  «)f  ft-malc.  i  49  mm. 
LtnKth  of  male,  i  j?s  mm 


Fig.  1 197,    Diaptomus  conipedatus,  maXt.    ^,  fifth  feet.     X  126. 
B,  terminal  segments  of  right  antenna.     X  193.     (Original.) 


52  (50,  51)  Terminal  hook  of  right  exopodite  of  fifth  foot  of  malt-  falciform, 
lateral  spine  at  distal  third  of  segment,  sei'ond  Iw.sal  seg- 
ment of  right  foot  broad  at  distal  end  with  i)rotiiis  at 
external  distal  angle. 

Diaptomus  sanguifuus  Forbes  1876. 


Mississippi    Valley.       Occur*    in 
spriiiK.  in  st;i>:nanl  pooJv 

Ix-ngth  of  fi-malc.  1.4  lu  j  1;  mm 
Length  of  male,  i  to  2  ram. 


Fig.  1198.  Diaptomus  sanguineus,  yl,  terminal  seg- 
ments of  right  antenna  of  male.  X  i93-  ^.  hlth 
feet  of  same.     X  no.     (Original.) 


768  FRESH-WATER   BIOLOGY 

53  (49)         Terminal  segment  of  right  exopodite  of  male  fifth  feet  of  usual 

length,  lateral  spine  terminal 54 

54  (55)^       Inner  surface  of  left  endopodite  of  male  fifth  foot  rugose,  terminal 

, ,  spines  of  endopodites 

'  ^  of  female  fifth  feet  very 

long. 

Diaptomus  stagnalis 
Forbes  1882. 


A    very    large    species 
found   in   the    Mississippi 
Valley  in  the  spring. 
Length  of  female,  4  to 

4.5  mm. 

Length  of  male,  3.5  to 

4  mm. 


Fig.  1199.    Diaptomus  stagnalis.    ^ ,  fifth  foot  of  female.     (After  Forbes.) 
B,  fifth  feet  of  male.     (After  Herrick.  and  Turner.) 

55  (54)  In  male,  segments  of  right  fifth  foot  short  and  broad,  terminal  hook 
long  and  strongly  curved,  lateral  spine  long  and  straight; 
in  female,  dorsal  process  on  fifth  cephalothoracic  segment, 
endopodites  of  fifth  feet  short  and  one-segmented. 

Diaptomus  saltillinus  Brewer  1898. 


Found  in  Nebraska. 


Length  of  female,  1.5  mm. 


Length  of  male,  1.25  mm. 


Fig.  1200.  Diaptomus  saltillinus.  A.  terminal  segments  of  right  antenna  of  male.  X  193- 
feet  of  same.  X  126.  C,  fifth  foot  of  female.  X  19.3.  D,  dorsal  process  of  same. 
(Original.) 


COPEPODA 


769 


56  (48,  63)  Right  endopodite  of  fifth  foot  of  male  distinctly  longer  than  first 

segment  of  exopodite.  . 

57 

57  (60)         Second  segment  of  right  exopodite  of  male-  fifth  foot  has  oblique 

ridge  on  posterior  surface \g 


58  (59)         First  segment  of  right  exopoch'te  of  maK-  lifth  f.K.t  has  transversa' 
ridge  on  the  posterior  surface. 

Diaptomus  asymmt trims  Marsh  nx>7. 


Fig.  1201.  Diaptomus  asymmetricus . 
male.  X  103.  B,  abdomen  of 
(Original.) 


A,  fifth    feet    of 
female.      X   yy. 


In  the  male  fifth  f(jol  the  lateral 
spine  of  the  terminal  »cKinrnt  i* 
about  one-half  as  lung  as  ihc  seg- 
ment; the  first  segment  of  the  fcnuir 
abdomen  has  a  prominent  swelling  on 
the  right  side.     Found  in  Cul*a. 

LenKth  of  female,  i.jg  mm. 

Length  of  male,  i.i6  mm. 


59  (58)         First  segment  of  right  exopodite  of  male  fifth  foot  has  two  curved 
processes  on  posterior  surface. 

Diaptomus  J  or  sal  is  Marsh  ujo;. 


In  the  male  fifth   UnA  the  I '.•'-'■ 
spine  of  the  terminal  s*Tment   • 
or  e.xceeds  in  len>:th  the  s«-Rnui.; 
fifth   cephalothoracic   seRmrnt   .:    ; 
female    i.s    armnl     with    t»-o    .1   r  . 
proies.ses.     Found    in    lA)uiMan.i   .1:. 
Florida  and  probably  in  other  state 
bordering  on  the  (iulf  of  .Mcxiio. 

Length  of  female.  1 . 1  i  mm. 

Length  of  male,  i.oog  mm. 


;  1202.  Diaptomus  darsalis.  .4.  fifth  feet  ol  m*l«  X  U* 
B,  |)rofile  dorsjil  surface  of  cephalothorax  ol  Icmalc  .X  v--* 
((jnginal.) 


770 
6o  (57) 


FRESH-WATER  BIOLOGY 

Second  segment  of  right  exopodite  of  fifth  foot  of  male  does  not 
have  oblique  ridge  on  posterior  surface 6i 


6i  (62)        Lateral  spine  of  terminal  segment  of  right  exopodite  of  male  fifth 
foot  terminal,  endopodites  distinctly  two-segmented. 

Diaptomus  bakeri  Marsh  1907. 


In  the  female  fifth  foot  the  exopodites  are 
distinctly  three-segmented,  the  endopodites 
distinctly  two-segmented.  Found  in  Cali- 
fornia. 

Length  of  female,  1.27  mm. 

Length  of  male,  1.124  mm. 


Fig,  1203.     Diaptomus  bakeri. 
X  no.    B,  fifth  foot  of  female. 


A,  fifth  feet  of  male. 
X  193.    (Original.) 


62  (61)  Lateral  spine  of  terminal  segment  of  right  exopodite  of  male  fifth 
foot  situated  on  distal  third  of  segment,  right  endopodite 
indistinctly  two-segmented,  left  one-segmented. 

Diaptomus  washingtonensis  Marsh  1907. 


The  first  abdominal 
segment  of  the  female 
has  a  digitiform  process 
on  the  right  posterior 
border.  Found  in 
Washington. 

Length  of  female, 

1. 187  mm. 

Length  of  male, 

1. 137  mm. 


Fig.  1204.    Diaptomus  washingtonensis.    yl ,  fifth  feet  of  male.     X  126. 
B,  abdomen  of  female.     X  no.    (Onginal.) 


COPEPODA 


71 


63  (48,  56)  Right  endopodite  of  fifth  foot  of  male  equals  or  only  slightly  ex- 
ceeds first  segment  of  exopodite (,» 


64  (65)  Terminal  segment  of  right  exopodite  of  male  fifth  fool  ha>  uhh^uc 
ridge  on  posterior  surface,  lateral  si)ine  exceeds  .scRment  in 
length Diaplomus  lilhuijutrifuiniis  Uvrtick  liiijt 


The  fifth  ccphalothoraric  soRmcnt  i.i  ir.r  umjue 
has  a  dorsal  pnui-ss,  and  thi-  «-nd«»p«>ditr*  of  the 
fifth  feet  are  commonly  two  M-Kmcntr<l.  Ki.untl  in 
New  Mexico  and  Colorado.  As  thr  rvamr  irvli- 
Gates,  this  form  was  ori^nally  <lt"x-ril>c«l  l»y  Her- 
rick,  from  material  coUectcil  in  All»u<iucr<iuc.  N  M. 
It  is  found,  however,  from  Colorado  to  thr  City  ol 
Mexico,  and  seems  to  be  a  tyfiical  fonn  o<  the 
Southwest. 

Length  of  female.  1.7''  mm. 

Length  of  male,  1.58  mm. 


Fig.  1205.  Diaptomus  albuquerquensis.  ^.dor- 
sal process  of  female.  X  180.  B,  fifth  feet  of 
male.     X  49.     (Original.) 


65  (64) 


Terminal  segment  of  right  exopodite  of  male  fifth  foot  (loes  not 
have  oblique  ridge  on  posterior  surface;  lateral  spine  short, 
about  one-half  length  of  segment. 

Diaptomus  novatncxicanus  Merrick  1895. 


Fig.  1206.  Fifth  feet  of 
male  Diaptomus  novamexi- 
canus.  (After  Herrick  and 
Turner.) 


F'ound  in  New  Mexico. 
Length  of  female,  i.i  t< 


66  (47) 


Terminal  orocesses  of  left  exopodite  of  fifth  fcx-t  of  male  digili- 
^form^dght  endopodite  shorter  than  first  segment  of  exopc. 
dite 


772  FRESH- WATER   BIOLOGY 

67  (70)  ■       First  segment  of  exopodite  of  male  fifth  foot  without  hyaline 
appendage 68 


68  (69)  Right  endopodite  of  male  fifth  foot  triangular  in  form,  first  ab- 
dominal segment  of  female  has  digitiform  process  on  right 
posterior  border Diaptomus  nudus  Marsh  1904, 


Found    in    lakes    near    Pikes   Peak, 
Colorado. 

Length  of  female,  1.132  mm. 
Length  of  male,  1.115  di°i- 


Fig.  1207.  Diaptomus  nudus.  A.  fifth  feet  of 
male.  X  105.  B,  abdomen  of  female.  X  105. 
(Original.) 


69  (68)  In  male  fifth  foot,  second  basal  segment  with  hyaline  appendage 
on  inner  margin,  first  segment  of  right  exopodite  with  trans- 
verse ridge,  second  segment  with  obHque  ridge  and  hyaline 
process  near  the  outer  margin. 

Diaptomus  purpureus  Marsh  1907. 


Found  in  Cuba.  This  is  a  conspicuous  species,  both  on  account  of 
the  large  size  and  the  purple  color  of  the  furcae,  furcal  setae,  and  distal 
ends  of  the  antennae. 

Length  of  female,  2.56  mm. 

Length  of  male,  2.24  mm. 


Fig.  1208.    Fifth  feet  of  male  Diaptomus  purpureus.     X  76.     (Original.) 


COPEPODA 


773 


70  (67)         First  segment  of  right  exopoditc  of  male  fifth  foot  has  hx-alinc 
appendage , 


71  (72) 


Hyahne  appendage  of  first  segment  of  exojxxlite  of  male  fi/lh  fool 
at  mner  distal  angle,  endopKxlite  of  right  foot  about  equals 
first  segment  of  exopodite. 

Diaptomus  signimmia  Lilljclxjrg  iMH<). 


Fig.  i20g.  Diaptomus  signicauda.  /I,  abdomen 
of  female.  X  118.  B,  fifth  feet  of  male. 
X  174-     (Original.) 


The  first  segment  of  ihc  abdcimcn  ol 
the  female  ha.s  a  difo'tifurm  pr««'-^»  •■" 
the   ri^ht   posterior   border       K'- 
mountain    regions    of    wrMrrn     ' 
States.     It  reprf>tnt 
that  are  f()un<l  in  tli' 
of  the  western  p;irl  1.; 
The  peculiar  apjK-ml,; 
ment  of  the  fcmali- 
the  name  to  the  s|k-.  .t  ^    ,. 
teristic  of  the  Kroup.     lOli' 
Rocky  Mountains  and  far' 
likely  to  contain  this  or  all' 

Length  of  female,  o  •, 

Length  of  m.ilc  our. 


72  (71)  Hyaline  appendage  of  first  segment  of  exopodite  of  male  fifth  fo»il 
on  inner  distal  half,  cndoi)odite  of  right  fifth  fool  much 
shorter  than  first  segment  of  exopodite. 

Diaptomus  siciloidcs  Lilljcborg  iHvS<>. 


Found  in  the  Mississippi  Valley  and  west  to  C  alifurnia.  A»  D  '^'f*^ 
ensis  is  typical  of  the  Northern  States,  so  D.  suMrs  m.tv  ♦>r  ronMdrfr.1 
as  typical  of  a  region  a  little  farther  to  the  south.     It  •  -^ 

Long  Island  on  the  east  to  the  Rocky  Mountains  on  : 
not  the  exclusive  form,  is  more  a|)t  to  hv  seen  th,in  .r  ^ 

along  the  Ohio  River. 

Length  of  female.  i.cX)  to  i.2iS  '"f" 

Length  of  male,  i.oi  to  i.ii.'S  nam. 


Fig.  1210.  Fifth  feet 
of  male  Diaptomus 
siciloides.  X  122. 
(Original.) 


73  (3,  8)      Endopodites  of  first  swimming  feet  comiH.scd  of  three  s,-pmrnt. 


74 


774  FRESH-WATER   BIOLOGY 

74  (75)  Endopodites  of  all  swimming  feet  composed  of  three  segments, 
antennae  of  23  segments  (according  to  Herrick  24),  furca 
short.     Only  one  species. 

OsphKanticum  lahronectum  Forbes  1882. 


Found  widely  distributed  in  the  United  States,  more  frequently 
in  the  Mississippi  Valley  but  never  in  large  numbers,  so  that  it  is 
comparatively  rare  in  collections. 

Length  of  female,  1.7  mm. 

Length  of  male,  1.36  mm. 


Fig.  1211.     Abdomen  of  female  Osphranticum  labronectum.     X  51. 
(Original.) 


75  (74)         Endopodites  of  all  swimming  feet  composed  of  three  segments, 
antennae  of  25  segments,  furca  long. 

Limnocalanus  macrurus  Sars  1862. 


Found  only  in  deep  lakes.  It  is  especially  interesting,  as  it  is  the  only 
species  of  the  Centropagidae  found  in  both  Europe  and  America.  It  is 
widely  distributed  in  northern  Europe  and  Asia  and  is  found  in  salt  water 
as  well  as  in  fresh.  It  is  considered  a  representative  of  the  "fauna  re- 
licta,"  that  is,  it  is  a  salt  water  form  which  has  become  adapted  to  the 
environment  of  fresh  water. 

Length  of  female,  2.4  mm. 

Length  of  male,  2.2  mm. 


Fig,  1212.     Abdomen  oiicxmXe  Limnocalanus  macrurus.     X  37.     (Original.) 


76  (2)  Antennae  short,  never  longer  than  cephalothorax,  generally  much 

shorter,  and  composed  of  from  six  to  seventeen  segments; 
antennae  of  male  symmetrically  geniculate;  fifth  feet  rudi- 
mentary, composed  of  from  one  to  three  segments. 

Family  Cyclopidae. 

Only  one  genus Cyclops   .    .    77 


COPEPODA 


The  main  points  to  be  noted  in  the  specific  determination  of  the  Rcnus  ut: 
length  and  number  of  segments  in  the  antenna  of  the  female; 
armature  of  the  antennal  segments,  espcciallv  oi  the  lermiiuU'scjfmcnlA; 
form  of  the  abdomen,  especially  the  form  and  armature  of  the  (ureal  rami' 
form  and  armature  of  the  rudimentary-  fifth  feet; 

structure  of  the  second  antennae,  of  the  maxillii)e<les.  and  of  the  swimminic  feet 
These  last  structures  are  of  less  importance. 

77  (98)         Antennae  composed  of  twelve  or  more  segments. 

78  (92,  93)  Antennae  composed  of  seventeen  segments 71; 

79  (80)         Fifth  feet  composed  of  one  segment  armed  with  one  sf)inc  anci 

two  long  setae Cyclops  atcr  Hcrrick  i88i. 

It  is  a  large  dark-colored  species,  rather  rare,  probably  diMrihutc«l  very 
widely,  and  growing  in  shallow  water.  In  spite  of  its 'wide  dinnbutian. 
however,  it  is  a  rare  form. 

Length  of  female,  1.77  to  2.88  mm. 
Fig.  1213.     Fifth  foot  of  Cyclops  atrr.    X  J'/).     iOri<inAl  . 


80(79)         Fifth  feet  composed  of  two  segments.  .  ^I 

81  (84,  89)  Second  segment  of  fifth  feet  armed  with  seta  and  short  spine.     82 

82  (83)         Spine  of  second  segment  of  fifth  feet  small  and  near  i-nd  of  .v-g 

ment;  last  three  segments  of  female  antenna  without  hya- 
line membrane Cyclops  viridis  J  urine  i8io. 


Fig.  1 2 14.  Abdomen  of  fe- 
male Cyclops  viridis,  var. 
americanus.  X  77>  (Origi- 
nal.) 


Fig.  1 2 15.  Abdomen  of 
female  Cyclops  viridis, 
var.  brevispinosus.  X 
66.     (Original.) 


Cyclop 

(or 


Fi/lh    (oo«    ol 
tiridii.       X    ilS. 


ruciiuil. 


(1  laki-s. 
mil) 


A  widely  distributed  species,  being  found  both  in  jxxils  anc 
form  and  general  appearance,  so  that  it  has  receive<l  a  number  of  ditlerrnl 
which  are  now  reduced  to  varieties,  since  it  has  been  ftuind  that  there  arr  intr 
showing  all  the  stages  between  the  extremes.     W  he 
colored,  while  its  relatives  living  in  the  open  waters  ol 


It   varies   k'riMtl\ 
litlerrnl 


III 


When  living  i'l  l>«»*'b 


It  IS  apt   t..  i<     'ri4y 
)f  our  lakes  are  lolorli-ss  and  llm«»^i  tran»- 
par^ent?  lEspVcially"nodcVabIe"is"th^^  the  form  of  the  fur..d    r.n.i    .v.  ^h.  wn  in 

Figs.  1214  and  1215.     The  forms  found  in  pools  generally  have  com|Kirai:  ■  A 

furcal  rami;  on  the  other  hand,  the  forms  in  deep  waters  have  Ions  an..  «• 

Even  in  the  Hmnetic  forms  there  is  wide  variation.       n  typi.  .U  virulis  tlu  ;.   . 
the  outer  angle  of  the  furcal  ramus.     This  is  replaced  in  the    orm  whuh  Hrrr  »• 

spinosus  by  a  short  broad  spine.     This  variety  is  a  common  limnetic  form  u.  « 

lakes;  a  form  with  the  furca  armed  at  its  outer  angle  with  a  srta  ''•j;'  'M»'; •" 
from  mridis  in  the  structure  of  the  swimming  feet  and  ot  the  lilt  1  ic-rt. 
common  in  shallow  waters,  and  is  the  variety  that  is  m.)st    rt-quent  y  scrti  ^^ 

United  States.     Wherever  a  collection  is  made  one  is  likely  to  get  some  form  oi  i^.-w.  *aa 
generally  it  will  be  americanus. 

Length  of  female,  1.25  to  1.5  mm. 


FRESH-WATER   BIOLOGY 

Spine  of  second  segment  of  fifth  foot  stout,  located  at  about  middle 
of  segment;  last  three  segments  of  female  antenna  with 
delicate  pectinate  hyaline  membrane. 

Cyclops  strenuus  Fischer  1851. 


It  is  one  of  the  most  common  forms  on  the  continent  of  Europe,  but  has 
been  found  in  America  in  only  one  locality,  —  a  pond  in  the  Adirondacks.  It 
is  probable,  of  course,  that  it  will  be  found  in  other  localities,  but  it  is  a  curi- 
ous fact  that  hitherto  it  has  been  found  only  in  a  single  collection.  In  its 
general  form  it  closely  resembles  viridis. 

Length  of  female,  1.35  mm. 


Fig.  1217.    Fifth  foot  of  Cyclops  strenuus.     X  358.     (Original.) 


84  (81,  89)  Second  segment  of  fifth  feet  armed  with  two  setae 85 

85  (86)         Second  segment  of  fifth  feet  elongate,  inner  setae  spine-like,  much 

shorter  than  outer.  .    .    .      Cyclops  bicuspidatus  Claus  1857. 


Fig.  1218.  Abdo- 
men of  Cyclops  bi- 
cuspidatus. X  76. 
(Original.) 


Fig.  1 2 19.  Abdo- 
men of  Cyclops  bi- 
cuspidatus, var. 
navus.  X  62. 
(Original.) 


Fig.  1220.  Fifth  foot 
of  Cyclops  bicuspi- 
datus. X  227. 
(Original.) 


The  furca  of  this  species  is  very  characteristic.  It  not  only  has  a  lateral  seta  at  a  little  more 
than  one-half  its  length,  but  it  has  a  httle  depression  armed  with  minute  spines  on  its  outer 
margin  at  a  little  less  than  one-fourth  of  its  length.  These  characteristics  —  the  position  of  the 
lateral  seta,  the  lateral  depression  with  the  elongated  furca  —  are  presumptive  evidence  that  a 
species  with  seventeen  segmented  antennae  is  bicuspidatus.  If,  in  addition,  one  can  make  out 
the  two  terminal  setae  on  the  second  segment  of  the  fifth  feet,  he  can  be  pretty  certain  of  his 
identification.  Cyclops  bicuspidatus  is  most  commonly  a  limnetic  species,  and  is  the  Cyclops 
which  may  be  considered  as  characteristic  of  the  Great  Lakes.  While  the  form  described  and 
figured  is  the  common  one,  this  species  has  varieties  simila"  to  those  noted  for  viridis,  and  we 
sometimes  find  in  pools  a  form  agreeing  in  general  structure  with  the  typical  forms,  but  with  a 
short  furca.  This  modification  was  named  navus  by  Herrick,  and  the  name  can  be  well  retained 
as  a  varietal  distinction.  Navus,  however,  is  not  so  common  in  pools  as  the  corresponding 
variety  of  viridis.  Fig.  12 18  shows  the  typical  form  of  furca  in  bicuspidatus,  and  Fig.  i2ig  the 
form  in  the  variety  navus. 

Length  of  female,  i.i  mm. 


86  (85)        Second  segment  of  fifth  feet  short,  armed  with  two  nearly  equal 
setae 87 


COPEPODA 


87  (88) 


Setae  of  fifth  feet  very  elongate,  last  anlennal  scgmcnl  armeti  wiih 
serrate  hyaline  plate;  common. 

Cyclops  Icuckarti  Cbus  1857. 

This  sixties  \s  <      "  .., 

of  the  furcic.     N 
segmented  antrtu; 
of  short  rami,  with  ilu    l.iii  : 
about  midway  of  its  liiit'th       I 
the  structure  of  thi-  lift  I    •     ■ 
be  quite  sure  of  the   i-: 
American  species  has  il 
tion  of  tenuis,  ami,  vi  fa- 
only  one  locality.     Thi 

in  another  place,  is  pc  : 

is  almost  world  wide  in  its  < 
been  found  in  all  continents. 
variations  which  are  fouml  in 
are  also  world  wide,  so  that 
Fig.  1221.      Cyclops  leuckarli.      A,  abdomen      seems  to  have  no  efle*  t  <jn  lli. 
of  female.      X  69.      B,  fifth  foot  of  same.  Length  of  female.  1  a  li.n. 

X  232.     (Original.) 


(87)         Setae  of  fifth  feet  of  moderate  length,  last  antennal  st-gmcnl  with- 
out hyaline  plate Cyclops  tniuis  Mav>h  iQio. 


It  has  been  found  in  .Arizona  and  in  the  Isthmus  o(  Panama. 
Length  of  female,  i.i  mm. 


Fig. 


Fifth  foot  of  Cvc/u/)5 /fwttii.     X  2:1.    (OrifinaL) 


89  (81,  84)  Second  segment  of  fifth  feet  armed  with  three  setae.    .  ■  o 

00  (91)  With  sensory  club  on  twelfth  anlennal  segment,  hyaline  plaU  of 
seventeenth  antennal  segment  smooth  or  srrrale.  oRg  .sacs 
standing  out  from  abdomen.  .    Cyclops  albidus  Junnc  1820. 


77^  FRESH-WATER   BIOLOGY 

91  (90)  With  sensory  hair  on  twelfth  antennal  segment,  hyaHne  plate  of 
seventeenth  antennal  segment  deeply  notched,  egg  sacs 
lying  close  to  abdomen.    .    .    .     Cyclops  fuscus  Jurine  1S20. 


Cyclops  fuscus  and  C.  albidus  resemble  each  other  very  closely,  and  it  is  only . 
by  a  careful  examination  that  they  can  be  distinguished.  They  are  very  com- 
mon, especially  in  pond  collections,  Cyclops  albidus  being  found  much  the  more 
frequently.  They  are  much  larger  than  C.  leuckarti  and  the  furcal  armature  dif- 
fers in  that  the  lateral  seta  is  placed  near  the  end  of  the  ramus  (Fig.  1223).  The 
form  of  the  fifth  feet  and  of  the  furcal  rami  will  readily  serve  to  show  when  we 
have  one  of  these  two  species,  and  in  most  cases  it  will  prove  to  be  Cyclops  albidus. 
Length  of  female,  about  2  mm. 

Fig,  1224.    Antennal  segments  of  female  Cyclops  fuscus.     X  i37-     (Original.) 


92  (78,  93)  Antennae  composed  of  sixteen  segments,  fifth  feet  of  three  seg- 
ments       Cyclops  modestus  Herrick  1883. 


This  species  is  comparatively  rare  altho  it  has  been  found  in  a  con- 
siderable number  of  places.  It  occurs  as  far  east  as  Pennsylvania,  as 
far  west  as  Wyoming,  while  its  northern  and  southern  limits  are  Wis- 
coDBin  and  Alabama. 

Length  of  female,  1.2  to  1.25  mm. 


Fig.  1225.  Cyclops  modestus.  A,  abdomen  of 
female.  X  179.  B,  fifth  foot.  X  448. 
(Original.) 


93  (78,  92)  Antennae  composed  of  twelve  segments,  fifth  feet  of  one  segment. 

94 


94  (97)        Fifth  feet  armed  with  three  setae,  swimming  feet  composed  of 
three  segments •    95 


779 


95  (96) 


COPEPODA 

Furcae  of  variable  length,  armtd  cxitrnally  with  a  njw  - 
spines;  very  common.    .    .     Cyi lops  srrruJutus  I is^ht:: 


The  loiiK  twelve  scxmcntctl  antennae  uui  thr  trt 

rate  marKine<l  furral  rami  M-nc  u>  «lf-  '    •' 

species.     The  fiKure  i»f  ihi-  alHlonjrn  'I 
acteristic  structure  of  the  f ureal  r.tn- 
gocxl   deal    of    variation    in    the    : 
When  scrrulalus  is  limnetic   in 
rami  are  lonj,'  and  slen<ler;    ihi^ 
variety  clt'Kans  Herritk.     When  il  iivcs  m  i- 
littoral  waters,  the  furcal   rami  arc  <ih<irt  an  ■ 
this  form  is  known  as  varir'-    '       '  " 

abdomen  l'if,'ure<l  may  he  m; 
latus,  dedans  hc'\i\^,  mut.\\  lu 

sfwndingly  shorter.  Found  every  wiicri:  liic  »u*U  over. 
Length  of  female,  o.8  to  1.25  mna. 


Fig.  1226.  Cyclops  serrulatus.  A,  abdo- 
men of  female.  X  67.  B,  fifth  foot  of 
same.     X  213.    (Original.) 


96  (95)         Furcae  short,  without  lateral  row  of  spines. 

Cyclops  prasinus  Kischcr  iH/x>. 


It  is  a  minute  limnetic  form.     It  resembles  serruiaius  in  \is  lonx  twdvr- 

segmented  antennae,  but  its  abdomen  is  ver>'  different.     The  fun  .-J  

resemble  leuckarti  in  the  fact  that  the  lateral  seta  is  jjlace*!  at  a\> 
way  of  the  length,  but  the  species  is  distinguishe<l  at  a  glance,  not  ■ 
its  smaller  size,  but  by  the  fact  that  the  antennae  are  comiiosc<l  0/  t^cl'.c 
segments.     Cyclops  prasinus  is  widely  distril)ulc>d.  esixxially  in  ibc  laxxrr 
bodies  of  water.     It  is  common  in  the  Great  Lakes. 
Length  of  female,  0.48  mm. 


Fig.  1227. 


Abdomen  of  female  Cyclops  prasinus.     X  I37-     (Ori«iaaL) 


07  (04)         Fifth  feet  armed  with  one  seta,  swimming  feet  of  two  scgmcnls. 

Cyclops  varUijfts  SAn>  \^ 3. 

Cyclops  varicans  occurs  in  Panama  and  Guatemala,  but  there  are  no  authentic  rrcurU*  ol  it« 
occurrence  in  the  United  States. 

98  (77)         Antenna  composed  of  eleven  segments  or  less 99 

99  (102,  103)  Antennae  composed  of  eleven  segments 100 

100  (loi      Rami  of  swimming  feet  composed  of  ^l^^'/^'P"^^^-"-,     .,     .     .  . 

Cyclops  pitiilcratus  Koch  i^js. 


This  stout    dark-colored  species  is  not  uncommon  in  shallow  Ukr»  and 

.inant  S^is  and  is  readily  recogni.cHl  by  the  character,  pvcn  m  ihc  key. 

Length  of  female,  i.i  mm. 


stagnant  pools,  and 


Fig.  1228.    Abdomen  of  female  Cyclops  pkaUratus.     X   69.     (l)ri«in*U 


x^ 


780  FRESH-WATER    BIOLOGY 

loi  (100)     Rami  of  swimming  feet  composed  of  two  segments. 

Cyclops  bicolor  Sars  1863. 

It  is  not  common,  but  is  occasionally  seen.  The  only  species  with 
which  it  is  Hkely  to  be  confused  is  phaleratus,  and  the  difference  in  the 
segmentation  of  the  swimming  feet  makes  the  distinction  easy,  as  the 
rami  have  only  two  segments,  while  in  phaleratus  they  have  three.  The 
fifth  foot  consists  of  a  single  segment  and  bears  one  spine. 
X  Length  of  female,  0.5  mm. 

\  Fig.  1229.     Fifth  foot  of  Cyclops  bicolor.     X  450-     (Original.) 

102  (99,  103)  Antennae  composed  of  eight  segments. 

Cyclops  fimhriatus  Fischer  1853. 

Is  the  only  species  with  antennae  of  eight  segments,  and,  if  found,  can  easily  be  recognized 
by  this  characteristic  if  one  is  sure  that  he  is  examining  mature  forms. 
Length  of  female,  0.7  to  0.84  mm. 

103  (99, 102)    Antennae  composed  of  six  segments. 

Cyclops  aequoreus  Fischer  i860. 


Found  only  in  brackish  water.  It  has  been  found  in 
America  in  waters  connected  with  the  Gulf  of  Mexico, 
and  those  connected  with  the  Pacific  Ocean  in  Panama. 


Fig.  1230.     Abdomen  and  fifth  feet  of  female  Cyclops  aequoreus. 
X  73-     (Original.) 


104  (i)         Cephalo thorax  and  abdomen  not  distinctly  separated,  so  that  the 

whole  body  is  somewhat  worm-like;  antennae  short,  never 
composed  of  more  than  eight  segments. 

Family  Harpacticidae  .    .     105 
All  species  of  Harpacticidae  are  very  minute.     Only  a  few  species  have  been  described  and 
those  very  inadequately.     Probably  there  are  many  undescribed  species  and  other  genera 
than  those  mentioned. 

105  (108)     Antennae  composed  of  six  segments,  endopodites  of  all  swimming 

feet  composed  of  two  segments,  segments  of  endopodite  of 
fourth  foot  fused  so  as  to  appear  as  one,  endopodite  of  first 
foot  slightly  elongate;  found  in  fresh  and  brackish  waters, 
in  New  Mexico Marshia  .    .    106 

106  (107)     Furca  of  female  two  and  one-half  times  as  long  as  broad,  furca  of  male 

four  times  as  long  as  broad,  median  furcal  setae  fused  at  base. 
Marshia  albuquerquensis  Herrick  1895. 

107  (106)     Furcae  of  female  and  male  twice  as  long  as  broad,  median  furcal 

setae  not  fused  at  base.    .   Marshia  hrevicaudala  Herrick  1895. 

108  (105)     Antennae  composed  of  eight  segments,  endopodites  of  swimming 

feet  composed  of  two  or  three  segments,  endopodite  of  third 
foot  usually  much  longer  than  exopodite,  endopodite  of  male 
fifth  foot  always  of  three  segments. 

Canthocamptus  .    .     109 


COPEPODA 


109  (120)     Anal  plate  without  spines,  or  sjiines  are  simple-,  i.e..  .lu  n..i  n.i%.- 


two  points 


no 


110(113)     Sides    of    last    abdominal    segment    Ikivc   spine-like    prolonRalioii 
caudad 

Ill  (112)     Spines  of  anal  plate  few  in  number,  noi  cAcccning  iivt-  or  s.x. 

Cantliocamptiis  slaphylitwidfs  iVar^t-  I.X)^. 


^Ifc 


Fig.  1231.     Anal  plate  and  furta  <>(  i  anthomrnpiw     ;.. 
(Aftir  I'l-arsc  1 


112  (ill)     Spines  of  anal  plate  numerous. 

Cant/ii),(inif)ti(s  st<ipliyliuus  (Jurinc)  i8ao. 


Fig.  1232.     Last  segment  and  furcai-of  maXc  Cantkuamptui  tUipkyitmmt 
(After  Schmcil.j 


113  (no)     Sides  of  last  abdominal  segment  do  not  have  spine-like  i>rolonpntion 

caudad ; 

114  (115)     Furca  long  and  slender,  nearly  four  times  as  long  .i.s  uidc. 

Canthocamplus  idahocnsis  Marsh  igoj. 


Fig.  1233.    Furcaeof  female  rdw/A"r<Jwi/)/Mi  I /.Jf.<'t>i<      X  1  .-a 


115  (114)  Furca  short,  its  length  not  exceeding  twice  its  width      ...      116 

116(119)  Furca  with  two  setae '" 

117  (118)  Anal  plate  with  spines.  .    Canthocamptus  illinoisnisis  ForU 

118(117)  Anal  plate  without  spines.    .      Canthocamptus  hicmalis  PcarM.-  i  .>05. 


/ 


Fig   1-34.     AmJ  plate  of  female  Tjn/AiVdw^tej  Ai**»«/u.     ><  144- 
>^  ■  (After  I'can*e.) 


782  FRESH-WATER   BIOLOGY 

1 19  (116)     Furca  with  three  setae.  .   Canthocamptus  northumhricus  Brady  1880. 
This  is  probably,  next  to  minutus,  the  most  widely  distributed  species  in  North  America. 

120  (109)     Spines  of  anal  plate  bifid.    .  .    Canthocamptus  minutus  Claus  1863. 


This  is  the  most  common  species  and  is  found  everywhere  in  the  north- 
em  continents. 


Fig.   1235.     The  last  segment  and  furcae  of  male  Canthocamptus  minutus. 
(After  Schmeil.) 


SlPHONOSTOMATA 

The  parasitic  Copepoda  pass  all  or  a  part  of  their  lives  as  para- 
sites upon  fish  and  other  animals.  They  are  exceedingly  numer- 
ous in  both  salt  and  fresh  water,  and  very  interesting  because  of 
the  strange  forms  which  many  of  them  assume,  —  forms  which 
would  appear  to  be  in  no  way  related  to  the  structure  of  a  copepod. 
Many  of  them  would  be  taken  for  worms.  Some  bore  into  the 
tissues  of  their  hosts,  others  dwell  in  the  gills,  and  still  others  in 
the  nasal  cavities.  One  species  is  very  abundant  on  the  sheeps- 
head  of  the  Central  States. 

The  appendages  are  profoundly  modified  to  adapt  them  to  their 
parasitic  existence.  The  swimming  feet  are  more  or  less  rudimen- 
tary. The  appendages  about  the  mouth  are  modified  into  sucking 
or  prehensile  organs.  The  antennae  are  similarly  modified.  In 
some  the  second  antennae  are  armed  at  the  end  with  hooks  to 
enable  the  animal  to  retain  its  hold  on  its  host.  In  some  that  are 
semiparasitic,  the  appendages  from  the  opposite  sides  are  joined 
together  in  a  sucker.  Sometimes  the  segmentation  of  the  body 
disappears  entirely.  The  appendages  in  some  are  reduced  to  mere 
protuberances,  or  may  be  hke  roots  penetrating  the  body  of  the 
host. 

And  yet  all  these  forms  are  free-swimming  in  their  early  stages. 
When  hatched  from  the  egg  they  have  the  typical  nauphus  form 


COPEPODA  ^g^ 

of  the  true  copepods,  and  go  through  a  process  of  degeneration 
later.  In  some  the  male  dies  immediately  after  reaching  the  (  ychps 
stage;  in  others,  the  male,  while  highly  organized,  is  very  small  and 
lives  as  a  parasite  on  the  body  of  the  fenKilc. 

The  parasitic  Copepoda  are  much  more  numerous  in  salt  watt-r 
than  in  fresh.  In  an  ordinary  examination  of  fresh-water  collec- 
tions one  is  not  apt  to  find  them,  although  the  male  of  ErgasUus 
is  occasionally  seen.  An  examination  of  almost  any  group  of  fish. 
however,  will  show  that  they  are  not  at  all  rare. 

It  is  a  most  fascinating  study  to  compare  the  structure  of  these 
degenerate  forms  with  the  highly  organized  free-swimming  species. 
thus  finding  evidence  of  the  true  copepod  structure  in  animals  that 
at  first  sight  would  seem  to  be  far  removed  from  the  co|K'P<k1.s. 
The  structural  relationships  of  these  peculiar  forms  are  only  im- 
perfectly understood,  so  that  no  satisfactory  classification  has  been 
made,  and,  pending  more  thorough  knowledge,  all  are  grou[x*d 
together,  in  a  somewhat  unscientific  way,  under  the  term  "  Siphom^ 
stomata."  Although  it  is  well  known  that  these  forms  are  very 
numerous  in  the  fresh  waters  of  America,  the  family  of  the  K^.-  . 
silidae  is  the  only  one  which  has  been  studied  from  a  systen.  •; 
standpoint.  Almost  total  ignorance  prevails  in  regarti  to  the  spe- 
cies of  the  other  families.  From  the  studies  in  other  countries 
something  is  known  of  these  famihes,  and  it  may  be  assumed  that 
representatives  of  all  of  them  can  be  found  in  American  waters. 
For  the  sake  of  completeness  of  record  these  families,  six  in  all. 
will  be  characterized  briefly. 

1.  Ergasilidae.  These  resemble  very  closel)'  the  free-swimming 
copepods,  the  general  form  being  much  like  that  of  the  Cyclopidae. 
The  second  antennae  are  armed  at  the  ends  with  h(K>ks.  On  the 
ventral  side  of  the  body  of  the  male  there  are  ordinarily  i)alches 
of  pigment  of  a  deep  steel-blue  color.  The  males  are  free-swimming 
through  the  whole  period  of  their  lives.  The  synopsis  of  the 
Ergasilidae  is  adapted  from  C.  B.  Wilson. 

Ergasilus  is  the  only  genus  of  this  family,  and  specimens  arc  not 
unfrequently  taken  in  hmnetic  collections.  The>-  ha\e  Ixrn  found 
in  nearly  all  parts  of  the  United  States. 

2.  CcUigidae.     The  body  is  flat,  the  caudal  part  of  the  abdomen 


784  FRESH-WATER   BIOLOGY 

much  reduced.     The  antennae  of  the  second  pair  are  armed  with 
hooks  at  the  ends,  but  they  are  much  shorter  than  in  the  Ergasilidae. 

3.  Dichelestidae.  The  body  is  elongated,  the  thoracic  segments 
distinct,  the  abdomen  rudimentary  except  for  the  elongated  genital 
segment.  At  least  the  last  two  pairs  of  swimming  feet  are  rudi- 
mentary.    The  maxillipedes  are  armed  with  hooks. 

4.  Lernaeidae.  The  body  is  worm-like  and  unsegmented,  and 
the  abdomen  rudimentary.  Processes  growing  from  the  head  serve 
to  attach  the  animal  to  the  host.     The  four  swimming  feet  are 

either  very  small  or  entirely  lacking.  A  represen- 
tative of  this  family  is  found  on  the  sheepsheads  of 
the  Mississippi  Valley. 

5.  Lernaeopodidae.  The  head  is  distinct,  the  rest 
of  the  body  sac-shaped,  and  generally  unsegmented. 
The  second  maxillipedes  are  very  large,  and,  arch- 
ing over  the  head,  are  joined  together  to  form  an 
organ  for  attachment  to  the  host.  The  swimming 
feet  are  entirely  lacking. 

6.  Chondracanthidae.     The  body  is  indistinctly 
^fodalhni^m\lln,     Segmented,  and  the  abdomen  rudimentary.     The 

Sou?  and  Qili^nS     first  two  palrs  of  swimming  feet  are  rudimentary, 
lo^^' *^   ^^^    ''     the  others  lacking.     The  second   antennae   bear 

hooks.     The  male  is  small,  distinctly  segmented,  and  lives  as  a 

parasite  on  the  female. 


KEY  TO  NORTH  AMERICAN  FRESH-WATER  ERGASILIDAE 

I  (8)  Head  completely  fused  with  first  thoracic  segment,  with  no  indi- 
cation of  union;  carapace  elongate,  much  longer  than  wide, 
and  more  than  half  entire  length 2 


2  (5)          Anterior  margin  of  carapace  evenly  rounded,  first  antennae  hardly 
reaching  end  of  first  segment  of  second  pair _.     3 


3  (4)  Second  antennae  one-third  entire  length. 

Ergasilus  funduHKroyeT  1863. 

Basal  segment  of  second  antennae  much  swollen  and  widened  distally;  second  segment  with 
I  large  process  on  its  outer  border.     Foimd  on  the  gills  of  Fundulus  ocellaris. 


COPEPODA 


78s 


4(3) 


Second  antennae  half  the  entire  length. 

Ergasilus  la hni,  j ,  K  ( . .  \  i  r  1  *  ^ 


The  two  basal  segments  without  swellings  or  |.r.Kci««.  (ound  oo  the 
striped  bass,  Roccus  linealus.  •"«««  w  uic 


Fig.  1237.     Ergasilus  liibracii.     (After  WiUjoj 


Anterior  margin  of  the  carapace  projcctinK  stronRly  at  the  center 
in  a  rounded  knob,  first  antennae  much  longerihan  in  2.         6 
Terminal  claw  of  second  antennae  simple. 

Ergasilus  ccntrarchidiirum  Urighl  i88i. 


Both  rami   of  fourth  feet  threc-segmentc<l.     Found   on  the  (amilv 
Centrarchidae,    the    redeye,  Ambloplites   rupestris.   snvall-mouth   hUtk 

bass,  Micropterus  dolomieu,  etc. 


Fig.  1238.    Ergasilus  ccnirarcliidarum.     (Aitcr  NViLvm.) 


7  (6)  Terminal  claw  toothed  on  the  inner  margin. 

Ergasilus  an  r ulcus  Wilson  igii. 


Exopodites  of  fourth  feet  two-seKmonlnl.     Found  on  the  NucKtU. 

Lepomis  pallidus. 


Fig.  1239.    Eri^a^thi-.  i>uruifu\.      ^  \nrr  »m 


\\\cx   v\  iivin.j 


786 


FRESH-WATER  BIOLOGY 


8  (i)  Head  fused  with  first  thoracic  segment,  but  fusion  indicated  by 

distinct  indentations  on  lateral  margins;  carapace  half  en- 
tire length  and  violin-shaped 9 

9  (10)        Second  antennae  as  long  as  carapace. 

Ergasilus  versicolor  Wilson  191 1. 


Found  upon  species  of  catfish. 


Fig.  1240.     Ergasilus  versicolor.     (After  Wilson.) 


10  (9)  Second  antennae  only  one-half  length  of  carapace. 

Ergasilus  chautauquaensis  Fellows  1887. 


Suborder  Branchiura 

There  is  but  one  family  in  this  suborder,  —  the  Argulidae.  They 
are  ectoparasites  upon  fish,  and  are  commonly  known  as  fish  lice. 
They  have  compound  eyes,  four  or  five  pairs  of  swimming  feet,  and 
the  first  maxillipedes  are  modified  into  a  pair  of  sucking  disks.  In 
connection  with  the  mouth  is  a  true  stinging  organ  which  pene- 
trates the  skin  of  the  host.  They  are  found  most  abundantly  in 
the  branchial  chamber  of  the  host,  but  may  attach  themselves  to 
other  parts  of  the  body.  It  is  a  matter  of  interest  in  this  connec- 
tion, as  has  been  noted  by  Wilson,  that  they  attach  themselves  in 
such  a  way  as  to  place  the  long  axis  of  the  body  parallel  to  that  of 
the  host,  so  that  they  will  be  less  Hkely  to  be  brushed  ofi  in  its  move- 
ments. To  this  end,  too,  the  under  side  of  the  body  of  the  Argulus 
is  armed  with  backward-pointing  spines,  which  aid  in  keeping  it 
in  place.  Argulus  is  strictly  dependent  on  the  blood  of  its  host 
for  food,  but  can  and  does  frequently  swim  about  freely.  Inas- 
much as  the  eggs  are  laid  attached  to  stones  and  similar  objects,  it 
must  leave  the  host  at  the  breeding  season.     They  are  not  con- 


COPEPODA 


787 


fined  to  a  single  species  of  fish  for  a  host,  hut  seem  ahlc  to  make 
use  of  a  great  variety,  and  may  even  attach  themselves  to  other 
aquatic  animals,  Hke  tadpoles.  Some  of  them  can  live  almovi 
equally  well  in  both  salt  and  fresh  water. 

The  following  key  to  the  species  of  Ar^uhis  which  Im-, 
described  from  the  fresh  waters  of  America  is  adapted  from  \Vi 
paper  on  the  Argulidae. 


KEY  TO  NORTH  AMERICAN  FRESII-WATKR  Akc.l  LII)\L 

1  (4,  9)      Carapace  lobes  overlap  base  of  abdomen. 

2  (3)  Diameter  of  sucking  disks  0.25  mm. 

Arguliis  catoslomi  Dana  and  llirnclt 


Spines  on  antennae  rcduccH  in  number,  small  and  mrak'. 
abdomen  small  and  orbicular;  found  on  »u<k«T.  Catoti^ 
mus  commersoni,  and  chub  sucker,  Lrtmysam  imtfUj  »^ 

longus. 


FiC.  1241.    Argulus  catoitomi-     lAficr  Wi 


3  (2)  Diameter  of  sucking  disks  0.15  mm 


Argulus  amfricanus  Wilson  i<x>v 

Spines  on  antennae  large  and  strong,  reenforced;  abdomen  large  and  broadly  cordate.    Found 
on  mudfish,  Amia  calva. 

4  (i,  9)      Carapace  lobes  just  reach  base  of  abdomen 5 

5  (8)  Carapace  orbicular,  wider  than  long 6 

6  (7)  Anal  sinus  narrow  and  slit-like.  A  rgulus  versicolor  Wilson  i  (X>3 .  male. 

7  (6)  Anal  sinus  broadly  triangular.    .    .Ir^w/wj  macuhsus  Wilson  IQ03. 
Anal  papiUae  lateral;    bases  of  antennae  widely  scparate.l;  found  upon  the  mUKaUoOft, 

Lucius  masquinongy . 

8(5)  Carapace  orbicular,  longer  than  wide. 

Argulus  dppcwiv  U'.>^U^  \\  \\'>^M\   x-. 
Found  upon  a  sucker. 
9(1,4)        Carapace  lobes  do  not  reach  abdomen 

10  (16)         Swimming  legs  with  flagclla 

11  (13)         Carapace  orbicular,  wider  than  long 


10 
1 1 


788 


FRESH-WATER   BIOLOGY 


Abdomen  medium,  oval,  anal  sinus  short,  slit-like,  papillae  sub- 
terminal Argulus  versicolor  Wilson  1903,  female. 


Anal  papillae  subterminal;  bases  of  antennae  close  to  mid- 
line of  carapace;  found  on  the  common  pickerel,  Lucius 
reticulata. 


Fig.  1242.     Argulus  versicolor,  itmaXe.     (After  Wilson .) 


13  (11)         Carapace  elliptical,  longer  than  wide 14 

14  (15)         Flagella  on  anterior  swimming  legs. 

Argulus  lepidostei  Kellicott  1877. 


Carapace  elliptical,  longer  than  wide,  its  lobes  very  short, 
barely  covering  two  pairs  of  legs;  abdomen  broad,  triangu- 
lar, cut  to  the  center  or  beyond  with  acute  lobes;  found  on 
the  gar  pike,  Lepidosteus  osseus. 


Fig.  1243.     Argulus  lepidostei^     (After  Wilson.) 


15  (14)         Flagella  on  all  four  pairs  of  swimming  legs. 

Argulus  ingens  Wilson  19 12. 

Male  16  mm.,  female  21  to  25  mm.  long.    By  far  the  largest  American  species.     From  the 
alligator  gar,  Lepidosteus  tristoechus,  in  Moon  Lake,  Miss. 

16(10)         No  flagella  on  swimming  legs.  .    .   Argulus  stizostethi'K.t\\icotii^?>o. 

Carapace  eUiptical,  longer  than  wide;  abdomen  elongate,  cut  to  the  center  or  beyond;  the 
lobes  lanceolate-acuminate;  found  on  the  blue  pike,  Stizostedion  canadense. 


IMPORTANT   PAPERS   ON  FRESH-WATER  COPEPODA 

Van  Douwe,  C,  and  Neresheimer,  E.  1909.  Copepoda.  Die  Siisswasser- 
fauna  Deutschlands.     Heft  11. 

Forbes,  Ernest  B.  1897.  A  Contribution  to  a  Knowledge  of  North  Ameri- 
can Fresh-water  Cyclopidae.  Bull.  111.  State  Lab.  Nat.  Hist.,  5:  27-82; 
13  Pl- 


COPEPOIJA  -5;^ 

GiESBRECHT,  W.,  and  ScHMEiL,  O.     1898.     Cop.-ixJ.      T   f.ynuu. ■.,... 

Tierreich,  6  Lief. 
GUERNE,  J.  DE,  ET  RiCHARD,  J.     1889.     Revision  <k  s  I  .iianidc-s  deau  doucc. 

Mem.  Soc.  Zool.  France,  ii:  53-181;  4  pi. 
Herrick,  C.  L.,  and  TuRxNer,  C.  H.     1895.     Synoi)sis  of  ihc  Kntomoblraca  o( 

Minnesota.     Geol.  and  Nat.  Hist.  Survey  Minn.,  Zool.  Scri.-  IT         :  ,.t. 

81  pi. 
Marsh,  C.  D.     1893.     On  the  Cyclopidae  and  ('ahinidac  of  Cini r.u  w  i^tuUMn. 

Trans.  Wis.  Acad.,  9:  189-224;  5  pi. 

1895.  On  the  Cyclopidae  and  Calanidae  of  Lake  St.  Clair.  Lake  .Mu!  . 
and  certain  of  the  inland  lakes  of   Michigan.     Bull.  Mi<h    I-isK  ( 
No.  5;  24  pp.,  9  pi. 

1897.  The  Limnetic  Crustacea  of  Green  Lake.  Trans.  Wis.  .\i  ad.,  1 1 ;  lOj 
168;  10  pi. 

1903.     The  Plankton  of  Lake  Winnebago  and  Green  Lake.     Bull.  Wis.  Gcol 

and  Nat.  Hist.  Survey,  12:  1-94;  22  pi. 
1907.     A  Revision  of  the  North  American  Species  of  Diaptomus.     Traiw 

Wis.  Acad.,  15:  381-516;  15  pi. 

1910.  A  Revision  of  the  North  American  Species  of  Cyclops.  Trans.  Wis 
Acad.,  16:  1067-1135;  10  pi. 

ScHACHT,  F.  W.     1897.     The  North  American  Sjui  io  ..t  J):.:t>:,  mu^.     Bull 
111.  State  Lab.  Nat.  Hist.,  5:  97-207;  15  pi. 

1898.  The  North  American  Centropagidae  belonging  lo  me  v.tiur.i  c^ 
phranticum,  Lmnocalanus,  and  Epischiira.  Bull.  111.  Stale  Lab.  Nat 
Hist.,  5:  225-269. 

ScHMEiL,  Otto.     1892.     Deutschlands  freilebcnde  Siisswasscr-Cope[KHlcn.     I 
Cyclopidae;  192  pp.,  8  pi. 
1893.     Deutschlands  freilebende  Slisswasser-Copepocien.    II.  IhaiMan  lu.u 
100  pp.,  8  pi. 

1896.  Deutschlands  freilebende  Siisswasser-CopeiKxlen.  III.  Ccnlroi>agi 
dae;  144  pp.,  12  pi. 

Wilson,   C.   B.     1903.     North  American  Parasitic  CopeixxLs  of  the  Family 
Argulidae.     Proc.  U.  S.  Nat.  Mus.,  25:  635-74-^  -^o  pi. 

191 1.  North  American  parasitic  Copepods  Belonging  to  the  Family  Erga 
silidae.    Proc.  U.  S.  Nat.  Mus.,  39:  263-400;  20  pi. 


CHAPTER   XXIV 
THE    OSTRACODA 

By  R.  W.  SHARPE 

Instructor  in  Biology,  Dewitt  Clinton  High  School,  New  York  City 

An  early  author  says  of  the  Ostracoda,  "these  little  creatures  are 
enclosed  in  a  bivalve  shell  of  lime  and  seem  to  be  very  lively  in 
their  native  element,  being  almost  constantly  in  motion  by  the 
action  of  their  antennae,  or  walking  upon  plants  and  other  solid 
bodies  floating  in  the  water."  Also  "by  opening  and  closing  their 
valves,  they  enjoy  light  and  move  at  their  will,  sometimes  burying 
themselves  in  the  mud,  sometimes  darting  through  the  water,  the 
humid  air  of  their  sphere.  If  they  meet  with  any  unforeseen  object, 
they  conceal  themselves  all  at  once  in  their  shells  and  shut  the 
valves,  so  that  force  and  address  seek  in  vain  to  open  them." 

The  Ostracoda  are  found  abundantly  in  all  kinds  of  fresh  and 
salt  waters.  They  owe  their  name  to  the  possession  of  a  two- 
valved  limy  shell,  which  is  hinged  dorsally,  and  encloses  the  entire 
body.  They  are  commonly  more  or  less  bean-shaped  (Fig.  1244), 
and  seen  from  above  (Fig.  1255  5)  are  usually  oval  or  egg-shaped. 
In  many  cases  the  shells  overlap  each  other,  or  there  may  be  a 
ventral  flange  present.     They  average  about  i  millimeter  in  length. 

The  body  of  these  little  creatures  is  not  segmented,  and  is  com- 
pletely enclosed  in  its  bivalved  shell,  which  is  hinged  along  the 
dorsal  margin  by  means  of  a  hinge  ligament,  somewhat  as  with 
the  molluscan  bivalves.  These  valves  are  kept  closed  by  adductor 
muscles,  their  points  of  attachment  being  indicated  by  a  number 
of  lucid  spots  about  the  middle  of  each  valve  (Fig.  1255a). 
These  are  called  "muscle  impressions"  and  may  often  be  of  sys- 
tematic value.  At  the  anterodorsal  end  of  the  body  is  a  single 
eye,  although  it  may  occasionally  be  double.  Most  commonly  the 
shells  of  the  sexes  are  of  the  same  size  and  shape,  although  second- 
ary sexual  characters  may  appear  here.  For  instance,  the  males 
of  the  genus  Candona  are  larger  and  of  a  different  shape  (Fig. 
1300),  while  in  Cypris  and  Notodromas  the  females  are  the  larger. 

790 


THE    OSTRACODA  ^ 

Baker,  in  1753,  is  said  to  be  the  first  author  who  sumcienlly  de- 
scribed any  of  these  small  forms  so  that  the  description  could  l>c 
recognized  as  referring  to  a  CypHs.  In  the  work  "Kmi)loyment 
for  the  Microscope"  an  anonymous  correspondent  descriJxrs  an 
insect  with  a  bivalve  shell,  somewhat  resembling  a  fresh-water 
mussel,  and  gives  a  figure  of  it  lying  on  its  back. 

Linnaeus,  in  his  "Systema  Naturae,"  in  1748,  mentions  a 
species  under  the  name  ''Monoculus  concha  pedala."  For  many 
years  the  general  term  ''Monoculus"  was  in  use  fur  all  en- 
tomostraca  until  finally,  in  1776,  0.  F.  Mailer,  in  his  "Zoologiae 
Danicae  Prodromus,"  first  established  the  genus  C>/>n5,  as  well 
as  a  number  of  other  genera  of  the  cntomostraca. 

In  1894  G.  W.  MiiUer  published  his  masterly  work  on  the  Ostra- 
coda  of  the  Gulf  of  Naples.  His  descriptions  and  figures  are  most 
carefully  and  accurately  made,  and  in  connection  with  his  similar 
work  on  the  fresh-water  Ostracoda  of  Germany,  published  in  iqoo, 
may  well  form  the  best  published  basis  for  future  wurk.  He  de- 
scribes about  125  species  from  the  Gulf  of  Naples  and  some  65  for 
Germany. 

Structure.  —  It  is  not  uncommon  for  the  extremities  and  ventral 
edges  of  the  shell  of  Cypris  to  exhibit  a  number  of  suhparallel 
canals  (Fig.  1271)  which  radiate  outwards,  and  arc  called  "pwre 
canals."  The  same  regions  may  be  tubcrculate.  the  right  valve 
alone  with  tubercles  as  in  the  subgenus  Cy/>r/;/()///5  (Fig.  1270).  or 
the  left  valve  alone  similarly  tubcrculate  as  with  the  subgenus 
Heterocypris.  Various  species  of  other  groups  may  thus  be  simi- 
larly marked.  Occasionally  the  shell  may  show  a  series  of  longi- 
tudinal markings,  as  Ilyodromus  (Fig.  1250)  or  a  network  of 
anastomosing  and  parallel  lines,  as  Cypria  exscidpta. 

Exclusive  of  the  abdominal  appendages,  called  the  furca.  there 
are  seven  pairs  of  appendages  in  the  C\prididai-.  These  may  be 
enumerated  as  follows:  first  antenna,  second  antenna,  mandible, 
first  maxilla,  second  maxilla,  first  leg,  and  second  leg,  naming  one 
of  each  pair  (Fig.  1244). 

The  anterior  lip  or  labrum  (Fig.  12^^)  f^rms  a  prominence  pro- 
jecting between  the  bases  of  the  second  antennae  and  anteriorly 
covering  the  oral  orifice.     The  posterior  lip  or  labium  (Fig.  1  .'45) 


792 


FRESH-WATER    BIOLOGY 


forms  a  thin  membrane,  reenf orced  by  a  pair  of  very  strong  chitinous 
rods,  each  expanded  into  a  transverse  plate  armed  at  their  extremi- 
ties with  a  series  of  about  seven  strong  teeth.  Posteriorly  the  lip 
joins  a  sternumlike  vaulted  plate,  carinated  along  the  middle,  and 
placed  between  the  bases  of  the  first  pair  of  maxillae. 


First  antennae 
\  Second  an^enr,^e 
\  \  Eye 


Branchial  Plate  of  Mandible 
!        Stomach 

Food  balls 


Branchial  setae 
Intestine 

Ovary 


Second  foot 
'..  Furca 

Dorsal  seta 

-Sub-terminal  claw 
Terminal  claw 
^^^  ^'•Terminal  seta 
First  foot 
Branchial  plate  of  maxilla 


natatory  setae      Labrum 

Fig.  1244.     General  anatomy  of  Cypris  virens  Jurine.     (After  Vavra.) 

The  mandibles  (Fig.  1245)  are  each  composed  of  a  chitinous  elon- 
gate body,  and  a  well-developed  pediform  palp  (Fig.  1 245  b^) .  They 
are  located  on  either  side  of  the  body  immediately  behind  the 
base  of  the  second  antennae  with  its  upper  acuminate  extremity 
(Fig.  1245  ^2)  articulated  to  the  inner  surface  of  the  corresponding 
valve  just  in  front  of  the  adductor  muscle  impressions,  whereas 
the  lower  incurved  extremity  is  wedged  in  between  the  lips.  The 
greater  part  of  the  body  (Fig.  1245  ^^)  is  hollowed  to  receive  the 
powerful  adductor  biting  muscles.  The  cutting  edge  (Fig.  1245  b^) 
is  divided  into  several  strong,  bifurcate  teeth.  The  palp  (Fig. 
1245  60  forms  a  thick,  fleshy,  somewhat  pediform  jointed  stem, 
curving  downwards,  and  bears  on  its  outer  side  a  narrow  plate,  a 
so-called  branchial  appendage  (Fig.  1245  ^^)  which  is  provided  with 
a  number  of  plumose  setae. 


THE   OSTRACODA 


793 


The  first  pair  of  maxillae  (Fig.  1245  c)  is  formed  of  a  thick,  mus 
cular,  basal  part,  from  the  extremities  of  which  four  dij^iiifomi 
processes  originate.  The  larger  of  these  prominences  ( Fig.  1  ^45  c'l 
is  jointed  and  movable  and  must  evidently  be  regarded  a,s  a  palp 
whereas  the  three  remaining  form  the  immediate  continuation  .)f 
the  basal  part  and  are  the  true  masticatory  lobes.  The  first  <jnc  of 
these  is  usually  armed  with  two  strong  spines  (Fig.  1 245  c^  and  Fig. 
1270  e)  which  may  or  may  not  be  toothed,  and  are  regarded  as  of 
specific  importance.     To  the  outer  side  of  the  basal  part  a  large 


Fig.  1245.     (a)  Lower  lip  or  labium;  {b)  Mandible  with  palp;  (c)  First  maiilU  with  braachbl  pUta; 

{d)  Second  maxilla  of  female  with  palp  {Cypris  ifuonirtum). 

semilunar  lamella  (Fig.  1245  c^)  is  attached,  which  is  generally  called 
the  branchial  plate.  This  plate  may  be  seen  to  move  rhythmically 
in  the  living  animal,  and  is  for  the  purpose  of  renewing  the  sup|)ly 
of  fresh  oxygen-laden  water  within  the  shell  ca\  it >•.  It  is  dircctwl 
obliquely  upwards  and  exhibits  along  the  posterior  edge  a  scries  of 
dense  and  regular  finely  plumose  setae,  from  16  to  20  in  numlx-r. 

The  second  pair  of  maxillae  (Fig.  1245^)  consists  of  the  same 
principal  parts  as  the  first,  though  ditTerent  in  ai)pearance.  Thr 
basal  part  (Fig.  1245  d')  is  much  smaller,  not  divided  at  the  end.  and 
terminating  in  a  single  masticatory  lobe.  The  branchial  lamella 
(Fig.  1245  d^)  are  usually  semicircular  and  provided  with  a  few  plu- 
mose setae,  while  the  palps  (Fig.  1245  (P  and  Fig.  1290  d-    "-"  -f 


794  FRESH-WATER   BIOLOGY 

different  shapes  in  the  sexes.  In  the  female  they  are  conical 
(Fig.  1245  a'^),  while  with  the  male  (Fig.  1299  e)  they  are  con- 
verted in  a  peculiar  manner  into  powerful  prehensile  organs  which 
serve  for  grasping  the  female  during  copulation.  The  palps  of 
the  right  and  left  sides  in  the  male  are  different  in  size  and  shape 
(Fig.  1246  e-f).  The  form  of  these  palps  is  regarded  as  of  specific 
importance. 

The  two  pairs  of  antennae  are  found  in  the  head  region,  and  in 
most  cases  are  provided  with  long  natatory  setae,  which  aid  in 
swimming  (Fig.  1268^).  The  mandibles  and  first  maxillae  serve 
as  mouth  parts.  The  fifth  pair  may  be  modified  in  some  cases,  as 
in  the  Limnicythere,  serving  as  legs  —  in  most  cases  as  maxillipeds 
or  second  maxillae.  The  fifth  pair  is  known  as  the  first  legs 
(Fig.  1260  J),  and  the  sixth  pair  is  known  as  the  second  legs  (Fig. 
1285  d).  The  second  legs  are  commonly  not  ambulatory,  but  are 
bent  backwards  within  the  shell.  They  are  often  called  the 
*' cleaning  feet"  on  account  of  their  observed  use  in  cleaning  the 
valves  of  any  foreign  matter.  The  mouth  parts  commonly  carry 
a  number  of  setae  which  create  a  current  of  water  between  the 
valves  for  respiratory  purposes. 

The  general  color  of  the  surroundings  seems  to  have  some  rela- 
tionship to  the  general  color  of  the  forms  present.  For  instance, 
all  those  living  in  algae-rich  habitats  are  notably  green,  as  many 
species  of  Cypris,  while  those  creeping  about  on  the  bottom  amongst 
dead  leaves  and  ooze,  are  commonly  devoid  of  any  especial  pig- 
ment, as  are  most  species  of  Candona.  The  color  of  the  various 
forms  varies  from  yellowish  white  to  yellow,  green,  blue,  and  violet 
to  purple.  The  species  of  Candona  are  commonly  of  a  pearly 
to  yellowish  white,  while  Cypris,  Cypridopsis,  and  Cypria  —  forms 
that  inhabit  algae-rich  regions  —  commonly  show  a  greenish  color. 

The  food  canal  begins  with  a  mouth,  which  is  bounded  by  upper 
and  lower  lips.  It  is  interesting  here  to  observe  that  the  marine 
forms  belonging  to  the  genus  Pyrocypris  are  provided  with  phos- 
phorescent glands  in  the  upper  lip,  which  cause  much  of  the 
phosphorescence  of  the  sea.  From  the  mouth  the  food  passes 
through  a  short  esophagus  to  a  stomach,  which  is  commonly 
followed  by  a  short  constriction  separating  it  from   the   short 


THE   OSTKACODA 

Stomach-like  intestine  (Fig.  1244).  The  intestine  opens  at  Uie 
origin  of  the  furcal  appendages. 

Propagation.  —  The  male  sexual  organs  are  usually  large,  of 
complex  structure,  and  may  consist  uf  a  whorled  sack  or  spiny 
cylinder,  the  ejaculatory  duct  (Fig.  iJ4()/;j,  cunnecting  with  the 
testes  and  vas  deferens,  which  may  lead  to  a  more  or  less  chilinous 
plate  or  penis  (Fig.  1246  a).  The  testes  usually  consist  of  glands 
which  are  partly  extended  within  the  shell  proper  and  the  shell 
membrane,  and  may  show  through  the  shell  as  three  or  four  gran- 
ular bands  (Fig.  1271  &),  as  in  Candona  and  Cypris.  The  arrange- 
ment of  these  testes  may  constitute  a  good  generic  character,  as 
in  Spirocypris  (Fig.  1267),  where  the  testes  originate  in  the  ante- 
rior part  of  the  shell  in  parts  of  circles  or  circles. 

The  ovaries  may  show  through  the  shell  in  its  posterodorsal 
part,  and  are  arranged  somewhat  as  the  testes  (Fig.  1244).  They 
usually  lead  to  a  chitinous  plate  by  a  vaginal  canal  or  oviduct, 
which  retains  the  semen  and  undeveloped  eggs  as  with  Cypris,  and 
commonly  lie  between  the  two  lamellae  of  either  valve,  and  extend 
diagonally  to  the  posterior  extremity,  where  they  curve  up  to  form 
a  nearly  semicircular  band.  Here  the  true  germinal  layer  is  found, 
which  forais  the  ovicells.  These  ovicells  are  poured  from  the 
ovary  into  the  body  cavity,  where  they  generally  accumulate  in 
its  posterior  part  on  either  side  of  the  intestine.  Here  they 
attam  their  full  development  and  are  fertilized,  after  which  they 
are  laid. 

The  inner  genital  organs  of  the  male  are  more  complicated 
(Fig.  1246).  As  the  ovaries,  they  are  situated  between  the  lamellar 
of  the  valves,  and  commonly  consist  of  a  number  of  narrow  and 
elongate  bands  on  either  side,  which  are  generally  to  be  found 
filled  with  numerous  fine,  thread-like  bodies  (Fig.  i246(/),  the  sper- 
matozoa, which  may  occasionall}'  be  curled  up  in  si)iral  groups.  In 
addition  there  are  present  a  number  of  large  nuclear  cells  (Fig. 
1246  g).  These  are  the  gemiinal  <  .lis.  <.r  >pennat»K-ysts.  fnim 
which  the  spermatozoa  develop. 

The  efferent  or  ejaculatory  apparatus  (Fig.  124O/O  conM>i-s  ol 
the  spiny  cylinder  already  mentioned.  It  seems  to  be  comiK>sc<l  of 
an  inner  tube  (Fig.  1246  c),  supported  by  a  complicated  chitmouc 


796 


FRESH-WATER   BIOLOGY 


skeleton  of  whorled  radiating  spines.  The  efferent  duct  leads 
to  a  tube,  the  vas  deferens,  which  in  turn  leads  to  the  penis 
(Fig.  1246  a). 

These  forms  may  also  be  propagated  from  unfertilized  eggs,  i.e., 
by  parthenogenesis.  In  such  cases  there  may  be  a  sexual  genera- 
tion followed  by  a  number  of  such  parthenogenetic  generations. 
Again,  in  some  forms  males  have  never  been  discovered,  even 
after  as  many  as  18  years  of  continuous  observation  by  very  carer 


Fig.  1246.  Cyprinotus  dentate  ShsiTpe.  (a)  Penis,  X  210;  (b)  Efferent  or  ejaculatory  apparatus;  (c)  Cross- 
section  of  same,  X  293;  (d)  Part  of  a  spermatozoon,  X  525;  (e)  Right  maxillary  palp  of  male,  X 
158;  00  Left  palp  of  same;  (g)  Extremity  of  testicular  tube,  showing  spermatocysts,  X  120;  (h)  Ma- 
ture spermatocysts,  X  120. 

ful  observers.  Herpetocypris  reptans  is  a  good  example.  Thus 
some  authors  distinguish  four  types  of  the  method  of  propagation, 
as  follows: 

1.  Always  sexual  as  in  Notodromas  monacha,  Cyclocypris  laevis, 
Cypria  ophthalmica. 

2.  Temporarily  parthenogenetic,  as  in  Candona  Candida,  Cypri- 
do p sis  vidua. 

3.  Locally  parthenogenetic,  as  in  Cypris  incongruens. 

4.  Always  parthenogenetic,  as  in  Herpetocypris  reptans. 


THE   OSTRACODA  ~    - 

The  method  of  propagation  has  been  much  ust^l  as  a  ;.-■ 
character,  but  much  more  must  be  known  of  its  constancy  t  . 
it  can  be  finally  accepted  as  at  all  reliahle.      I'lu-  form  of  the  penis 
and  of  the  vaginal  plate,  however,  may  hot  h  be  accepted  its  constant 
characters. 

The  eggs  are  provided  with  small  lim\-  shells,  and  commonl\ 
develop  in  from  5  to  14  days.  They  are  laid  in  characteristic 
ways.  For  example,  the  eggs  of  Candona  camlnhi  are  whitish. 
and  are  laid  singly,  without  being  fastened  together;  those  «>f 
Cypris  incongruens  are  orange  red,  while  those  of  Cypridopsis 
vidua  are  dark  green.  Both  are  laid  in  i)ackets  on  the  leaves  and 
stems  of  water  plants,  especially  the  under  sides  of  Lemna  leaves. 
The  eggs  of  N otodromas  monacha  are  first  white  and  later  yellowish. 
They  are  oval-elongate,  and  are  laid  in  rows,  pole  to  jkiIc,  on 
the  roots  of  Lemna.  The  eggs  of  Ilcrpetocypris  reptans  are  spher- 
ical and  of  a  yellowish  color,  which  deepens  later  —  indeed,  when 
freshly  laid,  they  may  be  almost  white. 

Bottom  forms,  such  as  Candona  and  Ilcrpetocypris,  laboriously 
contrive  by  creeping  and  cra^vling  to  reach  Lemna  and  other  sur- 
face plants.  They  first  reach  the  roots,  and  later  the  upin-r  sur- 
faces, where  they  appear  to  scrape  a  place  with  their  antennae,  and 
then  deposit  and  fasten  their  eggs  with  line  threads.  All  this  must 
be  quite  an  acrobatic  feat  for  them,  as  they  must  balance  them- 
selves meantime.  After  finishing,  they  pemiit  them.selves  to  fall 
to  the  bottom.  It  is  here  worthy  of  remark  that  these  biological 
distinctions  such  as  habitat,  means  of  locomotion,  food,  means  of 
propagation,   and   egg   laying,   all   have   their   value    in    si>ccific 

distinctions. 

Their  eggs  also  have  remarkable  vitality.  An  instance  is  on 
record  of  samples  of  dried  mud  being  sent  to  England  from  Jeru- 
salem and  entomostraca  being  raised  therefrom  {Cypns  and  /).;/>/i- 
nia)  after  a  lapse  of  from  24  to  30  years.  G.  O.  Sars.  of  Nonvay, 
has  reported  raising  them  from  dried  mud  sent  him  from  Australia 
and  China.  In  fact,  he  has  described  many  new  species  from 
material  sent  to  him  in  this  way. 

The  eggs  hatch  into  nauplii,  which  resen.ble  the  adult,  although 
varying  much  in  the  shape  of  the  shell  and  internal  structure. 


798  FRESH-WATER   BIOLOGY 

They  molt  many  times  before  reaching  maturity.  The  change 
that  takes  place  is  most  complete.  The  shell  falls  off,  and  all  the 
internal  parts  are  shed,  even  to  the  minutest  hairs. 

The  nervous  system  is  composed  of  a  so-called  brain  or  supra- 
esophageal  ganglion,  and  several  other  gangha  and  connecting 
nerve  structures.  The  most  important  branches  lead  to  the  eyes, 
which  are  either  double  as  in  Notodromas  (Fig.  1247),  o^";  more 
commonly,  as  a  single  median-dorsal  pigment  spot. 

The  most  common  sense  organs  other  than  the  eyes  are  found 
on  the  second  antennae  (Fig.  1290  t).  These  resemble  a  club  and 
hence  are  often  called  ^'sense  clubs."  Other  sense  organs  appear 
on  the  second  antennae  of  the  male,  especially  such  fornis  as 
Candona,  Cypria,  and  Notodromas  (Fig.  1298  c). 
Most  Ostracoda  are  omnivorous.  Decaying 
vegetation  and  small  animals  form  a  large  part 
of  their  diet.  Cypridopsis  has  been  observed 
forming  skeleton  leaves.  Some  will  eat  their 
own  kind,  if  opportunity  offers.  While  in  cap- 
tivity most  forms  will  eat  from  thin  slices  of 
potato.  Notodromas  is  an  exception  to  most 
others,  as  it  has  the  curious  habit  of  swimming 
back  down  and  clings  to  the  surface  film  in  an 
Fig.  1247.  Notodromas  mo-  endeavor  to  obtain  food.    Some  forms  may  also 

nacha  (O.  F.  M.).  (a)  Lens;  •' 

(di^ForebiLin^^^'''''^'''^'  attack  Hviug  or  dying  animals.  Instances  are 
also  on  record  of  their  having  attacked  Melicerta 
ringens,  a  common  fixed  rotifer.  Thus  they  act  principally  as 
scavengers,  as  their  greediness  and  oftentimes  great  numbers 
would  constitute  them  no  inefficient  agent  in  the  work  of  purifying 
standing  waters. 

The  fresh-water  Ostracoda  entirely  lack  any  such  organ  as  a 
heart.  The  respiratory  process  therefore  takes  place  through  the 
entire  upper  surface  of  the  body,  and  through  the  inner  cell  layers 
of  the  shell.  A  number  of  respiratory  plates  are  fastened  to  the 
mouth  parts,  the  motions  of  which  keep  up  a  continuous  stream 
of  fresh  oxygen-laden  water  pouring  through  between  the  valves. 

It  is  self  evident  that  favorable  or  unfavorable  life  conditions 
exert  a  striking  influence  on  the  distribution  of  Ostracoda  in  iso- 


THE   OSTKAKJin 

lated  waters,  although  this  fact  has  nul  received  the  attention  it 
should.  Even  though  in  general  they  seem  to  be  no  more  sc-nsiiivc 
to  their  surroundings  than  the  Cladocera  or  the  Coi>epoda  vet 
there  is  no  doubt  that  the  amount  <.f  light,  of  i,ressure,  of  4ru. 
tions  in  temperature  and  composition  of  the  water,  the  rate  of 
flow  of  the  same,  the  nature  of  the  bottom,  and  the  presence  or 
absence  of  algae,  etc.,  must  certainly  exert  a  real  or  intrinsic  in- 
fluence  on  the  prosperous  development  of  all  these  Kntomostraca, 
Direct  or  intense  hght  certainly  accelerates  all  their  life  i)rocesses, 
as  may  be  evidenced  in  the  fact  that  all  free  and  actively  swim- 
ming forms  are  quite  likely  to  turn  towards  a  source  of  light,  or, 
in  other  words,  are  positively  heliotropic.  Shady  areas  in  i)ooU 
are  not  nearly  so  likely  to  contain  the  free  swimming  forms  such 
as  Cypris,  Cypria,  Cyclocypris,  and  Xoiodromas  excei)t  occasionally 
or  sporadically,  while  the  lighter  and  sunnier  areas  of  the  same 
body  will  contain  them  in  abundance;  in  other  words,  the  more 
uniform  the  distribution  of  light,  the  more  nearl\-  uniform  becomes 
the  distribution  of  any  certain  form.  On  the  other  hand,  it  seems 
a  general  rule  that  the  less  able  these  forms  are  to  swim,  the  greater 
the  certainty  that  they  are  confined  to  the  deeper  and  darker 
areas,  in  the  ooze  and  slimy  debris  of  the  bottom.  It  also  apjx-ars 
that  some  species  may  be  affected  but  little  by  depth,  and  there- 
fore light  and  pressure;  Cypridopsis  vidua  has  been  found  in  all 
depths  from  i  centimeter  to  full}'  300  meters. 

Experience  teaches  that  practically  no  forms  are  found  in  pure 
spring  water  or  in  well  water.  Even  so.  we  fmd  practically  none 
in  waters  that  have  been  polluted  with  (l\es.  or  by  chemical 
means,  although  many  different  degrees  of  power  of  resistance  in 
this  regard  may  be  found.  Some  species  may  be  enclosed  in  the 
smaller  glass  aquaria  and  live  almost  indefinitely  without  change 
of  water,  even  though  the  water  becomes  quite  foul.  For  example, 
Cypria  opthalmica  has  been  known  to  survive  in  such  acjuaria  long 
after  the  larger  forms  have  died.  Cyclocypris  I  ircis  will  al.so  live 
many  months  in  water  that  has  not  been  freshened.  Some  few 
forms  have  been  known  to  exist  in  suljihur  waters,  others  in  hot 
springs  and  even  in  sewer  drains.  Cypris  inconi^rucns  has  been 
found  in  a  pond  fed  by  the  drainage  from  a  barnyard  manuic 


8oo  FRESH-WATER   BIOLOGY 

heap.  This  species  really  seems  to  be  indifferent  to  any  variation 
in  the  pollution  of  the  swampy  water  in  which  they  normally  live, 
variations  and  situations  that  would  be  fatal  to  most  other  Ostra- 
coda.  These  forms  have  also  been  found  in  more  or  less  perma- 
nent ponds  fed  in  part  from  the  drainage  from  cesspools  and  from 
leaky  sewers. 

Many  bodies  of  water  of  different  degrees  of  swiftness  are  like- 
wise determinative  of  different  forms.  Brooks  and  rivers  are  not 
especially  good  habitats,  as  plant  life  there  is  not  abundant,  and 
most  free-swimming  Ostracoda  seemingly  delight  to  hang  to  such 
supports.  However,  most  forms  may  be  occasionally  or  adven- 
titiously found  in  such  waters,  as  well  as  in  quieter  waters.  Nolo- 
dramas  is  typically  an  inhabitant  of  pure,  fresh  pools,  although  it 
is  a  good  swimmer,  and  has  the  curious  habit  of  trying  to  support 
itself  on  the  surface  film. 

Among  those  forms  depending  upon  the  Ostracoda  in  part  for 
food,  one  must  certainly  include  the  young  of  many  fishes,  and 
even  the  adult  Coregonus  or  whitefish  has  been  found  with 
Candona  in  the  stomachs.  Some  of  the  larger  marine  fishes  seek 
Ostracoda  in  the  mud.  Even  aquatic  birds  may  include  them  in 
their  bill  of  fare,  as,  for  example,  the  shoveler  or  spoonbill  duck 
has  been  found  with  Ilyodromus  and  Cypria  in  its  stomach. 

Owing  to  the  variations  in  habitat,  and  the  vicissitudes  to  which 
most  fresh-water  Ostracoda  are  subject,  and  because  of  the  vari- 
able and  inconstant  nature  of  their  surroundings,  it  is  almost  im- 
possible to  work  out  their  exact  distribution.  Cyclocypris  laevisy 
Cypria  opthalmica,  Cypria  exsculpta,  and  Cypridopsis  vidua  seem 
to  be  cosmopoHtes  in  temperate  zones,  and  the  most  indifferently 
distributed  of  any,  as  they  are  found  in  all  pools,  ponds,  swamps, 
lakes,  and  rivers  of  both  mountainous  and  level  areas.  Their  small 
size  permits  them  to  be  readily  carried  about,  and  their  power  of 
adaptation  and  scavenger  habits  permit  them  to  thrive  in  almost 
any  apparently  adverse  situation.  Notodromas,  as  already  stated, 
appears  only  in  pure  standing  waters,  and  mostly  in  immense 
numbers.  Less  abundantly,  but  still  very  widely  distributed, 
may  be  found  various  species  of  Candona,  Cypris  fuscata,  and  Her- 
petocypris  reptans. 


THE   OSTRACODA  g^j 

The  vertical  distribution  of  these  forms  has  not  been  fully  worked 
out.  Various  species  of  Candona,  Ilyocypris,  as  well  a,s  CypridopUs 
vidua  and  CyclocypHs  laevis  have  been  found  at  dei)ths  of  at  least 
300  meters,  while  a  few  have  been  rq.orted  from  depths  of  fuUy 
2500  meters. 

The  constancy  of  color,  form,  and  size  of  most  of  these-  species  15 
still  an  open  question,  and  yet  requires  much  careful  work.  He- 
cause  of  differences  in  methods  of  measurin^^  and  the  chante  that 
undeveloped  or  sexually  immature  indixiduals  become  destTilx-tl, 
it  is  certain  that  there  exist  many  discrepancies  as  to  published 
descriptions,  and  therefore  of  reports  on  distribution. 

Despite  these  discrepancies  and  uncertainties,  it  is  likely  that 
local  varieties  exist  in  many  quite  restricted  arcius,  that  in  many 
cases  are  so  far  divergent  that  one  would  be  disi)osed  to  aM-riljc 
them  to  different  species.  On  this  account,  if  for  no  other,  it  Ls 
advisable  to  be  very  careful  concerning  the  estal)lishment  of  new 
species.  In  all  cases  the  appendages  should  be  very  critically 
examined,  and  if  these  show  differences  and  the  shells  are  const:int 
in  general  markings  and  form,  then  only  should  a  new  sixties 
be  created.  Of  course,  very  exact  and  minute  descriptions  arc 
indispensable. 

The  distribution  of  Ostracoda  seems  to  be  both  actively  and 
passively  brought  about.  The  creeping  forms  may  be  said  to  be 
actively  distributed,  while  the  free-swimming  forms  are  passively 
distributed.  Those  that  creep  must  actively  exert  thems^-lves  if 
in  deep  water,  often  against  the  force  of  the  stream,  to  prevent 
themselves  from  being  buried  in  the  mud.  Pa.ssively.  the  swim- 
mers may  be  distributed  by  high  water  or  by  direct  means  of 
transport.  The  amount  of  water  is  of  more  consecjuence  than  the 
flow  of  water.  Even  though  the  amount  of  water  is  great,  they 
still  can  remain  in  the  place  of  their  temi>orary  abode,  while  in 
brooks  or  rivers  they  are  carried  away  by  the  force  of  the  current, 
and  may  become  lost.  In  rainy  seasons,  therefore,  the  natural 
increase  may  be  very  scanty,  while  in  drirr  pcri.Mls  many  indi- 
viduals of  both  sexes  find  one  another,  and  the  eggs  deiH).sited  always 
have  a  sufficient  opportunity  of  fmding  necessary  nu.i.turc-  fur 
development. 


8o2  FRESH-WATER    BIOLOGY 

Migration  from  one  region  to  another  may  be  brought  about  by 
swimming  beetles  such  as  Belostoma,  Gyrina,  etc.  Cyclocypris  has 
been  observed  hanging  to  the  legs  of  such  beetles,  even  though  the 
beetles  were  actively  using  their  legs.  Birds  may  also  be  of  great 
importance  as  carriers  of  both  the  minute  flora  and  fauna  of  a 
region.  The  eggs  of  Ostracoda,  and  even  the  animals  themselves, 
may  be  carried  about  on  the  bills  and  feet  of  aquatic  birds,  and 
even  fishes  may  act  as  a  means  of  transport  from  one  region  to 
another. 

The  Ostracoda  belong  to  the  plankton.  In  common  with  certain 
other  organisms,  such  as  Rhizopods,  Diatoms,  Hydra,  etc.,  they 
appear  in  the  plankton  under  certain  conditions  of  temperature 
and  food,  and  hence  are  said  to  belong  to  the  adventitious  plank- 
tonts,  in  distinction  to  such  forms  as  Cyclops,  which  are  always 
in  the  plankton,  and  therefore  called  continuous  planktonts, 
or  those  that  appear  periodically,  as  Daphnia  and  some  Rotifer  a, 
when  they  are  called  periodic  planktonts.  For  evident  reasons  the 
creeping  or  burrowing  forms  rarely  occur  in  ordinary  plankton 
catches. 

According  to  their  habitat  and  mode  of  locomotion,  the  ostracod 
adventitious  planktonts  may  be  classified  as  follows : 

A.  Free  swimming. 

1.  Limnetic,  with  surface  habits,  as  Notodromas  monacha. 

2.  Free  swimming,  below  the  surface,  as  Cypris  laevis, 

C.  incongruens,  C.  vidua,  etc. 

B.  Creeping  or  burrowing. 

1.  Creeping  on  water  plants  or  ooze,  as  Herpetocypris  rep- 

tans. 

2.  Burrowing  in  the  slime  or  ooze,  as  Candona  Candida ^ 

and  Limnicy there. 

Little  is  surely  known  of  the  duration  of  life  of  special  forms. 
Some  species  are  present  the  entire  year.  They  live  over  the 
winter,  and  are  also  found  in  different  developmental  stages  under 
the  ice.  It  is  an  easy  matter  to  collect  mud  under  ice  in  midwinter, 
place  it  in  a  small  aquarium  jar  and  set  in  a  moderately  warm 
place,  and  very  shortly  find  plenty  of  Cypris,  Cypria,  and  Candona. 


THE    ()STk.\(()|)A 

Notodromas  appears  purely  as  a  suninuT  form.  It  winlcre  in 
different  ''egg  stages,"  develops  in  Ai)ril  or  May.  ami  I  n. 

ber  has  entirely  disappeared.     Cypridopsis  vidua  and  ■  .„- 

coiigruens  appear  in  early  spring  and  last  until  late  autumn  I  .,■ 
spring  forms  appear  to  have  a  much  shorter  lil\-  history. 

These  forms  may  be  collected  in  great  variety  and'  abundance 
by  drawing  a  Birgc  or  cone  net  ihrou.^h  submerged  plants  prt-st-nt 
in  ponds,  slow  streams,  and  lakes,  and  by  stirring  uj)  the  lx)ttom 

ooze  and  slime,  and  drawing  the  weighted  net  to  and  fr •  ■-  '^  - 

bottom. 

In  this  manner  not  only  the  free-swininiing  forms  may  be  cap- 
tured, such  as  Cypris,  Cypridopsis,  etc.,  but  typically  })ottom  forms 
such  as  Candona,  Herpetocypris,  etc.,  may  also  be  include<l.  By 
emptying  the  mud  and  all  other  accumulations  in  a  beaker  of 
water,  and  stirring  well,  it  will  usually  result  in  many  of  the  Ostra- 
coda  getting  air  caught  between  their  vaives,  thus  causing  them  to 
float  on  the  surface,  from  which  they  may  be  readily  removed 
with  a  "medicine  dropper"  or  pipette.  The  use  of  a  small  hand 
lens  is  advisable  in  determining  whether  or  not  Ostracoda  arc 
surely  present.  In  any  case,  the  ''catch"  may  now  be  concen- 
trated by  carefully  pouring  oil  the  contents  of  the  beaker  from 
the  sediment  in  the  bottom  into  a  small  dip  net  made  of  Swiss  or 
bolting  cloth. 

After  washing  out  as  much  of  the  soluble  or  other  matter  as  is 
possible,  the  remainder  may  be  emptied  into  a  Syracuse  watch 
glass  or  other  shallow  vessel  containing  but  a  small  (|uantity  of 
water.  Thus  the  catch  is  condensed  to  such  bulk  as  may  now  be 
easily  transferred  to  small  vials  of  preser\ati\-e  tluid  such  as  90 
per  cent  alcohol,  or  a  mixture  of  80  per  cent  alcohol  and  glycerin 
in  about  the  proportion  of  10  to  i.  However,  killing  had  k-tler 
be  done  in  about  70  per  cent  alcohol,  which  should  \yc  gradually 
increased  in  strength,  as  in  this  manner  the  shells  are  more 
likely  to  remain  open  than  when   killed    in   alcohMl   ..f  :,   hi-h.-r 

percentage. 

If  a  large  quantity  of  living  forms  should  be  desired,  the  entire 
catch  of  a  locaHty  may  be  poured  into  a  si)ecial  pint  strainer  jar 
(Fig.  1248). 


8o4  FRESH-WATER   BIOLOGY 

This  may  be  made  out  of  a  common  pint  fruit  jar,  by  inserting 

a  funnel  through  one  side  of  the  cover  for  pouring  in  the  catch, 

and  so  arranged  that  the  excess  water  may  run  off  through  an 

overflow  tube,  after  passing  through  a  cloth  strainer 

made  of  the  same  material  as  the  dip  net,  and  which 

is  distended  and  held  in  place  by  two  narrow  wire 

loops  soldered  to  the  inner  end  of  the  overflow  tube. 

■  --___^' .     The  strainer  cloth  is  made  in  the  form  of  a  bag  nearly 

^"D      ^      as  long  as  the  depth  of  the  jar,  with  its  upper  end  held 

"  in  contact  with  the  inner  end  of  the  overflow  tube  by 

a  couple  of  rubber  bands. 

In  many  cases  it  is  recommended  that  the  collected 
material  be  allowed  to  stand  in  a  shallow  vessel  after 
reaching  the  laboratory,  when  the  creeping  forms  will 

Fig.  1248.    Diagram  ^  ^'  j     T  j      ,.1, 

of  strainer  jar;     aDDcar  ou  the  surfacc  of  the  ooze  and  slime,  and  others 

(i)   Funnel  intake;        -^ -t^ 

(3)  clotWraiSr'.  ^111  collcct  about  the  edges  of  the  vessel,  commonly  on 
the  side  nearest  the  source  of  Hght,  or  the  opposite. 

If  it  is  thought  desirable,  small  portions  of  the  ooze  and  slime 
may  be  examined  under  the  low  power  of  the  compound  micro- 
scope. Even  the  creeping  Cyprididae  are  easier  to  find  than  the 
Cytheridae,  such  as  Limnicythere,  as  they  are  more  active  and 
readily  gather  about  the  edges  of  any  shallow  vessel. 

No  satisfactory  work  in  identification  can  be  accomplished  in 
most  cases  until  the  body  with  its  appendages  is  removed  from  the 
shell.  It  is  not  necessary  to  place  the  specimens  in  weak  acid  so 
as  to  decalcify  the  shell,  as  a  little  practice  with  dissecting  needles 
and  microscope  will  soon  enable  one  to  remove  the  parts  from  the 
shell  without  destroying  them. 

After  a  preliminary  examination,  place  the  specimen  in  a  small 
drop  of  Farrant's  medium  or  in  glycerin.  The  shell  may  now  be 
opened  with  a  pair  of  No.  12  needles,  which  are  mounted  in  handles, 
or  by  the  flexible  probing  needles  used  by  dentists.  Free  the  body 
from  the  shell  entire,  if  possible,  and  afterwards  separate  the  ap- 
pendages, beginning  with  the  antennae  and  taking  them  in  order  to 
the  furca  at  the  posterior  extremity.  This  is  not  an  especially 
difficult  process,  excepting  possibly  the  maxillae,  which  are  com- 
monly very  small  and  securely  joined  in  place,  so  that  even  the 


THE   OSTRA(  ODA  Ro^ 

finest  needle  is  scarcely  efficient  as  a  dissecting  instrument.  T  - 
of  the  above  two  mounting  media  bring  out  to  view  even  the  .....  l 
hairs  or  ciliated  structures.  Alcohol  or  water  are  not  advisable  as 
dissecting  media  and  should  be  risked  with  few  specimens.  Fur- 
thermore, Farrant's  medium  makes  a  very  good  permanent  mount, 
providing  there  is  not  too  much  on  the  slide.  Kither  medium 
should  be  added  to  the  slide  in  small  drops,  then  spread  out  in  a 
thin  layer  before  attempting  to  dissect  therein.  It  is  commonly 
best  to  make  a  preliminary  examination  of  the  di«»scclion  with  a 
f-inch  objective,  to  see  that  the  mount  has  been  well  prci)arcd 
and  arranged.  If  so,  add  a  small  additional  amount  of  the  me- 
dium, cover  with  cover  glass,  and  the  mount  is  permanent,  pro- 
vided the  work  is  neatly  done,  too  much  medium  is  not  added,  and 
the  mounts  are  kept  stored  in  a  horizontal  position  when  not  in  use. 

The  valves  should  be  preserved  entire,  if  possible,  and  removed 
to  one  side  of  the  slide  for  further  study.  It  is  often  (le^iral)le  that 
they  be  removed  to  a  separate  slide  and  mounted  in  b.d-.un,  es- 
pecially if  the  slides  are  to  be  permanent  and  subject  to  muth 
handling. 

Drawings  as  well  as  study  of  a  side  view  should  always  Ik-  made 
from  one  of  the  valves,  rather  than  from  the  entire  sixi'imcn.  as 
otherwise  a  distorted  view  is  likely  to  result. 

The  dorsal  view  is  more  difficult  to  get  -  indeed,  it  is  often 
advisable  not  to  attempt  it.  Unless  this  view  is  obtained  directly 
above  the  specimen,  it  is  worthless.  Sometimes  one  valve  alone 
may  be  used  by  fastening  it  to  a  needle  or  similar  object,  and 
then  studying  while  covered  with  glycerin,  or.  it  the  valve>  arc 
dissimilar  the  entire  animal  may  thus  be  mounted  so  that  an 
exact  profile  may  possibly  be  obtained.  It  is  indeed  often  i^^- 
sible  to  get  very  good  dorsal  profdes  from  many  six-cimens  while 
they  are  in  alcohol  and  glycerin  in  a  s>Tacusc  watch  ghuv«i. 

The  following  characters  have  been  retained  as  of  most  value 
in  the  following  key:  presence  and  length  of  natatory  sc-tae  of 
the  second  antennae,  segmentation  of  the  second  antennae,  form 
and  number  of  spines  of  the  first  n.axillary  i>rocess.  armature  ol 
the  second  leg,  arrangement  of  the  spennatic  gland,  and  armature 
and  shape  of  the  furca. 


8o6 


FRESH-WATER   BIOLOGY 


KEY  TO  NORTH  AMERICAN  FRESH-WATER  OSTRACODA 

1  (2)       Second  antenna  two-branched;  one  branch  rudimentary,  immobile, 

the  other  elongate,  flexible,  with  long  natatory  setae  (Myo- 
docopa);  or  both  branches  well  developed,  movable,  and 
natatory  (Cladocopa)  ;  or  both  branches  flattened,  similar 
tofeetof  the  Copepoda(PLATYCOPA).   .  .   Marine  Tribes. 

These  groups  are  not  represented  in  fresh  water  so  far  as  known. 

2  (i)       Second  antenna  simple,  subpediform,  clawed  at  apex.     Mostly  fresh- 

water forms Tribe  Podocopa  .    .     3 

3  (4)       Three  nearly  similar  pairs  of  legs.     Furca  rudimentary.     Second  an- 

tenna with  flagellum  (Fig.  1251  (i^),  and  httle  adapted  for 
swimming Family  Cytheridae  .    .      5 

4  (3)       Two  dissimilar  pairs  of  legs.     Furca  commonly  weU  developed.     Sec- 

ond antenna  without  flagellum  and  commonly  with  natatory 
setae 9 

5  (6)       Parasitic  on  gills  of  Crustacea.     Terminal  claws  of  legs  with  four  large 

teeth  (Fig.  1249  a) Entocythere  Marshall  1903. 

Only  one  species  of  this  genus  known. 

Entocythere  cambaria  Marshall  1903. 


Length  0.60  mm.  Males  abundant.  Shell  thin,  frag- 
ile and  transparent.  First  antenna  six-segmented.  Sec- 
ond antenna  four-segmented.  Flagellum  unsegmented. 
Caudal  rami  short  and  thick.  Parasitic  on  gills  of  cray- 
fish {Camharus).  Wisconsin.  A  most  remarkable 
form,  in  that  Ostracoda  rarely  adopt  parasitic  habits. 

Fig.  1249. 

Entocythere   cambaria.     (a)  End  of  third  leg; 

(b)  Side  view,  X  50.     (After  Marshall.) 


6  (5)       Not  parasitic.     Crawlers  or  burrowers.     Terminal  claws  of  legs  with 

not  more  than  two  teeth,  or  plain  (Fig.  i26od). 

Limnicy there  Brady  1868  .    .     7 

7  (8)       Shell   decidedly  reticulate,  with  two  lateral  furrows.     Furca  blunt, 

about  three  times  as  long  as  wide  (Fig.  1250  a). 

Limnicy  there  reticulata  Sharpe  1897. 


Length  0.66  to  0.70  mm.  and  0.25  mm.  wide.  Grayish 
white.  Shell  conspicuously  marked  with  a  honeycomb- 
like network  of  polygonal  reticulations,  and  deep  lateral 
furrows  (Fig.  1250  ft).  Furca  (Fig.  1250a)  cylindrical, 
thick  and  blunt,  about  three  times  as  long  as  wide,  with 
two  small  setae.  Posterior  dorsal  part  of  carapace  tapers 
to  a  point.     Muddy  bottom  of  ponds.     Illinois,  April. 

Fig.  1250. 

Limnicythert  reticulata,     (a)  Furca;  (6)  Dorsal  view; 

(c)  Side  view,  X  54- 


THI-:   OSTRACODA 


807 


8  (7)       Shell  faintly  reticulate,  with  one  lateral  furrow.     Furca  tapering  to  a 
seta  Hke  extremity  (Fig.  1251  b). 

Limnuythac  illinoisensis  Sharpc  1897 


k: 

scKnirnictl 
alnxif  wvrn 

y 
1. 
ot  iitali  alliK-ti  Miih 

Itvth  at    tip      Sandy    J. 
Illinois  Kivrr.  I^ayuiu.  iuvi  ix».t 
shores.     May. 


"I 


Kir.    ij<i 
Limmi(\lkrrf  iiii»(ni#»itt 

sal  vir».  <^     J    .:.   . 

flagcilum.  J 
maJf 


'«)  t> 


9  (10)     Abdomen  without  furca.     Second  legs  not  backwanlly  uirtM  tc(i. 

Family  I)AK\visruD\i . 
Darwinula  stcvcnsoni  Hraiiy  and  RolxTlson  1870. 


Length  0.70  to  0.80  mm.     Kicht  shell  <-■.  < 
left.     Abdomen  ending  in  a  olindriial  un; 
(Fig.  1252a).     Sandy  or  muddy  Ixiito"- 
improvisa  Turner   i8qs,  is  a  synonym 

Fig.  ijsj. 
Dardinula  slnensoni.     (a)  Tip  of  abdomen.  X  166. 


10  (9)     Abdomen  with  furca.     Second  legs  backwardly  bent. 

Pamily  C'yprididak  . 

11  (12)     Furca  rudimentary,  with  a  long  seta  at  tip  (Fig.  1253)-  • 

12  (ii)     Furca  band-like,  with  claws  and  setae  at  tip  (Fie    i-^^j)     . 


13 


Natatory  setae  of  second  antennae  long,  reaching  .it  kaM  l.»  iji>s 
of  terminal  claws.  Second  foot  beak-shajH-d  at  tip.  willi  a 
terminal  claw.    .    .    .     Subfamily  Cvpkidopsin  v  J 


14  (15)     Shell  broad  from  above,  tumid.     Second  antenna  five-s<-gnicntrtl 

Only  one  species  in  North  America.     The    "^f » ^/^^P^"}^"  ."^ 
American ostracod.  .    .  CypnchpstsvuiiuiO.V.Mu]}^ 

Length  0.60  to  0.70  mm.,  plump.     Markc«l  <lor«lK 
ith  three  prominent  dark  han.is.     \  cry  comn»on.  « 


with  three  i)ror 
are  present. 

Fig.  1253.    CyprUcpsis  tuitt*.    Furca.  X  1  So. 


8o8 


FRESH-WATER  BIOLOGY 


15  (14)     Shell  rather  narrow  from  above,  compressed  (Fig.  1254  b).    Second 

antenna  four-segmented Potamocypris  Brady  1870. 

Only  one  species  in  North  America. 

Potamocypris  smaragdina  (Vavra)  1891. 


Length  0.65  mm.  Shell  grass  green,  nearly 
crescent-shaped,  and  thickly  covered  with  long, 
closely  appressed  hairs.  Pools  and  ditches,  July, 
August,  and  September.  Eggs  vermilion  red. 
Ponds  and  ditches,  April,  July,  August.  South 
Chicago,  Mexico. 


Fig.  1254. 

Potamocypris  smaragdina.     (a)  Side  view,  X  4°; 

(6)  Dorsal  view;  (c)  Furca,  X  150. 


16  (17)     With  two  distinct  eyes  (Fig.  1255  h) 18 

17(16)     With  eyes  fused,  ornone  apparent  (Fig.  1258  c) 22 

18  (19)     First  maxillary  process  with  six  spines.     Furca  with  three  long  setae 

and  no  spines  (Fig.  1255  c-^) 20 

19  (18)     First  maxillary  process  with  six  spines.     Furca  with  four  long  setae 

and  no  spines  (Fig.  1256  c) 21 


20  Second  antenna  six-segmented  in  both  sexes.     Second  leg  terminat- 

ing in  three  setae,  one  of  which  is  reflexed. 

Notodromas  Lilljeborg  1853. 
Only  one  species  in  North  America. 

Notodromas  monacha  (O.  F.  Muller)  1785. 


Length  1.18  mm.  "Hump- 
backed"; brownish  yellow. 
Active  swimmers,  resembling 
the  Cladocera  in  many  move- 
ments. Occasionally  hang  to 
surface  film  of  water,  back 
down,  as  Cyprois.  Permanent 
fresh  ponds  with  algae.  North- 
ern Indiana,  spring  and  sum- 


FiG.  1255. 
Notodromas  monacha.  (a)  Side 
view  of  male,  X  30;  (b)  Dorsal 
view,  X  30;  (c)  Maxillary  spines, 
X  100;  (d)  Furca  of  female,  X 
60;  (e)  End  of  second  leg,  X  no. 


THE  OSTk.\(  ODA 


809 


21 


Second  antenna  five-segmented   in  l)oth  si-xes.     Second  leg  U-nnl- 
nating  in  one  claw  and  one  rdU-xcd  st-ta  (I-jk.  i.-yOb). 

Only  one  species  found  ni  Aorlh  Anurici. 

Cyprois  tpuirf^inoia  Strautt  l8>|. 


I^nKth  1. 5.1  ram.,  bmfilh  avf 

mm    1. .  -I-  -    '  I  ■  '  -  '  - 

vdl, 
less 

water.     ^ 

moniuha  1 

ments.     Ma>    . 

lorn  (leljris.     d: 

later  dry  up.    S«  > 

sli^'htly  curvr«l; 

miinly  loriK-     .^1 

caRO,  III.     (Jack:»jii  l^t.,.  A^il. 

May,  June. 


Fig.  I  :<,»', 
Cytrois  martinala         : 
tcmalc,  X  i^; 
X  ?«;:    (<•)    hur 
(<i)   .Maiillary  «, 


22  (2.^)     Natatory  setae  of  the  second  antennae  entirely  lacking  (Fig.  i:c>S  c). 

Subfamily  Ca.ndunlnak  .    .     91 

23  (22)     Natatory  setae  of  the  second  antennae  very  evident,  usually  extend- 

ing at  least  to  tips  of  terminal  claws  (Figs,   i  :(*s  e  and 
1290  c) 24 

24  (25)     Terminal  segment  of  second  leg  with  three  long  setae  and  no  claws, 

—  one  seta  reflexed  (Fig.  12 58  /)). 

Ilyocypris  Brady  and  Norman  1S89  .         ^6 

25  (24)     Terminal   segment   of   second   leg    with    at    least    Dnc   claw   (Fig. 

12686), — and  usually  beak-shaped iS 

26  (27)     Shell  with  many  prominent  tubercles,  knobs,  and  furrows.     Nata- 

tory setae  reaching  to  tips  of  terminal   claws,  or  slighUy 
beyond Ilyocypris  gibba  KAV\\y\*Mr  \^-^^ 


Length  0.85  to  0.05  mm.     Shell  much  tuhftoiUl* 

anteriorly  and  posteriorly,  and  dct-idc<JK   fv:rT..»rvl 
anterodorsally.     Two  prominent  tiil»cr. 
of   the   eye  siH.t.       Poor   swimmer*     _  \ 
straight,  its  terminal  k\.: 
plain.     Termiii.il  M-ta 

of  torminaUlaw.     Sw.i     .  .n        ,    ,    .      . 

the  spring  months.     In  .omj^ay  wiiii  /.  .'yjJ;  ».  usu- 
ally.    Colorado,  March. 


Ftc    i:c7 

Ilyocypris  tihhc.     <J^  Skk  virw.  X  4S: 

(ft)  Donil  view,  X  44. 


8io 


FRESH-WATER  BIOLOGY 


27  (26)     Shell   with   weak   tubercles,    knobs,   and    furrows.     Natatory  setae 
reaching  scarcely  to  tips  of  terminal  claws. 

Ilyocypris  hradyi  Sars  1890. 


Length  about  as  /.  gibha.  Height 
of  female  0.45  to  0.5  mm.,  breadth 
0.32  to  0.5  mm.  Male  slightly  larger. 
Scarcely  free  swimming,  but  creeps  or 
burrows.  Shell  weakly  tuberculate 
and  not  furrowed  posterodorsally. 
Habitat  and  occurrence  as  /.  gihba. 
Furca  strong  curved,  and  much  broad- 
ened at  base.  About  ten  times  as  long 
as  width  in  middle.  Dorsal  seta  plu- 
mose and  bent  near  tip.  Distal  half 
of  dorsal  part  of  furca  ciliate.  These 
two  species  are  quite  variable,  thus 
causing  much  confusion  in  diagnosis. 
Both  species  are  also  found  in  Britain 
and  Germany. 


Fig.  1258. 
Ilyocypris  bradyi.      (a)  Furca,  X  200;   (b) 
End   of   second    leg,  X  150;    (c)   Dorsal 
view,  X  45;   (d)  Side  view,  X  45- 


28  (29)     Natatory  setae    of    the   second    antenna   shortened,  no   swimmers. 

Second  leg  with  a  beak-Hke  end  segment  and  a  claw  (Fig. 
1268  b) Subfamily  Herpetocypridinae  .    .     30 

29  (28)     Natatory  setae  of  the  second  antenna  long,  reaching  at  least  to  tips 

of  terminal  claws.     Second  leg  as  above. 

Subfamily  Cypridinae  .    .     42 


30  (31) 


Furca  abnormal,  with  three  claws,  —  the  usual  dorsal  seta  being 
replaced  by  a  claw.  Shell  faintly  longitudinally  striated 
(Fig.  1259) Ilyodromus  Sars  1894. 

Only  one  species  known  in  America. 

Ilyodromus  pectinatus  Sharpe  1908. 


Length  1. 10  to  1.18  mm.  Shell  with 
reticulate  patterns  anteriorly  and 
posteriorly.  Posterior  edge  of  furca 
decidedly  pectinate.  The  only  known 
species  of  the  genus  with  a  pectinate 
furca.  In  ponds  and  slowly  flowing 
streams,  with  Typha,  Iris,  Chara,  etc. 
South  Carolina. 

Fig.  1259- 

Ilyodromus  pectinatus.  (o)  Side  view,  X  45". 

(6)  Furca>  X  140. 


THE   OSTRAC(JI)\ 


>!   I 


31  (30)     Furca  normal,  with  two  spines  and  tw.,  Mia.   ,  l-.^.  ,  ,r.  j  /. 

32  (33)     Second  segment  of  first  leg  with  two  seta,  on  unlcr.or  „uirg,n  ^t^. 

1260  d).     Three  spmes  on  first  maxillary  pr.Kc-vs  ^ 

C  hhuuxdotltcca  Sau&sure  iS : 

33  (32)     Second  segment  of  first  leg  with  one  seta  <,„  anterior  margin  (KIk 

12//  6).     Two  spmes  on  first  maxillary  pnKrt-is 

Hcrpctocypris  Hrady  .md  Norman  i8h 

34  (35)     Shell  plain,  no  special  markings  of  any  sort.     Seen  from  above   the 

shell  is  decidedly  wedge-shaped  anteriorly  (Fig.  ,,fx)).  ' 

Chlamydotltcca  aitcka  SauMurc  1858. 


Lcnjs'th  T,.\o  mm  .  Im  i.--  ■ 
breadth  1.80  mm.  N< ' 
of  the  largest  siktocs  «.i 
Natatory  setae  of  th. 
reach  to  tijw  of  tcrmin.i 
known.  Sirn  from  .: 
rnuch  more  we<li,'«'-sh.i;. 
C.  mixicana.     It  al>-. 

stri|x-s  in  the  shell.     Fu: 

about    18   times   as    Iopk    .1 
faintly  pectinate  on   the  di  .• 
Texas,    Mexico.     Ditchi-i  an«i  j..  i< 
tober. 


Fig.  ij6o. 
Chlamydothfca   aUtka.      (d)   Side   ^-icw,  X«$, 
(b)  Dorsal  view;  (c)  Fuica.  X  IVK  U)  Fml 

ICK,  X  US. 


35  (34)     Shell    with    semicontorted    and    radially    arranged    colored    Iwinds. 
Shell  more  tumid  from  above  (Fig.  1  'f>!  1  -h 


36  (37)     Shell  with  at  least   six  sinuous  radiating  dark-green    baml.s   on  its 
sides C/iliimydol/nrii  htrruki  Turner  iSq^, 


LenRth   .vcx>    i: 
width  1.4 <  mm.     I 
sinuous  and  radi.i 
bands.     Claws  of  J»f>; 
smooth.    Termiiul  ila 
as  lonjr  as  entire  I'  1' 
h.df  the    dor<il    i 
twenty  times  as 
canal  basin.     Ohi-i 


Fir..   1 161. 

Chlamydotketa   ktmtki.     («)  SiAt  rifw.  X  tf; 

(6)  Donalvif*:     •>   K»r«»    •   too. 


8l2 


FRESH-WATER   BIOLOGY 


37  (36)     Shell  with  but  three  such  bands. 


Chlamydotheca  mexicana  Sharpe  1903. 


Length  2.75  mm.,  height 
1.55  mm.,  width  1.60] mm. 
No  males  yet  found.  Two 
or  three  narrow  greenish 
bands  irregularly  arranged 
on  sides  of  shell.  Furca 
straight,  about  twenty- 
three  times  as  long  as  wide 
and  faintly  toothed  on 
about  one-half  of  dorsal 
margin.  Ponds;  Septem- 
ber.    Durango,  Mexico. 


Fig.  1262. 

Chlamydotheca  mexicana. 

(a)  Side  view,  X  25; 

{b)  First  leg,  X  100; 

(c)  Furca,  X  125. 


38  (39)     Length  about  four  mm Herpeiocypris  harhatus  Forbes  1893. 


Width  1.60  mm.,  height  2.00  mm.  Shell 
fairly  full,  but  not  plump.  Large,  hairy,  yel- 
lowish brown  in  alcohol,  with  reddish  patches 
on  either  side.  One  of  the  largest  of  the 
fresh-water  ostracoda.  Valves  equal.  Furca 
about  twenty  times  as  long  as  wide,  slightly 
sinuate.  Yellowstone  River,  Wyoming.  July, 
August. 


Herpetocypris  barhatus. 


Fig.  1263. 
(a)  Side  view  with  shell  removed;  {b)  Furca. 


(After  Forbes.) 


39  (38)     Length  less  than  three  mm 40 

40  (41)     Dorsal  edge  of  furca  with  five  combs  of  coarse  teeth  (Fig.  1264  h). 

Herpetocypris  reptans  Baird  1850. 


Length  2.00  mm.  to  2.50mm.,  height 
0.80  mm.  Brownish  yellow.  Furca 
about  sixteen  times  as  long  as  wide, 
slightly  curved;  its  dorsal  edge  armed 
with  jive  combs  of  coarse  teeth.  Furca 
claws  coarsely  toothed.  Muddy  bot- 
toms, ponds;  April  to  September. 
California. 


Fig.  1264. 

Herpetocypris  reptans.     (a)  Side  view; 

(6)  Furca. 


THE  OSTRACODA 
41  (40)     Dorsal  edge  of  furca  plain  (Fi^.  120;  /,). 

Ucrpctocypris  trshulhuiria  Cushnun  1908. 


IxrnKth    J.  10  mm 

mm  .    v. -I'l.    _  ..- 

txtra 

I'urta  > 

as    wi.l,.,    ,I^    .u«,  jj^^^       j.^^^^ 

NcwfoundUnd.     Mmy. 


llfTfffUHyfrrii     !' 
view;     {h)   I 
ihowin*  un^ 


42  (43)     Natatory  setae  of  second  antenna  reach  i..  u\>>  ,,t  terminal  i 

slightly  beyond.     Second  leg  with  a  lu-ak  like  cn«l  ^ 
andaclaw(Fig.  i268  6,(').  .   Subfamily  Cvi-kiui'.  , 

43  (42)     Natatory  setae  of  the  second  antenna  reach  bevontl  tips  of  u-rmw»al 

claws   by   about   one-halt    their   length.     Second    leg    with 
three  terminal  setae  of  ditTerent  lengths,  two  of  ihcm  rc- 
flexed,  the  other  short  and  claw  like  (Fig.  iiaoc,  f\. 
Subfamily  Cvclck'YPKIdin  ■' 

44  (45)     Testes,  if  present,  originating  in  anterior  part  of  shell  m  iurm  of 

concentric  circles  or  half  circles  (Fig.  1266). 

S piracy pr is  SharjK*  1903   . 

45  (44)     Testes,  if  present,  not  originating  in  anterior  part  of  shell  in  form  of 

concentric  circles  or  half  circles  (Fig.  1271  />). 

CyprisO.V.  Mullrr  17- 


46  (47)     Shell  not  tuberculate,  excessively  hairy  (Fig.  uof)  <;). 

Spirocypris  passiticu  Sharpc  190; 


I  r  n  p»  h     I  ^9    mm  . 


.ili, 
tors 
1  ,  . 


i.iiUiCllj,  ,Nc»   JcXif; 


FlC.     IJM.. 

Spirocypris  passaica.     (a)  Side  view,  X  Jo;  (6)  I)or**I  view,  u)  FufVA. 


14 


FRESH-WATER   BIOLOGY 


47  (46)     Shell  very  tuberculate,   sparsely  hairy  and  unusually  plump  (Fig. 
1267  c) S piracy pris  tuberculata  Shsiipe  igoS. 

Length  0.93  mm.,  height 
0.53  mm.,  width  0.70  mm. 
Purplish  brown,  with  one  or 
two  dorsal  transverse  lighter 
bands.  Right  valve  sHghtly 
overlaps  the  left  anteriorly. 
Natatory  setae  extend  but 
slightly  beyond  the  ter- 
minal claws.  Furca  about 
thirty-two  times  as  long  as 
wide.  Shallow,  weedy,  and 
swampy  ponds;  spring. 
Chicago  and  northern  In- 
^         diana. 

Fig.  1267. 
Spirocypris  tuberculata.     (a)  Side  view,  X  43;   {b)  Furca;   (c)  Dorsal  view. 


48  (49)     First     leg     four-segmented,    third    and     fourth     segments     united 
(Fig.  1268  c).  .    .    Subgenus  Eurycypris  G.  W.  Miiller  1898. 
Only  one  species  in  this  subgenus. 

Cypris  {Eurycypris)  puhera  O.  F.  Miiller  1785. 


Length  2.10  mm.,  height 
1.25  mm.,  breadth  1.20  mm. 
Greenish  in  color.  A  dark 
patch  at  its  highest  and  cen- 
tral part  as  seen  from  the  side. 
Shell  sparsely  hairy.  Anterior 
and  postero-ventral  margins 
with  prominent  external  tuber- 
cles. Two  prominent  tuber- 
cles at  postero-ventral  part  cf 
shell.  This  character  alone  is 
suflBcient  to  identify  this  species 
of  c>^pris.  First  leg  four-seg- 
mented. Furca  nearly  straight, 
about  twenty-four  tinies  as  long 
as  wide.  Ponds;  April  to  June. 
Oregon. 


Fig.  1268. 
Cypris  {Eurycypris)  pubera. 

(a)  Side  view,  X  10; 

(b)  End  of  second  leg; 

(c)  First  leg; 

(d)  Furca; 

(e)  Second  antenna; 

(/)  Posteroventral  part  of  shell. 


49  (48)     First  leg  plainly  five-segmented  (Fig.  1277  b),  third  and  fourth  seg- 

ments not  united 50 

50  (51)     Inner  anterior  edge  of  right  shell  thickly  tuberculate  (Fig.  1270  a). 

Subgenus  Cyprinotus  Brady  1885    .    .      52 


THK  OSTKACODA 
SI  (50)     Inner  anterior  edge  of  right  shell  plai„  n.-jg.  ,  _,^,  ^y 

5.  (53)     Dorsal  seU  of  furca  .ore  than  one.h.f  ,..„„.  of  .Merlin.,,  .,,, 
53  (5.)     Dorsal  -a^of  Jurca^not  ™re  than  ,„..ha,f  length  of  ,u. 


>lcnnin.tl 


54  (55)     Left  shell  larger  than  the  right,  an.l  its  cIlu- 
1270  h).      "       *" 


'•>  not  lulxrculatcil-ig, 
^6 


55  (54)     Left  shell  smaller  than  the  right  and  with  •.  tmv..    f 

along  the  inner  margin  iV^:^^^^:^:'^  "^^^^^'^^-'^  ^^^^^i« 
Cypris  (Cyprinotus)prll,uida  Sh 


56  (57)  Right-shell  margin  tuberculate  only  at  anterior  and  |>ostcn.vcnlral 
margins.  Shell  about  four-sevenths  as  high  as  Um^  (Kig. 
1270  a).    .    Cypris  {Cyprinotiis)  inconfirucns  Ramdohr  1S08. 


Shell  (IruM'ly  iti^irntnl 
transluicnt  ycllowiikh   m 
.•^mcxtth.    1.^'npth  t  {o  ?o  • 
Left  valv. 
airvitl,  al 
wide.      .^1 

In  qutir 
JiKobal 

even    in     tcmix>rar>"    ; 

watering  tmu^h^      f  ' 
JVnnsylvania. 

(<i)K 
of:; 

Spin«  ol  bnrt  n 
19a 

■■*.  X 

8i6 


FRESH-WATER   BIOLOGY 


57  (56)     Right-shell  margins  unusally  tuberculate,  as  in  Fig.  12716.    Shell 

not  more  than  one-half  as  high  as  long  (Fig.  1271  a). 

Cypris  (Cyprinotus)  dentata  Sharpe  1910. 
Shell  brownish  yellow 
and  translucent  in  alco- 
hol. Length  1.35  to  1.60 
mm.,  and  height  not  more 
than  one-half  as  great. 
Shell  pointed  posteriorly, 
and  anterior  half  of  ven- 
tral margin  slightly  sinu- 
atein  the  male,  but  nearly 
straight  with  the  female. 
Natatory  setae  reaching 
well  beyond  the  terminal 
claws.  Males  common. 
Furca  gently  curved, 
about  sixteen  times  as 
long  as  wide.  Spines  of 
first  maxillary  process 
toothed.  Temporary 
ponds.  Stamford,  Ne- 
braska. 

Fig.  1 27 1. 
Cypris  (Cyprinoius)  dentata. 
{b)  Right  shell  from  within,  X  30;  (c)  Furca,  X  105. 

58  (59)     Dorsal  seta  of  furca  less  than  width  of  furca  from  subterminal  claw 

(Fig,  1272c).  .  Cypris  {Cyprinotus)  burlingtonensisTxirneT  1894. 


(a)  Left  shell  from  within 


Length  1.50  mm.,  height  0.70  mm.,  width  0.70  mm. 
Yellowish  brown  with  bluish  black  longitudinal 
stripes  on  dorsum  and  sides.  Hairy.  Natatory  setae 
extend  slightly  beyond  tips  of  terminal  claws. 
Maxillary  spines  toothed .  Furca  slender  and  straight, 
about  eighteen  times  as  long  as  wide.  Dorsal  seta 
close  to  subterminal  claw.  Shallow,  temporary,  grassy 
pools.     Ohio,  Georgia,  Delaware. 


Fig.  1272. 

Cypris  (Cyprinotus)  burlingtonensis.     (a)  Side  view,  X  16; 

[b)  Dorsal  view;   (c)  Furca. 


59  (58) 


Dorsal  seta  of  furca  more 
claw 


than 


width  of  furca  from  subterminal 
60 


60  (61)     Shell  with  no  markings,  translucent.     Right  valve  the  larger. 

Cypris  {Cyprinotus)  americanus  Cushman  1905. 
Length  1.50  mm.,  breadth 0.70  mm., 
height  0.80  mm.  Colorless.  _  Natatory 
setae  reach  to  tips  of  terminal  claws. 
Fourth  segment  of  first  leg  with  four 
short  extra  spines.  Terminal  segment 
of  second  leg  constricted  in  the  middle, 
and  with  two  longitudinal  rows  of 
minute  spines  extending  from  the 
constriction  to  the  tip.  Furca  nearly 
straight  and  about  twenty  tirnes  as 
long  as  wide.  Ponds  and  ditches. 
Nantucket,  Mass. 

Fig.  1273. 
Cypris  (Cyprinotus)  americanus.    (a)  Side 
view,  X  30;    (b)  Dorsal  view;  (c)  Furca, 
X  150;     (d)   End  of  first  leg  showing 
extra  spines,  X  150. 


8,7 


THE  OSTRACODA 

6i  (60)     Shell  reticulated,  thin,  the  spermarics  showing  through.      I 

Cypris  {Cyprnwtus)  crnid  Tu: 

0.6s  mm.,  width  o.sgt<.oy«  mm      N  "'..•;... 

lary  spmcs  smocuh.    l-„urll,  m-kuh-u- 
extra  short  spines,     l-urca  i  urvtnl     . 

ponds  and  canal  basins.     Ohio.  ««i*«  wrruy 

Cypris  (Cyprinotus)  crena.     (a)  SidJ tiew.  X  15;  (*)  Furca  ol  mtk. 

62  (63)    Furca  normal,  with  two  spines  and  two  setae  (Fig.  W7S</) 

Subgenus  Cyprii 

63  (62)    Furca  abnormal,  the  terminal  seta  missing  (Fig.  ii^c). 

Paracypris  .W-w  Subgenus 


H 


66 


64  (65)     Both  spines  of  first  maxillary  process  smooth 

65  (64)     Both  spines  of  first  maxillary  process  toothed  (Fig.  i  270  r;. 

66  (67)     Shell  bluish  black,  with  two  yellowish  areas  in  region  of  eye  spot 

(Fig.  1275  a) Cypris  {Cypris)  virais  ]\inx\i:  \^20. 

Length  1.70  to  2.00  mm.,  height  0.90  to  i.oo  mm.     Shell  coverctl  with  short  !  ur>    x'\\ 
left  valve  slightly  overlapping  the  right.     Ventral  edge  flanged  antoriorlv      N.f 
reach  to  tips  of  terminal  claws.     Dark  to  yellowish  green.     Furca  weakly  s'shajir. 

and  from  eighteen  to  twenty  times  as  long  as  average  width,  and  its  dorsal  mar^ ...-.w. 

Very  variable.     Weedy  ponds;  April  to  July.     Massachusetts.  Mexico.  Ohio.  Wiscoosm. 


Fig.  1275- 
Cypris  (Cypris)  virens.     (a)  Side  view.  X  i8;  (6)  Dorsal  view;  (c)  Furca. 

67  (66)     Shell  bright,  deep  green,  smooth,  with  minute  punctures. 

Cypris  {Cypris)  iiUissinui  C'haml)crs  1877. 

,_  Length  0.80  mm.,  height  040  mm.     I 

^  two  terminal  claws  nearly  same  Irn^'th      i 

ing  snow,  Mt.  Libert.  C'olora<lo.     .\llit 

Fig.  ii76.    Cypris  (Cypris)  aUistimt      Kurca. 

6S  (69)     Terminal  three  segments  of  first  leg  longer  than  two-lhirdi  of  il* 

terminal  claw  (Fig.  1277/)) •    •  1^ 

69  (68)     Terminal  three  segments  of  first  leg  shorter  than  two-lhinls  of  lU 

terminal  claw 7' 


FRESH-WATER   BIOLOGY 


70  (71)     Shell  thin,  and  dirty  to  ocherous  yellow. 

Cypris  {Cypris)  testudinaria  Sharpe  1897. 

Length  1.15  mm.,  height  0.75  mm., 
width  0.65  mm.  Natatory  setae  just  reach 
tips  of  terminal  claws.  Terminal  claw  of 
first  leg  one-sixth  longer  than  the  last  three 
segments.  Terminal  claw  of  second  leg 
one- third  as  long  as  terminal  segment. 
Furca  slightly  curved,  its  dorsal  edge  ser- 
rate two-thirds  its  length,  and  sixteen  to 
eighteen  times  as  long  as  wide.  Dorsal 
seta  two-thirds  as  long  as  terminal  one, 
and  width  of  ramus  from  subterminal  claw. 
Terminal  seta  fully  one-half  as  long  as  the 
terminal  claw.  Ejaculatory  duct  five  times 
as  long  as  wide,  with  spines  thickly  set  over 
the  entire  surface  (Fig.  1277c),  instead  of  in 
wreaths,  as  is  common.  Ponds  in  woods. 
Illinois. 


Fig.  1277- 
Cypris  {Cypris)  testudinaria.     (o)  Furca;  {b)  First  leg; 
(c)  Part  of  ejaculatory  duct  of  male,  and  origin  of 
vas  deferens. 


71  (70)  Shell  dark  green  to  chestnut  brown  with  transverse  lighter  patches  dor- 
solaterally  (Fig.  1278(1-6). 

Cypris  {Cypris)  fuscata  Jurine  1820. 


Length  1. 30 mm.,  height  0.80  to 0.95  mm.,  width 
0.80  to  0.8s  mm.  Right  shell  overlaps  left. 
Sparsely  hairy.  Terminal  claws  of  first  leg  less 
than  one-third  longer  than  the  last  three  segments. 
Furca  weakly  S-shaped  to  nearly  straight,  and 
from  eighteen  to  twenty  times  as  long  as  wide. 
Terminal  seta  of  furca  weak,  not  more  than  one- 
third  as  long  as  terminal  claw;  dorsal  seta  less  than 
width  of  furca  from  subterminal  claw  and  about 
one-half  as  long  as  the  terminal  seta.  Sexual. 
Common  everywhere  in  shallow,  grassy  ponds  and 
swamps;  April  to  June. 


Fig.  1278. 
Cypris  (Cypris)  fuscata.    (a)  Variety  major,  dorsal  view, 
X  20;  (b)  Variety  minor,  dorsal  view;  (c)  Side  view 
variety  major;  {d)  Furca,  X  125. 


72            Shell  dark  green  with  two  light  patches  in  region  of  the  eyes  (Fig. 
1279  a) Cypris  {Cypris)  reticulata  Zsiddsich  1S44. 

Length  i.io  to  1.30  mm.,  height  0.72  mm.,  width 
0.65  mm.  Shell  usually  reticulate  or  tesselated. 
Somewhat  superficially  resembhng  Cypris  fuscata 
major.  Natatory  setae  reach  slightly  beyond  the 
terminal  claws.  Fiurca  straight,  weakly  bent  near  the 
end,  and  from  ten  to  twelve  times  as  long  as  wide,  and 
faintly  toothed  along  the  dorsal  margin.  Terminal 
seta  slender  and  of  the  same  length  as  the  dorsal  one, 
which  is  situated  about  width  of  furca  from  subter- 
minal claw.  Abundant  in  small,  temporary  grassy 
pools.  Illinois,  Massachusetts,  New  York,  New 
Jersey. 

Fig.  1279. 
Cypris  (Cypris)  reticulata,     (a)  Dorsal  view,  X  275;  (&)  Furca,  X  1323. 


THE   OSTRACODA 


810 


73  (74)     Posterior  margin  of  furca  pectinate  (Fig.  i  ,So  c). 

Cypris  iPanicypris)  pcrdegans  Hcrrick  1887. 
LonKth  v^omm  .  hciKht  i  7  j  mm.,  width  1^ 


mm.  Color  «U-ar  1..1I.  .. 
patti'rn  in  r K-ar  ! 
shell  is  acutely  w, 
the  side  the  ujHm  r 
parallel,  with  a  I 
ventrally.  TerM!; 
two  small  claws  and  ..u«. 
spine  like.     Weetly  jxjnds 


.    ,„  Fk.    ijRo. 

Lyprts  (Paracypris)  ptftUtam.     («)  Sidt  vk«   X  •; 
{b)   Dorsal  view;  (c)  Funa. 


11,.^    «.,.v.    . 


^\.*         l>uf««i    «r<« 


74  (73)     Posterior  margin  of  furca  plain  (Fig.  12S1  r). 

Cypris  {Paracypris)  grandis  ChamlxTs  1S77. 


Length  .^60  mm.,  heijjht  2  '• 
mm.      I'rom    ahove.    shell    r-  . 
Bluish  white  to  iKile  Kfirnish 
Arkansas  River,  Colora<lo.     .Miuudc  dooo  loct. 
A  doubtful  form. 


Fig.  ij8i. 
Cypris  (Paracypris)    gramdis.      («)   Sidr  rim.  X  4. 
(b)  Dorsal  view;    (c)  Furca;  id)  MatilUry   palpi 

of  male.    (After  Chantben.) 


75  (76)  Terminal  segment  of  second  leg  small,  with  two  short  claws.  .in<l  a 
long  refiexed  seta  (Fig.  12S2  </).  Second  antenna  of  maic 
with  two  sense  organs  on  fourth  segment. 

Cyprid  Zenker  1S5.J 


76  (75)  Terminal  segment  of  second  leg  long  and  narrow,  with  short  cbw. 
and  two  long  reflexed  setae  (Fig.  ijdo  0.  Second  antenna 
of  male  without  sense  organs  on  the  fourth  segment. 

C^'c/ocypm  Brady  and  Norman  iSSi^  .    .     8q 


77  (78)     Right-valve   margin    not    crcnulate   anteriorly.     X'alves    alvnjt    the 

same  size  (Fig.  1284(1-6).   .    .    .     Subgenus  Cy/^rt. 

78  (77)     Right-valve  margin  crenulate  anteriorly.     N'alves  of  deciderlly  differ- 

ent sizes  (Fig.  1287  a-b). 

Subgenus  Physocyprui  Xavra  iS;i 


79  (80) 

80  (79) 


Terminal  claws  of  second  leg  approximately  equal  (Fig.  1 2S:  </)•        >^ « 
Terminal  claws  of  second  leg  evidently  unequal  (Fig.  1 285  <0 


820 


FRESH-WATER   BIOLOGY 


8 1  (82)     Terminal  claws  of  furca  not  more  than  one-half  as  long  as  furca 
(Fig.  1283  b) 83 


82  (81)     Terminal  daws  of  furca  three-fifths  as  long  as  furca  or  longer  (Fig. 
1282  c) Cypria  [Cypria)  dentifera  Sharpe  1897. 


Length  0.69  mm.,  height  0.38 
mm.,  width  0.26  mm.  Brownish 
yellow,  with  dark  brown  markings 
and  reddish  blotches.  Right  valve 
overlaps  left  anteriorly.  Left- 
valve  margins  crenulate,  anteriorly. 
Natatory  setae  reach  length  of 
antennae  beyond  tips  of  terminal 
claws.  Terminal  short  claws  of 
second  leg  approximately  equal 
and  as  long  as  the  terminal  seg- 
ment. Furca  stout,  ten  times  as 
long  as  wide,  its  subterminal  claw 
with  a  comb  of  remarkably  long 
teeth.  Males  common.  Algae- 
rich  ponds.  Illinois,  Ohio,  New 
York,  New  Jersey. 


(c)    Side  view  of  left'  valve',  X  30;  (6)  Dorsal  view;  (c)  Furca;  (i)  End  of 
second  leg. 


Cypria    {Cypria)   dentifera. 


83  (84)     Shell  covered  with  a  close  reticulum  of  longitudinally  subparallel 
Hnes  (Fig.  1283  c).     Abdomen  without  processes. 

Cypria  {Cypria)  exsculpta  Fischer  1855. 


Length  0.60  to  0.75  mm.,  height 
0.38  to  0.42  mm.,  width  0.25  to  0.28 
mm.  Shell  thin,  covered  with  anasto- 
mosing subparallel  lines.  Color  clear 
chestnut  brown.  Common  in  streams 
and  p)onds  everywhere.  Also  com- 
mon in  bottom  tows  in  river  chan- 
nels, lake  and  river  shores.  Caudal 
rami  short,  stout  and  much  curved; 
both  terminal  claws  smooth;  dorsal 
setae  situated  slightly  beyond  middle 
of  ramus.  Distribution  world  wide. 
This  species  may  be  at  once  identi- 
fied by  means  of  the  reticulum  of 
anastomosing  subparallel  lines  on  the 
valves.  These  may  be  readily  seen 
with  a  two-thirds-inch  objective. 


Fig.  1283.  ,.  ^ 

Cypria  (Cypria)  exsculpta.   (o)  Dorsal  view,  X  45;  (b)  Furca;  (c)  Striations  on  shell;  {d)  Spiny  cyUnder 

of  ejaculatory  duct,  in  sack. 


THE   OSTRACODA 


84  (83)     Shell   plain,   with   small   i)uiicta.     Abdomen   with    two   ■ 
processes ^ypria  {Cypria)  opOuilmi<a  ] 

Lcnglh  0.56  to  o.Oo  mm  , 
mm.,  widlho.jjloo.  t'>mr; 
ik'ar  Ijrown,  with  •!. 
riorlyan<liK)Sli-rii.rl\ 
Natatory   sotac  vcr\ 
terminal  tiaws  liy  n. 
of  the  antrnna.     1(. 
lonK  as  widi-.     Suri 
river   chanmis  ami 
l'cl)ruary  to  OitoUr 

and  ditches  where  there  i:*  Utile  or  i^  . fac- 
tion.    Georgia,  Illinois  MinnrtoU.  thrf  •■■ 

Yu..  ijs^, 
Cypria  (Cypria)  opikalmica      (4)  «vWr  rirw.  X  m. 
(b)  Dorsal  view;  (o   Furci.  X  I5T|;   (/)  Fmit. 
X  100. 


85  (86)     Shell  clear  to  brownish  yellow,  with  a  few  scattered  punrla. 

Cypria  (Cypriu)  obcsa  Sharpc  iSg;. 


Length  0.78  mm.,  hcixht  0.48  mm  ,  width 

0.33  mm.     Plump.     Furi  n  '      ■      '      ■  -  -, 

times  as  long  as  wide,  it 

times  width  of  ramus  fron. 

and  as  long  as  the  terminal  st  t-i      \\Ac%  i.L_,-^^ 

mon.     In    tow  of   sandy    bkc    »horr,    M*y 

Illinois. 

Fic.  ia8s. 
Cypria   (Cypria)  obesa.      («)    Doml  vim 

(6)Furca;  (r)  Maxillary  palp* o(  auk;  Id)  >*c.-*ti 

leg. 


86  (85)     Shell  white,  smooth,  and  shining,  with  numerous  almost  confluent 

puncta Cypria  {Cypria)  mons  Chambers  1877. 

e  Length  0.70  mm.     A  douhtful  form,  not  well  described 

\                 X"      ^  Colorado,  Mt.  Elbert.     Altitude  1 1. 000  fert 

)              (           \  F.o.  ..sr, 

Ct               V               Jh  Cypria  [Cypria)  mons.    (j)  Dorsal  \-iew.  u»>^..W  %«•».  X  ift. 

^ ^^  (.Alter  Chambers 


87  (88) 


Left  shell  higher  than  right.     Terminal  short  setae  ..i   >....iid  leg 
about  twice  as  long  as  the  terminal  segment  (l-ig.  i.-S;). 

Cypria  [Physocypria)  pustulosa  Shar]xr  1807. 

Length  0.51  mm.,  height  o  i'^  n.m     *i*th 
0.22  mm.     Clear  hrownisli  witi' 
Kxtremitics  of  shell  hairy      \ 
flange  on  left  valve  (Fig    '    ""• 
setae  three  times  as  lonf,- 
tween  the  i)lace  of  their   1 
terminal    claws.     Furca    ; 
length  of  terminal  claw      I  ' 
situated  alM)Ut  middle  of  ( 
in  river  channels,  surface  *»d  liotto*; 
lakes,  and   lake  and   river   »horr».    ^ 
SeptemlH-r      Illinois. 

Tb;   {b\  kight  xalvt.    U)   Firn  k«;   U)  Fare*. 
(e)  Second  le«. 


822 


FRESH-WATER  BIOLOGY 


(87)     Left  shell  same  height  as  right,  but  longer.     Terminal  short  setae  of 
second  leg  about  as  long  as  terminal  segment. 

Cypria  (Physocypria)  inequivalva  Turner  1893. 

~  Length  0.42   to  0.55  mm.,  height  0.35 

to  0.38  mm.,  width  0.26  to  0.28  mm. 
Shell  with  irregular  cross-shaped  spots 
dorsoanteriorly  and  posteriorly.  Furca 
curved,  slender,  its  dorsal  seta  rudimen- 
tary or  absent.  Males  common.  Amongst 
algae  of  shallow  ponds.     Ohio,  Georgia. 

Fig.  1288. 
Cypria  (Physocypria)  inequivalva.     (a)  Side  view,  X  44;   {b)  Dorsal  view;   (c)  Furca. 


89  (90)     Dorsal  seta  of  furca  rudimentary  or  absent  (Fig.  1289  c). 

Cydocypris  laevis  O.  F.  Miiller  1785. 


Length  0.45  to  0.48  mm.,  width  0.24  to  0.28  mm., 
height  0.30  to  0.3s  mm.  Color  lemon  yellow  to  chestnut 
red  or  horn  brown.  Plump,  and  left  shell  overlapping  the 
right  anteriorly.  Furca  stout,  nearly  straight,  six  times 
as  long  as  wide.  Terminal  seta  more  than  one-half  length 
of  terminal  claw.  Common  in  weedy  streams,  ponds,  and 
swampy  regions;  April  to  November.  Delaware,  Indi- 
ana, Illinois,  New  York,  New  Jersey. 


Fig.  1289. 

Cydocypris  laevis.     (a)  Dorsal  view,  X  60:  (b)  Side  view,  X  451 

(c)  Furca. 


90  (89)     Dorsal  seta  of  furca  plainly  well  developed.     Terminal  claws  of  furca 
strong,  and  much  bent  at  tip  (Fig.  1290  e). 

Cydocypris  forbesi  Sharpe  1897. 


Length  0.55  mm.,  width  0.36 
mm.,  height  0.39  mm.  A  small 
form.  Plump  and  sepia  brown  in 
alcohol.  Natatory  setae  four  times 
length  of  terminal  claws.  Penulti- 
mate segment  of  second  antenna 
with  but  one  seta.  Terminal  seg- 
ment of  second  leg  three-eighths 
as  long  as  the  preceding  segment 
(Fig.  1290/).  Furca  about  eight 
times  as  long  as  wide.  Both  ter- 
minal claws  strongly  bent  at  tip, 
nearly  smooth.  Right  palp  of  sec- 
ond maxilla  of  male  larger  than 
the  left  one.  Terminal  seta  about 
as  long  as  width  of  furca.  Males 
common.  Ponds  in  woods;  April. 
lUinois. 


Fig.  1290, 
Cydocypris  forbesi.     (a)  Side  view,  X 
60;    lb)    Dorsal    view;    (c)    Second 
antenna;     (d)    Maxillary    palps    of 
male;  (e)  Furca;   (f)  Second  leg. 


91 


THE   OSTRAC'ODA 

Terminal  segment  of  second  leg  with  three  unlik. 
IS  reflexed(Fig.  I20I  J).   .    Subfamily  ( 


»23 


92  (94)     Shell  reticulate,  very  tumid.     Small,  plump  forms  not  ■ 

mm.  long.     Second  antenna  of  l>oih  sc-xes  1.. 

Pur(UanJon<i  Harlwig 


93 


Shell   profusely   ornamented   with   p<.lygonaI    areas   an<i    tubcrdr* 
(lug.  1 291  a). 

Paracandona  citplcctdla  Hradv  and  Norman  1880 


Lcnpth  0.56  to  o  <;«  mm  ,  Kri-ht   ^  ..  ^-  ^  ,^, 
mm.,  width  0.^2  t.  "  . 

larger.     One  ternii 
fused  to  terminal 
stout,  si.x  timesasIuiiKa,  v-iiii 
length  of  suhterminal  tbw.     I . 
scarcely  evident.     .\o  otlu-r  ( 
cod  shows  the  ornamentation 
and  tubercles.      The  siK-rifu    i, 
refers  to  the  striking  external  ai;.  ,i:ai.r       -.•_. 
low,  swampy  regions,  in  mud  and  drlm»  o<  ihr 
bottom;  spring  months.     .New  ]trsty 


Fig.  ijqi. 
Paracandona  euplectella.    (a)  Side  view.  X  y*.   (*)  iJor- 
sal  view;   (c)  I'urca;  (</)  Second  lot;   (#/  Ut 

palp. 


94  (92)     Shell  plain,   at  least  not   reticulate  or  excessively   tubcrcuUtc  or 
tumid. Q5 


95  (96)     Furca  abnormal,  terminal  seta  absent  (Fig.  i2()2  b). 

Typhlocypris  \'ejdovsky  1882 


97 


96  (95)     Furca  normal,  with  2  claws  and  2  setae  (Fig.  ij«)4  h). 

Camloiui  Haird  1S50   .    .     oq 


97  (98)     Furca  nearly  straight.     Dorsal-valvo  margins  evenly   curved  (Fig. 
1292  a-b) Typhlocypris  pcircci  Turner  1895. 


Length  0.70  t»)  0.70  mm  .    -^    '* 
mm.,  height  o,,  \  to  OM  v 
tinged    with    yelK)W      '^J  < 
compres-siil.    Funa  n^ 
twelve  times  as  lorn: 

claw  more  than  twi>-il,.. 

one.    i^exual.   l'jaiuLit.>rv  duit  »'i 
of  chitinous  spines.     .^h.illow.  *■ 
June.     Georgia. 

Fio.  i.H»j. 
Tvphhcyprii  peirtei.    (<i>  Side  v4n»  o<  (rm«W.  X  »K 
l6)  Furci  o(  idaI*.  (< )  Prtm 


824 


FRESH-WATER   BIOLOGY 


98  (97)     Furca  decidedly  gurved. 
1293  a).      .    . 


Dorsal-valve  margins    ''  humped  "  (Fig. 
TypJilocypris  delawarensis  Turner  1895. 


Lengdi  0.95  mm.,  width  0.43  mm.,  height  0.54  mm.  Color 
greenish  yellow  with  brown  blotches.  Maxillary  spines  plain. 
Terminal  claws  of  furca  slender  and  plain.  Furca  slender  and 
much  curved.  Creeks;  March.  Delaware.  (A  doubtful  form, 
not  well  described.) 

Fig.  1293. 
Typhlocypris  delawarensis.     (a)  Side  view,  X  is;   (b)  Furca. 


99  (100)     Shorter  seta  of  terminal  segment  of  second  leg  outwardly  flexed 

(Fig.  1294(71) Candona  reflexa  Shsivpe  iSgj. 

Shell  twice  as  long  as  high,  cine- 
reous. Second  leg  five-segmented, 
its  terminal  segment  as  wide  as  long, 
and  about  one-third  as  long  as  the 
penultimate  segment.  Furca  eight 
times  as  long  as  wide  and  slightly 
curved.  Dorsal  seta  as  long  as  sub- 
terminal  claw.  This  is  the  only 
Candona  known  with  the  peculiar, 
partly  reflexed  seta  of  the  second 
foot,  and  it  may  be  a  characteristic 
of  a  young  stage.  Tows  along  lake 
shores  along  the  bottom;  April  to 
November.     lUinois. 

Fig.  1294. 
Candona  reflexa.     (a)  Second  leg; 
{b)  Furca;   (c)  First  leg. 


100  (99)     Shorter  seta  of    terminal  segment  of    second   leg  not    outwardly 
flexed  (Fig.  1296  h) loi 


loi  (102)     Length  of  shell  more  than  1.50  mm 


Candona  crogmani  Turner  1894. 

Length  1.52  mm.,  height  0.76  mm.,  width  0.58  mm. 
Shell  thin,  pellucid,  inequivalve,  greenish  yellow.  Max- 
illary spines  plain.  Second  leg  indistinctly  segmented. 
Furca  straight,  ten  times  as  long  as  average  width,  its 
terminal  claws  pectinate.  Dorsal  seta  one-third  length 
of  furca  from  subterminal  claw.  Shallow,  temporary 
ponds;  December.     Georgia. 


Candona  crogmani. 


Fig.  1295. 
(a)  Side  view,  X  15;   (*)  Dorsal  view; 
(c)  Furca. 


102(101)     Length  of  shell  not  more  than  1.50  mm 103 

103  (104)     Length  of  shell  less  than  one  mm io5 

104  (103)     Length  of  shell  more  than  one  mm 108 


8^5 


THE   OSTRACODA 

105  (106)     Subterminal  claw  of  furai  clcci(._  .. 

Candotui  simpsoni  Sharp<-  iR<j7 


l^'^Uy  S-shapedfFig.  ii^fid). 


LenKth  0.7?  mm 
mm.     \'ill<i\vi>li  v.: 
ri«lit.     Ui)iHT  aii.l 
paralk'l.      I-urca    turvol 
lon>,'as  wide  with  the  mi! 
S-sliapi'd       a    marknl  . 
twice  width  of  funa  fr(Ji 
two-thirds    its    U-nKth.     1 
and  river  shores,  and  poiuli 
Illinois. 


^jXUi^   aiiMJ    AuluUltt. 


,,     ,         .  Fig.  iju6. 

Landona  simpsoni.    (a)  Side  view.  X  47.  '<>.  ^«cum  m; 
(f)  Second  aoteniu:  (rf)  Kuroi. 


106(105)     Subterminal  claw  not  S-shapcd  (Fig.  1297  f) ,0- 

107  Shell  with  dorsal  and  ventral  margins  nearly  parallel  (Fig.  i2Q7tf). 

Candona  paralida  (i.  \V.  MuUcr  1900. 


X  at 


Length  0.78  to  0.S5  mm.,  height 
width  0.35  to  0.42  mm.     Height  t 
I  to  18.     Furca  straight.  alx)ut  sf\. 
wide,  its  terminal  seta  rudiment ar\ 
claws  doubly  pectinate  with  unusu. 
seta  about  twice  width  of   furca  imn.   M.i.trrminal 
claw.     Second  leg  five-scgmcntctl.     Swampy  poodt; 
May.     Colorado. 


Fig.  1J97. 
Candona  paralMa.     (a)  Side  view.  X  sik;  (fc)  Sccoad  liK 
(c)  Furca;  (d)  Terminal  daws  of  furca. 


108(109)     Furca  plainly  curved  (Fig.  1301  /») 

109  (108)     Furcanotplainly  curved,  approximately  .straight  (Fig.  i^gSJi 


no 


(in)     Both  claws  of  furca  plainly  S-shaped  (Fig.  i2()S  J). 

Candona  si^nwidcs  Sharpc  1S07. 


Length  of 
I  .(\\  mm.  Si  ■ 
Furca  long  a; 
times  as  w 
Dorsiil  s*'t.i  .1 
of  furca  froni 
male  not  ki 
shores;  .Ma\ 


Catulona    iic»^ 
mnlc.  X  :s 


826 


FRESH-WATER   BIOLOGY 


III  (no) 


Both  claws  of  furca  not  S-shaped  —  gently  curved  (Fig.  1299  a). 

Candona  recticauda  Sharpe  1897. 
Male  1. 1 8  mm.  long,  0.70 
mm.  wide.  Shell  curved  with 
scattered  papillar  elevations. 
The  spermatogonia  show 
through  as  four  bands.  Sec- 
ond leg  six-segmented.  Furca 
straight,  about  thirteen  times 
as  long  as  wide,  with  a  dorsal 
sinus  base  of  furca  very  broad. 
Right  maxillary  palp  of  male 
club-shaped  (Fig.  1300(f).  Bot- 
tom of  ponds;  February.  Illi- 
nois. 

Fig. 1299. 
Candana  recticauda.  (a)  Furca; 
(b)  Secondleg;  (c)  End  of  second 
antenna;  (d)  Right  maxillary 
palp  of  male;  (e)  Left  maxillary 
palp  of  male. 


112(113)     Second  leg  six-segmented 114 

113(112)     Second  leg  less  than  six-segmented 116 


114(115) 


Shell  with  fine  longitudinal  striations  when  in  glycerin.  Max- 
illary palps  of  male  enormously  thickened,  their  fingers  fully 
as  thick  as  the  stem  (Fig.  1300  d). 

Candona  fabaef or  mis  Fischer  1854. 

Length  i.oo  to  1.26  mm.,  height 
0.47  to  o-somm.,  width  0.49  to  0.5 1 
mm.  Shell  yellowish  transparent, 
strongly  compressed,  the  left  valve 
overlapping  the  right  at  both  ex- 
tremities, and  also  with  dorsal 
flanges.  Furca  ten  times  as  long 
as  wide,  straight.  Abundant  in 
small  pools  in  March,  April,  and 
September.     Georgia,  Illinois. 

Fig.  1300. 
Candona  fabaeformis.    (a)  Side  view  of 
male,  X  30;   {b)  Side  view  of  female, 
X  30;    (c)    Furca;    (d)   Right  max- 
illary palp  of  male,  X  75- 


115  (114)     Shell  without  fine  longitudinal  striations.     Maxillary  palp  of  male 
with  finger  about  one-half  as  thick  as  stem  (Fig.  1301  c). 

Candona  acuminata  Fischer  1854. 

Length  1.2c  to  1.50  mm.,  height  0.60  mm.,  width 
0.46  to  0.50  mm.  Posterior  extremity  of  shell  sharply 
pointed.  Dorsally  about  as  Candona  fabaeformis,  but 
less  compressed,  and  dorsal  flanges  weaker.  Furca 
eight  times  as  long  as  wide,  decidedly  curved,  and 
much  the  broader  at  its  base.  River  shores  and 
ponds  with  rich  vegetation;  April,  May,  and  Septem- 
ber.   Texas. 

Fig.  1301. 

Candona  acuminata,     (a)  Left  shell  of  female,  X  20; 

(6)  Furca;  (c)  Left  maxillary  palp  of  male. 


THE   OSTRACODA 


Ii6  Shell  decidedly  arched  dors: 

(Fig.  1302  a).    .    .    . 


ly,  much 
Camlona 


llu-  highest  in  ' 
i\iniliiiii  ().  F.  M 


LcriKth  i.o.:;  to  i.^o  mm  .  hcJKht  0(0 
four  or  indistinctly  live  s«•^;^u•ntc.|      I 
long  as  avcra«t'  wi.lth.  dri  i. lolly  <ur-. 
mon.     Shallow,  tcmjiorary  (jonds  aiiM  n 
September.     Massachusetts. 


Candona  Candida. 


Fig.  hoj. 

(a)  Side  view  of  (enulr 

(couUc,  X  7$. 


8,7 


^a„»  .4 


REFERENCES   ON   NORTH   AMKRICAX    1  KKsH  \\  \ri.k 
OSTRACODA 

Brady  and  Norman.     1889.    A  Monograph  ol  the  Marine  and  Frt-sh-Wairr 

Ostracoda  of  the  North  Atlantic  and  North-western  FurojK-.     Sci.  Trans. 

Royal  Dublin  Soc,  Ser.  2,  4  :  63-270. 
Herrick,  C.  L.     1887.     Contribution  to  the  Fauna  of  the  Culf  of  Mexico 

and  the  South.     Memoirs  of  Denison  Sci.  Ass'n,  i  :  1-56. 
Marshall,    W.     S.     1903.     Entocythcrc   camhur'm.     \    rarasilic    rktr.icNl. 

Trans.  Wis.  Acad,  of  Sci.  Arts  and  Letters,  14  : 1 17-144. 
MtJLLER,  G.  W.     1894.     Die  Ostracoden  des  Golfes  von  N\-aiK-l.     M..n..Ki    -'• 

Fauna  und  Flora  des  Golfes  von  Neapel.     Berlin. 
1900.     Deutschlands  Siisswasser-Ostracoden.      Zoologica.  Hc-fl  30,  1 1 
Sharps,  R.  W.     1897.     Contributions  to  a  Knowledge  of  the  North  A- 

can   Fresh-Water  Ostracoda  included  in    the   Families  Cylhcridac  and 

Cyprididae.     Bull.  111.  State  Lab.  of  Nat.  Hist.,  4: 414-484. 
1903.     Report  of  the  Fresh- Water  Ostracoda  of  the  United  Slates  National 

Museum,   including  a  Revision  of  the  Subfamilies  and   (k-nera   of    the 

Family  Cyprididae.     Proc.  U.  S.  Nat.  Mus..  j6:  960-1 001. 
1908.     A  Further  Report  on  the  Ostracoda  of  the  United  States  National 

Museum.     Proc.  U.  S.  Nat.  :Mus.,  35  : 399-430- 
1910.     On  some  Ostracoda,  mostly  new,  in  the  Collection  of  the  Unitol 

States  National  Museum.     Proc.  of  the  U.  S.  Nat.  Mu.s..  3-^:  v<5-U«- 
Turner,  C.  H.     1893.     Additional  Notes  on  the  Cladocera  and  Ostracoda  of 

Cincinnati,  Ohio.     Bull.  Sci.  Lab.  Denison  Univ..  S.  pi.  i  :  1-18. 

1894.  Notes  on  American  Ostracoda,  with  Descriptions  of  nr-.v  <— — ^ 
Bull.  Sci.  Lab.  Denison  Univ.,  8,  pt.  2,  13-26. 

1895.  Fresh-Water  Ostracoda  of  the  United  States.     Gi-ol.  and  Nat.  Hi>l. 
Survey  of  Minn.,  Zool.  Ser.,  2:  277-337- 

Vavra,W.     1891.     Monographic  Ostracoden  Hohmens.     Arehiv.  der  n.ilun%-. 
Landesforschung  von  Bohmen,  Bd.  \T1I.  no.  3. 


CHAPTER  XXV 
HIGHER    CRUSTACEANS    (MALACOSTRACA) 

By  a.   E.   ORTMANN 

Curator  of  Invertebrate  Zoology,  Carnegie  Museum,  Pittsburgh. 

To  the  higher  Crustaceans  (subclass  Malacostraca)  belong  such 
forms  as  the  sow-bugs,  scuds,  shrimps,  prawns,  crayfishes  or  craw- 
fishes, and  crabs.  These  popular  names  are  not  sharply  defined,  but 
it  appears  convenient  to  restrict  the  name  sow-bugs  to  the  Isopods, 
that  of  the  scuds  to  the  Amphipods.  For  the  Mysidacea,  the  term 
opossum-shrimps  has  been  introduced,  while  the  names  shrimps  and 
prawns  belong  to  certain  Decapods,  and  are  ahnost  synonyms:  the 
former  is  now  used  chiefly  for  the  smaller  forms,  the  latter  for 
the  larger  ones.  Crayfishes  and  Crawfishes  are  the  Decapods  of  the 
genera  Cambarus  and  Potamohius.  Often  for  these  also  the  name 
crabs  is  used,  but  this  is  a  misnomer,  and  it  should  be  restricted  to 
marine  forms  of  the  type  of  the  common  edible  blue  crab. 

The  great  majority  of  the  Malacostraca  belong  to  the  sea, 
occurring  in  all  regions,  near  the  shore  as  well  as  on  the  bottom 
of  the  deep  sea,  and  floating  and  swimming  on  the  surface.  But  a 
considerable  number  have  entered  the  fresh  water,  and  are  found 
in  rivers,  creeks,  ponds,  lakes,  etc.  A  few  forms  are  known, 
which  live  parasitic  upon  other  aquatic  creatures. 

They  are  omnivorous,  feeding  on  vegetable  and  animal  matter, 
both  Hving  and  dead,  but  dead  and  decaying  matter  is  preferred 
by  most  of  them.  Asellus  (of  the  Isopods)  distinctly  prefers  de- 
caying vegetable  matter,  while  Palaemonias  (of  the  Decapods) 
seems  to  be  speciaHzed  as  a  mud-eater:  at  any  rate,  the  pecuHar 
hair-tufts  on  the  claws  probably  serve  the  same  purpose  as  in  the 
alKed  tropical  forms,  where  it  has  been  observed  that  they  are 
used  in  gathering  mud,  like  a  small  brush. 

Generally,  the  fresh-water  Malacostraca  are  not  very  conspicu- 
ous, some  because  they  are  rather  small  and  easily  escape  detec- 
tion, while  others,  which  are  larger,  keep  in  hiding,  under  stones 

828 


fflGHER   CRUSTACEANS    (MALyoMK.U  A  g,^ 

and  logs,  in  holes,  or  among  vegetation.     But  they  arc  present 
practically  everywhere,  and  in  most  budies  of  water,  even 
ones,  one  or  several  forms  may  be  expected  to  occur.     C". 
forms  (burrowing  crayfishes)  do  not  Ii\f  iu  opcFi  water,  but  burrow 
in  the  ground,  going  down  to  the  groimd-waicT;    their  presence  i^ 
indicated  by  piles  of  mud,  brought  out  of  the  holes. 

Fresh-water  Malacostraca  are  found,  with  exception  of  the  An- 
tarctic regions,  practically  all  over  the  world,  including  the  Arctic. 
but  naturally  are  most  abundant  in  the  tropics.  A  numU-r  of 
groups  are  distinctly  characteristic  of  temperate  climates,  and  al 
least  one  group  (genus  Cambarus,  crayfish)  has  reached  its  hiKhesl 
development  in  North  America.  Here  Malacostraca  an-  found 
ever3rwhere,  but  chiefly  in  the  interior  basin  with  its  >;rcat  and 
diversified  river  systems.  They  become  rather  scarce  on  the  west- 
ern plains  and  in  the  arid  regions,  but  are  not  entirely  nW 
there.  The  various  forms  are  adapted  to  dilTerent  surroumi...,.  . 
some  prefer  large  rivers,  others  creeks  or  jx)nds.  or  small  |)ools. 
springs,  and  even  subterranean  waters. 

They  belong  to  very  difTerent  groups  of  the  subclas>  .Ma! 
traca.     The  latter  has  been  divided,  in  the  more  recent  sy>; 
into  ten  orders,  and  of  these  four  possess  representatives  in  our 
fresh  waters:    Isopoda,   Amphipoda.   Mysidacea.   and    Deca: 
These  differ  very  much  in  their  outer  features,  in  general  -     . 
of  body,  size,  color,  and  details  of  mori)hology,  so  that  it  is  hard 
to  give  a  short  general  account  of  their  characters. 

The  body  may  be  only  a  few  millimeters  long.  u|)  to  one  or  two 
centimeters  (Isopods,  Amphipods),  or  it  ma\-  be  somewhat  longer 
(Mysidacea  and  some  Decapods),  while  in  otlur  cases  (prawns  and 
crayfishes  among  the  Decapods)  it  may  reach  the  considerable 
length  of  ten  centimeters  and  over.  In  tlu-  smaller  forms,  ihe 
color  is  generally  inconspicuous,  whitish  or  gra>ish.  often  more  or 
less  transparent.  The  larger  forms  have  more  distinct  color*. 
which  may  become  quite  brilliant  in  certain  parts  of  the  IkkIv:  the 
large  claws  of  the  genus  PaJjcmon  (prawns)  are.  in  the  male  sex. 
often  red,  blue  or  purple.     The  crayfishes  are.  in  genenU.  of  j^tx-n- 

ish  or  brownish  olive  tints,  but  as  a  nde  adult  mak^  an '- 

vividly  colored,  and  in  some  species  the  adult  male  assumc-s  a 


830 


FRESH-WATER   BIOLOGY 


entirely  different  from  the  greenish  female  and  young:  lighter  or 
darker  red.  At  least  two  species  are  remarkable  for  their  striking 
color  in  both  sexes:  one  is  red,  the  other  is  beautifully  blue. 

The  morphological  characters  of  the  Malacostraca  are  the  follow- 
ing: 


ant 


perp 

Fig.  1303.    Diagram  of  a  higher  Crustacean.     (After  Caiman.) 

The  body  is  enclosed  in  a  comparatively  hard  shell,  which  is 
articulated,  forming  a  number  of  successive  segments  or  somites, 
which  have  a  very  constant  number.  Each  somite  may  be  com- 
pared to  a  ring,  which,  however,  is  not  completely  circular,  but  the 
upper  part,  called  tergum  or  tergite,  is  convex,  while  the  lower, 
sternum  or  sternite,  is  rather  fiat.  The  two  unite  on  each  side, 
the  tergite  projecting  over  the  sternite,  and  this  projecting  part  is 
called  the  pleuron.  All  these  parts  (as  well  as  the  appendages) 
consist  of  a  hornlike  substance,  called  chitin,  very  often  reinforced 
by  a  considerable  amount  of  calcareous  matter. 

In  the  anterior  part  of  the  body  we  have  a  headpiece,  to  which  are 
added  several  more  or  less  obscure  somites  that  are  chiefly  indi- 
cated by  their  appendages.  As  the  foremost  appendage  we  may 
regard  the  eyes  (e  in  Fig.  1303).  These,  however,  may  not  be  true 
appendages.  Then  follow  two  pairs  of  feelers,  called  antennulae 
(antl)  and  antennae  (ant);  one  pair  of  mandibles  (mand),  and  two 
pairs  (first  and  second)  of  maxillae  (max) . 

Behind  these  parts  the  segmented  body  begins,  including  fifteen 
somites,  which  all  (barring  reductions)  bear  appendages,  with  the 
exception  of  the  last,  the  telson  (/).     According  to  the  appendages, 


HIGHER   CRUSTACEANS   (MALACOsI  KACAi  831 

the  body  is  distinctly  divided  into  two  parts:  the  iinlerior,  ihonuc 
or  trunk  {th),  comprising  the  first  eight  somites;  the  iKJstcn  t. 
abdomen  {ahd),  with  the  six  following  (to  which  the  teiM>n  is  ad.l.  1  . 

The  appendages  of  the  thorax  are  called  thoracic  limbs.  Some 
or  all  of  the  first  three  of  them  are  in  many  cases  s|Hiiali/.« .' 
maxilHpeds  (maxp),  and  in  this  case  the  following  live  are  i.:  ^ 
peraeopods  (perp).  The  abdominal  appendages  are  ailled  plct>|xxls 
(pip),  but  those  of  the  last  (sixth)  pair  are  often  difTerentialetl  m  a 
peculiar  way,  so  as  to  form  with  the  telson  a  taudal  fan.  and  in 
this  case  the  name  uropods  (urp)  is  used  for  them. 

The  detail-structure  of  the  appendages  of  the  dilTerent  re;,aons 
of  the  body  is  very  different.  The  eyes  (only  doubtfully  n  gardtd 
as  appendages)  may  be  entirely  sessile,  or  may  be  elevated  ujxin 
short,  subcyHndrical,  more  or  less  movable  eye-stalks.  The  an- 
tennulae  have  an  articulated  base,  with  one  or  two  terminal,  articu- 
lated branches  (flagella).  The  antennae  have  an  articulated  basal 
part,  with  one  terminal,  articulated  flagellum,  and  often  the  Ixisal 
part  has  a  lateral  scalelike  process:  the  antennal  scale  t)r  scapho- 
cerite. 

The  mandible  consists  of  a  more  or  less  solid  part,  to  which  an 
articulated  palpus  may  be  attached.  The  maxillae  are  of  various 
shapes,  and  are  probably  to  be  regarded  as  mcxlifietl  antcri-r 
thoracic  appendages.  They  consist  of  an  inner  and  an  nuirr 
branch  (endopodite  and  exopodite),  which,  however,  are  often 
augmented  by  certain  parts  belonging  originall)-  to  the  gill  ap|>a- 
ratus. 

The  most  marked  difference  is  between  the  thoracic  and  the  ab- 
dominal appendages.  The  fonner  consist  originally  of  a  larger, 
seven-jointed  inner  branch  (endopodite),  and  a  smaller,  articu- 
lated outer  branch  (exopodite),  but  the  latter  may  be  absent. 
The  seven  joints  of  the  endopodite  are  rather  constant.  allhouKh 
some  of  them  may  become  united,  or  others  may  be  sulxlividetl. 
They  have  received  separate  names,  which  are,  from  the  proximal 
to  the  distal  end:  coxa,  basis,  ischium,  mems.  caq^us.  proixxlu*. 
dactylus  (or  coxopodite,  basipodite.  etc.).  In  certam  thoracic 
limbs,  the  last  two  joints  (propodus  and  dactylus)  assume  ■  '-  m- 
liar  position,  forming  a  chela  (j^inchers,  claws). 


832  FRESH-WATER   BIOLOGY 

The  typical  pleopods  consist  of  a  simple  basal  part,  with  two  sub- 
equal,  terminal,  articulated  branches.  But  in  many  cases  differen- 
tiations and  reductions  are  observed,  the  most  important  being 
that  of  the  uropods,  referred  to  above,  and  the  transformation  of 
certain  pleopods  into  copulatory  organs  in  the  male. 

In  certain  forms  (Mysidacea  and  Decapoda)  the  dorsal  shell  of 
the  most  anterior  part  of  the  body  (head)  is  produced  backward, 
and  covers  more  or  less  the  thoracic  somites  in  the  shape  of  a  shield, 
curved  down  over  the  sides,  which  is  called  the  cephalo thorax  or 
carapace  (car).  Very  often  the  carapace  has  a  median  anterior 
projection,  called  the  rostrum  (r). 

The  branchial  apparatus  of  the  Isopods  is  formed  by  the  pleo- 
pods. In  all  other  groups  special  appendages  (gills)  of  the  thoracic 
somites  assume  this  function;  they  may  be  attached  to  the  sides 
of  the  thorax,  or  to  the  basal  parts  of  the  thoracic  limbs. 

The  genital  openings  of  the  male  are  always  originally  on  the 
coxopodite  of  the  eighth  trunk-leg  (or  fifth  peraeopod),  those  of  the 
female  on  the  sixth  (or  third  peraeopod),  but  in  certain  cases  either 
one  of  these  may  shift  to  the  sternite. 

All  Malacostraca  of  the  fresh  water  have  separate  sexes,  and 
very  often  the  males  are  distinguished  by  secondary  sexual  char- 
acters (size,  color,  development  of  claws).  Copulation,  or  rather 
conjugation,  seems  to  take  place  in  all  of  them,  although  this  has 
been  observed  in  detail  only  in  very  few  forms:  it  is  best  known  m  I 
the  crayfishes. 

Propagation  is  by  eggs.  In  the  smaller  forms  (Isopoda,  Amphi- 
poda,  Mysidacea),  very  Httle  is  known  about  propagation  and 
development,  and  with  regard  to  the  North  American  forms  of 
these  groups  investigations  are  altogether  lacking.  But  from  what 
is  known  of  exotic,  chiefly  European,  forms  it  is  probable  that  in  all 
the  eggs  are  carried  by  the  female  for  a  certain  period,  before  the 
young  are  set  free.  In  the  Isopods,  the  female  develops  during 
the  breeding  season  pecuHar  lamellae  at  the  base  of  some  thoracic 
legs  (four  pairs  in  Asellus),  which  serve  to  cover  and  to  hold  the  eggs. 
In  the  Amphipods  and  Mysidacea  similar,  but  greatly  variable,  de- 
vices are  present.     In  the  Decapods,  no  such  apparatus  is  known, 


HIGHER   CRUSTACEANS  (M ALACOSTRACA)  833 

but  here  the  eggs  are  attached  to  the-  pk-oixxls  and  arc  carried 
under  the  abdomen  of  the  mother  till  the  youn^r  ^ri-  ready  to  hate  h. 

Within  these  brood-pouches  the  embryonal  develupmenl  lakc-s 
place.  After  the  young  have  reached  a  more  ur  less  advanced 
stage,  they  leave  the  egg,  but  alwa>'s  remain  a  certain  time  in  ihr 
brood-room  of  the  mother.  In  the  Isoi)o(ls  iAscllus)  the  ynuu^ 
leave  the  egg  at  a  rather  early  stage,  and  they  have  yet  to  undergo 
considerable  changes;  in  the  other  groups  the  lar\-a  hatches  in  a  more 
advanced  stage,  and  the  subsequent  changes  are  slight.  In  none 
of  our  fresh-water  crustaceans  are  free  swimming  lar\'ae  known,  but 
these  might  be  present  in  the  families  Atyidae  and  Falaemonidae. 
in  which  such  have  been  observed  in  their  allied  marine  forms. 

Of  the  life  history  of  the  Isopods,  Ampliipods,  Mysidacea.  and 
most  of  the  Decapods,  practically  nothing  is  known.  However,  in 
the  Decapod-genus  Camharus  (crayfishes)  more  complete  informa- 
tion is  at  hand. 

After  hatching,  the  young  crayfishes  remain  for  a  short  time 
with  the  mother,  but  soon  leave  her,  and  grow  in  the  beginning  at 
a  rather  rapid  rate,  each  increase  in  size  being  connected  with  a 
moulting  of  the  shell.  Later,  they  grow  less  rapidly,  and,  after  the 
first  summer,  we  may  distinguish,  in  general,  a  spring  and  an 
autumn  moult.  The  total  length  of  Hfe  seems  to  be  .sevend  years: 
four,  five,  or  even  more.  Sexual  maturity  may  be  reache<i  within 
the  first  year,  at  least  in  some  species.  Males  and  females  attain 
about  the  same  size,  but  in  most  species  (except  the  burrowing) 
the  male  possesses  much  stronger  chelae  than  the  lemale. 

A  very  pecuhar  difference  is  found  among  the  males,  which  at 
first  was  believed  to  be  dimorphism,  but  has  now  been  recognized 
as  alternating  conditions  in  the  Hfe  of  the  same  individual.  Malts 
of  the  first  form  have  been  distinguished  from  males  of  the  sc-cund 
form;  the  former  is  the  fully  developed  and  se.xually  potent  form, 
while  the  latter  is  an  impotent  form.  Generally  speaking  the  first 
form  is  assumed  by  the  male  in  autumn,  and  lasts  through  the 
winter  (copulating  season),  while  the  other  is  assumetl  in  >pring, 
and  lasts  through  the  summer.  Young  male>.  in  their  first  summer, 
are  always  of  the  second  fonn.  Tlie  ditTennce  between  thcM-  two 
forms  is  seen  in  the  sexual  organs:   in  the  .uales  of  the  second  form 


834  FRESH-WATER  BIOLOGY 

these  organs  are  softer,  the  horny  tips  are  undeveloped,  and  the 
copulatory  hooks  on  the  ischiopodites  of  the  peraeopods  are  small. 

According  to  the  general  rule,  that  the  males  assume  the  first 
form  in  autumn,  the  copulating  season  falls  in  the  autumn,  and 
copulation  may  be  repeated  in  the  winter  months.  The  male 
seizes  the  female  and  holds  it,  stemites  against  sternites,  chiefly 
by  the  aid  of  the  hooks  of  the  ischiopodites  of  the  peraeopods. 
The  sperm  is  discharged  and  stored  in  the  female's  annulus  ven- 
tralis,  a  pocket  on  the  thoracic  sternum,  which  thus  serves  as 
receptaculum  seminis.  Oviposition  takes  place  later,  generally  in 
spring. 

This  seasonal  cycle,  as  described,  is  not  observed  in  all  species, 
but  there  are  some,  in  which  the  alternation  of  the  two  forms  of 
the  male  is  irregular  and  not  connected  with  the  seasons,  and 
where  copulation  and  oviposition  are  also  irregular.  It  has  been 
found  that  regularity  of  the  annual  cycle  is  connected  with  a  habi- 
tat in  water  which  is  subject  to  regular  and  considerable  seasonal 
changes  of  temperature  (species  living  in  rivers  and  ponds),  while 
irregularity  of  the  life-cycle  is  found  among  those  which  live  pref- 
erably in  water  with  slight  temperature  changes  and  that  at  the 
same  time  is  rather  cool  (species  of  mountain  streams  and  of  cool 
springs  or  groundwater). 

The  fresh-water  Malacostraca  depend  entirely  upon  the  presence 
of  water,  and  cannot  leave  the  water  as  a  rule.  This  holds  good 
for  the  Isopoda,  Amphipoda,  and  Mysidacea,  and  also  for  the 
Atyidae  and  Palaemonidae  among  the  Decapoda.  In  the  water,  the 
Isopods  (except  the  parasitic  forms)  crawl  around  on  the  bottom, 
under  stones,  or  climb  among  water  weeds,  but  do  not  move  by 
swimming.  The  Amphipods  are  very  lively  in  their  movements, 
which  consist  chiefly  of  swimming,  often  lying  upon  the  side.  The 
swimming  is  often  done  in  jerks,  by  curving  and  stretching  the 
compressed  body.  They  move  also  by  climbing  among  water  weeds, 
but  hardly  ever  by  crawling.  All  Mysidacea  are  distinctly  swim- 
ming forms,  and  so  are  the  Atyidae  and  Palaemonidae  among  the 
Decapods,  while  the  movements  of  the  crayfishes  are  of  various 
kinds,  but  fall  under  two  main  heads:  crawling  and  swimming. 
The  first  is  the  general  mode  of  locomotion.     It  is  not  very  rapid 


HIGHER   CRUSTACEANS   (MALACOSTRACA)  835 

and  may  take  place  in  all  three  directions:  forward,  backward, 
and  sideward.  More  rarely  the  crayfishes  move  by  swimming,  and 
chiefly  so  when  alarmed  and  trying  to  escape;  this  swimming  is 
always  backward,  and  is  effected  by  quickly  repeated  strokes  of 
the  abdomen.  This  kind  of  locomotion,  however,  is  kept  up  only 
for  short  distances. 

With  regard  to  the  habitat,  not  much  detail  is  known  in  the  iso- 
pods  and  amphipods.  They  seem  to  prefer  more  quiet  bodies  of 
water,  small  streams  and  springs,  to  the  larger  rivers.  Some  of 
them  are  not  very  particular  as  to  their  habitat,  and  consequently 
possess  a  very  wide  geographical  distribution,  while  others  are  very 
restricted,  possibly  on  account  of  special  habitat  preferences.  The 
only  Mysidacean  found  in  North  America  (Mysis  relicta)  inhabits 
the  Great  Lakes  to  a  considerable  depth  (as  do  two  species  of  the 
Amphipod-genus  Pontoporeia).  The  genus  Palaemon  oi  the  Deca- 
pods is  known  only  from  our  largest  rivers  (Mississippi  and  Ohio). 

In  the  genus  Camharus,  very  complex  conditions  are  observed 
and  the  different  species  differ  considerably  in  their  ecology.  Al- 
though they  all  need  water  for  their  existence,  it  is  a  general  rule 
that  all  crayfishes  are  able  to  leave  the  water  temporarily,  and 
some  may  stay  out  of  the  water  for  a  considerable  time,  and  do  so 
habitually.  Of  course,  in  order  to  moisten  their  gills,  they  always 
have  to  return  to  the  water. 

In  the  water,  the  crayfishes  try  to  hide,  either  under  rocks,  logs, 
water  weeds,  etc.,  or  they  construct  artificial  hiding  places  (holes 
and  burrows).  The  latter  tendency  is,  as  will  be  seen,  especially 
developed  in  certain  ecological  groups.  In  connection  with  this 
tendency  to  hide  probably  is  the  fact  that  the  crayfishes  seem  to  be 
more  or  less  nocturnal. 

With  regard  to  their  ecological  preferences,  different  types  have 
been  distinguished  in  the  genus  Camharus.  These  are  the  fol- 
lowing : 

I.  Species  living  in  quiet  waters:  slowly  running,  large  rivers, 
ponds,  lakes.  To  this  group  belongs  chiefly  the  subgenus  Cam- 
harus, and  its  distribution  over  the  coastal  plains  and  the  interior 
basin  expresses  this  ecological  habit,  since  here  such  conditions  are 
pre-eminently  found.     But  certain  species  of  the  subgenus  Faxonius 


836  FRESH-WATER  BIOLOGY 

also  prefer  these  surroundings.     These  species  are  content  with 
hiding  under  other  objects,  and  make  holes  only  incidentally. 

2.  Species  living  preferably  in  water  with  a  rather  strong  current. 

{a)  Species  of  the  larger  rivers.  The  subgenus  Faxonius  is  typi- 
cal for  this  habitat,  and  the  location  of  its  center  of  distribution  in 
the  central  basin  with  its  large  rivers  expresses  this. 

{h)  Species  Hving  in  small  streams  of  the  uplands.  The  repre- 
sentatives of  this  habitat  belong  chiefly  to  the  subgenus  Bartonius, 
and  its  distribution  over  the  Appalachian  Mountains  and  the  Alle- 
gheny and  Cumberland  Plateau  clearly  indicates  this. 

Of  course,  there  are  all  transitions  between  habitats  (a)  and  (b), 
as  many  of  the  river  species  go  well  up  into  the  head-waters,  and 
vice  versa.  Yet  the  original  differentiation  in  the  habitat  of  the 
subgenera  Faxonius  and  Bartonius  is  very  evident.  All  these  spe- 
cies in  running  water  are  good  burrowers,  and  they  generally  ex- 
cavate holes  under  protecting  stones,  etc.  In  some  of  the  species 
from  the  mountain  streams  this  faculty  of  burrowing  is  rather  highly 
developed,  and  leads  us  to  the  next  ecological  type. 

3.  Burrowmg  species  (''chimney  builders ") .  These  species  have 
retired  from  the  open  water  into  the  ground  water,  and  one  may 
understand  the  origin  of  this  peculiar  habit  by  imagining  that 
forms  in  the  small  upland  streams,  with  well-developed  burrowing 
faculties,  were  forced,  in  periods  of  draught,  w^hen  the  streams  in- 
habited by  them  began  to  dry  up,  to  dig  down  in  the  bed  into  the 
gravel  and  mud,  to  reach  the  water.  Or  one  may  imagine,  that 
they  ascended  in  the  streams  up  to  the  sources,  and  went  under 
ground,  where  the  water  appears  in  the  shape  of  springs.  In  a 
number  of  species  this  tendency  has  been  carried  to  an  extreme,  and 
it  is  known  that  these  Hve  habitually  under  the  surface  of  the 
earth,  in  the  ground-water,  where  they  excavate  more  or  less  com- 
plex systems  of  holes,  burrows,  or  tunnels,  which  open  upon  the 
surface  in  one  or  more  openings.  These  burrows  are  built  by  the 
crayfish,  by  using  the  chelae  in  digging  (hence  the  similarity  of  the 
chelae  in  both  sexes),  and  the  material  removed,  mud,  clay,  etc., 
is  carried  to  the  surface,  where  it  is  piled  up  around  the  mouth  of 
the  burrow  in  irregular  or  regular  piles,  generally  known  by  the 
name  of  ''mud  chimneys."     These  burrows  and  chiefly  the  mud 


HIGHER   CRUSTACEANS   (MALACOSTRACA)  837 

chimneys  have  attracted  much  attention,  and  the  idea  has  been 
advanced  that  the  chimneys  are  constructed  by  the  crayfish  for  a 
certain  definite  (useful)  purpose.  But  recent  investigations  seem  to 
point  to  the  conclusion  that  the  regular  shape  of  the  chimneys, 
when  present,  is  accidental,  and  the  mud  piles  are  nothing  but  the 
natural  product  of  the  burrowing,  disposed  of  in  the  most  con- 
venient way  (around  the  mouth  of  the  hole) .  The  burrows  them- 
selves are  rather  irregular,  more  or  less  complex,  and  consist  of 
simple  tunnels,  often  branching,  and  one  or  more  pockets,  or  widen- 
ings  of  the  tunnel.  They  go  down  into  the  ground  from  one  to 
several  feet,  but  always  deep  enough  as  to  contain  ground-water,  at 
least  at  the  bottom. 

Burrowing  species  are  found  chiefly  in  the  subgenus  Bartonius, 
and  form  a  very  well  defined  morphological  group,  and  it  is  just 
this  group  of  this  subgenus,  which  has  spread  out  from  the  original 
territory  (the  mountains),  and  has  descended  into  the  plains.  On 
the  western  and  southwestern  plains  is  found  another  group  of 
burrowers  which  belong  to  the  subgenus  Cambarus. 

Another  special  ecological  group  should  not  be  forgotten.  These 
are  the  cave  species.  With  the  exception  of  the  Mysidacea,  all 
our  fresh-water  Malacostraca  have  developed  certain  forms  which 
are  adapted  to  the  life  in  subterranean  waters,  and  live  in  caves, 
springs,  artesian  wells,  etc.  This  peculiar  habitat  has  affected 
their  structure  greatly,  and  the  most  important  and  interesting 
feature  is  the  loss  of  the  eyes.  Some  of  these  forms  are  entirely 
blind,  having  lost  the  visual  elements  of  the  eyes  (cornea  and  pig- 
ment), while  in  others  the  reduction  is  only  partial. 

Among  the  Isopods,  the  only  North  American  fresh-water  form, 
belonging  to  the  Cirolanidae,  is  a  blind  subterranean  form  (Giro- 
lanides  texensis,  Fig.  1304).  Of  the  Asellidae,  some  live  in  caves  and 
have  suffered  the  loss  of  the  eyes.  This  is  especially  true  of  the 
genus  Caecidotea,  the  species  of  which  have  been  found  in  caves  of 
Virginia,  Georgia,  Tennessee,  Kentucky,  Indiana,  Illinois,  and  in 
subterranean  waters  in  Texas.  Mancasellus,  which  possesses  eyes, 
has  often  been  found  in  caves  or  in  streams  issuing  from  caves ;  it  also 
lives  in  the  Great  Lakes. 


838  FRESH-WATER  BIOLOGY 

The  fresh- water  Amphipods  are  remarkable  for  the  development  of 
eyeless  cave  forms;  in  fact,  there  is  a  strong  tendency  among  them 
toward  underground  life.  Of  the  20  species  known,  10  or  11  seem 
to  be  inhabitants  of  caves,  wells,  or  springs.  Not  all  of  them  have 
the  eyes  reduced, but  the  species  of  the  genQYSiCrangonyx,Stygonectes , 
and  A  pocrangonyx  are  actually  bHnd,  and  there  is  a  bHnd  species 
in  each  of  the  genera  Eucrangonyx  and  Gammarus,  while  the  other 
species  of  these  two  genera  show  all  transitional  stages  from  well- 
developed  eyes  to  more  or  less  reduced  eyes.  The  correlation  be- 
tween subterranean  hfe  and  reduction  of  the  eyes  is  very  evident  in 
this  group. 

The  only  species  of  the  decapod-family  Atyidae  found  in  the 
United  States,  Palaemonias  ganteri  (Fig.  131 1),  is  a  bHnd  cave-form, 
and  it  was  discovered  only  recently  (1901)  in  the  waters  of  Mam- 
moth Cave  in  Kentucky.  This  form  has  eye-stalks,  but  the  visual 
elements  of  the  eye  are  gone.  This  is  an  extremely  interesting 
form  on  account  of  its  primitive  structure  as  well  as  its  geographical 
relations.  Most  of  the  members  of  this  family,  which  is  strictly  a 
fresh-water  group,  are  found  in  the  tropical  and  subtropical  regions 
of  both  hemispheres,  but  a  form  very  closely  alHed  to  the  American 
is  known  from  caves  in  Carniola,  Austria. 

In  the  family  Palaemonidae  is  included  Palaemonetes  antrorum, 
v/hich  was  discovered  in  an  artesian  well  in  Texas.  Also  this  species 
is  provided  with  eye-stalks,  but  the  eyes  themselves  are  obliterated. 

Within  the  genus  Camharus  of  the  family  Potamobiidae,  five 
cave  species  are  known.  They  are  all  blind,  but  the  eye-stalks  re- 
main. These  species  belong  to  different'  subgenera,  and  the  best 
known  is  the  famous  blind  crayfish  of  Mammoth  Cave  in  Ken- 
tucky {Camharus  pellucidus),  which  is  also  found  in  other  caves 
in  Kentucky  and  in  Indiana.  It  belongs  to  the  subgenus  Fax- 
onius,  and  represents  a  rather  ancient  t^-pe,  so  that  we  are  jus- 
tified in  regarding  it  as  an  old  immigrant  into  the  subterranean 
waters.  Three  species  (C.  hamulatus,  C.  setosus,  and  C.  ayersi) 
belong  to  the  subgenus  Bartonius,  representing  a  primitive  section 
of  it.  The  first  of  these  is  found  in  Nickajack  Cave  in  eastern 
Tennessee,  while  the  two  others  are  from  caves  in  the  Ozark  region 
in  Missouri.     These  three  species  also  must  be  old  immigrants  into 


HIGHER   CRUSTACEANS   (MALACOSTRACA)  839 

the  caves.  The  fifth  of  the  blind  species  is  C.  acherontis,  found  in 
caves  in  Florida.  This  belongs  to  the  subgenus  Cambarus,  and  is 
a  member  of  a  rather  highly  advanced  section  of  the  subgenus 
which  is  common  on  the  coastal  plain,  and  is  to  be  regarded  as  a 
more  recent  addition  to  the  cave  fauna. 

The  economic  value  of  the  fresh-water  Malacostraca  is  very 
different  in  the  different  groups.  While  the  isopods,  amphipods, 
and  Mysidacea  are  small,  the  decapods  are  larger,  but  also  of  these 
the  Atyidae  and  certain  Palaemonidae  attain  only  a  •  medium 
size.  These  groups  naturally  have  only  an  inferior  value  for  man, 
and  are  generally  overlooked  and  neglected.  Of  the  larger  forms, 
certain  species  of  Palaemon  (prawns,  also  called  shrimps) ,  and  the 
crayfishes  have  attracted  attention,  and  are  used  by  man,  pri- 
marily as  food.  Although  this  is  generally  the  case  in  Europe  and 
with  a  number  of  tropical  forms,  in  North  America  they  are  not 
very  popular,  and  are  only  occasionally  eaten;  yet  there  is  no 
doubt  that  Potaniohius  and  Cambarus  are  to  be  regarded  as  part 
of  the  natural  food  supply  of  this  country.  Other  uses,  for  instance 
as  fish  bait,  should  be  mentioned  incidentally. 

On  the  other  hand,  some  kind  of  damage  or  injury  done  to  man 
or  man's  work  has  also  been  noticed  in  so  far  as  certain  burrowing 
species  are  Hable  to  damage  dams  or  levees,  or  to  interfere  with 
farming  operations.  The  latter  species  are  also  reported  to  be 
injurious  to  crops,  chiefly  to  sprouting  plants. 

In  the  general  economy  of  nature,  all  the  higher  crustaceans 
perform  a  twofold  task.  First,  on  account  of  their  general  habit 
of  devouring  masses  of  decaying  vegetable  and  animal  matter, 
they  are  to  be  counted  among  the  scavengers,  and  second,  they 
themselves  serve  as  food  for  other  animals.  They  are  most  impor- 
tant as  fish-food,  and  even  the  larger  forms  are  eaten  by  the  larger 
fishes.  In  addition,  a  number  of  other  creatures  feed  upon  them 
(amphibians,  water  snakes,  birds,  and  certain  mammals). 

Collecting  Malacostraca  is  comparatively  easy:  the  chief  thing 
is  to  ascertain  their  whereabouts.  This  is  done  along  the  banks 
of  streams,  ponds,  or  lakes  by  turning  over  stones  or  logs,  by 
investigating  overhanging  banks,  or  examining  bunches  of  water 


840  FRESH-WATER  BIOLOGY 

weeds.  The  smaller  forms  may  be  taken  in  num.bers  by  transfer- 
ring water  weeds,  dead  leaves  or  other  rubbish  found  on  the  bottom 
into  tubs  or  dishes,  and  picking  out  the  specimens  with  a  pair  of 
pincers.  The  larger  forms  must  be  caught  by  hand,  or  with  a 
small  dip-net  (minnow  netting).  For  many  forms  the  seine  is  a 
very  successful  implement. 

In  collecting  the  burrowing  crayfishes  special  efforts  are  neces- 
sary. It  sometimes  happens  that  the  crayfish  can  be  induced  to 
come  to  the  mouth  of  its  hole  by  destroying  the  entrance.  But 
generally  -the  collector  should  not  hesitate  to  go  after  the  crayfish 
by  digging  it  out  Of  course,  a  spade  or  shovel  is  most  efficient, 
although  often  too  heavy  to  be  carried  along,  but  a  strong  garden- 
ers' trowel  is  very  convenient:  the  best  tool  is  a  so-called  pioneers' 
bayonet.  With  this  the  ground  should  be  loosened  around  the 
hole,  and  the  dirt  be  taken  out  with  the  hands,  care  being  taken 
always  to  follow  the  direction  of  the  hole.  By  digging  deep  enough 
(i  to  3  feet),  finally  the  pocket  will  be  reached,  in  which  the  cray- 
fish fives,  and  then  it  may  be  taken  out. 

Preservation  should  always  be  in  alcohol.  Formalin  should  be 
avoided,  except  in  cases  of  necessity.  Even  then  the  specimens 
should  never  be  left  in  the  formafin  for  a  long  time:  it  hardens 
them  too  much,  makes  all  the  appendages  brittle,  and  renders 
them  unfit  for  safe  handling.  The  best  results  are  obtained  by 
killing  them  in  weak  alcohol  and  transferring  them  into  stronger 
(2  to  3  changes),  until  they  finally  are  in  75  to  80  per  cent  alcohol: 
when  so  treated  all  appendages  remain  soft  and  flexible  as  in  fife. 

For  scientific  study  no  special  work  is  required  in  the  case  of 
the  larger  forms,  and  all  systematic  characters  may  be  seen  with 
the  bare  eyes  or  by  the  use  of  a  hand-lens.  In  the  smaller  forms 
it  is  necessary  to  study  the  appendages  separately.  They  should 
be  teased  out  under  a  dissecting  microscope  (using  two  pairs  of 
pincers)  and  mounted  in  the  usual  way  upon  microscopic  sHdes. 
Care  should  be  taken  that  the  appendages  are  taken  out  in  the 
proper  order,  so  that  they  do  not  become  mixed.  For  the  micro- 
scopic investigation  a  very  low  power  is  sufficient. 


HIGHER    CRUSTACEANS    (MALACOSTRACA)  841 

KEY    TO    NORTH    AMERICAN    FRESH-WATER    MALACOSTRACA 

1  (26)     Without  carapace,  but  first  thoracic  somite  coalesced  with  the  head. 

Eyes  (when  present)  sessile.     Thoracic  Hmbs  without  exopo- 
dites,  first  pair  modified  as  maxillipeds 2 

2  (11)     Body  depressed.     Pleopods  biramous,  uniform  in  shape,  with  excep- 

tion of  the  uropods  and  the  anterior  pairs  of  the  male. 

Order  Isopoda .    .     3 

3  (4)     Uropods  lateral,  forming  with  the  telson  a  tail-fan. 

P^amily  Cirolanidae. 
Only  one  genus  and  one  species  in  the  United  States. 

Cirolanides  texensis  Benedict  1896. 

This  is  a  blind  form,  which  has  been  found  in  an  arte- 
sian well  in  Texas.  All  other  representatives  of  this 
family  are  marine.  Many  of  them  are  ectoparasites  on 
fishes. 

Fig.  1304.    Cirolanides  texensis  Benedict.    X  4. 
(After  Richardson.) 

4  (3)     Uropods  inserted  at  the  posterior  end  of  the  telson,  not  forming  a  tail- 

fan 5 

5  (10)     Pleopods  covered  by  a  thin  opercular  plate,  the  modified  first  pair. 

Body  symmetrical.     Free  living.     Family  Asellidae  .    .     6 
This  is  a  typical  fresh- water  family. 

6  (7)     Mandibles  without  a  palp.     Last  six  pairs  of  thoracic  legs  with  dacty- 

lus  biunguiculate Mancaselliis  Harger. 

P'ive  species,  Hving  in  springs  and  caves,  some  in  rivers  and  lakes.     Eyes  present  in  all,  but 
small. 

7  (6)     Mandibles  with  a  three- jointed  palp.     Last  six  pairs  of  thoracic  legs 

with  dactylus  uniunguiculate 8 

8  (9)     Eyes  present.     Head  narrower  than  the  first  thoracic  segment.     Telson 

not  longer  than  broad Asellus  Geoffroy. 


Seven  species  in  rivers,  creeks,  ponds,  ditches, 
springs,  lakes.  Some  (as  Asellus  communis  Say) 
widely  distributed,  others  more  local.  Common  in 
ponds,  ditches,  etc.,  living  among  decaying  vegeta- 
ble matter. 


Fig.  1305.    Asellus  communis  Say.     X  2.     (After  Smith.) 


842 


FRESH-WATER  BIOLOGY 


9  (8)     Eyes  wanting.     Head  not  narrower  than  the  first  thoracic  segment. 

Telson  much  longer  than  broad.     .    .     Caecidotea  Packard. 
Four  species,  in  caves,  springs  issuing  from  caves,  and  artesian  wells. 

10  (5)     Pleopods  not  covered  by  an  opercular  plate.     Body  of  female  pecu- 

liarly deformed,  unsymmetrical,  that  of  the  male  more  or 
less  normal  and  symmetrical.  Parasitic  upon  higher  crus- 
taceans       Family  Bopyridae. 

Only  one  genus  in  the  North  American  fresh  waters. 

Probopyrus  Giard  and  Bonnier. 


Chiefly  a  marine  group;  the  only  genus 
known  from  the  fresh  water  of  North 
America,  enters  with  its  hosts,  being  found 
parasitic  upon  the  gills  and  in  the  gill  cav- 
ities of  Decapods  of  the  genera  Palacmo- 
netes  and  Palaemon.  Three  species  are 
known,  and  are  found  along  the  Atlantic 
coast  from  New  Hamsphire  to  Florida,  and 
in  the  Mississippi  River  in  Louisiana. 

Fig.  1306.  Probopyrus  pandalicola  Packard.  A, 
Male;  X  30.  B,  Female;  X  3.  (After  Richard- 
son.) 

II  (2)  Body  compressed.  Pleopods  divided  into  two  sets,  the  first  three 
pairs  with  multiarticulate  rami,  the  last  two  pairs  generally 
similar  to  the  uropods,  with  unsegmented  rami.  No  sexual 
modification  of  pleopods  in  the  male. 

Order  Amphipoda   .    .      12 

12(25)     Antennulae  with  secondary  flagellum.     Telson  clef t  or  entire.  .   .     13 

13  (14)  Fifth  peraeopods  shorter  than  the  preceding.  Second  maxillipeds 
smaller   than   the   first.     Uropods   with   two   nearly   equal 

rami Family  Lysianassidae. 

Only  one  fresh-water  genus  in  North  America.  .  Pontoporeia  Kroyer. 

This  family  is  chiefly  marine;  two  spe- 
cies live  in  rather  deep  wafer  of  the  lakes 
Superior  and  Michigan.  These  species 
are  closely  allied  to  certain  European 
fresh-water  forms,  and  probably  immi- 
grated into  the  lakes  at  the  close  of  the 
glacial  time. 

Fig.  1307.    Pontoporeia  hoyi  Smith.     X  4. 
(After  Smith.) 


14  (13)     Fifth  peraeopods  longer  than   the  preceding.      Second   maxillipeds 

generally  larger  than  the  first.     Uropods  with  two  unequal 
rami  or  without  rami.    .    .    .     Family  Gammaridae.    .     15 
A  family  represented  both  in  the  sea  and  in  fresh  water,  and  containing  a  great  number  of 
forms. 

15  (20)     Telson  cleft.     Uropods  biramous 16 

16  (19)     Inner  ramus  of  uropods  rudimentary.     Telson  cleft  not  more  than 

three-fourths  the  distance  to  the  base 17 


HIGHER  CRUSTACEANS    (MALACOSTRACA) 


843 


17  (18)     Outer  ramus  of  third  uropods  uniarticulate. 

Eucrangonyx  Stebbing. 
Five  species  are  known,  living  in  ponds,  springs,  and  wells.     Eyes  either  well  developed  or 
more  or  less  rudimentary.     One  species  is  blind. 

18  (17)     Outer  ramus  of  third  uropods  biarticulate Niphargus  Hay. 

A  single  species  in  caves  in  Tennessee,  with  the  eyes  wanting  or  very  rudimentary. 

19  (16)     Inner  ramus  of  uropods  not  rudimentary,  one-half  or  three-fourths 

as  long  as  the  ©uter.     Telson  cleft  to  the  base  or  nearly  so. 

Gammarus  Fabricius. 


Six  species,  two  of  them  {G.  fascialus  Say 
and  G.  litmiaeus' Smith),  rather  abundant  in 
rivers,  lakes,  and  smaller  bodies  of  water. 
The  other  species  are  more  local.  Eyes 
present,  but  one  species  is  a  blind  cave- 
form  of  Cuba. 


Fig.  1308.    Gammarus  litnnaeus  Smith.     X  2. 
(After  Smith.) 


20  (15)     Telson  entire 21 

21  (24)     Third  uropods  with  rami 22 

22  (23)     Third  uropods  uniramus.    Telson  short  and  broad.    Crangonyx  Bate. 
Three  species  are  known,  all  without  eyes,  living  in  caves  and  wells,  and  with  very  local 

distribution  (Kentucky,  Indiana,  Connecticut,  Wisconsin). 

23  (22)     Third  uropods  biramous,  inner  ramus  rudimentary,  outer  uniarticu- 

late.   Telson  long Stygonectes  Hay. 

Only  one  blind  species,  foimd  in  an  artesian  well  in  Texas. 

24  (21)     Third  uropods  without  rami.      . Apocrangonyx  Stebbing. 

One  species,  blind,  from  a  well  in  Illinois. 

25(12)  Antennulae  without  secondary  flagellum.  Telson  entire.  Third  uro- 
pods uniramous Family  Orchestiidae. 

This  family  is  abundantly  represented  in  the  sea. 

Only  one  genus  and  species  in  the  fresh  water  of  North  America. 

Hyalella  knickerhockeri  (Bate)  1862. 

This  species  possesses  a  very  wide 
range,  and  is  found  in  rivers,  ponds  and 
lakes  from  Maine  to  Florida  and  Cali- 
fornia (and  extends  southward  into  Cen- 
tral America).  This  genus  (Hyalella)  is 
remarkable  for  the  fact  that  all  its  spe- 
cies are  found  exclusively  in  fresh  water 
and  are  restricted  to  North  and  South 
America. 

Fig.  1309.    Hyalella  knickerhockeri  Bate. 
X  5-     (After  Smith.) 

26  (i)  With  a  carapace.  Eyes  upon  movable  eye-stalks.  Thoracic  limbs 
with  or  without  exopodites,  one,  two,  or  three  of  the  ante- 
rior pairs  modified  as  maxiUipeds 27 


844  FRESH-WATER   BIOLOGY 

27  (28)  Carapace  coalesced  dorsally  with  not  more  than  three  of  the  thoracic 
somites.  Thoracic  limbs  with  natatory  exopodites,  first 
pair  modified  as  maxillipeds.  Pleopods  more  or  less  re- 
duced and  greatly  different  in  the  two  sexes.  Eggs  carried 
in  a  brood  pouch  at  the  base  of  the  thoracic  legs. 

Order  Mysidacea. 

This  order  forms  part  of  the  old  division  Schizopoda.  The  Mysidacea  live  chiefly  in  salt 
water.  The  system  of  this  group  needs  a  thorough  revision,  and  no  satisfactory  division  into 
larger  groups  (families)  has  been  published. 

Only  species  in  North  America.   .    .    .    Mysis  relicta  Loven  1862. 


Fig.  1310.     Mysis  relicta  Loven.     X  2.     (After  Smith.) 

Very  few  Mysidacea  are  known  from  the  fresh  water,  and  the  present  is  identical  with  a 
species  living  in  lakes  in  northern  Europe  (Ireland,  Scandinavia,  Russia).  It  is  found,  in 
North  America,  under  similar  conditions,  in  the  lakes  Superior  and  Michigan,  down  to  a 
considerable  depth  (150  fathoms). 

In  Europe,  this  form  has  been  much  discussed,  and,  as  the  name  indicates,  was  supposed  to 
point  to  a  former  connection  between  the  sea  and  the  lakes  in  which  it  hves.  It  was  believed 
that  these  lakes  were  cut  off  from  the  sea  and  became  fresh-water  lakes,  but  retained  part  of  the 
original  marine  fauna  adapted  to  the  fresh-water  conditions:  these  animals  were  called  "marine 
rehcs,"  and  Mysis  relicta  was  taken  for  one  of  the  most  prominent  examples  of  this  kind.  How- 
ever, this  theory  has  been  greatly  shaken  recently,  and,  as  far  as  it  concerns  the  North  American 
stock  of  Mysis  relicta,  there  is  no  reason  to  assume  that  it  is  a  marine  relic,  but  we  are  to  regard 
it  as  an  immigrant  into  the  Great  Lakes  in  glacial  times  (as  Lysianassa). 


28  (27)  Carapace  coalesced  dorsally  with  all  of  the  thoracic  somites.  Tho- 
racic Umbs  rarely  with  exopodites,  the  first  three  pairs  modi- 
fied as  maxillipeds.  Pleopods  not  much  reduced,  and  not 
very  different  in  the  two  sexes,  except  the  anterior  ones. 
Eggs  carried  under  the  abdomen,  attached  to  the  pleopods. 

Order  Decapoda    .    .     29 


29  (34)  Body  and  rostrum  compresssed.  Pleura  of  second  abdominal 
somite  overlapping  those  in  front.  First  two  pairs  of  perae- 
opods  chelate.  Anterior  pleopods  of  the. male  not  trans- 
formed into  copulating  organs 30 


HIGHER   CRUSTACEANS   (MALACOSTRACA) 


845 


30  (31)     Chelae   of  peraeopods  weak,  subequal,  fingers  with  terminal  hair- 
tufts Family  Atyldae. 

Only  species  in  North  America.    .    .     Palaemonias  ganleri  Hay  1903. 

A  typical  and  char- 
— '  ucteristic  fresh-water 
^roup,  abundant  in  the 
tropics,  but  certain 
forms  are  found  in  tem- 
pera te  regions,  and 
their  distribution  is 
quite  pecuHar,  they 
being  found  at  rather 
isolated  localities,  re- 
mote from  each  other. 
This  discontinuity  is  a 
mark  of  antiquity  of 
the  c^roup.  One  of 
these  isolated  forms  is 
founu  in  North  Amer- 
ica, Palaemonias  ganleri 
The  nearest  place  where  related 


Palaemonias  ganleri  Hay. 


(After  Hay.) 


Hay,  and  is  blind,  Hving  in  Mammoth  Cave  in  Kentucky 
forms  are  found  is  in  the  West  Indies. 


31  (30)  Chelae  of  peraeopods  inequal,  the  second  pair  larger,  often  much 
larger,  than  the  first,  and  very  strong.  Fingers  without 
terminal  hair- tufts.    .    .    .    Family  Palaemonidae   .    .     32 

A  family  abundant  in  the  sea,  but  also  of  great  importance  in  the  fresh  water.     All  transi- 
tional stages  between  life  in  the  sea  and  in  fresh  water  are  found  here. 


32  {T)^)  Mandible  without  palpus.  Second  pair  of  peraeopods  only  slightly 
larger  than  the  first,  both  of  them  rather  weak.  Size  of 
body  medium Palaemonetes  Heller. 

Contains  a  number  of  species 
which  Uve  in  salt  and  brackish 
water.  One  of  them  (P.  vulgaris 
Say)  is  fovmd  along  our  Atlan- 
tic coast.  Other  species  have 
become  true  fresh- water  forms: 
Two  have  been  described  from 
the  United  States:  P.  paludosa 
Gibbes  and  P.  exilipes  Stimp- 
son,  both  from  CaroHna,  but  they 
are   supposed    to  be    identical. 


Fig 


1312.     Palaemonetes  exilipes  Stimpson.      X  i.     (After  Smith.) 
This  form  has  also  been  found  in  Florida,  in  the  Illinois  River,  and  in  Lake  Erie, 


2>2>  (32)  Mandible  with  palpus.  Second  pair  of  peraeopods,  in  the  male, 
excessively  developed,  very  long  (often  longer  than  the 
whole  body),  with  strong  chelae.     Size  of  body  considerable. 

Palacmon  Fabricius. 

This  genus  (sometimes,  but  erroneously,  called  Bithynis)  is  extremely  abundant  in  the  fresh 
water  of  the  tropics.  Only  one  species  is  recorded  from  the  United  States:  P.  ohionis  Smith, 
which  is  found  in  the  Mississippi  and  lower  Ohio  Rivers  (up  to  Cannelton,  Ind.).  Little 
more  is  known  about  this  species  than  that  it  exists  and  that  it  is  locally  used  as  food.  (Not 
even  a  figure  of  it  has  been  published.) 


846 


FRESH-WATER  BIOLOGY 


34  (29)  Body  subcylindrical  in  its  anterior  part,  abdomen  depressed.  Ros- 
trum depressed.  Pleura  of  second  abdominal  segment  not 
overlapping  those  in  front.  First  three  pairs  of  peraeopods 
chelate,  the  first  pair  much  larger  than  the  others. 

Family  Potamobiidae   .    .     35 

An  exclusive  fresh-water  family  of  old  age,  and  the  most  important  group  of  higher  crusta- 
ceans in  the  fresh  waters  of  North  America.  Its  general  distribution  includes  Europe,  north- 
eastern Asia,  North  and  Central  America.  In  the  United  States  two  genera  are  found:  one, 
containing  a' few  species,  is  believed  to  be  identical  with  the  European  genus  (Potamobius);  the 
other  (Cambarus)  is  restricted  to  America,  and  has  very  many  species.  The  differences  .of 
these  genera  are  found  chiefly  in  the  sexual  apparatus.  _  ,  , ,    , 

In  the  southern  hemisphere,  in  Australia,  New  Zealand,  South  America,  and  Madagascar 
this  family  is  represented  by  an  allied  one,  Parastacidae  while  in  the  tropical  belt  similar 
forms  are  missing.  This  peculiar  distribution  has  given  origin  to  much  speculation,  and 
chiefly  the  close  affinity  of  the  southern  forms  has  been  introduced  as  evidence  for  the  former 
connection  of  the  southern  continents.       ,    ,      ,  ,     ,  r     ,  •  ,     •     ,        j 

Through  Huxley's  book  (1880)  this  family  has  become  a  standard  group  for  biological  study. 


35  (36)  Male  copulatory  organs  rather  simple.  Peraeopods  of  male  without 
hooks  on  the  ischiopodite.  Female  without  receptaculum 
seminis.  A  pleurobranchia  present  on  the  last  thoracic 
somite Potamobius  Leach. 

This  is  the  genus  which  includes  the  Euro- 
pean crayfishes,  frequently,  but  incorrectly, 
called  Astacus.  It  possesses  five  species  in 
North  America,  the  range  of  which  is  on  the 
western  Pacific  slope,  from  California  to 
British  Columbia.  One  species  {P.  gamheli 
Girard),  has  crossed  the  continental  divide 
in  the  region  of  Yellowstone  Park,  and  is 
found  on  both  sides  in  the  drainages  of  the 
upper  Columbia  River  and  of  the  upper 
Missouri. 

The  European  species  (about'  six)  have 
frequently  been  subjects  of  systematic,  ana- 
tomical, biological,  and  embryological 
studies.  The  best  known  species  is  the 
common  crayfish  of  Central  Europe,  Pota- 
mobim  astacus  (Linnaeus) . 


Fig.  13 13.    Potamobius  trowbridgei  Stimpson. 
X  i     (After  Hagen.) 


A  species  found  abundantly  in  the  drain- 
age of  the  lower  Columbia  River  in  Wash- 
ington and  Oregon,  and  of  considerable 
economic  value. 


HIGHER   CRUSTACEANS   (MALACOSTRACA) 


847 


36  (35)  Male  copula tory  organs  more  or  less  complex.  Some  peraeopods  of 
the  male  with  hooks  on  the  ischiopodite.  Female  with 
receptaculum  seminis  (annulus  ventralis)  upon  the  sternum 
of  the  thorax.     No  pleurobranchiae  present. 

Cambarus  Erichson   .    .37 


./""N. 


Restricted  to  North  America  east  of  the 
Rocky  Mountains,  Mexico,  Guatemala, 
and  Cuba.  It  contains  between  seventy 
and  eighty  species,  which  fall  into  six  sub- 
genera, four  of  which  are  represented  in 
the  United  States. 

The  geographical  distribution  of  the 
species  of  Cambarus  is  very  interesting, 
and  apt  to  furnish  evidence  for  the  geo- 
logical changes  of  our  river-systems.  This 
genus  is  also  eminently  fit  for  ecological 
studies  on  account  of  the  great  diversity 
of  the  habit-preferences  of  the  single 
species. 

Besides  the  four  subgenera  treated  here, 
two  others  have  been  distinguished  {Para- 
cambarus  and  Procambarus),  but  they  do 
not  possess  representatives  in  the  United 
States. 


Fig.  13 14.     Cambary,sbartoni  Yahricras. 
X  I.     (After  Paulmier.) 


The  most  common  species  in  the  eastern 
United  States,  found  in  small  streams  of 
the  Appalachian  chain  from  Tennessee 
and  the  Carolinas  to  Maine  and  New 
Brunswick. 


37  (44)     Sexual  organs  of  male  with  more  than  two  tips 38 

38  (43)     Third,  or  third  and  fourth,  peraeopods  of  the  male  with  hooks  on  the 

ischiopodite.     Sexual  organs  of  male  blunt  or  truncated, 
with  one  soft  tip,  and  several  short,  horny  teeth. 

Subgenus  Cambarus  Ortmann   .    .     39 

Distribution:  Chiefly  southern  and  southwestern  in  the  United  States. 

39  (42)     Male  with  hooks  on  third  peraeopods 40 

40  (41)     Areola  narrow.     Chelae  elongated. 

Section  of  Cambarus  simulans  Faxon  1884. 

The  areola  is  the  posterior,  median  dorsal  part  of  the  carapace,  included  between  the  lines  which 
bound  the  lateral  (branchial)  regions.    The  areola  is  "  obliterated,"  when  these  lines  come  into  contact. 

Two  species  in  the  southwestern  United  States  and  Mexico. 


41  (40)     Areola  obliterated  in  the  middle.     Chelae  short  and  broad. 

Section  of  Cambarus  gracilis  Bundy  1876. 

Three  species,  burrowing  forms,  on  the  coastal  plain  from  South  Carolina  to  Texas,  and 
northwards  over  the  prairie  region  to  Wisconsin. 


848 


FRESH-WATER   BIOLOGY 


42  (39)     Male  with  hooks  on  the  third  and  fourth  peraeopods.     Chelae  elon- 
gated.    .    .    .     Section  of  Cambarus  blandingi  Harlan  1830. 


About  seventeen  species,  falling  into  four  groups,  distributed  over  the  Atlantic 
and  Gulf  coastal  plain,  and  passing  up  the  Mississippi  valley  into  the  interior  basin. 
C.  blandingi  (Harian)  is  the  type  species  of  this  group  and  of  the  whole  genus.  Its 
distribution  covers  practically  all  of  the  range  of  the  section.  The  other  species  are 
more  local,  and  some  of  them  are  probably  mere  local  races.  The  blind  species, 
C.  acherontis  Loennberg,  from  Florida,  belongs  here. 

Species  of  lakes,  ponds,  or  sluggish  rivers,  avoiding  strong  current. 


Fig.  1315.    Cambarus  {Cambarus)  blandingi  Harlan.     Copulatory  organ  of  male.     X  4- 
(After  Faxon.) 

In  other  species,  the  horny  tips  of  these  organs  are  more  or  less  different,  and 
furnish  important  specific  characters. 


43  (38)  Second  and  third  peraeopods  of  the  male  with  hooks  on  the  ischiopo- 
dite.  Sexual  organs  of  male  with  one  soft,  and  two  horny, 
elongated  points Subgenus  Camharellus  Ortmann. 


Only  one  species  is  found  in  the  United  States:  C.  shufeldti  Faxon,  from  Louisi- 
ana; a  few  more  species  are  known  from  Mexico. 

This  species  appears  to  be  geographically  isolated  from  its  related  forms  (in 
Mexico). 


Fig. 


1316.     Cambarus  (Cambarellus)  Shufeldti  Faxon. 
(After  Faxon.) 


Copulatory  organ  of  male.      X  4. 


44  (37)     Sexual  organs  of  male  with  two  tips,  one  soft,  the  other  horny. 


45 


45  (50)     Sexual  organs  rather  slender,  the  terminal  tips  more  or  less  elongated, 

straight  or  gently  curved.     Ischiopodite  of  third  peraeopods 
of  male  with  hooks,  rarely  also  that  of  fourth. 

Subgenus  Faxonius  Ortmann   .    .     46 

Distribution:  Pre-eminently  in  the  large  rivers  of  the  central  basin  (Mississippi  and  Ohio, 
and  their  tributaries).     Very  few  species  have  reached  the  Atlantic  drainage  system. 

46  (47)     Sexual  organs  of  male  with  the  tips  free  only  for  a  short  distance. 

Hooks  on  third,  or  on  third  and  fourth,  peraeopods. 

Section  of  Cambarus  limosus  Rafinesque  18 17. 

Five  species,  of  which  C.  limosus  (Rafinesque)  (very  generally  called  C.  affinis  Say,  which 
name,  however,  is  a  synonym)  is  the  best  known:  it  is  found  on  the  /Atlantic  side  of  the  Alle- 
ghenies  in  rivers,  ponds,  canals,  from  New  York  and  Pennsylvania  to  Virginia.  The  allied 
species  are  found  at  a  great  distance  from  this,  in  Kentucky,  Indiana,  and  Missouri,  and  among 
them  is  the  blind  cave-species  C.  pellucidus  (Tellkampf). 


47  (46)     Sexual  organs  of  male  with  the  free  tips  longer.     Hooks  on  third 
peraeopods  only ...     48 


HIGHER   CRUSTACEANS    (MALACOSTRACA) 


849 


48  (49)     Tips  of  sexual  organs  rather  straight. 

Section  of  Cambarus  propinquus  Girard  1852. 

About  ten  species  belong  here,  but  some  of  them  are  mere  local  races.  The 
most  important  ones  are  C.  propiiujuus  Girard,  and  C.  rusticus  Girard,  both  found 
in  the  larger  and  smaller  rivers  of  the  interior  basin.  The  other  forms  also  belong 
to  these  river  systems,  but  extend  also  into  the  lower  Mississippi  drainage,  to  the 
Atlantic  side  in  Georgia  and  South  Carolina,  and  to  the  Great  Lakes  and  the  St. 
Lawrence  system. 


Fig. 


1317.    Cambarus    (Faxonius)   rusticus   Girard.     Copulatory   organ  of  male.     X 
(After  Faxon.) 


A  species  characteristic  for  the  lower  Ohio  and  its  tributaries, 
the  copulatory  organs  are  more  or  less  different. 


In  other  species 


49  (48)     Tips  of  sexual  organs  gently,  but  distinctly,  curved. 

Section  of  Cambarus  virilis  Hagen  1870. 

Twelve  species  are  known,  but  again  some  may  be  only  local  forms."  C.  virilis  Hagen  pos- 
sesses a  wide  range  in  the  rivers  of  the  central  basin  from  Arkansas  and  Kansas  to  Canada. 
A  very  abundant  species  is  C.  immunis  Hagen,  which  prefers  stagnant,  often  temporary,  pools 
of  the  western  prairies.  The  other  species  are  found  chiefly  in  the  lower  Mississippi  drainage 
in  Mississippi,  Arkansas,  Kansas,  Oklahoma. 

50  (45)  Sexual  organs  rather  stout,  terminal  tips  rather  short,  strongly  re- 
curved. Ischiopodite  of  third  peraeopods  of  male  with 
hooks Subgenus  Bartonius  Ortmann    .    .      51 

Distribution:  Chiefly  in  and  near  the  Appalachian  Mountains,  but  some  species  on  the 
coastal  plain  and  the  western  plateau. 

51(52)     Eyes  rudimentary.     Chelae  subelongated.     Carapace  subcylindrical. 
Section  of  Cambarus  hamulatus  Cope  and  Packard  1881. 
Three  cave  species  belong  here  (see  p.  837).  , 

52(51)     Eyes  present.     Chelae  subovate.    Carapace  more  or  less  ovate.   .      53 

53  (54)     Rostrum  with  marginal  spines. 

Section  of  Cambarus  cxtraneus  Hagen  1870. 
Three  species,   rather  local  in  Kentucky,  Tennessee,   Northern  Alabama,   and  Northern 
I  Georgia. 

Rostrum  without  marginal  spines 55 

Areola  wide,  or  a  little  narrower. 

Section  of  Cambarus  bartoni  Fabricius  1798. 

About  four  species,  distributed  over  the  Appalachian  Mountains,  where  they  live 
in  mountain  streams,  descending  more  or  less  toward  the  lowlands.  The  best- 
known  form  is  C.  ftar/owj  (Fabricius)  (Figs.  1314  and  13 18),  which  covers  the  whole 
range  of  the  section,  and  has  developed  a  number  of  more  or  less  well  defined  local 
races. 


Fig. 


:3i8.     Cambarus  {Bartonius)  bartoni  Fabricius. 
(After  Hagen.) 


Copulatory  organ  of  male.     X    4. 


In  this  subgenus,  the  shape  of  this  organ  is  rather  uniform  in  all  species,  which 
is  in  strong  contrast  to  the  variability  seen  in  the  other  subgenera. 


850  FRESH-WATER  BIOLOGY 

56  (55)     Areola  very  narrow,  linear,  or  entirely  obliterated. 

Section  of  Cambarus  diogenes  Girard  1852. 
Five  species,  all  burrowing  forms  and  chimney  builders.  Some  (the  more  primitive  forms) 
are  found  in  the  Appalachian  Mountains  and  upon  the  Allegheny  and  Cumberland  Plateau; 
others  have  descended  to  the  Atlantic  coastal  plain,  and  have  spread  over  the  interior  basin, 
and  westward  to  the  Rocky  Mountains,  so,  for  instance,  C.  diogenes  Girard.  Again  other 
species  are  local  forms  of  the  lowlands. 


IMPORTANT   PAPERS    ON   NORTH  AMERICAN    HIGHER 
CRUSTACEA 

Andrews,  E.  A.     1904.    Breeding  Habits  of  Crayfish.    Amer.  Nat.,  38:  165- 

206. 
Embody,  G.  C.     1912.     Distribution,  Food  and   Reproductive  Capacity  of 

Same  Fresh-Water  Amphipods.     Int.  Rev.  ges.  Hydrobiol.,  Biol.  Suppl. 

III.  27  pp. 
Faxon,  W.     1885.    A  Revision  of  the  Astacidae.    Mem.  Mus.  Comp.  Zool. 

Harvard,  10:  1-186. 
Hagen,  H.  a.     1870.     Monograph  of  the  North  American  Astacidae.     111. 

Cat.  Mus.  Comp.  Zool.  Harvard,  No.  3;  109  pp. 
Harris,  J.  A.     1903.     An  Ecological  Catalogue  of  the  Crayfishes  belonging 

to  the  Genus  Cambarus.     Kansas  Univ.  Science  Bull.,  2:  51-187. 
Hay,  W.  p.     1896.    The  Crawfishes  of  the  State  of  Indiana.     Rep.  Indiana 

Geol.  Surv.,  20:475-506.. 
1899.     Synopsis   of  North  American  Invertebrates.      VI.      The  Astacidae 

of  North  America.     Amer.  Nat.,  T)^:  957-966. 
Huxley,  T.  J.     1880.    The  Crayfish.     The  International  Scientific  Series. 

New  York. 
Kingsley,  J.   S.     1899.     Synopsis  of  North  American  Invertebrates.    III. 

The  Caridea  of  North  America.     Amer.  Nat.,  2,3'-  709-719- 
Ortmann,  a.  E.     1905.     The  Mutual  Affinities  of  the  Species  of  the   Genus 

Cambarus,  and  their  Dispersal  over  the  United  States.     Proc.  Amer. 

Philos.  Soc,  44:  91-136. 
1906.    The  Crawfishes  of  the  State   of  Pennsylvania.     Mem.    Carnegie, 

Mus.,  2:343-523. 
Packard,  A.  S.     1886.    The  Cave  Fauna  of  North  America.     Mem.  Nat. 

Acad.  Sci.,  4:  1-156. . 
Pearse,  a.  S.     1910.     The  Crawfishes  of  Michigan.     Mich.  State  Biol.  Surv., 

i:  9-22. 
Richardson,  H.     1905.    A  Monograph  on  the  Isopods  of  North  America. 

Bull.  U.  S.  Nat.  Mus.,  54;  727  pp. 
Smith,  S.  I.     1874.    The  Crustacea  of  the  Fresh  Waters  of  the  United  States. 

Rep.  U.  S.  Comm.  Fish.,  2:  637-665. 
Steele,  M.     1902.    The  Crayfish  of  Missouri.    Bull.  Univ.  Cincinnati,  No. 

10;  54  pp.,  6  pi. 
Weckel,  Ada  L.     1907.    The  Fresh- water  Amphipoda  of  North  America. 

Proc.  U.  S.  Nat.  Mus.,  32:  25-58. 


CHAPTER   XXVI 
THE    WATER-MITES   (HYDRACARINA) 

By  ROBERT  H.  WOLCOTT 

Professor  of  Zoology  in  the  University  of  Nebraska 

Conspicuous  among  aquatic  organisms  on  account  of  their 
activity  and  the  brilHance  of  their  coloring  are  the  water-mites, 
forming  the  group  Hydracarina.  These  attractive  httle  creatures 
may  be  met  with  in  water  almost  anywhere,  but  being  carnivorous 
and  thus  dependent  on  the  presence  of  much  animal  life,  and  hav- 
ing a  life-time  extending  over  a  number  of  months,  they  are  found 
regularly  and  in  abundance  only  in  pools  which  are  moderate  in 
depth,  permanent  in  character,  and  which  possess  a  considerable 
plant  growth.  There  in  the  vegetation  of  the  bottom  and  the  shore 
they  live,  clambering  about  over  the  surface  of  the  plants,  swim- 
ming across  from  one  stem  or  leaf  to  another,  and  feeding  on 
Crustacea,  insect  larvae  or  other  animals  which  they  may  be  able 
to  overpower  and  capture.  A  few  species  are  pelagic,  spending 
most  of  their  time  in  the  open  water  of  the  lake  or  pond,  while 
other  forms,  as  Tyrrellia,  are  found  wandering  over  the  moss  and 
debris  which  accumulates  along  a  swampy  portion  of  the  shore. 
Feltria  is  a  genus  containing  small  forms  that  are  found  only  in  the 
mountain  streams  of  Europe;  yet  in  general  water-mites  are  not 
abundant  in  flowing  streams  except  in  sheltered  places  where  there 
is  a  growth  of  vegetation  which  protects  them  from  the  rapid  cur- 
rent. Two  genera  are  parasitic  in  fresh-water  mussels,  and  the 
larvae  and  pupae  of  others  attach  themselves  to  aquatic  insects  or 
other  animals.  Most  of  them  are  fresh-water  forms,  but  a  very 
few  have  been  described  which  are  marine  and  a  few  others  have 
accustomed  themselves  in  certain  localities  to  life  in  brackish  water. 

Hydrachnids  are  generally  distributed  over  the  world  but  seem 
to  reach  the  greatest  abundance  in  the  clear,  cool  waters  of  the 
spring-fed  lakes  and  pools,  rich  in  plant  hfe,  which  are  so  charac- 
teristic of  all  temperate  latitudes,  and  which  dot  our  northern  states 

851 


852  FRESH-WATER   BIOLOGY 

and  Canada.  An  interesting  occurrence  was  the  finding  of  a  spe- 
cies of  Leber tia,  a  genus  usually  found  in  alpine  and  more  northern 
waters,  in  a  spring  at  Omaha,  Nebraska,  the  only  record  of  the 
genus  in  a  state  where  bodies  of  water  of  that  character  are  almost 
lacking.  At  present  about  seventy  genera  are  known,  containing 
several  hundred  described  species,  the  number  of  which  is  fast 
increasing. 

The  water-mites  are  found  at  all  seasons  of  the  year,  even 
under  the  ice  in  winter.  Certain  ones,  especially  of  the  red  mites, 
are  abundant  in  pools  in  early  spring,  but  the  greatest  number  of 
species  appear  as  adults  during  the  latter  part  of  the  summer  or  in 
the  fall.  They  are  small  forms  usually  from  i  to  2  millimeters 
long,  rarely  exceeding  a  length  of  5  millimeters,  but  on  the  other 
hand,  in  the  adult  condition,  rarely  measuring  less  than  half  a 
millimeter. 

The  color  varies  greatly,  but  is  most  frequently  either  some  shade 
of  red  or  green;  the  same  species  may  at  the  same  locaHty  and  at 
the  same  time  be  both  red  and  different  shades  of  green  or  bluish 
green.  The  color  is  partly  due  to  pigment  deposited  in  the  epidermal 
cells,  but  from  above  or  beneath  blackish,  brownish  or  greenish 
spots  are  seen,  which  vary  in  size  and  intensity  and  are  due  to  the 
stomach  and  its  blind  diverticula  seen  through  other  more  superfi- 
cial structures.  A  whitish,  yellowish,  or  reddish  Y-shaped  dorsal 
mark,  or  markings  of  various  form  seen  on  the  dorsal,  lateral,  or 
posterior  surfaces,  are  due  to  the  presence  of  excretory  matter  in 
the  so-called  Malpighian  vessels,  and  thus  are  very  variable  in 
number  and  extent.  Hence  while  color  is  a  clue  to  identification 
which  may  be  of  service  to  the  experienced  observer,  it  cannot  be 
reHed  upon,  and  is  of  little  or  no  value  in  the  discrimination  of 
species. 

As  seen  in  the  water  the  hydrachnids  appear  at  first  glance  like 
small  water  spiders,  possessing,  as  they  do,  four  pairs  of  legs  and  a 
pair  of  palpi  corresponding  to  the  pedipalps  of  spiders.  But  they 
can  at  once  be  referred  to  the  mites  when  it  is  noted  that  there  is 
no  trace  of  segmentation  or  of  division  of  the  body  into  regions. 

The  body  is  compact  and  usually  more  or  less  globular,  eUip- 
soidal,  or  ovoidal,  though  in  some  cases  compressed  dorso-ventrally 


THE   WATER-MITES    (HYDRACARINA) 


853 


or  laterally,  and  in  the  males  of  certain  species  of  Arrhenurus  pro- 
longed posteriorly  into  a  curious  handle-like  appendage.  The  form 
is  more  definite  in  the  higher  forms  than  in  those  which  seem  most 
primitive.  The  skin  in  some  forms  is  soft  and  the  surface  smooth, 
but  more  usually  it  is  marked  by  fine  striae  like  the  hues  on  the 
palm  of  the  hand,  and  in  the  lower  forms  it  is  often  granulated  or 
papilla  ted.  Other  species  possess  chitinous  plates,  which  may  be 
few  and  small  or  larger  and  more  numerous,  and  may  even  com- 
pletely enclose  the  body  in  a  sort  of  armor.  These  chitinous  plates 
do  not  seem  to  mark  either  higher  or  lower  types  and  occur  in 
different  famiHes.  Glands  occur  here  and  there  on  the  surface,  and 
also  hairs  and  bristles,  which  are  frequently  accompanied  by  small 
pieces  of  chitin. 

There  is  usually  a  pair  of  eyes,  but  each  can  be  seen  on  close 
examination  to  be  double,  and  in  some  cases  the  two  of  each  side 
are  separate.  They  are  of  only  moderate  size,  but  prominent, 
owing  to  the  presence  of  dark  pigment.  There  may  be  also,  in 
some  of  the  lower  forms,  a  ^' fifth" 
or  median  eye,  in  the  median  line 
between  the  others. 

The  four  pairs  of  legs  are  artic- 
ulated to  an  equal  number  of 
coxal  plates,  or  epimera.  These  are 
frequently  more  or  less  fused,  may 
even  form  a  single  large  plate  cover- 
ing the  whole  ventral  surface,  and 
may  also  extend  up  on  the  sides  so 
as  nearly  to  enclose  the  body,  as  in 
Frontipoda.  Sometimes  the  body  is 
constricted  above  this  plate,  giving 
to  the  animal  in  lateral  view  the 
appearance  of  a  broad-crowned  cap 
or  fiat-based  knob,  the  legs  springing 
from  the  upper  side  of  the  projecting 
epimeral  plate.  The  legs  are  each 
composed  of  six  segments,  and  vary  greatly  in  length,  in  the 
form  of  individual  segments,  and  in  the  character  of  the  spines, 


Fig.  1319.  Pionacercus  leuckarti  Piersig,  a 
European  form,  showing  extreme  modi- 
fication of  the  last  pair  of  legs  in  the 
male.  (Legs  shown  on  one  side  only; 
palpi  not  shown.)  (Modified  from 
Piersig.) 


854  FRESH-WATER   BIOLOGY 

bristles  and  hairs  which  they  bear.  They  are  usually  terminated  by 
two  movable  claws,  but  there  may  be  only  one,  or  rarely  the  leg  may 
end  in  a  spine  or  bristle.  The  more  active  and  the  pelagic  forms 
have  longer  legs  with  fewer  and  longer  spines  and  bristles,  the  less 
active  shorter,  stouter  legs  with  more  thickly  set  and  shorter  bristles. 
In  some  cases  a  number  of  long  hairs  in  a  close-set  row  on  the  outer 
segments  of  the  leg  seem  to  aid  in  swimming  and  so  are  called  swim- 
ming-hairs; while  in  other  cases  curiously  modified  leg  segments 
and  spines  characterize  the  male  and  serve  as  accessory  organs  in 
pairing  (Fig.  1319). 

The  genital  opening  is  situated  behind  or  between  the  epimera 
and  is  usually  flanked  by  plates  which  bear  characteristic  cup-like 
or  knob-like  structures  known  as  acetabula,  the  exact  nature  and 
function  of  which  is  unknown.  There  may  be  in  addition  movable 
flaps,  which  may  or  may  not  cover  the  acetabula,  and  in  some  cases 
such  flaps,  by  fusion  with  the  genital  plates,  seem  to  have  become 
immovable. 

Between  the  anterior  epimera  is  a  plate,  which  has  been  termed, 
from  its  form,  the  maxillary  shield,  and  which  is  the  ventral  side  of 
a  chitinous  box  called  the  camerostom,  which  encloses  the  mouth- 
parts.  To  this  are  articulated  the  five-jointed  palpi;  at  its  anterior 
end  is  the  mouth-opening,  through  which  project  the  stiletto-like 
or  sabre-like  mandibles;  and  on  its  dorsal  surface  are  the  two 
stigmata,  leading  by  air-tubes  into  two  air-sacs  placed  above  the 
pharynx,  from  which  a  system  of  tracheal  tubes  runs  through- 
out the  body.  In  the  forms  parasitic  on  the  fresh-water  mussels 
these  tubes  are  lacking.  The  maxillary  shield  is  frequently  pro- 
longed posteriorly  into  a  kind  of  ancoral  process,  and  the  anterior 
ventral  angle  of  the  camerostom  may  be  produced  into  a  sort  of 
rostrum.     All  these  structures  together  are  termed  the  capitulum. 

The  sexes  are  separate,  sexual  dimorphism  being  a  common  phe- 
nomenon, and  all  species  lay  eggs.  These  may,  rarely,  be  laid  free 
in  the  water,  but  are  more  usually  deposited  singly  or  in  mass, 
surrounded  by  a  gelatinous  envelope,  on  water  plants  or  other 
submerged  objects.  The  embryo  undergoes  considerable  develop- 
ment before  escaping  from  the  egg  membranes  at  which  time  it 
becomes  an  active  six-legged  larva  (Fig.  1320).     This  larva  after  a 


TPIE  WATER-MITES    ^HYDRACARINA)  855 

short  free  existence  becomes  a  parasite  either  on  an  aquatic  insect 
which  remains  habitually  in  the  water  or  on  one  which  leaves  the 
water  and  becomes  aerial.  Other  species  place  the  eggs  singly  in 
the  tissues  of  fresh  water  mussels,  or  in  masses  between  the  gills, 


Fig.  1320.    Various  types  of  hydrachnid  larvae  (each  figure  showing  the  legs  of  one  side  onlv) 
a,  Uiplodontus;  b,  Hygrobates;  c,  Arrhenurus;  d,  Hydrachna.     (Modified  from  Piersig.) 

and  still  others  in  the  substance  of  fresh-water  sponges  or  in  the 
gelatinous  matrix  of  a  colonial  protozoan.  In  these  cases  the  larva 
does  not  become  free  but  remains  in  the  body  of  the  mollusk  or 
other  animal  in  which  the  eggs  were  laid.     During  this  parasitic 


856 


FRESH-WATER   BIOLOGY 


existence  the  larval  appendages  drop  off  and  the  animal  takes  on 
the  character  of  a  pupa,  which  increases  greatly  in  size,  drawing 
nourishment  from  its  host,  and  beneath  the  skin  of  which  new 
appendages  are  gradually  developed.  From  this  quiescent  pupa 
emerges  an  active,  eight-footed  nymph  (Fig.  132 1)  possessing  legs 
and  palpi  frequently  quite  similar  to  those  of  the  adult,  but  with 
smaller  epimera  and  with  a  genital  field  lacking  the  structures  which 


d  e  J 

Fig.  13  2 1 .  Figures  showing  the  ventral  surface  of  the  body  of  the  nymphs  of  several  genera  ot  water-mites. 
(Appendages  are  similar  to  those  of  the  adult  and  not  shov/n  here;  compare  with  figures  of  adults  on 
succeeding  pages.)  a,  Arrhenurus;  b,  Limnesia;  c,  Sperchon;  d,  Hygr abates;  e,  Fiona;  /,  Lebertia. 
(Modified  from  Piersig.) 

distinguish  the  adult.  During  this  nymph  stage  the  mite  is  not 
usually  parasitic  except  in  the  case  of  the  mussel  parasites.  How- 
ever, Unionicola  crassipes  has  been  found  by  Soar,  in  all  stages,  in 
the  fresh-water  sponge,  and  the  author  has  taken  the  differ  nt  de- 
velopmental stages  of  a  species  of  Fiona  in  the  gelatinous  matrix 
of  a  colonial  protozoan.  Another  moult  must  occur  before  the 
mite  becomes  adult,  but  this  is  passed  through  rapidly  and  in  the 
forms  in  which  the  nymph  is  free  frequently  occurs  while  the  animal 
is  clinging  to  aquatic  plants.    This  moult  may  or  may  not  be  ac- 


THE   WATER-MITES    (HYDRACARINA)  857 

companied  by  the  loss  of  the  nymphal  appendages  and  the  develop- 
ment of  a  new  set,  and  the  skin  may  be  cast  all  at  once  or  in  several 
portions.  Instances  have  been  described  in  which  the  nymph  was 
produced  directly  from  the  egg  in  the  egg-mass. 

These  water-mites,  like  most  aquatic  animals,  spend  much  of 
their  time  in  active  motion,  swimming  with  comparative  rapidity 
through  the  open  water  or  more  slowly  walking  over  the  bottom  or 
cHmbing  about  on  plants  or  other  objects.  At  times  they  stop 
and  remain  stationary,  cHnging  to  whatever  object  they  may  rest 
upon,  but  a  touch  from  another  animal  sends  them  whirHng  on 
again  with  rapid  leg  movements.  When  prey  is  secured  they  stop 
to  suck  the  juices  from  the  body  of  the  victim,  casting  aside  the 
carcass  when  it  has  been  drained.  Aside  from  the  sense  of  touch, 
which  seems  quite  acute,  the  senses  are  poorly  developed,  or  at 
least  appear  to  be  little  used.  They  rarely  feign  death,  but  almost 
invariably  attempt  to  escape  a  threatened  danger  by  rapid  flight. 
The  less  uniform  rate  of  motion  they  exhibit  is  of  aid  in  distin- 
guishing them  from  other  forms,  especially  ostracods,  with  which 
they  may  be  confused.  The  leg  movement  also  aids  in  their  dis- 
crimination. 

Attractive  as  the  hydrachnids  are  to  the  student  of  fresh-water 
life  and  to  the  biologist,  they  are  of  economic  importance  only  as 
they  afford  an  element  in  the  food  of  fishes.  Examinations  of  the 
contents  of  fish  stomachs  frequently  show  that  they  have  been 
eaten,  and  their  abundance  at  times  would  seem  to  indicate  that 
under  such  circumstances  they  might  make  up  no  inconsiderable 
portion  of  the  food.  But  they  seem  to  go  to  pieces  very  quickly 
and  so  are  rarely  reported  in  any  numbers  in  the  results  of  exami- 
nations of  such  stomach  contents. 

In  collecting  these  little  fellows  one  needs  a  net,  a  number  of 
wide-mouthed  bottles  or  jars,  a  pipette,  and,  in  case  he  is  not  to 
examine  his  collections  within  a  few  hours,  a  bottle  of  formahn. 

The  most  serviceable  net  is  the  ''cone"  or  ''Birge"  net  (see 
page  68).  The  net  may  be  used  from  boat  or  shore  and  the  mate- 
rial, after  being  run  into  a  wide-mouthed  bottle  or  jar,  be  pre- 
served in  toio  at  once  by  adding  directly  a  little  strong  formalin 
and  shaking  thoroughly,  of  it  may  be  carried  home  in  the  fresh 


858  FRESH-WATER   BIOLOGY 

state.  Frequently  mites  may  be  collected  along  shore  by  the  use  of 
the  pipette,  being  picked  up  individually  as  they  swim  about 
in  sight. 

The  material,  if  preserved  in  formalin,  may  be  put  aside  for  future 
examination.  If  not,  it  should  be  poured  soon  into  a  fiat  dish, 
from  which  the  mites  may  be  picked  out  by  means  of  a  pipette. 
The  dish  should  be  looked  over  several  times,  as  some  tend  to  hide 
in  the  debris  at  the  bottom,  and  stirring  after  the  material  has  once 
settled  often  reveals  hidden  specimens. 

Five  per  cent  formalin,  into  which  they  may  be  put  directly,  is 
likely  to  make  them  brittle,  and  the  catch  is  better  preserved  in  a 
mixture  of  glycerine,  2  parts  by  volume;  pure  water,  3  parts  by  vol- 
ume; 2  per  cent  acetic  acid,  2  parts  by  volume;  absolute  alcohol, 
I  part  by  volume. 

If  the  mites  are  to  be  kept  alive  for  observation  their  cannibal- 
istic instincts  make  it  necessary  that  different  genera  be  segregated 
and  kept  in  separate  dishes,  with  a  small  amount  of  some  water 
plant  and  a  few  Crustacea  or  non-predatory  insect  larvae  as  food. 
Crowding  should  be  guarded  against. 

The  activity  of  water-mites  makes  them  difficult  objects  to  study 
alive,  but  by  the  cautious  addition  of  water  saturated  with  chloro- 
form vapor  they  may  be  narcotized,  and,  after  being  examined,  will 
come  out  from  under  the  influence  of  the  chloroform  apparently 
uninjured.  The  author  has  subjected  specimens  to  this  treatment 
on  several  successive  occasions  without  evident  harm. 

In  the  study  of  specimens  it  is  necessary  to  make  use  of  slide 
mounts.  The  mouth-parts  may  be  dissected  and  mounted  sepa- 
rately upon  sHdes,  and  the  palpi  and  legs  may  also  be  removed  and 
mounted.  If  the  specimens  have  been  kept  in  a  solution  contain- 
ing some  glycerine  an  opening  may  be  made  in  the  body-wall 
through  which  the  contents  of  the  body  can  be  pressed  out,  and  in 
that  way  transparent  mounts  of  the  complete  individual  secured. 
The  thickness  of  the  body  makes  it  difficult  to  secure  a  transparent 
mount  from  material  preserved  in  alcohol  or  formalin  mixtures, 
but  the  specimens  may  be  successfully  softened  in  some  cases  by  a 
weak  potash  solution  or  else  must  be  mounted  as  opaque  objects. 

In  the  identihcation  of  water-mites  care  must  be  used,  as  the 


THE   WATER-MITES    (HYDRACARINA)  859 

general  resemblance  between  them  is  close.  But  the  characters 
also  seem  to  be  very  constant  and  few  species  are  subject  to  marked 
variation.  The  accompanying  synopsis  will  aid  in  placing  speci- 
mens in  the  proper  genus.  The  statements  as  to  the  numbers  of 
species  refer  to  North  America  only. 

The  legs  and  the  corresponding  epimera  are  designated  by  Roman 
numerals,  beginning  with  the  most  anterior,  and  the  palpal  and  leg 
segments  are  referred  to  by  Arabic  numerals,  numbering  from  the 
base  outward.  Thus,  ep.  Ill  is  the  third  epimeron,  leg  seg.  IV  4, 
the  fourth  segment  of  the  fourth  leg,  and  pal.  seg.  5  the  distal 
segment  of  the  palpus.  In  most  illustrations  are  shown  the  ven- 
tral surface,  only  the  legs  of  one  side,  and  the  palpus,  detached  and 
more  highly  magnified;  these  are  the  characters  most  important 
and  most  readily  observed. 

The  arrangement  of  genera  and  higher  groups  here  used  is  the 
same  as  adopted  in  a  previous  paper  (Wolcott,  05).  It  is  not  in 
all  respects  satisfactory,  but  such  a  difference  of  opinion  exists 
among  students  of  the  group  in  this  regard  that  the  author  is  not 
willing  to  accept  any  other  system  since  proposed  without  himself 
working  the  whole  matter  over  again. 

KEY  TO  NORTH  AMERICAN  FRESH-WATER  HYDRACARINA 

1  (6)     Lateral  eyes  of  the  two  sides  close  together  in  the  median  line  and 

borne  on  a  common  eye-plate 2 

2  (5)     Pal.  seg.  5  deeply  set  into  4,  eye-plate  long  and   narrow. 

Family  Limnocharidae  .    .     3 
3(4)     Without  swimming-hairs Limnochares  La,tTeil\e  17 g6. 


A  very  large  clumsy  red  mite  with 
soft  body,  variable  in  form  but  in 
general  rectangular,  found  in  pools  in 
bogs  and  swamps.  Length  3.5-4  mm. 
One  species,  generally  distributed  and 
common  at  times. 

Fig.  1322.  Limnochares  aquaticus  (Lin- 
naeus). Ventral  surface,  female.  X  g- 
Inner  surface,  right  palpus.  X  95.  (Mod- 
ified from  Piersig.) 

4  (3)     With  swimming-hairs Cyclothrix  Wolcott  1905. 

Also  red,  but  oval  and  more  constant  in  form  and  recognized  at  once  by  the  swimming-hairs. 
One  species  found  also  in  ponds  and  lakes  with  boggy  or  swampy  shores,  and  known  from 
several  northern  states.     Somewhat  smaller  than  preceding  genus. 


86o 


FRESH-WATER  BIOLOGY 


5  (2)     Pal.  seg.  5  free,  eye-plate  broad,  consisting  of  two  lateral  portions 

connected  by  a  transverse  middle  piece.    Family  Eylaidae. 

One  genus  only £y/aw  Latreille  1796. 


A  red  mite  with  body  circular  in  outline 
and  usually  smooth;  with  palpi  slender  in 
form  and  richly  supplied  with  hairs  and 
spines,  many  of  them  feathered;  hind  legs 
without  swimming-hairs  and  allowed  to 
trail  motionless  behind  in  swimming. 
Several  species,  very  closely  allied  and  gen- 
erally distributed  and  often  very  abundant. 
Varying  in  size  from  about  2  to  5  mm. 


Fig.  1323.  Eylais  extendens  (Miiller),  a  Euro- 
pean species.  Ventral  surface  of  female.  X  7- 
Inner  side  of  right  palpus.  X  69.  Eye-plate. 
X  59-     (Modified  from  Piersig.) 


6  (i)    Lateral  eyes  of  the  two  sides  widely  separated  and  in  no  case  borne 

on  a  common  eye-plate 7 

7  (i8)     Distal  extremity  of  pal.  seg.  4  produced  beyond  the  point  of  inser- 

tion of   seg.  5,  the   two   segments   together  resembling   a 
pair  of  shears S 

8  (9)     Mandible  one-segmented,  the  terminal  portion  straight  and  stiletto- 

like       Family  Hydrachnidae. 

One  genus  only Hydmchna  La^treiHe  ijg6. 


Mites  of  some  shade  of  red  or 
brown,  and  sometimes  spotted 
with  black,  with  the  body  glob- 
ular, soft,  and  usually  papillated; 
capitulum  produced  into  a  snout. 
Species  numerous,  occurring  in 
swamps,  lakes  and  ponds  every- 
where and  usually  common. 
Varying  from  i  to  even  8  mm. 
in  length. 

Fig.  1324.  Hydrachna  geographica 
(Miiller),  a  European  species,  also 
found  in  New  England.  The  largest 
described  hydrachnid.  Ventral  sur- 
face, female.  X  4-  Palpus.  X  i6. 
(Modified  from  Piersig.) 


9  (8)     Mandible  two-segmented,  the  terminal  segment  curved   and  claw- 
like  Family  Hydryphantidae.  .   .     lo 


THE   WATER-MITES    (HYDRACARINA) 


86i 


lo  (ii)     Literal  eyes  of  each  side  separate  and  not  enclosed  in  a  capsule. 

Subfamily  Diplodoxtinae. 
One  genus  only Diplodontus  Duges  1834. 


A  large,  brownish-red  mite  with 
body  broad,  soft,  and  surface  papil- 
lated;  capitulum  forming  a  snout; 
palpi  very  small;  legs  slender,  with 
long  swimming-hairs.  One  cosmo- 
politan species,  generally  distributed 
in  this  country  and  abundant.  About 
2  mm.  long. 


Fig.  1325.  Diplodontus  despiciens  (MvX- 
ler).  Ventral  surface,  male.  X  i5-  Outer 
side,  palpus.  X 103.  (Modified  from 
Piersig.) 


II  (10)     Lateral  eyes  of  each  side  fused  and  contained  in  a  chitinous  capsule. 

Subfamily  Hydryphantinae.    .      12 


12  (17)     Without  swimming-hairs 13 


13  (14)     Median  eye  present Thyas  Koch  1837. 


A  genus  of  red  mites  of  moderate  size 
with  papillated  surface  often  with  chitinous 
plates;  with  capitulum  forming  a  snout;  legs 
with  only  short  spines;  a  bottom  and  shore 
form  in  swampy  situations.  Varying  in  sjze 
from  I  to  2  or  even  2.5  mm.  Few  species 
known  from  the  Northern  States  and  Canada 
and  not  common. 


Fig.  1326.  Thyasvenusta  Koch,  a  European, 
species.  Ventral  surface,  female.  X  i6.  Outer 
side,  left  palpus.    X  65.     (Modified  from  Piersig.) 


14  (13)     Median  eye  not  present 


IS 


862 


FRESH-WATER   BIOLOGY 


:S  (i6)     Genital  flaps  present,  acetabula  3,  knob-like 


Panisus  Kcenike  1896. 


Similar  to  the  preceding  in  appearance;  with  chitinous 
plates  more  or  less  developed,  in  our  one  described  species 
covering  most  of  the  dorsal  surface.  One  species,  P.  cata- 
phractus,  described  by  Kcenike  (1895)  from  Canada,  about 
1.2  mm.  in  length. 


Fig.  1327.  Panisus  cataphra.:tus  (Koenike).  Epimeral  area, 
genital  area  and  maxillary  shield.  X  43-  Outer  side,  left  palpus. 
X  93-     (After  Koenike.) 


i6  (15)     No  genital  flaps;  numerous  stalked  acetabula. 

Sporadoporus  Wolcott,  1905. 


A  red  mite  with  body  beset  by  small  conical 
papillae;  capitulum  produced  into  a  slender  snout. 
One  American  species,  not  yet  described,  known  so  far 
only  from  Yellowstone  Park,  a  little  under  medium 


Fig.  1328.  Sporadoporus  invaharis  (Piersig),  a  European 
form.  Ventral  surface,  female.  X  31-  Palpus.  X  123. 
(Modified  from  Piersig.) 


17(12)     With  swimming-hairs Hydryphantes  Koch  iS 37. 


A  brownish-red  mite,  with  a  median  eye 
surroimded  by  a  large  chitinous  plate; 
adapted  to  more  open  water.  Species 
several,  and  occurring  frequently.  A  little 
above  medium  size  ranging  from  1.2  mm. 
to  about  2.2  mm. 


Fig.  1329.  Eydryphantes  ruber  (de  Geer),  a 
European  species.  Ventral  surface,  female. 
X  17.  Outerside.leftpalpus,  of  female.  X42. 
(Modified  from  Piersig.) 


THE   WATER-MITES    iHYDRACARINA) 


863 


18  (7)       Distal  extremity  of  pal.  seg.  4  slightly  or  not  at  all  produced  be- 

yond the  insertion  of  seg.  5,  but  the  latter  free,  tapering,  the 

tip  bearing  small  claws  or  teeth,  or  ending  in  a  sharp  point. 

Family  Hygrobatidae  .    .      19 

19  (22)     Pal.  seg.  5  sharply  pointed,  claw-like,  opposable  to  the  projecting 

distal  flexor  margin  of  seg.  4,  forming  a  sort  of  pincer. 
Body  entirely  covered  by  a  porous  sheet  of  chitin,  divided  by 
a  suture  into  a  smaller  dorsal  portion  and  a  larger  ventral. 
Legs  with  swimming  hairs.  Subfamily  Arrhenurinae.  .     20 

20  (21)     Genital  area  lying  between  epp.  IV,  the  cleft  flanked  by  large  valves 

each  bearing  3  or  4  acetabula. 

Krendowskija  Piersig  1895. 


A  dark  brown  mite  of  medium  size,  broadly 
oval  in  form;  with  the  capitulum  movable  and 
protrusible,  and  the  camerostom  developed  into 
a  long  rostrum,  sabre-like  and  curved  upward. 
One  American  species.  A',  ovata  Wolcott,  occur- 
ring rarely  in  Wisconsin  and  Michigan.  Other 
species  are  described  from  Venezuela  and  southern 
Russia.     Each  is  a  little  over  i  mm.  in  length. 


Fig.  1330.  Krendowskija  ovata  Wolcott.  Epimeral 
area  and  genital  area,  female.  X  75-  Inner  side,  left 
palpus,  female.  X  250.  Side  view  of  female,  showing 
proboscis.     X  60.     (After  Wolcott.) 


(20)  Genital  area  lying  posterior  to  epp.  I\s  the  cleft  flanked  by  two 
plates  forming  together  an  elliptical  or  circular  area,  beyond 
which  are  laterally  extended,  wing-like  plates  with  numer- 
ous acetabula Arrhenurus  Duges  1834. 


cs,^ 


A  B  CD 

Fig.  1331.  Arrhenurus.  A,  A.  forpicatus  Neuman;  dorsal  surface  of  female.  X  27.  B,  Palpus  of 
A.  albator  (MuUer),  outer  side,  male.  X  113.  C,  A.  maculator  (MuUer),  dorsal  surface,  male.  X  30. 
D,  A.  globator  (Miiller),  dorsal  surface,  male.     X  39-    AH  European  species.     (Modified  from  Piersig.) 


The  females  of  this  genus  are  approximately  oval  in  form  and  possess  few  characters  by 
which  they  may  be  distinguished,  but  the  males  are  highly  and  variously  modified  in  form  and 
possess  complicated  accessory  sexual  structures,  including  a  copulatory  organ,  the  petiole.     Leg 


864 


FRESH-WATER   BIOLOGY 


seg  IV  4  is  also  usually  modified  in  the  male  by  the  possession  of  a  peg-like  projection  and 
characteristic  hairs.  The  species  vary  considerably  in  size,  from  about  0.55  mm.  to  nearly 
2  mm.  One  of  the  most  abimdant  and  widely  distributed  genera,  common  m  clear,  shallow, 
hard  waters  where  plant  Ufe  is  abundant,  with  about  200  species,  all  of  various  shades  of  bluish 
or  brownish  green,  or  red.    There  are  about  50  species  described  from  North  America. 

22  (19)     Pal.  seg.  5  not  opposable  to  4,  and  bearing  at  the  distal  end  small 

more  or  less  distinct  teeth  or  claws 23 

23  (44)     Epimera   in  both  male  and  female  united  and  more  or  less  fused 

into  a  single  epimeral  plate 24 

24  (39)     Body  more  or  less  compressed  dorso-ventrally  and  completely  en- 

closed in  a  chitinous  covering  usually  divided  into  a  smaller, 
elHptical  or  oval,  dorsal  plate  and  a  larger  ventral  plate. 

Subfamily  Aturinae.   .    .     25 

25  (26)     Four  smaller  plates,  variously  shaped,  anteriorly,  between  the  dorsal 

and  ventral T orrenticola  Fkisig  iSgy . 


A  rather  small  mite,  0.6  to  0.75  mm.  long  of  oval  form, 
with  the  capitulum  produced  into  a  sort  of  snout;  no 
swimming-hairs.  One  American  species,  rarely  found, 
and  apparently  identical  with  the  European  Torrenti- 
cola  anomala  (Koch). 


Fig.  1332.  Torreniicola  anomala  (Koch).  Ventral  surface, 
female.  X  27.  Outer  side,  right  palpus,  female.  X  no. 
(Modified  from  Piersig.) 


26  (25)     The  two  plates,  dorsal  and  ventral,  covering  the  whole  surface  .    .     27 

27  (30)     Rostrum  developed,  prolonged  and  curved  upward 28 

28  (29)     Genital  area  without  flaps  or  valves,  with  numerous  acetabula  free 

in  the  body  surface Tanaognathus  Wolcott  1900. 


rmm^ 


A  rather  small  mite,  strongly  compressed 
dorso-ventrally,  and  with  few  swimming- 
hairs.  One  species,  T.  spinipes  Wolcott, 
about  0.7  mm.  long,  known  only  by  a  few 
specimens  from  Michigan. 


Fig.  1333.  Tanaognathus  spinipes  Wdicott.  Epi- 
meral field  and  genital  area,  male.  X  42-  Outer 
side,  right  palpus,  male.    X  iQS-    (After  Wolcott.) 


THE   WATER-MITES    (HYDRACARINA) 


865 


29  (28)     Genital  cleft  flanked  by  two  large  movable  valves,  and  also  ace- 
tabula  set  free  in  the  body  surface.    Koemkea  Woicott  1900. 


A  beautiful  mite  of  striking  form, 
being  greatly  compressed  and  actually 
concave  dorsally;  with  swimming- 
hairs.  Brightly  and  variously  colored. 
One  widely-distributed  species,  K. 
concava  Woicott,  adapting  itself  to 
varied  conditions,  and  often  common. 
Of  small  size  measuring  0.6  to  0.7  mm. 
in  length. 


Fig.  1334.  Koemkea  concava  Woicott. 
Epimeral  field  and  genital  area,  male.  X  65. 
Inner  side,  palpus,  male.  X  278.  Side  view, 
capitulum  and  rostrum  female.  X  277. 
(After  Woicott.) 


30  (27) 

31  (36) 

32  (35) 

33  (34) 


Rostrum  short 31 

Suture  between  the  dorsal  and  ventral  plates  continuous,  completely 

enclosing  the  dorsal  plate,  or  open  posteriorly 32 

Acetabula  lying  near  the  genital  cleft,  no  modification  of  leg  IV  in 


the  male. 


33 


Ep.  IV  quadrilateral  in  form Mideopsis  Neuman  1880. 


A  mite  of  bright  colors,  with  body  almost  circular 
in  outline,  slightly  concave  dorsally;  a  short  rostrum; 
swimming-hairs;  3  acetabula  on  each  side,  outside  of 
which  are  narrow,  sickle-shaped  flaps.  One  species, 
M.  orbicularis  (Miiller),  common  to  Europe  and 
America  and  widely  distributed  in  this  country.  Of 
medium  size  averaging  about  i  mm.  in  length. 


Fig.  1335.  Mideopsis  orbicularis  {M.\i\\er).  Ventral  sur- 
face, female.  X  23.  Outer  side,  right  palpus.  X  123. 
(Modified  from  Piersig.J 


34  (33)    Ep.  IV  triangular Xystonotus  Woicott  1900. 

Body  elliptical;  capitulum  small  and 
camerostom  slightly  developed  into  a 
rostrum;  no  swimming-hairs;  3  acetabula  on 
each  side,  flanked  by  movable  flaps.  The 
genus  containing  a  single  species.  A',  asper 
Woicott,  known  only  from  two  female 
specimens  from  Michigan.  Of  small  size, 
0.61  mm.  long. 

Fig.  1336.  Xystonotus  asper  Woicott.  Ven- 
tral surface,  female.  X  43-  Outer  side  right 
palpus.     X 195.     (After  Woicott.) 


866 


FRESH-WATER   BIOLOGY 


35  (32)  Ace  tabula  arranged  along  the  posterior  margin  of  the  body,  in  one 
or  more  rows,  running  forward  on  either  side  nearly  to  the 
point  of  insertion  of  leg  IV,  which  leg  is,  in  the  male,  modi- 
fied     Aturus  Kramer  1875. 


Very  small  mites,  varying  in  length  from  0.33  to 
0.38  mm.,  with  the  posterior  margin  of  the  body 
cleft;  no  swimming-hairs;  leg  IV  of  male  with 
segs.  4  to  6  strikingly  moditied.  One  species, 
Aturus  mirahilis,  is  recorded  from  Canada  by 
Koenike.  The  genus  is  characteristic  of  rapidly 
flowing  streams. 


Fig.  1337.  Aturus  scaber  (Kramer),  a  European  spe- 
cies. Ventral  surface  of  male.  X  6i.  Outer  side  of 
palpus,  female.     X  150-     (Modified  from  Piersig.) 


36  (31)     Suture  open  anteriorly,  the  two  ends  passing  around  on  to  the  ven- 
tral surface 37 


37  (38)     Genital  area  with  4  acetabula  on  each  side  .  .  Axonopsis  Vitrsig  i^g^. 


A  very  small,  brightly-colored  mite 
about  0.45  mm.  in  length,  with  a  median 
cleft  in  the  posterior  margin  of  the  oval 
body;  the  anterior  epimera  extended 
beyond  the  capitulum;  few  swimming- 
hairs.  One  North  American  species, 
rare,  in  northern  lakes,  apparently  the 
same  as  the  European  A.  complanata 
(MuUer). 


Fig.  1338.  Axonopsis  complanata  (Miiller). 
Ventral  surface  of  female.  X  so.  Outer 
side,  right  palpus.  X  123.  (Modified  from 
Piersig.) 


i 


THE   WATER-MITES    (HYDRACARINA) 
38  (37)     Genital  area  with  numerous  acetabula  on  each  side. 


867 
Albia  Thon  1899. 


A  mite  of  medium  size,  averaging 
about  I  mm.  in  lengtii,  with  elliptical, 
strongly  compressed  body;  swimming- 
hairs  present.  One  North  American 
species,  rather  rare,  in  lakes  of  northern 
states,  frequently  pale  greenish  in  color. 
This  is  identical  with  the  only  Euro- 
pean species,  A.  slationis  Thon,  or 
very  closely  related. 


Fig.  1339.  Alhia  stationis  Thon.  Ven- 
tral surface,  female.  X  31.  Outer  side, 
palpus,  female.     (After  Thon.) 


39  (24)     Body  highly  arched,  in  some  cases  laterally  compressed,  with  no  such 
dorsal  and  ventral  plate.      Subfamily  Lebertunae.   .      40 

Legs  with  swimming-hairs  except  in  certain  species  of  Leberiia. 


40  (41)     Leg  IV  with  claws  at  tip,  epimera  only  partly  fused. 

Lebertia  Neuman  1880. 


Medium-sized  mites,  varjnng  in  length  from 
0.8  to  1.5  mm.,  with  ovoidal  body,  the  surface 
of  which  is  soft  or  hard,  in  some  cases  with 
small  flecks  of  chitin,  usually  striate,  but  rarely 
papillate;  capitulum  developed  more  or  less  into 
a  short  snout.  A  genus  of  frequent  occurrence 
in  colder  waters,  represented  by  several  closely 
allied  species  which  h;ive  only  been  recently 
recognized  as  distinct. 


Fig.  1340.  Lebertia  tau-insignita  (Lebert) .  of  various 
authors,  L.  dubia  Thon.  This  species  was  referred  to 
North  America  by  Koenike  in  1895.  but  he  has  re- 
cently identified  three  species  in  the  material  he 
studied,  all  of  them  hitherto  undescribed.  Ventral 
surface  of  female.  X  19.  Outer  side,  palpus, 
female.     X  70.     (Modified  from  Piersig.) 


41  (40)     Leg  IV  without  claws  at  the  tip,  ending  in  a  sharp  point,  epimera 
completely  fused 42 


868 


FRESH-WATER   BIOLOGY 


42  (43)     Body  laterally  compressed,  epimeral  plate  extending  up  on  the  lat- 
eral surface,  leaving  only  a  dorsal  median  furrow. 

Frontipoda  Koenike  1891. 


A  mite  of  medium  size,  somewhat  less  than 
I  mm.  long,  looking  curiously  like  a  very  flat 
elliptical  seed,  emarginate  at  the  hilum  where 
the  legs  are  bunched  together;  usually  of  a 
greenish  color.  One  species,  frequent  in  our 
northern  lakes  and  apparently  identical  with  the 
one  generally  distributed  European  species,  F. 
musculus  (Miiller). 


Fig.  1341.  Frontipoda  musculus  (Miiller).  Ventral 
surface,  female.  X31.  Outer  side  of  palpus,  female. 
X  93-      (Modified  from  Piersig.) 


43  (42)     Body  not   so  decidedly  compressed,  epimeral  plate   not  extending 
upward  on  the  lateral  surface.     .    .    .     Oxus  Kramer  1877. 


A  form  of  medium  size,  different  species  vary- 
ing in  length  from  0.64  to  1.4  mm.,  with  body 
elongate  in  form;  legs  crowded  toward  the  an- 
terior end.  Known  in  North  America  only  from 
Wisconsin,  where  the  one  species  seems  to  be 
rare.  This  is  undescribed,  but  is  similar  to  O. 
ovalis  (Muller)  and  O.  strigatus  (Miiller)  the 
common  European  forms. 


Fig.  1342.  Oi(:M5  OTa/i5  (Muller).  Ventral  surface, 
female.  X  30.  Oxus  strigatus  (WnW^r).  Outer  side, 
palpus  female.     X  90.     (Modified  from  Piersig.) 


44  (23)  Epimera  arranged  in  groups,  in  the  female  always  clearly  separate 
from  one  another,  in  the  male  closer  together  but  distinct, 
only  in  rare  cases  in  contact  or  tending  in  a  slight  degree  to 
fuse 45 


45  (64)     Epimera  in  four  groups,  in  the  male  in  some  cases  only  a  narrow 
interval  between  them 46 


THE  WATER-MITES    (HYDRACARINA) 


869 


46  (53)     Genital  area  usually  lying  far  forwards,  at  least  between  epp.  IV, 

and  the  epimeral  groups  often  separated  by  a  considerable 
interval,  no  ancoral  process  on  the  maxillary  shield. 

Subfamily  Sperchoninae     .     47 

47  (52)     Genital  acetabula  borne  on  a  plate,  no  flaps  present 48 

48  (49)     Acetabula  numerous Limnesiopsis  Piersig  1897. 


A  large  hydrachnid,  about  2  mm.  in  length,  with 
the  surface  of  the  body  beset  with  sharp  points.  One 
species,  L.  anomala  (Koenike),  described  from  Canada, 
and  generally  distributed  in  northern  lakes  but  no- 
where common. 


Fig.  IS43-  Limnesiopsis  anomala  (KoGnike).  Epimeral 
field  and  genital  area,  male.  X  25.  Outer  side,  palpus, 
njale.     X  49.     (After  Koenike.) 


49  (48)    Acetabula  few,  large 50 


50  (51)     Leg  IV  with  terminal  claws,  no  swimming-hairs. 

Tyrrellia  Koenike 


895- 


Body  almost  circular,  papillated 
with  one  or  two  dorsal  chitinous 
plates;  mouth-opening  in  the  middle 
of  a  disk-like  surface  at  the  anterior 
end  of  the  capitulum,  resembling  the 
condition  seen  in  the  Hydryphantidac; 
a  sluggish,  dark-brown  mite  of  medium 
size  averaging  1.2  mm.  in  length, 
known  from  Canada  and  found 
abundantly  some  years  since  at 
Reed's  lake,  near  Grand  Rapids, 
Michigan,  where  it  was  picked  up 
singly  with  the  pipette  in  the  debris  at 
the  margin  of  the  water  in  close  prox- 
imity to  a  swampy  portion  of  the  lake 
shore.  V^ery  rare  in  Birge  net  hauls 
at  the  same  place.  Two  species  taken, 
one  apparently  the  same  as  T.  circii- 
laris  Koenike,  previously  described. 

Fig.  1344.  Tyrrellia  circularis  Koenike. 
Ventral  surface,  female.  X  26.  Inner  side, 
palpus,  female.  X  4Q-  (Modified  from 
Koenike.) 


870 


FRESH-WATER   BIOLOGY 


51  (50)     Leg  IV  ending  in  a  point,  a  long  hair  a  little  back  from  the  tip,  swim- 
ming-hairs present Limnesia  Koch  1837. 


A  mite  varying  from  small  to  large  in  size, 
or  from  0.5  to  2  mm.  in  length,  with  oval 
body,  surface  striate,  sometimes  papillose, 
and  even  developing  a  chitinous  meshwork; 
two  eyes  on  each  side  separate.  Handsome 
mites  with  bright  red  spots,  very  active,  and 
among  the  most  powerful  and  voracious  of 
all.  Ten  North  American  species;  generally 
distributed  and  found  under  very  varied  con- 
ditions. 


Fig.  1345.  Limnesia  kistrionica  (Hermann), 
the  most  widely  distributed  North  American  spe- 
cies, also  found  throughout  Europe.  Ventral  sur- 
face, female.  X  16.  Outer  side,  palpus,  female. 
X  51-     (Modified  from  Piersig.) 


52  (47)     Genital  acetabula  along  the  margin  of  the  cleft,  covered  laterally 
by  flaps;  without  swimming-hairs.    Sperchon  Kramer  1877. 


Body  oval,  rarely  with  small  chitinous 
plates,  smooth,  or  papillate;  capitulum  very 
movable.  A  genus  found  in  northern  and 
mountain  lakes  and  streams.  Three  species 
recorded  from  Canada.  Species  small  to 
medium  in  size,  in  length  0.5  to  1.5  mm. 


Fig.  1346.  Sperchon  glandulosus  Koenike,  a 
species  recorded  both  from  Europe  and  Canada. 
Ventral  surface,  female.  X  24.  Outer  side  of 
palpus,  female.     X  94-     (Modified  from  Piersig.) 


53  (46)  Genital  area  lying  posterior  to  epp.  IV,  at  most  only  its  anterior 
end  lying  between  their  emarginate  posterior  angles;  an 
ancoral  process  present.    .    .     Subfamily  Pioninae.  .     54 


THE   WATER-MITES    (HYDRACARINA) 
54  (6i)     Posterior  margin  of  ep.  IV  rounded  or  transverse  .    . 


871 
55 


55  (58)     With  swimming-hairs , 56 


56  (57)  Transverse  diameter  of  ep.  IV  the  greater,  suture  between  epp. 
Ill  and  IV  complete;  no  prominent  papillae  on  pal.  seg.  4, 
acetabula  very  numerous Neumania  Lebert  1879. 


Mites  of  small  to  medium  size,  varj-ing 
in  length  from  0.5  to  i  .6  mm.,  with  soft  body, 
tending  more  or  less  to  develop  chitinous 
plates  or  beset  with  chitinous  points,  rarely 
smooth:  leg  IV  usually  with  feathered  spines. 
Brightly  colored,  red  or  bluish  forms,  active, 
but  not  markedly  voracious.  Several  North 
American  species,  common,  and  widely  dis- 
tributed. 


Fig.  1347.  Neumania  spinipes  (Miiller),  a 
European  species  represented  in  this  countrj'by  a 
closely  allied  form,  \entral  surface,  male.  X  40. 
Outer  side,  palpus,  male.  X  70.  (Modified  from 
Piersig.) 


57  (56)  Longitudinal  diameter  of  ep.  IV  at  least  equal  to  the  transverse 
suture  between  epp.  Ill  and  IV  incomplete  medially;  pal. 
seg.  4  usually  with  prominent  papillae;  5  or  6  acetabula  on 
each  side  on  one  or  two  plates. 

(Non-parasitic  species)  Unionicola}isi\dema.n  1842. 


58  (55)     Without  swimming-hairs. 


59 


872 


FRESH-WATER  BIOLOGY 


59  (60)  Posterior  margin  of  ep.  IV  rounded;  genital  area  midway  between 
epp.  IV  and  the  posterior  end  of  the  body,  genital  plates 
elongated  transversely Najadicola  Piersig  1897. 


A  large  mite,  i-S  to  2.5  mm.  long, 
the  gravid  female  often  very  large, 
reaching  a  length  of  even  6  mm.,  living 
in  fresh-water  mussels  and  laying  eggs 
in  masses  between  the  gills.  Honey- 
yellow  in  color,  more  or  less  distinctly 
finely  vermiculate  with  white  lines. 
One  North  American  species,  generally 
distributed. 

Fig.  1348.  Najadicola  ingens  (Koenike) . 
Epimeral  field  and  genital  area,  male. 
X  23.  (.After  Koenike.)  Inner  side,  pal- 
pus, male.     X  80.     (After  Wolcott.) 


60  (59)     Posterior  margin  of  ep.  IV  straight;  genital  area  at  the  posterior 
end  of  the  body,  genital  plates  not  elongated  transversely. 
(Parasitic  species)  Unionicola  Haldeman  1842. 


Varjdng  from  small  to  large  in  size, 
or  from 0.4  to  1. 9 mm.  in  length.  Some 
are  active,  free-swimming  mites  with 
long  legs,  with  swimming-hairs,  and 
leg  I  frequently  with  movable,  dagger- 
like spines.  Others  are  mussel  para- 
sites, with  shorter  legs  and  no 
swimming-hairs,  leg  IV  in  some  cases 
being  characteristically  modified  in 
the  male  sex.  In  both  types  strong 
spines  adjacent  to  the  genital  opening 
serve  together  as  an  ovipositor.  Cer- 
tain free-swimming  forms  are  regularly 
pelagic  and  very  transparent;  the  para- 
sitic forms  are  dull-colored.  Species 
numerousand  widely  distributed,  many 
of  them  very  abundant,  especially  the 
parasitic  forms.  The  latter  are  usually 
mussel  parasites  though  one  species 
has  been  recorded  from  a  South 
American  imivalve. 


Fig.  1349.  Unionicola  crassipes  (MiiUer), 
a  common  and  widely -distributed,  free- 
swimming  species,  common  to  North 
America  and  Europe.  Ventral  surface, 
female.  X  22.  Palpus.outer  side,  female. 
X  63.     (Modified  from  Piersig.) 


61  (54)     Posterior  margin  of  ep.  IV  with  a  prominent  acute  angle. 


62 


THE   WATER-MITES    (HYDRACARINA) 


873 


62  (63)  Medial  margin  of  ep.  IV  reduced  to  merely  a  medial  angle  which 
forms  a  common  angle  with  the  medio-posterior  angle  of 
ep.  Ill;  leg  segs.  IV  5  and  IV  6  of  male  modified. 

Tiphys  Koch  1837. 


Rather  small  mites,  in  length  from  0.54  to  i  mm., 
with  swimming-hairs  and  the  hind  leg  of  the  male 
strikingly  modified.  Few  North  American  species, 
rare,  in  our  northern  lakes,  as  yet  not  studied. 


Fig.  1350.  Tiphys  liUaceus  (Miiller),  the  most  common 
European  species.  Ventral  surface,  female.  X  28.  Outer 
side,  nght  palpus,  female.     X   123.      (Modified  from 

Piersig.) 


63  (62)     Medial  margin  of  ep.  IV  not  reduced,  and,  owing  to  the  angle  on 
the  posterior  margin,  ep.  IV  more  or  less  clearly  five-sided. 

Piona  Koch  1837, 

Oval  or  elliptical  forms  of 
various  sizes,  from  0.45  to  3  mm. 
long,  often  brightly  colored,  with 
swimming-hairs,  and  with  char- 
acteristic modifications  of  leg 
segs.  Ill  6  and  IV  4  in  the  male, 
the  latter  serving  to  assist  in 
grasping  the  female  in  pairing, 
the  former  to  carry  the  semen 
to  the  female  genital  opening. 
Hardy,  active  mites,  adapting 
themselves  to  a  great  variety  of 
conditions.  More  than  twenty 
American  species,  generally  dis- 
tributed over  the  continent. 

Fig.  1351.  Fiona  rufa  (Koch),  a 
European  species.  Ventral  surface, 
female.  X  22.  Outer  side,  palpus, 
female.  X  77-  (Modified  from 
Piersig.)  Fiona  constricla  (Wol- 
cott),  an  American  form.  Leg  seg- 
ment IV  4,  male.  X  107.  (After 
Wolcott.) 


64  (45)     Epimera  in  three  groups,  epp.  I  being  fused  together  behind   the 

capitulum,  the  groups  also  often  close  together  in  the  male. 

Subfamily  Hygrobatinae  .    .     65 


874  FRESH-WATER    BIOLOGY 

65  (66)     Leg  segs.  I  5  and  I  6  modified Atractides  Koch  1837. 


Small  to  medium-sized  mites,  vary- 
ing in  length  from  0.48  to  1.5  mm. 
with  surface  soft  and  striate,  or  with 
a  flexible  or  hard  porous  covering; 
swimming-hairs  present.  Species 
few  in  this  country,  rare,  in  northern 
lakes. 


Fig  .  1 3  5  2 .  A  trac  tides  s  pint  pes  Koch ,  a 
species  common  to  Europe  and  America. 
Ventral  surface,  female.  X  25.  Outer 
side  of  left  palpus,  female.  X  103. 
(Modified  from  Piersig.) 


66  (65)     Leg  segs.  I  5  and  I  6  normal Hygrobaies  Koch  1837. 


*^ 


Mites  var>'ing  in  size  from  small 
to  even  large,  or  0.5  to  2.5  m_m., 
brightly  colored  in  many  cases,  with- 
out swimming-hairs,  but  active,  and 
certain  species  frequently,  if  not  regu- 
larly, pelagic.  Several  species  of  gen- 
eral distribution  in  northern  United 
States  and  Canada. 


Fig.  1353.  Hygrobaies  longipalpis 
(Hermann),  a  species  found  in  North 
America,  Europe  and  Western  Asia. 
Ventral  surface,  female.  X  13 •  Outer 
side,  palpus,  female.  X  125.  (Modified 
from  Piersig.) 


In  collecting  water-mites  with  the  Birge  net  one  will  ahnost  always  findin 
the  collection  specimens  of  another  mite  of  small  size,  brown  in  color,  with 
short  legs,  with  the  body  indistinctly  separated  into  cephalothorax  and  ab- 
domen and  with  a  horny  body-covering.  This  belongs  to  the  horny  mites  or 
Oribatidae,  probably  to  the  genus  Notaspis,  and  is  a  vegetable  feeder  living  on 
aquatic  plants  beneath  the  surface  of  the  water.  It  can  not  swim,  and  will 
either  cling  to  objects  at  the  bottom  of  the  dish  or  float  on  the  surface.^  Sev- 
eral species  occur  and  are  generally  distributed.  The  species  increase  in  size 
and  num.ber  to  the  southward. 


THE   WATER-MITES    (HYDRACARINA)  875 

IMPORTANT  PAPERS  ON  NORTH  AMERICAN  FRESH- 
WATER MITES 

KoENiKE,  F.     1895.     Nordamerikanische  Hydrachniden.      Abh.   des  Natur- 
wiss.  Ver.  zu  Bremen,  13:   167-226.     Also  separate  Bremen,  1895. 
1912.     A  Revision  of  my  "Nordamerikanische  Hydrachniden."     Transl. 
by  E.  M.  Walker.     Trans.  Can.  Inst.,  1912:  281-296. 

Marshall,  Ruth.     1903.     Ten  Species  of  Arrenuri  belonging  to  the  Subgenus 
Megalurus  Thon.     Trans.  Wis.  Acad.  Sci.,  14:  145-172. 

1904.  A  New  Arrenurus  and  Notes  on  Collections  made  in  1903.  Trans. 
Wis.  Acad.  Sci.,  14:  520-526. 

1908.     The  Arrhenuri  of  the  United  States.     Trans.  Amer.  Micr.  Soc,  28: 

85-140. 
1910.     New  Studies  of  the  Arrhenuri.  Trans.  Amer.  Micr.  Soc,  29:  97-110. 
PiERSiG,  R.     1 901.     Hydrachnidae.     Das  Tierreich.  Lief.  13. 
WoLCOTT,  R.  H.      1899.     On  the  North    American  Species  of    the   Genus 
Atax  (Fabr.)  Bruz.     Trans.  Amer.  Micr.  Soc,  20:  193-259. 

1900.  New  Genera  and  Species  of  North  American  Hydrachnidae.  Trans. 
Amer.  Micr.  Soc,  21:  177-200. 

1901.  Description  of  a  New  Genus  of  North  American  Water-mites,  with 
Observations  on  the  Classification  of  the  Group.  Trans.  Amer.  Micr. 
Soc,  22:  105-117. 

1902.  The  North  American  Species  of  Curvipes.  Trans.  Amer.  Micr.  Soc, 
23:  201-256. 

1903.  The  North  American  Species  of  Limnesia.  Trans.  Amer.  Micr.  Soc, 
24:  85-107. 

1905.  A  Review  of  the  Genera  of  the  Water-mites.  Trans.  Amer.  Micr. 
Soc,  26:  161-243. 


CHAPTER   XXVII 
AQUATIC    INSECTS 

By  JAMES   G.   NEEDIL\M 

Professor  of  Limnology,  Cornell  University 

Insects  are  essentially  terrestrial  animals.  Their  organization 
fits  them  for  exposure  to  the  air.  On  land  they  are  numerically 
dominant,  and  it  is  a  comparatively  small  portion  of  the  group 
that  is  to  be  found  in  the  water.  But  the  lesser  portion  of  a 
group  so  large  is  in  itself  a  host,  including  a  very  great  variety  of 
forms. 

That  insects  are  primarily  terrestrial  and  that  they  have  been 
secondarily  adapted  to  aquatic  hfe  is  evidenced  in  many  ways. 
Their  complete  armor  of  impervious  chitin  and  their  respiratory 
apparatus,  consisting  of  internal  branching  chitin-lined  air  tubes 
(tracheae),  opening  to  the  outside  for  the  intake  of  air  through 
spiracles,  speak  strongly  against  an'  aquatic  origin.  It  would  be 
hard  to  imagine  an  organization  more  unsuited  to  getting  air  when 
in  the  water. 

Furthermore,  all  adult  insects,  even  those  that  hve  constantly 
in  the  water,  have  preserved  the  terrestrial  mode  of  respiration: 
they  all  breathe  air  directly,  instead  of  breathing  the  air  that  is 
dissolved  in  the  water.  They  have  merely  acquired  means  of 
carrying  air  from  the  surface  down  into  the  water  with  them  for 
use  there.  They  are  no  more  aquatic  in  their  mode  of  respiration 
than  is  a  man  in  a  diving  bell.  It  is  only  the  more  plastic  immature 
stages  that  have  acquired  a  strictly  aquatic  type  of  respiratory 
apparatus. 

Again,  it  is  only  isolated  and  rather  small  groups  of  insects  that 
inhabit  the  water.  A  few  of  the  smaller  orders,  like  the  stone- 
flies.  Mayflies,  dragonflies  and  caddisfiies  are  practically  all  aquatic 
in  their  immature  stages;   but  the  larger  orders  are  not  so. 

There  is  abundant  evidence  of  the  independent  adaptation  of 
the  various  groups.     Practically  all  the  adult  insects  found  in  the 

876 


AQUATIC  INSECTS  877 

water  are  either  bugs  or  beetles.  Of  those  aquatic  insects  having 
complete  metamorphosis,  the  pupa  is  strictly  aquatic  in  caddisflies 
only.  The  adaptations  of  the  immature  stages  have  chiefly  to  do 
with  their  respiratory  apparatus,  and  this  is  most  extraordinarily 
diverse.  This  will  be  discussed  later.  Suffice  it  here  to  say  that 
gills  of  several  sorts  may  be  developed  upon  either  the  outer  or 
inner  surfaces  of  the  body,  and  those  on  the  outside  may  be  dorsal 
or  ventral,  and  may  be  developed  upon  the  head  or  on  any  seg- 
ment of  the  thorax  or  abdomen :  thus  they  bear  all  the  usual-  signs 
of  independent  and  adaptive  origin. 

Finally,  it  is  to  be  noted  that  insects  have  not  invaded  the  water 
very  far.  Nearly  all  of  them  have  stopped  at  the  shores  or  in  shoal 
water;  .only  a  few  have  established  homes  for  themselves  in  deep 
water.  Only  the  phantom  larvae  of  Corethra  have  become  free 
swimming  and  are  regular  plankton  constituents;  possibly  a  few 
others  also,  for  a  Umited  distribution-period  immediately  follow- 
ing their  hatching  from  the  eg'g.  The  press  of  life  on  land  result- 
ing from  the  evolution  of  the  highly  successful  hexapod  type  of 
organization,  with  great  adaptabihty,  brief  life  cycle  and  excellent 
reproductive  capacity,  may  have  resulted  in  the  crowding  into  the 
water  of  those  moisture-loving  forms  whose  structures  were  best 
adapted  to  meet  the  new  conditions.  The  severity  of  the  competi- 
tion on  land  is  most  evident  to  the  careful  observer;  every  nook 
and  comer  has  its  insect  inhabitants  and  every  scrap  of  nutritious 
food  is  eagerly  sought  by  a  host  of  competitors.  It  is  easy  to 
conceive  that  a  great  variety  of  forms  already  accustomed  to  living 
by  the  water  side,  finding  food  more  abundant  in  the  water  than 
out  of  it,  might,  if  adaptable,  become  modified  for  entering  the 
water  for  a  greater  or  less  depth  and  for  remaining  there  a  greater 
or  less  time. 

And,  as  a  matter  of  fact,  adaptation  of  the  adults  has  proceeded 
only  a  little  way.  Some  adult  insects,  as  certain  caddisflies  and 
damselflies,  enter  the  water  only  to  lay  their  eggs,  and  they  remain 
enveloped  by  a  layer  of  adherent  air  while  beneath  the  surface. 
Some  Hve  constantly  in  the  water  but  maintain  communication  with 
the  surface  by  means  of  a  long  respiratory  tube,  as  does  Ranatra. 
The  most  nearly  aquatic  of  adult  insects  are  the  bugs  and  beetles  that 


878  FRESH-WATER   BIOLOGY 

have  developed  oar- like  hind  feet  and  have  become  good  swimmers; 
these  enter  the  water  to  depths  of  several  feet  and  spend  most  of 
their  time  near  the  bottom  in  shoal  waters,  but  they  must  come  to 
the  surface  at  intervals  for  air  which  they  carry  down  with  them 
beneath  their  wing  covers  or  adherent  to  the  pile  of  their  bodies. 
A  few  adult  insects  also  have  taken  to  walking  or  running  on  the 
surface  of  the  water,  but  these  are  naturally  the  most  minute  forms, 
as  springtails,  or  those  of  slenderer  build,  like  little  Diptera  and 
water  striders;  and  of  this  last-mentioned  group,  some  wander  far 
from  shore,  even  upon  the  surface  of  the  ocean.  But  there  are 
few  adult  insects  to  be  found  far  from  the  shelter  of  vegetation, 
and  it  remains  true  that  the  great  press  of  insect  Hfe  is  at  the  shore 
line. 

The  case  is  only  slightly  different  with  insect  larvae.  Most  of 
these  have  remained  near  shore.  As  compared  with  the  adults, 
their  smaller  size,  less  chitinized  skin  and  greater  plasticity  have 
allowed  much  more  complete  adaptation  to  aquatic  Hfe.  There 
are  some  larvae,  like  those  of  beetles  and  of  many  flies,  that  take 
air  at  the  surface  as  do  the  adult  beetles,  and  there  are  a  few  others, 
that,  descending  the  stems,  tap  the  air  spaces  of  plants  far  beneath 
the  surface  and  get  oxygen  from  that  unusual  source ;  but  there  are 
also  very  many  that  are  capable  of  a  truly  aquatic  respiration, 
being  able  to  utilize  the  air  that  is  dissolved  in  the  water.  Most 
of  these  larvae  when  newly  hatched  absorb  the  oxygen  directly 
through  their  skins;  and  a  few  of  them,  especially  such  as  live  in 
well  aerated  water,  acquire  no  better  means  than  this  during  their 
larval  existence,  but  most  of  them  develop  gills  of  some  sort. 

These  gills  are  delicate  outgrowths  of  the  thinnest  integument  of 
the  body.  Two  types  of  gills  are  usually  distinguishable,  blood 
gills,  and  tracheal  gills.  The  former  are  more  Kke  the  gills  of 
other  aquatic  animals;  the  latter  are  pecuHar  to  insects.  The 
blood  gills  are  simple  outgrowths  of  the  body  wall  into  which  the 
blood  flows.  The  interchange  of  gases  which  constitutes  the 
respiratory  process  takes  place  between  the  blood  within  the  gill 
and  the  water  outside  it  by  means  of  direct  diffusion  through  the 
thin  membranous  wall.  Such  gills  are  very  commonly  developed 
in  dipterous  larvae  as  paired  and  retractile  appendages  of  the  pos- 


AQUATIC  INSECTS  879 

terior  end  of  the  alimentary  canal,  but  they  also  occur  on  other 
parts  of  the  body. 

Since  tracheae  are  the  established  channels  of  air  distribution  in 
the  bodies  of  insects,  and  nearly  all  insects  are  hatched  from  the 
egg  in  possession  of  a  number  of  them,  it  is  natural  that  tracheal 
gills  should  be  more  commonly  developed  in  the  larvae  of  the 
group.     A  tracheal  gill  differs  from  a  blood  gill  chiefly  in  that  it  is 
traversed  by  minute  capillary  branches  of  tracheae,  and  the  air 
is  taken  up  by  and  distributed  through  the  tracheae.     Tracheal 
gills  are  usually  developed  apart  from  and  quite  independently  of 
the  spiracles  or  breathing  pores.     They  arise  from  the  thin  interseg- 
mental membranes  of  the  body.     They  may  be  developed  upon 
the  internal  walls  of  the  rectum,  forming  a  large  and  very  perfect 
gill  chamber,  as  in  the  young  of  dragonfiies.     More  frequently,  they 
are  developed  on  the  outside  of  the  body.      They  may  be  flat  and 
lamelliform,  as  in  the  three  caudal  gills  of  the  damselfiies  and  in  the 
paired  dorsal  abdominal  gills  of  Mayflies,  or  they  may  be  filamen- 
tous, simple,  branched  or  tufted,  as  in  most  other  forms.     Another 
sort  of  tracheal  gill  (the  so-called  ''tube  gill")  is  developed  directly 
from  the  pro  thoracic  spiracles  in  certain  diptera  at  the  assumption 
of  the  pupal  stage,  in  the  form  of  respiratory  trumpets  (mosquito 
pupae),  combs  (black  fly  pupae),  brushes  (midge  pupae),  etc.     With 
the  development  of  gills,  insect  larvae  have  become  independent  of 
the  surface.      Many  of  them  remain  wholly  submerged  through- 
out   their  entire    larval  life.      A  few    of    them    have  progressed 
farther  from  shore  and  into  deeper  water.    Corethra  has  been  already 
mentioned  as  a  plankton  organism.     A  few  larvae  of  midges  and 
a  few  caddis  worms  are  constant  denizens  of  the  bottom  silt  in  our 
deeper  fresh-water  lakes.     This  seems  indeed  considerable  prog- 
ress into  a  new  and  totally  different  environment,  when  one  re- 
members that  they  are  tied  by  parentage  to  the  shore. 

It  is  to  be  noted  in  passing  that  only  in  the  Coleoptera  and 
Hemiptera  has  the  adaptation  of  adults  and  immature  stages  been 
parallel.  In  the  other  groups  the  adults  do  not  live  in  the  water. 
The  possession  by  a  few  adult  insects  {Pteronarcys,  etc.,  among 
stoneflies,  and  Chirotonetes ,  etc.,  among  Mayflies)  of  rudimentary 
gills  does  not  indicate,  as  was  once  thought,  that  this  is  the  primitive 


88o  FRESH-WATER   BIOLOGY 

condition ;  it  indicates  only  that,  in  these  relatively  primitive  forms, 
structures  developed  to  a  considerable  extent  upon  the  immature 
stages  have,  in  the  rapid  and  incomplete  transformation  these  imder- 
go,  been  carried  over  in  rudimentary  form  into  adult  Hfe. 

Among  aquatic  insects  are  many  beautiful  and  interesting 
forms.  The  keys  and  figures  in  the  following  pages  should  enable 
anyone  who  has  learned  the  parts  of  the  body  of  a  grasshopper, 
or  who  has  mastered  such  elementary  knowledge  of  insect  anatomy 
as  every  textbook  of  zoology  or  of  entomology  affords,  to  identify 
most  of  the  insects  he  will  find  in  the  water.  There  are  many  gaps 
in  our  knowledge  of  all  the  groups;  even  the  adult  insects  are  not 
well  known  except  in  the  showier  groups,  which  have  always  been 
more  attractive  to  the  collector;  and  so  many  immature  forms  are 
still  imknown,  it  has  been  found  impracticable  to  attempt  to  give 
keys  even  to  the  genera  in  two  orders,  Plecoptera  and  Trichoptera. 
Limitations  of  space  have  compelled  restriction  to  the  larger 
groups  among  the  Diptera.  In  most  of  the  groups  having  com- 
plete metamorphosis,  the  characterizations  of  the  immature  stages 
have  been  adapted  from  the  accounts  of  European  writers,  very 
Httle  ha\dng  as  yet  been  done  on  them  in  America.  Here  is  an 
attractive  field  in  which  the  amateur  and  the  isolated  student  may 
still  find  pioneer  work  to  do. 

It  is  the  purpose  of  this  chapter  to  assist  the  student  toward 
acquaintance  with  such  insects  as  he  may  find  in  the  water.  The 
limitations  of  space  allow  but  brief  notice  of  the  natural  history  of 
any  of  the  groups  and  restrict  the  keys  to  dealing  with  famihes  and 
genera.  The  aim  is  to  supplement  the  general  works  on  entomology 
and  not  to  duplicate  any  part  of  them.  Keys  to  the  orders  of 
adult  insects  are  available  in  a  number  of  manuals  and  textbooks, 
hence  there  is  need  here  only  to  point  out  the  readier  recognition 
marks  of  those  orders  which  commonly  occur  in  the  water,  and  to 
give  a  key  to  the  immature  stages. 

Recognition  Characters 

There  are  but  nine  orders  of  insects  commonly  found  in  water 
in  any  stage:  Plecoptera,  Odonata,  Ephemerida,  Hemiptera,  Neu- 
roptera,  Trichoptera,  Lepidoptera,  Coleoptera  and  Diptera. 


AQUATIC   INSECTS  88 1 

The  Odonata  are  distinguished  by  the  venation  of  the  wings, 
especially  by  the  possession  of  a  distinct  nodus  and  stigma  of  the 
type  shown  in  Fig.  1388. 

The  Ephemerida  are  distinguished  by  the  venation  of  the  wings 
(Fig.  1387),  and  by  their  proportions  and  their  extensive  corruga- 
tion. 

The  Hemiptera  are  distinguished  by  the  possession  of  a  jointed, 
sucking  proboscis,  directed  backward  beneath  the  head  and 
thorax. 

The  Trichoptera  are  distinguished  by  the  hairy  covering  of 
their  wings,  the  absence  of  jaws  and  proboscis  (palpi  are  pres- 
ent) and  by  a  type  of  venation  of  wings  similar  to  that  shown 
in  Fig.  139 1. 

The  Lepidoptera  are  distinguished  by  their  covering  of  powdery 
scales,  and  by  the  possession  of  a  coiled  sucking  proboscis. 

The  Coleoptera  are  distinguished  by  the  hardened  fore  wings 
(elytra)  meeting  in  a  straight  line  down  the  middle  of  the  back. 

The  Diptera  are  distinguished  by  the  possession  of  a  single  pair 
of  wings,  with  very  few  cross- veins  in  them  (Fig.  1378). 

The  other  two  orders,  Plecoptera  and  Neuroptera,  lack  the  above 
combinations  of  characters  and  may  be  readily  recognized  by  their 
general  likeness  to  figures  pubHshed  in  the  following  paragraphs 
devoted  to  them. 

Besides  these  nine  orders,  there  are  three  others,  of  slight  impor- 
tance in  the  Ufe  of  the  water,  that  are  dehberately  ignored.  These 
are:  ^ 

(i)  The  Thysanura,  or  springtaijs,  common  on  the  surface  of 
water,  but  not  living  in  it.  TEey  will  be  readily  recognizable,  if 
collected,  by  their  very  minute  size,  entire  absence  of  wings,  mouth 
parts  retracted  within  the  head,  and  the  forked  spring  beneath 
the  abdomen  by  means  of  which  they  jump  freely. 

(2)  The  Orthoptera,  of  which  some  of  the  grouse  locusts  (family 
Tettigidae) ,  Hving  by  the  water  side,  occasionally  jump  in  and  take 
a  swim. 

(3)  The  Hymenoptera,  of  which  a  few  minute  egg  parasites, 
enter  the  water  as  adults  to  find  the  eggs  of  their  aquatic  victims, 
and  these  swim  with  their  wings  {Polynema,  etc.). 


882  FRESH-WATER    BIOLOGY 

Stoneflies  {Order  Plecoptera) 

The  stoneflies  constitute  a  small  and  primitive  group  of  insects 
of  inconspicuous  coloration  and  rather  secretive  habits.  They  are 
found  almost  exclusively  about  rapidly  flowing  water.  Every 
spring  brook  will  furnish  a  few  of  the  smaller  grayish  or  brownish 
species,  and  every  larger  rocky  stream  is  the  home  of  some  of  the 
larger  forms.  During  the  winter  months  the  small  black  Capnias 
appear,  often  in  great  abundance  on  the  surface  of  the  snow, 
Capnia  necydaloides  appearing  usually  in  December,  and  Capnia 
pygmaea,  in  March.  Several  species  of  Taeniopteryx  appear  also  in 
March,  and  may  often  be  seen  on  mild,  sunshiny  days  by  the 
borders  of  creeks,  slowly  and  laboriously  flying  along  the  banks  on 
warm  afternoons.  Species  of  Nemoura  appear  in  April,  emerging 
from  the  waters  of  cold  brooks,  and  making  short  flights  from  one 
gray  tree  trunk  to  another.  All  through  the  summer  the  larger 
species  are  emerging  from  rocky  streams,  but  these  are  very  se- 
cretive in  habits.  They  may  be  beaten  from  the  bushes  along  the 
stream  side,  but  are  oftenest  seen  in  numbers  about  street  lamps 
and  are  easiest  collected  when  attracted  to  lights.  The  green 
stoneflies  {Chloroperla,  etc.)  fly  mainly  in  midsummer,  and  frequent 
the  fresh  foliage,  in  the  midst  of  which  they  are  quite  incon- 
spicuous. 

Rudimentary  wings  occur  in  a  number  of  the  genera,  Capnia, 
Taeniopteryx,  Pteronarcella,  Ferla,  etc.,  and,  of  course,  the  wingless 
species  are  to  be  found  near  the  waters  from  which  they  emerge 
on  transformation  —  in  fact,  not  farther  therefrom  than  they  are 
able  to  run  or  climb.  The  males  alone  are  wingless  in  most  cases. 
The  eggs  of  the  females  are  practically  mature  at  transformation. 
While  there  is  dearth  of  observations  as  to  the  feeding  habits 
of  the  adults,  it  is  certain  that  they  will  lap  up  water  and  other 
fluid  substances,  and  the  small  grayish  species  eat  dead  grass  leaves 
and  other  solid  food.  The  mandibles  of  the  larger  forms  are  weak 
and  rudimentary.  The  adult  life,  therefore,  is  probably  very  brief. 
Concerning  the  egg-laying  habits  also,  there  is  dearth  of  actual 
observation.  Females  of  many  species  may  be  taken  when  carry- 
ing egg  masses  extruded  at  the  tip  of  the  abdomen;    but  just 


AQUATIC   INSECTS 


883 


where  these  are  deposited,  and  when  and  how,  are  matters  not 
yet  established.  One  species  of  Capnia,  an  undetermined,  late 
appearing  species  that  occurs  in  Lake  Forest,  111.  in  May,  is 
viviparous. 

The  nymphs  of  stoneflies  are  much  easier  to  fmd  and  to  collect 
than  are  the  adults.  By  Hfting  stones  or  other  obstructions  out 
of  the  bed  of  rapid  permanent  streams,  and  quickly  turning  them 
over  to  look  on  the  under  side,  the  nymphs  may  usually  be  seen 
lying  flat,  outspread,  with  widely  extended  legs  clutching  the  sur- 
face. They  are  always  associated 
with  Mayfly  nymphs  of  similar  ap- 
pearance, but  are  easily  distinguished 
by  the  presence  of  two  claws  on  the 
tip  of  each  foot,  where  the  Mayfly 
nymphs  have  but  one,  and  by  the 
lack  of  gills  upon  the  dorsal  side 
of  the  abdomen.  The  nymphs  of 
larger  species,  as  Perla  (Fig.  1354), 
are  not  easily  managed  in  ordinary 
aquaria.  They  cannot  live  long  in 
still  water,  and  soon  after  being 
placed  in  it,  they  manifest  their 
discomfort,  by  a  vigorous  swa>ing 
of  the  body  up  and  down.  This 
motion  brings  their  tufted  gills  into 
water.      Running    water    aquaria   are 


Fig.  1354.     The  nymph  of  a  stonefly,  Perla. 


better  contact    with    the 
essential  for  their  maintenance. 

Their  transformation  may  often  be  easily  observed  where  it 
occurs  naturally  out  of  doors.  It  always  takes  place  near  to  the 
edge  of  the  water.  Often  rocks  that  project  but  a  few  inches  above 
the  surface  are  favorite  places  of  emergence,  and  the  exposed  sur- 
faces of  these  may  sometimes  be  found  covered  several  layers  deep 
with  the  skins  of  the  nymphs  that  have  come  from  the  bed  of  the 
adjacent  parts  of  the  stream.  Transformation  usually  occurs  at 
night,  but  early  and  late  stragglers  may  often  be  found  by  morn- 
ing or  evening  light.  The  change  from  nymph  to  adult  is,  for  insects, 
comparatively  sHght :  wings  and  accessory  reproductive  organs  are 


884 


FRESH-WATER  BIOLOGY 


perfected,  and  regressive  development  of  gills,  external  armor,  and 
feeding  apparatus  occurs,  but  the  change  of  form  and  of  proportions 
of  the  body  is  slight. 

The  nymphs  of   stoneflies  are,  so   far  as  known,  carnivorous: 
they  feed  on  the  nymphs  of  Mayflies,  on  the  larvae  of  caddisflies 


%. 


Fig.  1355.    Pkromrcys  dorsaia,  adult  female.  FiG.  1356.    Pteronarcys  dorsata,  grown  nymph. 

and  small  diptera  and  perhaps  on  the  young  of  other  stoneflies. 
They  are  themselves  the  food  of  the  trout  and  of  other  fishes  that 
frequent  swift  waters.  Hudson  has  demonstrated  the  importance 
of  stoneflies  as  fish  food  in  the  mountain  streams  of  New  Zealand. 
Adults  and  nymphs  are  equally  serviceable  for  bait  in  all  our 
mountain  streams. 

While  no  keys  to  the  genera  of  the  nymphs  of  stoneflies  have  yet 
been  published,  if  the  adults  are  known,  the  nymphs  may  be 
readily  determined  by  comparison,  for  the  wing  venation  is  fully 


AQUATIC   INSECTS  885 

developed  in  the  wing  pads  of  the  nymph  and  is  comparable  in 
close  detail  with  that  of  the  adult.  It  is  only  necessary  to  remove, 
as  with  a  sharp  razor,  the  wing  pads  from  a  well-grown  nymph, 
young  enough  so  that  the  wings  will  not  be  already  crumpled 
within  their  sheaths,  mount,  and  examine  with  the  microscope. 
Since,  however,  it  is  easier  to  get  nymphs  than  adults,  and  nymphs 
only  will  often  be  available,  the  following  hints  may  be  of  assistance 
in  their  recognition.  Pteronarcys  (Figs.  1355  and  1356)  alone  has 
gills  upon  the  first  two  segments  of  the  abdomen.  Taenia pteryx  alone 
has  three- join  ted,  telescopic  gill  filaments  attached  singly  at  the  base 
of^  the  coxae.  Peltoperla  alone  has  conic-pointed  gill  filaments,  in 
a  few  small  clusters,  concealed  under  the  flaring,  overarched  mar- 
gins of  the  thoracic  segments.  Perla  and  its  alUes  have  copious 
tufts  of  fine  gill  filaments  before  and  behind  the  bases  of  all  legs. 
Chloroperla  and  its  allies,  and  Capnia  and  Leuctra  altogether  lack 
gills. 

Mayflies  {Order  Ephemerida) 

The  Mayflies  constitute  a  small  group  of  very  fragile  insects, 
all  of  which  are  aquatic  in  their  earlier  stages.  They  abound  in 
all  fresh  waters,  both  swift  and  stagnant.  Some  of  the  larger  May- 
flies are  very  well  known,  indeed,  from  their  habit  of  transforming 
all  at  one  time  and  appearing  in  great  swarms  along  shores  of  lakes 
(Fig.  1357)  and  banks  of  the  larger  streams.  They  fly  to  lights 
at  night,  and  sometimes,  under  the  arc  lamps  in  city  streets,  they 
accumulate  in  such  heaps  as  to  require  removal  in  wagons.  Such 
concerted  appearance  of  the  adults  of  a  single  species  gives  some 
conception  of  the  abundance  of  individuals  that  may  five  and  grow 
up  together  in  a  restricted  area;  but  it  is  to  be  borne  in  mind  that 
there  are  scores  of  other  species  living  in  the  same  waters,  the 
adults  of  which  are  rarely  seen  in  numbers,  of  which  the  individuals 
are  probably  quite  as  numerous.  When  their  period  of  trans- 
formation is  extended  through  the  summer  season  and  their 
habits  are  not  gregarious,  but  solitary  and  secretive,  they  may 
entirely  escape  the  notice  of  the  casual  observer. 

Mayflies  are  famed  for  their  ephemeral  existence  —  for  Kving  as 
adults  but  a  day.     They  are  peculiar  among  insects,  in  that  they 


886 


FRESH-WATER   BIOLOGY 


moult  their  external  chitinous  skin  once  again  after  they  transform 
from  the  nymphal  form  to  that  of  the  adult.  It  is  chiefly  these 
callow  and  immature  adults  (known  to  the  books  as  suh-imagoSy 
and  to  British  fishermen  as  dims)  that  fly  to  lights.     Emerging 


Fig.  1357. 


Mayflies  fallen  beneath  an  electric-light  post  on  Lake  Erie. 
H.  S.  Jennings.) 


(Photograph  by  Professor 


from  a  rent  in  the  back  of  the  old  nymph  skin,  they  spread  their 
newly  expanded  wings  and  rise  feebly  into  the  air,  and  if  a  light 
be  near,  they  swarm  to  it;  otherwise  they  settle  upon  any  conven- 
ient tree  or  building,  and  sit  stiffly  (Fig.  1358)  with  uplifted  wings 
until  ready  for  their  final  moulting.     This  may  occur  within  a  few 


AQUATIC    INSECTS  887 

minutes,  as  in  Caenis,  or  it  may  be  delayed  twenty-four  hours  or 
more,  as  in  most  of  our  larger  species.  Caenis  probably  lives  but  a 
few  hours  after  leaving  the  water;  but  the  larger  forms  live  through 
two  days,  their  transformation  from  the  nymph  occurs  in  one  night, 


Fig.  1358.    A  newly-emerged  Mayfly,  Eexagenia  bilineala. 

their  final  moult  the  next  night,  and  their  period  of  adult  activity 
and  egg-laying  and  their  death  the  next  evening. 

The  adults  are  peculiar  in  the  venation  of  their  wings  (Fig.  1387) 
and  in  the  extent  of  the  longitudinal  furrowing  of  the  same,  in 
the  lack  of  functional  mouth  parts  and  in  the  buoyant  function 
assumed  by  the  aHmentary  canal,  which,  being  no  longer  used  for 
food,  is  filled  with  air.  While  highly  speciaUzed  in  most  respects, 
one  very  generalized  character  has  been  retained  in  the  group: 
the  openings  of  the  oviducts  of  the  female  are  paired  and  separate. 

The  males  of  most  species  indulge  in  graceful  ante-nuptial 
flights,  that  to  the  observer  appear  most  delightful  and  exhilarating. 
They  assemble  in  little  companies  and  dance  up  and  down,  alter- 
nately rising  and  falhng,  flying  upward  and  falling  down  again  on 
outspread  wings  in  long  vertical  lines.  The  crepuscular  species 
such  as  Ephemera  and  Hexagenia,  that  compose  the  well-known 
swarms,  fly  out  over  the  surface  of  the  water,  where  the  females 
meet  the  males,  and  afterwards  settle  down  upon  the  surface  of  the 
water  to  liberate  their  eggs.     Caenis  swarms  over  the  edge  of  the 


888 


FRESH-WATER   BIOLOGY 


water  just  as  darkness  falls.     Some  of  the  less  nocturnal  species, 
as  Leptophlebia  and   Choroterpes,   swarm   out  in   the   sunlight  in 
sheltered  places  of  late  afternoons,  or  dance  up  and  down  among 
the  mixed   shadows  and  sunlight  beneath   the 
canopied  crowns  of  tall  stream-side  forest  trees. 
The  females  of  Baetis  creep  beneath  stones  at 
the  surface  of  the  water  and  deposit  their  eggs  in 
single-layered  patches  just  beneath  the  surface. 
The  adult  hfe  of  Mayflies  is  truly  ephemeral 
and  is  concerned  wholly  with  reproduction;  and 
the  struggle  for  existence  is  transferred  largely  to 
the  immature  stages.   The  nymphs  are  highly  and 
independently   specialized.     They   are   adapted 
to  all  sorts  of  aquatic  situations.     A  few,  like 
Hexagenia,    Ephemera,    and    Polymitarcys   (Fig. 
1359),  are  burrowers  beneath  the   bottom  silt. 
A  few,  like  Caenis  and  Ephemerella,  are  of  seden- 
tary habits  and    live  rather  inactively   on    the  ^^^- ^^X^-JrcvsX''^  °^ 
bottom,  and  on  silt- covered  stems.      Many  are 
active  cHmbers  among  green  vegetation;   such  are  Callihaetis  and 
Blasturiis;  and  some  of  these  can  swim  and  dart  about  by  means  of 
synchronous  strokes  of  tail  and  gills  with  the  swiftness  of  a  minnow. 
The  species  of  Leptophlebia  love  the  beds  of  slow-flowing  streams, 
and  all  the  flattened  nymphs  of  the  Heptageninae  Hve  in  swiftly  mov- 
ing water,  and  manifest  various  degrees  of  adaptation  to  withstand- 
ing the  wash  of  strong  currents.    The  form  is  depressed,  and  margins 
of  the  head  and  body  are  thin  and  flaring,  and  can  be  appressed 
closely  to  the  stones  to  deflect  the  current.     So  diverse  are  the 
nymphs  in  form  that  the  genera  may  be  distinguished  among  them 
by  a  beginner  more  easily  than  among  the  adult  Mayflies. 

Mayfly  nymphs  feed  largely  on  dead  vegetable  substances  —  the 
decaying  stems  and  leaves  of  aquatic  plants.  They  are  of  first 
importance  in  the  food  of  fishes.  But  we  are  as  yet  largely  in 
ignorance  of  the  conditions  that  make  for  their  abundance. 

The  study  of  this  group  has  been  greatly  neglected  by  entomol- 
ogists and  our  Mayfly  fauna  is  very  insufficiently  known.  The 
ecology  of  the  immature  stages  is  especially  in  need  of  investigation. 


AQUATIC   INSECTS    •  889 

Dragonflies  and  Damselflies  {Order  Odonata) 

This  is  another  isolated  group  of  insects,  larger  in  size  and  of 
stronger  build.  All  our  representatives  of  the  group  are  aquatic 
in  their  earher  stages,  but  there  are  a  few  Hawaiian  damselflies 
whose  nymphs  live  out  of  the  water,  on  moist  soil  under  the  leaves 
of  liliaceous  plants.  All  members  of  the  order  are  carnivorous  in 
all  stages.  They  are  indeed  among  the  most  important  of  carni- 
vorous forms  about  the  shores  of  all  fresh  waters. 

The  wings  of  the  adults  are  strongly  developed  and  have  a 
peculiar  venation  (Fig.  1388).  The  legs  are  not  used  for  walking, 
but  only  for  perching;  to  facihtate  perching  on  vertical  stems, 
they  are  set  far  forward  and  graduated  in  length,  so  that  they  hold 
the  body  when  at  rest  in  a  more  or  less  horizontal  position.  This 
facihtates  quick  stopping  and  starting  again.  Correspondingly 
the  wings  are  shifted  far  backward,  and  tilted  upward  at  their 
fore  margins,  and  the  side  pieces  of  the  thorax  are  askew. 

The  males  are  pecuHar  also  among  the  orders  in  having  the 
accessory  organs  of  reproduction  (copulatory  apparatus)  developed 
upon  the  ventral  side  of  the  second  abdominal  segment,  far  re- 
moved from  the  opening  of  the  sperm  ducts  upon  the  ninth  segment. 
The  eyes  are  very  highly  developed,  and  the  antennae  are  minute 
and  setaceous.  In  this  they  resembl  the  preceding  order  Ephem- 
erida,  but  the  two  groups  as  they  exist  to-day  are  highly  differenti- 
ated from  each  other,  although  more  or  less  intermediate  fossil 
forms  point  to  their  common  origin  in  the  past. 

Among  the  dragonflies  are  many  superb  flyers.  The  speed  on 
the  wing  of  Traniea  and  Anax  equals,  and  their  agihty  exceeds, 
that  of  swallows.  They  all  capture  their  prey  in  flight,  and  are 
dependent  on  their  wings  for  getting  a  living.  But  the  habit  of 
flight  is  very  different  in  different  groups.  Only  a  few  of  the 
strongest  forms  roam  the  upper  air  at  will.  There  is  a  host  of 
beautiful  species,  the  skimmers  or  LibelluHdae  (Fig.  1360),  that 
hovers  over  ponds  in  horizontal  flight,  the  larger  species  on  tireless 
wings,  keeping  to  the  higher  levels.  The  stronger  flying  Aeschnidae 
course  along  streams  on  more  or  less  regular  beats:  but  the  Gom- 
phines  are  less  constantly  on  the  wing,  flying  usually  in  short 


890  FRESH-WATER  BIOLOGY 

sallies  from  one  resting  place  to  another,  and  alighting  oftener  on 
stones  or  other  flat  surfaces  than  on  vertical  stems. 

The  damselflies  are  not  such  good  flyers.  The  common  black- 
wing  Calopteryx  (Fig.  136 1)  may  usually  be  seen  fluttering  gaily 
about  the  borders  of  creeks,  but  most  damselflies  are  Httle  in 


Fig.  1360.    The  Blue  Pirate  dragonfly,  Pachydiplax  longipennis.     (Drawn  by 
Mrs.  J.  G.  Needham.) 

evidence,  and  confine  their  locomotion  to  flitting  from  stem  to 
stem  amid  the  shelter  of  vegetation. 

The  dragonflies  eat  other  insects  in  vast  numbers  and  in  great 
variety.  A  large  part  of  their  food  consists  of  small  diptera:  and 
because  many  of  these  small  diptera  are  noxious  species,  mos- 
quitos,  etc.,  an  extended  inquiry  was  once  made  as  to  the  feasibiUty 
of  using  dragonflies  to  remove  these  pests :  it  appeared  that  dragon- 
flies  are  not  at  all  discriminating  in  their  feeding,  and  wiU  as  readily 
eat  useful  as  noxious  species.  Then,  too,  they  eat  other  dragonflies, 
apparently  preferring  forms  that  are  only  a  little  smaller  than  them- 
selves. Hagenius,  for  example,  eats  Gomphus,  and  Gomphus  eats 
Mesothemis,  and  Mesothemis  eats  Lestes,  and  Lestes  eats  Argia, 
and  Argia  eats  Ischnura,  and  so  on  from  the  greatest  even  unto  the 
least  of  them. 

Many  dragonflies  are  eaten  by  birds  and  other  animals  at  their 
transformation,  before  they  are  able  to  fly  and  escape;  and  some 
of  those  that  are  not  very  strong-flying  are  eaten  habitually  by 
birds  —  the  smaUer  Libellulines  by  king-birds,  and  the  smaller 
damselflies  by  swallows.  But  it  is  doubtful  whether  anything  that 
flies  is  able  to  capture  in  flight  one  of  the  swiftest  dragonflies. 


AQUATIC   INSECTS 


891 


There  is  much  diversity  of  egg-laying  habits  in  the  order.  All 
the  damselflies  and  many  dragonflies,  especially  Aeschnidae,  are 
provided  with  an  ovipositor,  by  means  of  which  punctures  are 
made  in  the  stems  of  aquatic  plants,  in  logs,  in  wet  mud,  etc.,  for 
the  reception  of  the  eggs.  The  eggs  are  placed  singly  in  the  punc- 
tures, and  usually  just  below  the  surface  of  the  water;  but  a  few 
damselflies  descend  the  stems  to  place  them  deeper,  and  some 
species  of  testes  place  them  habitually  in  the  stems  above  the  sur- 
face. Here  they  are  subject  to  the  attack  of  egg  parasites.  The 
females  of  those  dragonflies  that  lack  a  well-developed  ovipositor 
drop  their  eggs  upon  the  surface  of  the  water  while  in  flight  (usually 
descending  to  touch  the  surface,  and  thus  to  wash  them  free), 
whereupon  the  eggs  scatter  and  fall  to  the  bottom;  or,  they  settle 
on  some  plant  stem  at  the  surface  and  hang  them  in  gelatinous 
masses  about  the  stem.  In  certain  of  the  Cordulinae  these  masses 
are  long  gelatinous  strings,  containing  many  hundreds  of  eggs.  It 
is  easy  to  get  the  eggs  of  most  Libellulines  for  study.  When  a  fe- 
male is  seen  tipping  the  surface  of  the  water  with  her  abdomen 
while  in  flight,  if  she  be  captured  uninjured  and  held  by  the  tips 
of  the  fore  wings  (leaving  the  hind  wings  free)  and  dipped  against 
the  surface  of  the  water  in  a  glass,  in  imitation  of  her  own  motion 
while  at  large,  she  wifl  usually  liberate  eggs  in  great  abundance  in 
the  water.  These  require  about  three  weeks  for  hatching,  and  the 
nymphs  begin  to  eat  each  other  early  in  life. 

There  are  nymphs  of  Odonata  in  all  sorts  of  fresh  water.  Those 
of  some  of  the  larger  active  species  clamber  about  freely  among 


Fig.  1361.     Damselfly  nymphs;  a,  Calopteryx;  b,  Lestes. 

water  weeds,  and  even  chase  their  prey,  creeping  stealthily  upon  it 
until  within  range.     Most  damselflies  (Fig.  1361)  clamber  about 


892  FRESH-WATER  BIOLOGY 

among  green  stems,  where  they  are  quite  inconspicuous.  But 
nearly  all  dragonfly  nymphs  get  their  living  by  waiting  in  hiding 
for  the  approach  of  their  prey,  and  comparatively  few  of  them  roam 
freely  about  in  the  water.  Most  of  the  LibelluKdae  are  bottom 
sprawlers  (Fig.  1362) ;  most  of  the  Gomphines  are  burrowers  beneath 


Fig.  1362.     The  sprawling  nymph  of  Didytnops  transversa. 

the  bottom  silt,  and  the  nymphs  of  Cordulegaster  are  expert 
ambuscaders,  scratching  a  hole  in  the  sand  of  the  bottom  and 
gettmg  into  it,  kicking  the  sand  up  over  their  backs  until  covered 
excepting  the  tips  of  the  eyes  and  of  the  respiratory  orifice  at 
the  end  of  the  abdomen,  and  lying  in  wait  until  some  unsuspecting 
little  animal  suitable  for  food  wanders  within  reach. 

The  chief  organ  for  capturing  prey  in  the  nymphs  of  all  the 
Odonata  is  the  remarkably  developed  labium  (Fig.  1389^),  which 
has  become  elongated,  hinged  in  the  middle  and  folded  back  under 
the  thorax.  It  has  acquired  a  formidable  array  of  grappUng  hooks 
and  spines  at  its  tip.  It  is  often  longer  than  the  fore  legs  when 
extended  and  possesses  muscles  capable  of  extending  it  with  light- 
ning-like speed.  It  is  thrown  forward  and  opened  by  a  single 
movement,  and  when  it  closes  on  its  victim  it  is  withdrawn  again 
instantly,  dragging  the  struggling  captive  back  under  the  jaws, 
which  then  come  into  play. 

The  problem  of  getting  air  has  been  solved  in  two  ways  in  the 
nymphs  of   the  two  suborders  of   Odonata.     In   the  damselflies 


AQUATIC   INSECTS 


893 


(Fig.  1363),  there  are  developed  three  more  or  less  leaf  like  gills  upon 
the  tip  of  the  abdomen,  and  these  are  traversed  by  fine  tracheae, 
and  doubtless  assist  in  getting  air,  although  not  entirely  essential 
to  that  end.     In  the  larger  dragonfly  nymphs  there  is  developed 


Fig.  1363.    The  nymph  of  Ischnura  verticalis. 


within  the  abdomen  a  respiratory  chamber  made  out  of  the  hinder 
portion  of  the  modified  alimentary  canal.  Through  the  action  of 
the  abdominal  muscles,  the  water  is  alternately  drawn  into  this 
and  expelled  again.  This  chamber  is  lined  with  multitudes  of 
tracheal  gills,  and  abundantly  supplied  with  tracheae,  constitut- 
ing the  most  perfect  aquatic  respiratory  apparatus  developed  in 
insects. 

Transformation  occurs  in  most  Odonata  very  close  above  the  sur- 
face of  the  water.  The  larger  species  transform  for  the  most  part 
at  night:  the  damselflies,  at  any  time.  The  period  of  half  an  hour 
or  more  required  for  drying  the  wings  before  sustained  flight  is 
possible  is  a  time  of  great  peril  in  the  life  of  the  dragonflies.  It  is 
a  time  of  opportunity,  however,  for  the  coflector  of  Hfe  history 
material. 

Water  Bugs  {Order  Hemiptera) 

A  small  part  of  this  great  order  is  aquatic ;  a  number  of  families 
are  well  adapted  for  hfe  in  the  water;  a  few  run  over  the  surface 
and  a  few  others  live  habitually  on  the  wet  shores  and  forage  in  the 
flotsam  and  drift  of  the  waves.  Adults  and  nymphs  are  of  similar 
habits  and  are  generally  sufficiently  alike  in  structure  for  ready 
identification,  the  metamorphosis  being  slight.  All  are  distin- 
guished from  the  members  of  other  groups  by  the  possession  of  a 
jointed  puncturing  and  sucking  proboscis  that  is  directed  backward 
beneath  the  head.     The  families  are  so  diverse  in  structure  that 


894 


FRESH-WATER   BIOLOGY 


here  again  is  given  evidence  of  independent  adaptation  to  aquatic 
life,  and  nowhere  could  be  found  more  complete  intergradation  of 
habits  between  terrestrial  and  shore-loving  forms  and  those  that 
dwell  in  the  water. 

The  shore  bugs  (Acanthiidae)  and  toad  bugs  (Pelogonidae)  are 
essentially  terrestrial;  the  marsh  treaders  (Hydrometridae),  water 


Fig.  1364.    A  giant  water  bug,  Benacus,  clinging  to  a  vertical  surface  under  water. 

striders,  skaters,  etc.  (Veliidae  and  Gerridae),  have  passed  out  upon 
the  surface,  a  few  of  them  having  acquired  the  ability  to  dive  and 
swim.  The  Nepidae  and  Belostomatidae  are  fairly  adapted  forms 
that  do  not  depart  far  or  long  from  the  surface  of  the  water,  and 
only  the  Corixidae  and  Notonectidae  have  acquired  very  highly 
speciaHzed  apparatus  for  swimming  and  for  carrying  down  a  copious 
air  supply. 

There  are  no  tracheal  gills  developed  in  this  order.  Nymphs 
and  adults  alike  must  come  to  the  surface  for  air.  They  are  easily 
collected  by  sweeping  aquatic  vegetation  with  a  dip  net.  The 
Corixidae  stick  more  closely  to  the  bottom  than  do  other  forms. 


AQUATIC   INSECTS 


895 


Transformation  occurs  in  the  water,  and  is  only  a  little  more 
of  a  change  than  are  the  earlier  nymphal  moults.  The  adults  of 
many  genera  fly  from  one  body  of  water  to  another,  and  a  few  of 
the  largest  forms  (Fig.  1364)  have  a  habit  so  well  known  of  flying 
to  electric  lights  at  night  that  they  have  been  denominated  ''electric 
light  bugs."  These  immense  bugs  are  among  the  most  powerful 
members  of  the  order;  the  largest  of  the  dragon  fly  nymphs  are  no 
match  for  them;  they  will  frequently  attack  and  kill  frogs,  and 
they  have  even  been  found  preying  on  woodpeckers,  presumably 
encountered  in  flight.     Their  weapon  of  offense  is  the  stout  beak, 


Fig.  1365.     A  water  bug  (at  the  left)  and  a  backswimmer  (at  the  right), 
resting  at  the  surface  of  an  aquarium. 


which  is  capable  of  making  painful  wounds.  Even  the  smaller 
forms  of  Notonecta  (Fig.  1365)  can  puncture  the  fingers  of  the 
collector  if  carelessly  handled. 

The  eggs  of  the  more  strictly  aquatic  members  of  the  family  are 
fairly  well  known.  Those  of  Benacus  (Fig.  1366)  and  Amorgius 
are  deposited  on  the  vertical  stems  of  Typha,  etc.,  above  the 
surface  of  the  water;  these  are  among  the  largest  of  insect  eggs. 
Those  of  the  Nepidae,  Nepa  and  Ranatra,  are  distinguished  by 
long  appendages  at  the  micropylar  end,  and  are  inserted  into  the 
soft  tissues  of  plants  —  into  rotten,  water-soaked  wood,  or  into 


8g6  FRESH-WATER    BIOLOGY 

green  herbs.  Those  of  Notonecta  are  deposited  singly  on  the  sides 
of  plant  stems  under  water,  and  those  of  Corixa  are  deposited  in 
similar  places  or  stuck  on  to  the  back  of  crawfishes. 

The  surface-haunting  forms  are  characteristically  of  scavenger 
habits,  eating  the  insects  of  all  sorts  that  fall  upon  the  surface  of 


Fio.  1366.     The  eggs  of  the  giant  water  bug,  Benacm,  on  the 
base  of  a  Typha  stem. 

the  water;  while  the  more  strictly  aquatic  bugs  are  truly  predatory 
with  the  possible  exception  of  the  minute  Plea,  which  is  believed 
not  to  be  carnivorous  at  all.  The  highly  specialized  Corixidae  are 
able  to  remain  wholly  submerged  for  long  periods.  They  clamber 
about  amid  the  debris  of  the  pond  bottom,  and  when  they  come  to 
the  surface  for  air,  they  do  not  remain  there,  but  quickly  descend 
again  to  the  shelter  of  the  bottom  trash.  Of  all  Hemiptera  these 
are  the  ones  most  commonly  eaten  by  fishes. 


AQUATIC    INSECTS  8q7 

DoBSONS,  Fish  Flies,  Spongilla  Flies  {Order  Neuroptera) 

But  two  families  of  this  great  and  heterogeneous  order,  as  now 
commonly  restricted,  are  aquatic,  and  these  in  their  larval  stages 
only.  The  larvae  of  all  the  members  of  the  small  family  Sialididae 
are  free-ranging  carnivorous,  aquatic  forms,  and  in  the  family 
Hemerobiidae,  there  are  a  few  genera  whose  larvae  Hve  in  the 
water.  These  two  families  are  so  very  different  in  every  respect 
that  they  are  better  considered  separately. 

SiALiDiDAE.  Here  belong  a  few  of  the  most  primitive  of  insects 
having  complete  metamorphosis:  the  orl  flies,  fish  flies,  dobsons, 
etc.  They  are  mostly  of  large  size,  and  are  provided  with  ample 
wings,  which,  however,  serve  but  rather  poorly  for  flight.  The 
dobsons  are  among  the  largest  of  insects,  and  their  larvae,  known 
to  the  fishermen  as  hellgrammites,  are  famous  as  bait  for  black  bass. 

They  are  found  in  swift  streams  beneath  the  stones,  where  they 
cling  securely  by  means  of  their  stout  legs,  aided  by  a  pair  of  stout- 
clawed  processes  at  the  end  of  the  body.  They  are  provided  at 
the  sides  of  the  abdomen  with  paired  lateral  fleshy  processes,  and 
at  the  base  of  each  of  these  there  is  a  large  tuft  of  fine  tracheal  gills. 
They  are  blackish,  ugly- looking  crawlers,  of  slow  growth,  requiring 
apparently  several  years  to  develop.  When  grown  they  crawl 
out  on  shore  and  seek  a  suitable  place  beneath  a  log  or  stone; 
for  the  pupae  are  not  aquatic.  The  adult  female  lays  her  eggs  in 
broad  flat  masses  on  stones  or  timbers  above  the  edge  of  the  water, 
and  covers  them  over  with  a  chalky  white  incrustation.  The 
eggs  are  piled  several  layers  deep  and  are  very  numerous.  On 
hatching  the  young  fall  into  the  water,  and  begin  at  once  their 
predatory  existence.  But  one  species  of  dobson  is  found  in  the 
eastern  United  States,  the  common  Corydalis  cornuta  L.  The 
fish  flies  iChaiiliodes)  are  insects  of  similar  appearance  and 
habits,  about  half  as  large  as  the  dobsons,  ha\dng  an  expanse 
of  wing  of  about  one  and  a  half  inches.  Their  larvae  usually  fre- 
quent still  water,  where  they  clamber  over  and  under  logs.  A 
rotten  log  on  shore  furnishes  the  favorite  place  for  the  excavation 
of  a  pupal  chamber.  The  eggs  are  laid  above  the  water  in  naked 
patches  of  one  or  more  layers  on  either  dead  wood  or  green  leaves. 


898 


FRESH-WATER  BIOLOGY 


The  orl  flies  (Sialis)  are  still  smaller  having  an  expanse  of  wing  of 
an  inch  or  less.  They  are  plain,  blackish  in  color,  and  rather 
secretive  in  habits.  Sometimes  they  occur  in  such 
numbers  as  to  blacken  the  herbage  about  the  pond 
border.  The  larvae  (Fig.  1367)  live  among  the  stones 
and  gravel  in  the  bed  of  brooks,  and  in  the  borders 
of  ponds,  and  transform  in  the  wet  sand  on  shore. 
They  are  readily  distinguished  from  other  larvae 
by  the  long  tail-like  prolongation  of  the  last  seg- 
ment of  the  body.  The  female  lays  her  eggs  (Fig. 
1368)  in  broad,  single  layered,  blackish  patches  on 
some  stick  or  timber  above  the  surface  of  the 
water.  The  lateral  filaments  of  the  abdomen  in 
Sialis  are  thin-skinned,  and  contain  tracheae,  and  it 
is  possible  that  they  serve  as  organs  of  respiration; 
there  are  no  additional  clusters 
of  fine  gills  at  their  bases.  Un- 
like the  foregoing,  these  larvae 
descend  into  the  bottom  silt 
and  burrow  through  it,  and  their  long  ab- 
dominal filaments  are  close  laid  on  the  back, 
as  are  the  gills  of  the  burrowing  Mayfly 
nymphs. 

There  is  a  striking  general  similarity  be- 
tween the  larvae  of  the  Sialididae  and  those 
of  the  more  generaHzed  carnivorous  Coleoptera. 

Hemerobiidae.  Only  two  genera  in  this  large  family  of  attrac- 
tive insects  are  aquatic  in  our  fauna,  Climacia  and  Sisyra  (Fig.  1369). 
These  are  small  insects,  half  an  inch  or  less  in  expanse  of  wing, 


Fig.  1367.  The  larva 
of  the  orl  fly,  Sialis 
infumata. 


Fig.  1368.     The  eggs  of  the 
orl  fly;  from  a  photograph. 


Fig.  1369.     A  spongilla  fly,  Sisyra. 

the  former  yellow  and  brown  in  color,  the  latter,  plain  brown. 
Nothing  is  known  of  the  feeding  habits  of  the  adults.     Their  larvae 


AQUATIC   INSECTS 


899 


(Fig.  1370)  feed  upon  fresh- water  sponges,  and  live  within  the  oste- 
oles  of  the  same,  or  in  depressions  on  the  exterior  of  the  sponge  mass. 
They  puncture  the  tissue  of  the  sponge  with  their  long  decurved 
sucking  mouth  parts.  The  paired  appendages  of  the  abdominal 
segments  are  bent  downward  underneath  the  body,  and  curiously 
angulated;  they  are  moved  back  and  forward  with  a  rapid,  inter- 
mittent, shuttle-like  vibration.  In 
the  well-grown  larvae,  the  stomach 
has  no  posterior  opening,  and  the 
sponge  substance  taken  up  through 
the  slender  proboscis  appears  to  be 
wholly  absorbed.  Correspondingly, 
the  posterior  part  of  the  aHmentary 
canal  and  its  appendages  are  put  to 
a  new  use.  The  malpighian  tubules, 
or  nephridia,  are  metamorphosed  in 
large  part  into  silk  secreting  organs, 
the  rectum  into  a  silk  reservoir,  and 
the  terminal  aperture  into  a  spin- 
neret. When  grown  the  larva  leaves 
the  water  and  climbs  to  some  suitable 
supporting  surface,  and  spins  with  this 
apparatus  first  a  wide  canopy  over 
itself,  and  then  a  closer  fitting  inside 
cocoon.  Climacia  weaves  the  outer 
covering  in  a  beautiful  hexagonal 
mesh;  Sisyra  makes  both  coverings 
plain  and  close  woven.  Nothing  is  known  of  the  feeding  or  egg- 
laying  habits  of  the  adult,  or  of  any  other  particulars  except  that 
they  are  sparingly  attracted  to  lights. 

It  should  be  mentioned,  perhaps,  in  passing,  that  the  immature 
stages  of  another  genus  of  Hemerobiidae,  Polystoechotes,  the  genus 
containing  our  largest  representatives  of  the  family,  are  as  yet 
unknown. 


Fig.  1370.    The  larva  of  Sisyra. 


900 


FRESH-WATER   BIOLOGY 


The  Caddisflies  {Order  Trichoptera) 
The  caddisflies  constitute  a  large  group  of  insects,  nearly  all  of 
which  are  aquatic  in  their  immature  stages.  Among  the  adults 
are  many  pretty  species  of  soft  colors  and  great  elegance  of  form. 
Having  rudimentary  mouth  parts  they  are  short-lived.  They  are 
chiefly  nocturnal  in  habits  and  fly  to  lights,  often  in  great  num- 
bers. Some  are  diurnal  and  hover  over  water  in  long  sustained 
horizontal  flight;  others  dance  up  and  down  in  companies  imder 
the  shelter  of  streamside  trees.  No  insects  are  more  common 
about  the  wharf  lights  on  the  shores  of  our  great  lakes. 

The  larvae  exliibit  great  diversity  of  structure  and  habits.  Much 
excellent  work  has  been  done  on  them  in  Europe,  but  our  American 
forms  are  little  known.  The  most  familiar  larvae  are  the  well 
known  ''caddisworms"  that  construct  portable  cases  (Fig.  13  71), 


Fig.  1371.    Caddisworm  cases.     (Drawn  by  Mrs.  J.  H.  Comstock.) 


in  which  to  live,  and  carry  them  about  on  their  backs.  These 
cases  are  made  out  of  a  great  variety  of  materials:  sticks,  smaU 
stones,  sand  grains,  bits  of  sheU,  of  leaves  or  of  bark;  in  short,  almost 
any  solid  material  suitably  small  and  available.  In  many  species 
the  construction  of  the  cases  is  so  uniform  in  pattern  and  materials 
that  the  larvae  may  be  known  by  the  houses  which  they  drag 
about.  The  larvae  of  the  Phrygeaneidae  construct  cylindrical  cases 
made  of  bits  of  stems,  grass,  etc.,  placed  lengthwise  in  a  continu- 


AQUATIC    INSECTS 


901 


ous  spiral  band;  the  larva  of  Helico psyche  builds  out  of  sand  grains 
a  spirally  coiled  case,  shaped  like  a  snail  shell.  The  materials 
of  the  case  are  always  stuck  together  by  means  of  the  secretion  of 
the  salivary  glands.  Usually  the  cases  are  cylindrical  but  sometimes 
they  are  triangular,  or  square  in  cross-section.  Usually  the  sticks 
used  are  placed  lengthwise,  but  sometimes  crosswise,  as  in  stick 
chimneys,  to  make  the  bulky  and  cumbersome  dwellings  of  some 
of  the  Limnophilidae.  Sometimes,  on  the  other  hand,  they  are  con- 
structed so  light  and  thin  as  to  offer  little  hindrance  to  free  loco- 
motion, and  a  few  larvae  with  well-developed  swimming  fringes  on 
their  long  oarlike  feet  swim  freely 
about.  In  the  cases  that  are  con- 
structed by  most  larvae  of  the  two 
families  Hydroptilidae  (Fig.  1372) 
and  Rhyacophilidae,  no  extraneous 
materials  are  used,  but  only  the  se- 
cretion of  the  salivary  glands;  these 
cases  are  therefore  thin  and  parch- 
ment-like. Most  members  of  the 
great  family  Hydropsychidae  make 
no  portable  cases  at  all,  but  only 
runways  in  the  crevices  between  the 
stones  in  streams;  these  they  line 
with  silken  threads.  Some  of  these 
larvae,  among  which  are  the  com- 
monest members  of  the  genus  Hydro- 
psyche,  to   be  found   in   every  swift 

,  1  r  1       Ti  Fig.   1372.      Micro-trichoptera.      On   the 

stream,   Spm   webs  OI    open   mesn,   like     left,  a  lami;  on  the  right,  a  pupa  oi  another 

.  r  ^  smaller  species,  within  its  transparent  case. 

fishermen  s  semes,  out  from  the  up- 
stream ends  of  their  tubes  or  runways;  clearly,  this  is  for  the 
purpose  of  catching  any  little  organisms  set  adrift  in  the  stream. 
These  are  mainly  carnivorous  larvae;  many  members  of  other 
famines  have  a  mixed  diet  of  vegetable  and  animal  food,  but  a 
goodly  number  are  characteristically  herbivorous. 

There  are  caddisfly  larvae  for  all  sorts  of  waters,  and  lor  wet 
situations,  or  mossy  banks.  A  few  species,  accompanying  the 
"blood  worms,"  have  migrated  far  out  on  the  bottoms  of  our  larger 


902  FRESH-WATER   BIOLOGY 

lakes  into  deep  water.  The  gills  of  the  caddisfly  larvae  are  always 
of  the  filamentous  type,  never  lamelliform.  They  are  wanting  in 
members  of  several  families,  and  are  variously  disposed  about  the 
body,  singly  or  in  clusters,  in  many  others;  their  number,  form, 
and  arrangement  furnish  group  recognition  characters.  The  more 
typical  caddisworms,  having  their  gill  filaments  along  the  sides  of 
the  abdomen  completely  inclosed  within  the  case,  keep  water  flow- 
ing through  by  means  of  continual  undulating  motion  of  the  abdo- 
men; three  tubercles  at  the  base  of  the  abdomen  and  a  pair  of 
stout  prolegs  at  its  apex  serve  to  keep  the  walls  properly  spaced 
for  the  admission  and  the  flow  of  the  water.  The  case  is  always 
large  enough  so  the  larva  can  entirely  withdraw  itself  inside. 
By  this  means  it  doubtless  escapes  from  many  enemies.  But 
some  of  the  larger  fishes,  as,  for  example,  brook  trout,  eat  case 
and  all. 

The  pupa  of  caddisflies  is  peculiar  in  that  it  also  is  aquatic. 
It  is  formed  within  the  larval  case  or  tube,  the  larva  closing  the 
apertures  with  a  perforate  web  of  silk  before  its  final  moulting; 
this  web  admits  water  for  respiration,  but  keeps  out  enemies. 
True  tracheal  gills,  of  the  same  type  as  those  possessed  by  the  larvae, 
are  present  on  the  pupae  of  many  caddisflies.  All  the  pupae  are 
more  or  less  active;  some  maintain  constant  undulating  move- 
ments of  the  abdomen  to  keep  the  water  circulating,  and  at  the 
close  of  the  pupal  stage  all  work  their  way  out  of  the  larval  case, 
and  swim  to  the  surface  of  the  water  to  undergo  their  final  trans- 
formation. In  the  case  of  species  that  inhabit  swiit  waters  and 
transform  in  the  current,  this  takes  place  very  quickly,  the  adult 

emerging  instantly  on  reaching  the  sur- 
face and  flying  away  at  once.  Although 
the  adults  have  jaws  of  the  most  rudi- 
mentary sort,  the  mandibles  of  the  pupa 
are  often  large  and  conspicuous ;  they  are 
supposed  to  be  of  use  in  cutting  a  way 

Fig.  1373.    An  egg  ring  of  PAryganea.      OUt   of   the   larVal    CaSC. 

The  eggs  of  caddisflies  are  laid  in 
various  ways  and  places.  Some  are  dropped  in  the  surface  of 
still  pools  while  in  flight,     The  females  of  some  of  the  Hydro- 


AQUATIC   INSECTS  903 

psychidae  crawl  beneath  the  water  and  spread  their  eggs  in  a 
single  layer  over  the  lee  side  of  stones  in  the  gentler  currents. 
The  big  forms  of  Phryganea  fasten  their  pretty  green  eggs  in 
a  gelatinous  ring  (Fig.  1373)  on  the  stem  of  some  aquatic  plant. 

Aquatic  Moths  (Order  Lepidoptera) 

Of  this  great  order  of  insects,  only  a  few  moths  of  the  family 
PyraHdae  are  aquatic.  Many  moths  live  as  larvae  on  plants  by  the 
waterside,  and  a  few  burrow  in  the  tissues  of  submerged  aquatic 
plants,  obtaining  their  air  from  the  airspaces  of  the  plant  stems. 
The  aquatic  caterpillars,  like  their  terrestrial  relatives,  are  distin- 
guished from  larvae  of  other  orders  by  the  possession  of  a  brown 
chitinous  shield  covering  the  prothoracic  segment,  by  bristle-bear- 
ing tubercles  regularly  disposed  over  the  body  and  by  fleshy  grasp- 
ing prolegs  beneath  the  abdomen. 

There  are  three  types  of  aquatic  larvae  found  commonly  in  our 
fresh  waters,  two  in  ponds  and  one  in  rapid  streams. 

The  larvae  of  Nymphula  (Hydrocampa)  are  destitute  of  gills,  and 
greatly  resemble  pale  terrestrial  caterpillars.  They  live  in  flat 
cases  composed  of  two  pieces  cut  out  from  green  leaves  of  river- 
weed  or  water-lily,  and  fastened  together  and  lined  with  silk. 
They  live  near  the  surface  of  the  water.  During  the  pupal  stage 
the  cases  are  often  found  floating.  The  eggs  are  laid  on  or  under 
floating  leaves. 

The  larvae  of  Paraponyx  are  provided  with  abundant  branching 
gills,  which  surround  the  body  Hke  a  white  fringe.  These  larvae  live 
in  similar  cases  or  between  leaves  in  sheltering  crevices  that  are 
lined  with  silk. 

The  larvae  of  Elophila  fulicalis,  as  recently  described  by  Lloyd 
from  Ithaca,  N.  Y.,  live  on  the  stones  in  rapid  streams,  protected 
by  an  irregular  shelter  of  thin-spun  silk.  They  are  in  form  strongly 
depressed,  and  have  unbranched  gills  arranged  in  two  longitudinal 
lateral  rows.  They  feed  mainly  on  such  green  algae  as  grow  near 
at  hand.  Each  larva  when  grown  fashions  a  broadly  dome-shaped 
pupal  shelter  or  half-cocoon  under  some  portion  of  the  larval 
shelter,  with  a  row  of  marginal  openings  at  either  side  to  permit 
free  circulation  of  water  and  air  through  it. 


904 


FRESH-WATER  BIOLOGY 


Beetles  {Order  Coleoptera) 


Of  this  great  group  of  insects  only  a  few  families  are  wholly 
aquatic,  and  a  few  others  are  partially  so.  The  order  as  a  whole  is 
predominantly  terrestrial,  and  the  aquatic  families  show  unmistak- 
able signs  of  having  been  developed  from  terrestrial  ancestors. 
All  the  adults  and  pupae  are  strictly  terrestrial  in  their  mode  of 
respiration,  and  nearly  all  the  larvae  likewise  get  their  air  supply 
from  above  the  surface  of  the  water.  The  pupae  of  all  are  formed 
either  on  land,  or  in  direct  communication  with  the  air.  The 
families  that  are  strictly  aquatic  are  the  Dytiscidae,  HalipHdae, 
Parnidae  and  Amphizoidae;  those  that  show  complete  intergrada- 
tion  in  habits  are  the  Hydrophilidae  and  Dascyllidae.  The  Chrys- 
omehdae  are  scarcely  to  be  called  aquatic  at  all  in  any  proper 
sense,  although  two  of  the  subfamilies  live  on  water  plants. 

There  is  such  great  diversity  of  habits  and  structure  in  water 
beetles  that  the  families  may  be  best  considered  separately.  We 
begin  with  those  that  are  least  aquatic  in  habit. 

Two  small  groups  of  leaf  beetles  of  the  great  family  ChrysomeHdae 
feed  upon  water  plants;  the  Galerucellinae,  upon  the  floating  leaves 
of  members  of  the  water-Hly  family.  These  dingy  little  beetles 
lay  their  yellow  eggs  in  small  clusters  on  the  upper  surfaces  of  the 
leaves,  and  the  black-banded  larvae,  hatchmg  therefrom,  feed  upon 
the  tissues,  quite  as  their  more  famihar  relatives  feed  upon  land 
plants.  The  other  subfamily,  the  Donaciinae,  or  long-horned  leaf- 
beetles,  is  much  more  interesting.  The  larvae  feed  upon  the  roots 
of  aquatic  plants,  far  beneath  the  surface  of  the  water.  They  are 
provided  with  a  pair  of  spiracles  near  the  end  of  the  body  and 
these  spiracles  are  armed  with  sharp  corneous  processes,  capable 
of  being  thrust  into  plant  stems,  of  reaching  the  air  spaces  on  the 
inside,  and  of  obtaining  the  air,  rich  in  oxygen,  contained  therein. 
Thus  the  larvae,  while  destitute  of  gills,  and  strictly  air  breathers, 
get  their  air  supply  through  the  medium  of  the  plants,  while  Hving 
always  beneath  the  water.  The  pupal  stage  likewise  is  passed 
in  the  place  where  the  larva  lived  on  the  roots,  but  the  pupa  is 
inclosed  in  a  water-tight  cocoon,  attached  to  the  plant  tissue  and 
containing  air  in  free  communication  with  that  in  the  air  spaces  of 


AQUATIC   INSECTS  905 

the  plant.  The  adult  beetles  spend  their  lives  among  the  leaves 
of  the  plants,  flying  actively  about  when  disturbed.  They  are  of 
shining,  metaUic  coloration,  blue  or  green.  Those  that  Uve  on  water 
lilies  deposit  their  eggs  through  holes  eaten  in  the  leaves,  arranging 
them  in  a  curve  around  the  opening  on  the  under  side.  They  are  able 
to  place  them  thus  through  the  possession  of  a  long  extensile 
ovipositor. 

The  family  Hydrophilidae  is  in  part  terrestrial  and  in  part  aquatic, 
and  the  aquatic  members  show  all  degrees  of  adaptation  to  water 
life.  A  few  of  the  larger  forms  are  expert  swimmers,  but  many  of 
the  smaller  ones  are  fitted  only  for  dabbling  around  in  the  mud  at 
the  water's  edge.  The  best-known  member  of  the  family  is  perhaps 
the  big  black  Hydrophilus,  with  finely  fringed  swimming  legs  and 
with  keeled  sternum.  It  is  attracted  to  electric  lights  in  vast 
numbers  in  the  spring,  where  it  falls  beneath  them  and  flounders 
around  in  the  dust  of  the  street,  giving  a  fine  illustration  of  the  use- 
lessness  of  its  specialization  when  in  an  unsuitable  environment. 
The  larva  of  this  beetle  is  commonly  taken  in  ponds,  not  swimming, 
but  clinging  to  stems  at  the  surface,  its  squat,  hairy  body  not  well 
fitted  for  getting  through  the  water,  but  with  immense  rapacious 
jaws,  very  capable  of  seizing  large  Mayfly  nymphs  and  adult  Eu- 
hranchipus  when  these  swim  within  reach.  Another  hydrophilid 
which  often  swarms  into  trap  lanterns  set  over  streams  is  Berosus, 
whose  aquatic  larva  is  provided  with  lateral  paired  abdominal  ap- 
pendages somewhat  like  those  of  the  neuropterous  genus  Sialis. 

The  eggs  of  Hydrophilus  are  laid  in  a  white  membranous  capsule 
attached  to  plant  stems  and  leaves  at  the  surface  of  the  water. 

The  Amphizoidae  and  Parnidae  are  found  as  adult  beetles  clinging 
to  logs  and  stones  in  clear  flowing  streams.  The  former  family 
contains  but  a  few  far  western  species;  the  latter  is  widely  dis- 
tributed, and  contains  numerous  genera  and  species.  The  name 
''Riffle  beetles"  is  applied  to  them  to  indicate  the  seat  of  their 
greatest  abundance.  They  are  mostly  of  small  size  and  their 
coloration  is  usually  inconspicuous,  although  some  of  them  are 
striped  with  red  or  yellow.  The  adults  sun  themselves  on  the 
stones  that  protrude  from  the  water,  and  fly  readily  from  one  rest- 
ing place  to  another.     Many  of  the  larvae,  especially  the  larger 


9o6  FRESH-WATER   BIOLOGY 

ones,  are  strongly  depressed  in  form,  and  have  flaring  lateral  mar- 
gins to  the  body  segments  that  fit  down  closely  against  a  stone, 
limpet-like,  to  withstand  the  wash  of  the  current;  hence,  these 
are  able  to  maintain  a  footing  in  the  swiftest  waters.  The  common 
''water  penny,"  the  larva  of  Psephenus  lecontei,  illustrates  the 
extreme  of  flattening;  this  larva  has  developed  abundant  tracheal 
gills  from  the  thin  membrane  between  the  body  segments,  and  these 
are  completely  covered  over  by  the  projecting  lateral  margins  of 
the  body  segments.  The  adult  female  Psephenus  crawls  down  on 
the  lee  side  of  a  stone  and  deposits  her  yellow  eggs  in  broad  one- 
layered  patches  on  its  surface. 

The  Gyrinidae  or  whirligig  beetles  constitute  a  small  group  of 
strictly  aquatic  forms,  very  peculiar  in  structure  and  habits.  They 
are  well  known  to  every  one  as  shining  black  beetles  of  oval  form, 
that  gather  in  companies  upon  the  surface  of  brooks  and  ponds  and 
glide  about  in  irregular  curves  with  a  speed  which  the  eye  can  hardly 
follow.  When  captured  they  exude  a  whitish  repugnatorial  fluid, 
having  a  rather  disagreeable  odor.  They  hibernate  as  adult 
beetles  in  the  mud  and  in  their  season  of  activity  they  spend  much 
time  beneath  the  water,  in  which  they  can  dive  and  swim  dextrously. 
Their  fore  feet  bear  hooked  claws  with  which  they  can  cling  to  the 
bottom  when  desiring  to  remain  beneath  the  surface.  They  are  at 
once  distinguishable  from  other  water  beetles  by  the  unusual 
brevity  and  peculiar  formation  of  the  hind  legs,  and  by  the 
possession  of  divided  eyes,  there  appearing  to  be  one  pair  above 
for  vision  of  objects  in  air  when  the  beetle  lies  on  the  surface,  and 
one  below,  presumably,  for  seeing  things  in  the  water. 

The  larva  of  the  gyrinids  is  elongate  and  slender,  and  possesses 
at  the  tip  of  the  abdomen  two  pairs  of  backwardly  directed  grap- 
pling hooks,  and  long  slender  paired  filaments  arranged  segmen tally 
along  its  sides  somewhat  like  those  of  the  Neuropterous  genus 
Sialis.  Both  larvae  and  adults  are  carnivorous.  The  larvae  possess 
long  perforate  sickle-shaped  mandibles  well  adapted  for  punctur- 
ing the  skins  of  soft  midge  or  other  dipterous  larvae,  etc.,  and  for 
sucking  out  the  fluid  content  of  their  bodies.  The  pupae  of  the 
Gyrinidae  are  formed  in  thin  cocoons  attached  to  the  side  of  verti- 
cal plant  stems  above  the  water. 


AQUATIC   INSECTS  907 

The  little  family  of  Haliplidae  contains  two  genera  of  pretty  little 
beetles  of  brown  color  spotted  with  yellow,  Ilaliplus  and  Peltody- 
tes.  These  are  easily  distinguished  from  other  beetles  by  the 
sternal  plates  that  broadly  overlap  the  bases  of  the  hind  legs. 
These  beetles  abound  amid  thick  shore  vegetation,  and 
their  larvae  adhere  very  closely  to  the  trash,  and  are 
most  commonly  found  in  floating  mats  of  Spirogyra  and 
other  filamentous  algae.  They  are  among  the  most 
inactive  of  creatures,  and  in  coloration  and  in  form 
show  a  high  degree  of  protective  resemblance.  They 
are  easier  overlooked  than  discovered  even  by  the 
collector  searching  for  them.  The  stick-like  larva  of 
Haliplus  is  shown  in  Fig.  1374;  Peltodytes  is  strikingly 
different  superficially,  being  covered  all  over  its  body 
by  very  long  jointed  slender  bristle-like  processes.  //^^ 
Matheson  has  recently  shown  that  the  larvae  feed  upon 
filamentous  algae,  sucking  out  the  contents  of  the  cells,  |^  ^^J^| 
one  by  one,  and  that  the  eggs  are  deposited  by  the 
adult  beetles  within  the  coarser  algal  filaments. 

The  dominant  family  of  water  beetles  is  the  Dytiscidae, 
commonly  known  as  diving  beetles.  These  abound  in 
all  fresh-water  ponds.  All  are  aquatic  in  both  larval 
and  adult  stages,  but  all  take  air  at  the  surface  of  the 
water,  with  the  exception  of  some  of  the  smaller  larvae 
which  seem  to  be  able  to  absorb  their  oxygen  from  the 
water  without  having  developed  any  special  apparatus 
therefor.  All  are  carnivorous,  and  in  all  the  pupa  is 
formed  on  shore. 

In  fitness  for  swimming,  the  adult  beetles  differ 
greatly.  Some  of  the  larger  forms  like  Cyhister  are 
possessed  of  loner  oar-Hke  hind  lesrs  provided  \vith  close-  larva  of  'naii- 

,  .  .  plus.      (Drawn 

set  swimmmg  frmges,  and  the  long  regular  synchronous  W  Miss  Edna 
strokes  of  the  legs  drive  the  body  forward  with  great 
ease  and  swiftness;  whereas,  some  of  the  lesser  and  more  general- 
ized forms,  like  Bidessus,  with  scanty  swimming  fringes,  and  with 
legs  otherwise  Kttle  modified,  either  in  structure  or  in  movement, 
from  what  is  useful  in  walking,  swim  very  poorly.     These  do  more 


9o8 


FRESH-WATER    BIOLOGY 


climbing  than  swimming,  and,  consequently,  they  keep  nearer  to 
shore  and  to  the  shelter  of  submerged  trash.     In  an  aquarium 

beetles  of  the  size  of  Coptotomus 
and  Laccophilus  may  be  seen  feed- 
ing in  groups  on  the  bodies  of 
dragonfly  nymphs  and  tadpoles  much 
larger  than  themselves,  which  they 
have  overpowered.  Their  own  exceed- 
ingly hard  chitinous  armor  doubtless 
protects  them  from  being  eaten  by 
the  majority  of  aquatic  carnivorous 
%  animals. 

Egg-laying  appears  to  have   been 
observed   hitherto  only  in  DytiscuSy 
which    deposits    its    eggs    singly    in 
punctures  made  in  the  green  stems 
of  aquatic  plants. 
The   larvae   are   voracious   creatures,  armed   with   long  sickle- 
shaped  mandibles,  like  those  of  the  larvae  of  the  families  just  men- 
tioned, each  mandible  with  so  deep  a  groove  on  the  inner  side  that 
it  amounts  to  a  perforation  opening  at  the  tip  and  the  base.     The 


Fig.  1375.    A  predaceous  diving  beetle, 
Dyiiscus. 


Fig.  1376.     Side  view  of  the  head  of  the  larva  and  pupa  of  the  diving  beetle,  Eydroporus. 
(Drawings  by  Mrs.  Helen  Williamson  Lyman.) 


basal  aperture  Hes  just  within  the  mouth- opening  when  the  tips  of 
the  mandible  are  brought  together.  Nearly  all  the  larvae  of  this 
group  capture  only  living  prey,  but  a  few  like  Eydroporus  (Fig. 
1376)  will  eat  pieces  of  animals  that  have  been  killed  for  them. 


AQUATIC    INSECTS  909 

Many  of  the  largest  larvae  are  fiercely  cannibalistic  and  will  eat 
their  brethren  even  when  other  food  offers. 

Some  of  the  larvae  are  provided  with  swimming  fringes  on  the 
legs,  some  have  them  on  the  tail,  and  many  have  them  in  both 
places.  Some,  like  the  larvae  of  Acilius,  are  exceedingly  lithe  and 
graceful  creatures.  Others  (Fig.  1377)  scarcely  swim  at  all,  but 
creep  about  among  the  trash  at  the  shore  line. 


Fig.  1377.     The  larva  of  Coptolomus  inlerrogatus. 

In  the  present  state  of  our  knowledge,  it  is  not  possible  to  give 
keys  that  will  determine  genera  of  Dytiscid  larvae,  and  the  best 
means  of  identifying  native  larvae  is  by  comparison  with  the  beau- 
tiful figures  of  Schiodte,  who  long  ago  (1861)  described  the  European 
representatives  of  many  of  our  genera. 

The  Two-winged  Flies  {Order  Diptera) 

Of  this  immense  order  a  considerable  portion  has  taken  to  a 
more  or  less  aquatic  life.  A  majority  of  the  families  have  some 
members  that  develop  in  the  water,  but  only  a  few  of  the  smaller 
families  are  wholly  aquatic.  Those  best  fitted  for  hfe  in  the  water 
show  adaptations  of  the  most  diverse  sorts,  so  that  here  again  the 
families  are  best  considered  separately. 

Since  nearly  all  the  families  of  the  Diptera  have  some  aquatic 
members,  the  determination  of  the  adult  flies  must  be  left  to  the  aid 
of  the  keys  in  the  entomological  manuals  that  are  everywhere  avail- 
able. Each  of  these  families  has  a  characteristic  type  of  wing  ven- 
ation, and  some  aid  may  be  had  from  comparison  with  the  typical 
wings  shown  in  Fig.  1378. 

It  is  quite  impossible  in  the  space  at  command  to  give  keys 
to  the  genera  of  Dipterous  families,  these  being  very  numerous 


gio 


FRESH-WATER  BIOLOGY 


Fig.  1378.     Typical  wing  venation  in  the  aquatic  families  of  the  Diptera. 

a,  Psychoclidae       Moth  flies  h,  Tabanidae  Horse-flies 

b,  Tipulidae  Crane-flies  ,    i,  Stratiomyidae      Soldier  flies 


c,  Blephoceridae    Net-winged  midges 


d,  Dixidae 

e,  Culicidae 

/,  Chironomidae 
g,  Simuliidae 


Dixa-midges 
Mosquitoes 
Midges 
Black-flies 


j,  Leptidae  Snipe-flies 

k,  Dolichopodidae  Dolichopods 

I,  Fmpididae  The  empids 

m,  Syrphidae  Syrphus  flies 

M,  Muscidae  (5,  lat.) 


in  the  Chironomidae,  Tipulidae,  etc.,  or  even  to  enter  into  detailed 
statements  as  to  their  habits.  A  few  of  the  families  are  compara- 
tively small  and  unimportant.  The  moth  flies  (Psychodidae)  are 
very  minute,  being  among  the  smallest  of  flies,  and  live  as  larvae 


AQUAT  C    INSECTS 


911 


in  the  scum  and  about  the  edges  of  all  sorts  of  fresh  water, 
while  their  adults  swarm  in  thickets  about  the  shores  of  pools.  The 
Ptychopteridae  inhabit  swales,  their  larvae  living  in  the  rotting  trash 
at  the  edge  of  the  water,  and  the  adults  fluttering  about  the  tops 
of  the  adjacent  herbage.  The  dixa  midges  (Dixidae)  inhabit  spring 
brooks  and  clear  pools,  and  their  larvae  (Fig.  1379),  with  bodies 
bent  double,  slide  out  upon  the  surfaces 
of  wet  leaves  and  stones,  or  edge  off  into 
the  water  and  whirl  about  in  short  curves ; 
the  adults  dance  in  companies  above  the 
surface  of  the  water.  Some  larvae  of  the 
Rhyphidae  Kkewise  inhabit  pools,  and  the 
adults  sometimes  assemble  and  dance  in 
the  shelter  of  forest  trees  at  some  dis- 
tance from  the  water.  The  few  known 
aquatic  members  of  the  Leptidae  live  as 
larvae  in  streams  and  cHng  with  the  well- 
developed  claws  of  their  stout  muscular 
abdominal  prolegs  to  the  surfaces  of 
stones;  the  adults  flit  about  the  shore, 
displaying  their  unusually  gaudy  colors 
and  velvety  textures.  These  are  small  and  comparatively  un- 
important families. 

Then  there  are  a  few  large  families  of  which  but  a  small  proportion 
of  the  members  are  adapted  to  aquatic  life.  The  crane-flies  (Tipu- 
lidae)  are  essentially  terrestrial:  most  of  them  live  in  moist  earth  or 
wet  leaves.  Some  are  strictly  amphibious,  like  Epiphragjna  (Figs. 
1380  and  138 1).  They  possess  as  larvae  the  usual  terminal  spira- 
cles for  breathing  air,  but  have  these  set  upon  a  respiratory  disc 
that  can  be  closed  by  folding  together  on  the  middle  line,  and  they 
have  a  bundle  of  four  anal  gills  that  may  then  be  protruded  for 
use  under  water.  There  is  a  fine  development  of  fringes  about  the 
respiratory  disc  of  other  species,  and  these  fringes  spread  out  upon 
the  surface  film,  holding  the  spiracles  up  to  the  air,  while  the  larvae 
are  moving  about  in  the  water  below.  A  few  only  of  the  syrphus 
flies  (Syrphidae)  are  aquatic,  but  the  larvae  of  certain  of  these,  the 
common   ^'rat-tailed  maggots"   are  most  pecuhar  and    interest- 


Fio.  i,:!79.     Larva  (R)  and  pupa  (5)  of 
the  dixa-midge.     (After  Johannsen.) 


912 


FRESH-WATER   BIOLOGY 


ing.  A  very  ordinary  sort  of  white  fleshy  legless  fly  larva  has 
the  supporting  base  of  the  terminal  spiracles  drawn  out  into  a  flexu- 
ous  slender  tube,  as  long  as  or  longer  than  the  body.  The  larva 
Kves  in  the  mud  in  shoal  water,  and  with  this  tube  reaches  up  to 
the  surface  for  air.     A  good  many  aquatic  forms  are  included  among 


Fig.  1380.     The  CTane-&y  Epiphragma/ascipemus, 
adult  female. 


Fig.  1381.     Epiphragma:  a,\a.Tva.;  b, 
end  of  larva  from  above;  c,  pupa. 


the  host  of  higher  diptera  that  are  here  dismissed  as  Muscidae 
in  the  broad  sense,  but  the  larvae  of  these  (Fig.  1382)  differ  from 
their  terrestrial  relatives  by  characters  of  less  moment  than  those 
just  mentioned. 

A  few  small  families  are  most  interesting  for  their  fitness  for 
special  places  in  the  water,  both  larval  and  pupal  stages  being 
passed  in  similar  situations.     The  net-winged  midges  (Blepharo- 


AQUATIC   INSFXTS  913 

ceridae)  live  in  rapid  streams,  and  are  peculiar  in  the  very  strongly 
depressed  form  of  both  larva  and  pupa,  and  in  the  row  of  ventral 
sucking  discs  which  the  larva  has  developed  for  hanging  fast. 

The  black-flies  (Simuliidae)  also  live  in  running  water.  The 
larvae  adhere  to  stones  and  timbers  by  a  single  sucking  disc  at 
the  hinder  end  of  the  flask-shaped  body,  which  thus  hangs  sway- 
ing in  the  current  with  head  downstream. 
Above  the  mouth  on  the  front  of  the  head 
there  are  two  processes  which  bear  the  name 
of  '^fans."  These  are  composed  of  a  very 
large  number  of  scythe-shaped  rays  fringed 
along  the  side.  Set  at  an  angle  upon  the 
pedicel,  like  the  fingers  of  a  reaper's  cradle 
upon  the  handle,  together  these  constitute  -^ 

a  net  for  retaining  small  organisms  adrift  ^Ton^disc  I?Vs™k-fl '^trA'-a' 
in  the  water,  and  for  holding  them  up  to  ^'^p^'^o''- 
the  mouth.  This  is  an  aboriginal  plankton  apparatus.  Simulium 
larvae  play  in  the  rapids,  spinning  silken  threads  in  the  water,  and 
swinging  on  them  from  place  to  place.  Occasionally  the  threads 
thus  spun  in  the  troughs  of  fish  hatcheries  have  been  sufficiently 
numerous  to  entangle  and  kill  newly  hatched  trout.  These  threads 
are  spun  from  the  salivary  glands;  a  final  use  for  the  secretion  of 
these  glands  is  the  making  of  the  open-meshed  half-cornucopia- 
shaped  cocoon  in  which,  attached  to  the  sides  of  the  rocks  or  tim- 
bers, the  pupal  stage  is  passed;  a  branched  prolongation  of  the 
tracheal  lining  of  the  prothoracic  spiracles  constitutes  the  so-called 
*'tube  gills,"  by  means  of  which  the  black-fly  pupa  is  able  to 
get  its  air  supply  while  wholly  submerged. 

The  soldier  flies  (Stratiomyiidae)  live  as  larvae  on  the  surface  of 
still  water.  They  float  stiff  and  rigid  and  stick-like,  with  a  circlet 
of  water-repellent  bristles  surrounding  the  terminal  spiracles,  keep- 
ing open  the  way  to  the  air.  The  pupa  is  formed  within  the 
larval  skin,  without  further  outward  indication  of  the  change  than 
a  slight  angulation  of  the  latter  posteriorly.  The  adult  soldier 
flies  hover  familiarly  about  the  arrow  heads  on  shore  at  egg- 
laying  time,  and  at  other  times  frequent  flowers  to  feed  on  their 
nectar. 


914 


FRESH-WATER   BIOLOGY 


There  remain  three  large  families  of  the  diptera  of  very  great  im- 
portance. Two  of  these,  the  Culicidae  and  the  Tabanidae,  are  impor- 
tant because  of  the  damage  they  do,  and  the  other,  the  Chironomidae, 
because  of  the  food  it  furnishes  to  fishes.  The  mosquitoes  (Culi- 
cidae), since  the  discovery  of  their  importance  to  man  as  agents 
for  the  dissemination  of  the  germs  of  malarial  and  other  fevers, 
have  suddenly  become  well  known.  A  number  of  good  books  are 
now  available  containing  descriptions,  figures,  and  detailed  accounts 
of  the  habits  and  Hfe  histories  of  the  economic  species.  Some  of 
the  most  interesting  members  of  the  family  are  not  included  in  these 
books  among  the  pests,  since  the  adults  do  not  bite.  Corethra^ 
whose  phantom  larvae  are  a  part  of  the  plankton,  is  one  of  these, 
and  Pelorempis,  the  large  culicid  inhabitant  of  cold  springs  is 
another. 

The  biting  adults  of  the  large  horse-flies  (Tabanidae)  are  like- 
wise serious  pests  of   the  domesticated  animals.      Their  naked 


Fig.  1383.    The  speckled  midge,  Tanypus  carneus,  male. 


translucent  larvae,  tapering  to  either  end  and  ringed  with  fleshy 
tubercles,  are  carnivorous,  and  are  found  in  the  trash  of  the 
bottom  in  all  shoal  fresh  waters.  But  two  genera,  Tahanus  and 
Chrysops,  are  of  much  importance  in  our  fauna. 

The  midges  (Chironomidae,  Fig.  1383)  constitute  undoubtedly 


AQUATIC  INSECTS 


915 


the  largest  single  complex  of  aquatic  Diptera.  They  are  a  host; 
indeed,  the  typical  genus  Chironomus  is  a  host  in  itself.  Their 
larvae  (Fig.  1384),  with  no  better  apparatus  than  a  few  blood  gills 
at  the  end  of  the  abdomen,  and  their  pupae,  with  nothing  better 
than  ''tube  gills"  protruded  from  the  prothoracic  spiracles,  are 


Fig.  1384.     The  larva  of  Chironomus.     (After  Johannsen.) 

able  to  live  in  all  waters,  from  springs  to  stagnant  pools  and  from 
rills  to  deep  lake  bottoms.  They  are  chiefly  herbivorous  and  are 
of  very  great  importance  in  furnishing  the  food  of  a  multitude  of 
the   larger  animals,  including   fishes.    The   larvae   construct  for 


Fig.  1385.     Dwelling-tubes  of  midge  larvae  {Chironomus)  from  the  lake  bottom. 
(Photograph  by  T.  L,  Hankinson.) 


themselves  some  sort  of  shelter,  fastening  the  materials  their  envi- 
ronment offers  together  with  the  silk-like  secretion  of  their  salivary 
glands;  some  in  rapid  streams  build  cases  on  the  stones;  others, 
on  the  lake  bottom,  build  soft  flocculent  tubes  of  silt  (Fig.  1385). 


9i6 


FRESH-WATER   BIOLOGY 


These  latter  larvae  are  red  in  color  and  are  known  as  ■'  blood  worms." 
The  color  is  due  to  haemoglobin  in  the  blood  plasma;  the  capacity 
of  this  substance  for  oxygen  gathering  seems  to  enable  these  blood 
worms  to  live  in  water  that  is  poor  in  oxygen. 


In  the  preceding  pages  the  principal  groups  of  aquatic  insects 
are  briefly  characterized,  and  typical  forms  are  figured.  Hints  are 
given  for  the  recognition  of  the  nymphs  of  Plecoptera  on  page  885, 
and  of  the  larvae  of  aquatic  Lepidoptera  on  page  903 .  In  the  fol- 
lowing pages  keys  are  given  for  determining  the  adults  of  Trichop- 
tera  and  Hemiptera,  and  for  both  adults  and  immature  stages  of 
the  other  orders.  An  understanding  of  the  venation  of  the  wings 
is  essential  to  the  study  of  adult  insects  of  most  orders,  and  the 
following  figure  (Fig.  1386)  is  given  to  illustrate  the  wing  venation 
and  explain  the  terminology  used. 


Fig.  1386.     The  venation  of  the  wings  of  a  stonefly,  Chloroperla.     The  designation  of  veins  is  given 
here  for  all  succeeding  wing  figures: 

C,  Costa  M,  Media 

Sc,  Subcosta  Cm,  Cubitus 

R,  Radius  A,  Anal  veins. 

The  radius  has  a  main  stem  (Ri)  and  a  principal  branch  {Rs)  on  the  posterior  side. 
Media  is  often  twice  forked,  and  Cubitus  once  forked;  the  recognizable  branches  are  numbered  from 
front  to  rear:  three  anal  veins  are  likewise  recognized. 


AQUATIC   INSECTS  917 

KEY  TO   THE   ORDERS   OF  AQUATIC   INSECT  LARVAE 

1  (8)     Larvae  with  wings  developing  externally  (called  nymphs  in  this  chapter) 

and  no  quiescent  pupal  stage 2 

2  (7)     With  biting  mouth  parts 3 

3  (6)     With  long,  lilamentous  caudal  setae;  labium  not  longer  than  the  head, 

and  not  folded  on  itself  like  a  hinge 4 

4  (5)     Gills  mainly  under  the  thorax;    tarsal  claws  two;  caudal  setae  two. 

(Stoneflies;  see  page  883)   .    .    .   Plecoptera. 

5  (4)     Gills  mainly  on  the  sides  of  the  abdomen;    tarsal  claws  single;    caudal 

setae  generally  three.    (Mayflies ;  see  page  921)..  Ephemerida. 

6  (3)     Caudal  setae  represented  by  three  broad,  leaf-Uke  respiratory  plates 

traversed  by  tracheae,  or  by  small  spinous  appendages;  labium 
when  extended  much  longer  than  the  head;   at  rest,  folded 
like  a  hinge,  extending  between  the  bases  of  the  fore  legs. 
(Dragonflies  and  damselflies;  see  page  928)    .    .   Odonata. 

7  (2)     Mouth  parts  combined  into  a  jointed  beak,  which  is  directed  beneath 

the  head  backward  between  the  fore  legs. 

(Bugs;  see  page  933)    .    .    .   Hemiptera. 

8  (i)     Larvae  proper,  with  wings  developing  internally,  and  invisible  till  the 

assumption  of  a  quiescent  pupal  stage 9 

9  (18)     With  jointed  thoracic  legs 10 

10  (11)     With  slender,  decurved,  piercing  mouth  parts,  half  as  long  as  the 

body;   small  larvae,  Hving  on  fresh- water  sponges. 
Family  Hemerobiidae  (see  page  934)  of    .    .     Neuroptera. 

11  10)     With  biting  mouth  parts 12 

12  (15)     With  a  pair  of  prolegs  on  the  last  segment  only  (except  in  Sialis, 

Fig.  1367,  which  has  a  single  long  median  tail-like  process  at 
the  end  of  the  abdomen)  these  directed  backward,  and 
armed  each  with  one  or  two  strong  hooks  or  claws.   .    .     13 

13  (14)     Abdominal  segments  each  with  a  pair  of  long,  lateral  filaments. 

Family  Sialididae  (see  page  935)  of  .    .   Neuroptera. 

14  (13)     Abdominal  segments  without  long,  muscular,  lateral  filaments,  often 

with  minute  gill  filaments  cylindric  larvae,  generally  living 
in  portable  cases.  (Caddisflies;  see  page  936).   .  Trichoptera. 

15  (12)     Prolegs,  when  present,  on  more  than  one  abdominal  segment;    if 

present  on  the  last  segment,  then  not  armed  with  single  or 
double  claws  (except  in  gyrinid  beetle  larvae,  which  have 
paired  lateral  abdominal  filaments),  often  entirely  want- 
ing  16 

16  (17)     With  five  pairs  of  prolegs,  and  with  no  spiracles  at  the  apex  of  the 

abdomen.     .     .     (Moths;  see  page  903)     .    .     Lepidoptera. 

17  (16)     Generally  without  prolegs;    never  with  five  pairs  of  them;    usually 

with  terminal  spiracles;  long,  lateral  filaments  often  present 

on  the  abdominal  segments. 

(Beetles,  adults;  see  p.  937 ;  larvae;  see  p.  943)    .     Coleoptera. 

18  (9)     Without  jointed  thoracic  legs;    with  abdominal  prolegs,  or  entirely 

legless (Flies,  etc. ;  see  page  943)   .    .     Diptera. 


9l8  FRESH-WATER  BIOLOGY 

KEY  TO  NORTH  AMERICAN  MAYFLIES 
Imagos 

1  (13)     The  cubital  and  first  anal  veins  strongly  divergent  at  the  base  (Fig. 

1387).     Venation  never  greatly  reduced 2 

2  (3)     The  posterior  fork  of  the  median  vein  very  deep,  almost  reaching  the 

wing  base;  two  long  simple  intercalaries  between  the  first 
and  second  anal  veins Campsurus. 

3  (2)     The  posterior  fork  of  the  median  vein  (M3-M4)  forked  for  not  more  than 

three-fourths  of  its  length 4 


Fig.  1387.     The  wings  of  Ephemera.     (Drawn  by  Dr.  Anna  H.  Morgan.) 

4  (5)     Between  the  first  and  second  anal  veins  is  a  bunch  of  three  or  four  long 

straight  intercalaries,  conjoined  basally  before  their  attach- 
ment to  the  principal  veins;  the  second  anal  vein  nearly 
straight  and  unbranched Polymitarcys. 

5  (4;     Between  the  first  and  second  anal  veins  are  only  shorter,  sinuate,  and 

sometimes  forking  intercalaries,  attached  directly  to  the 
first  anal;  the  second  anal  vein  sinuate  and  often  branched 
(Fig.  1387) 6 

6  (7)     The  posterior  fork  of  the  median  vein  forked  two- thirds  to  three-fourths 

its  length;  vein  Cu2  not  more  strongly  bent  at  base  than 
the  first  anal Euthyplocia. 

7  (6)     This  fork  of  the  median  vein  occupying  not  more  than  half  its  length; 

vein  Cu2  more  strongly  bent  at  base  than  is  the  first  anal 
(Fig.  1387) 8 

8  (12)     The  third  anal  vein  simple,  but  attached  to  the  hind  margin  by  a 

number  of  cross  veins;  in  the  narrow  posterior  fork  of  the 
median  vein  there  are  one  or  more  cross  veins  before  the  origin 
of  the  intercalary;  male  forceps  four-jointed 9 

9  (10,  11)     Caudal  setae  three  in  both  male  and  female;  fore  tarsus  of  female 

imago  three-fourths  as  long  as  the  tibia.    .    .    .     Ephemera. 

10  (9,  11)     Caudal  setae  two  in  the  male  and  three  in  the  female;  fore  tarsus 

of  the  female  two-thirds  as  long  as  the  tibia.   .     Pentagenia. 

11  (9,  10)     Caudal  setae  two  in  male  and  female;  fore  tarsus  of  female  as  long 

as  the  tibia Hexagenia. 


AQUATIC   INSECTS 


919 


12  (8)     The  third  anal  vein  with  a  simple  terminal  fork  and  unattached  to  the 

hind  margin,  although  a  few  isolated  short  intercalaries 
lie  between;  in  the  wider  posterior  fork  of  the  median  vein 
there  is  no  cross  vein  before  the  origin  of  the  intercalary; 
male  forceps  three-jointed Potamanthiis. 

13  (i)     The  cubital  and  first  anal  veins  parallel  at  base  (in  a  few  forms  with 

reduced  and  scanty  venation,  appearing  a  little  diverg- 
ent)       j^ 

14  (15)     Hind  tarsi  with  five  freely  movable  segments;  eyes  of  the  male  simple 

and  remote;  venation  never  greatly  reduced;  intercalary 
veins  between  the  first  and  second  anal  veins  unattached 
basally  and  in  two  pairs,  of  which  the  pair  nearer  the  hind 
angle  is  the  longer Heptagenia. 

15  (14)     Hind  tarsi  usually  with  but  four  freely  movable  segments,  the  basal 

segment  being  more  or  less  completely  consolidated  with  the 
tibia;  eyes  of  the  male  enlarged,  often  approximated  on  the 
dorsal  side  and  divided  into  superior  and  lateral  portions 
with  corneal  facets  of  different  size;  venation  various, 
sometimes  greatly  reduced;  intercalary  veins  between  the 
first  and  second  anal  never  as  above 16 

16  (17)     The  three  anal  veins  nearly  parallel  to  the  hind  margin  of  the  wing 

and  to  each  other,  ending  in  the  outer  margin;  in  the  hind 
wing  the  branches  of  the  radial  vein  are  strongly  unilateral 
on  the  anterior  side Bactisca. 

17  (16)     Anal  veins  strongly  divergent  distally,  usually  both  the  second  and 

the  third  ending  in  the  hind  margin;  forks  of  the  radial  vein 
in  the  hind  wing  more  symmetrical 18 

18  (39)     The  posterior  division  of  the  median  vein  with  a  normal  posterior 

fork;  hind  wings,  when  present,  usually  but  Uttle  longer 
than  broad  and  with  a  copious  venation 19 

19  (32)     The  intercalaries  between  the  first  and  second  anal  veins  variable, 

but  usually  more  or  less  independent,  and  not  directly 
dependent  from  the  first  anal;    three  well-developed  caudal 

setae  (except  in  Blasturus,  in  our  fauna) 20 

20(31)     Hind  wings  present 21 

21  (28)     Bisector  of  the  posterior  fork  of  the  median  vein  and  bisector  of  the 

cubital  fork  unattached  basally;  between  the  latter  and 
vein  Cu2  no  intercalaries;  vein  Cu2  in  the  hind  wing  rarely 
preserved;  caudal  setae  generally  much  longer  than  the 
body;  penultimate  segment  of  the  male  forceps  shorter 
than  the  antepenultimate 22 

22  (27)     In  the  hind  wing  the  subcostal  vein  reaches  nearly  to  the  wing  apex; 

male  forceps  three-jointed 23 

23  (26)     Hind  wing  with  a  slight  concavity  at  the  middle  of  costal  margin; 

five  to  six  longitudinal  veins  between  Mi  and  Mo;  vcinlets 
numerous  about  the  wing  margins  and  cross  veins  numerous 
in  the  hind  wings 24 

24  (25)     Third  anal  vein  of  the  hind  wing  wanting;  caudal  setae  of  about 

equal  length Leptophlehia, 


920 


FRESH-WATER  BIOLOGY 


25  (24)     Third  anal  vein  of  the  hind  wing  present,  and  often  followed  by  one 

or  two  additional  intercalaries;  median  caudal  seta  dis- 
tinctly shorter  than  the  others Blasturus. 

26  (23)     Hind  wing  with  an  angular  lobe  projecting  forward  from  the  middle 

of  the  costal  margin;  four  longitudinal  veins  between  Mi  and 
M2;  wing  margins  free  from  veinlets,  and  few  cross  veins  in 
hind  wing Habrophlebia. 

27  (22)     In  the  hind  wing  the  subcostal  vein  terminates  in  the  costa  at  hardly 

more  than  half  the  length  of  the  wing,  just  beyond  the 
obtuse  angulation  having  a  thickened  margin;  forceps  of 
male  more  or  less  distinctly  four-jointed.   .    .     Choroterpes. 

28  (21)     Bisectors  of  the  posterior  fork  of  the  median  vein  and  of  the  cubital 

fork  both  tending  to  attach  themselves  to  the  posterior 
branch  of  their  respective  forks;  between  the  latter  and  vein 
Cu2  are  generally  some  short  intercalaries  (the  cubital  region 
thus  being  better  developed  than  in  group  21);  caudal  setae 
about  as  long  as  the  body;  penultimate  segment  of  the  male 
forceps  longer  than  the  antepenultimate 29 

29  (30)     Veins  Cu2  and  ist  A  separate  to  base Ephemerella. 

30  (29)     Veins  Cu2  and  ist  A  fused  toward  the  base Drunella. 

31  (20)     Hind  wings  absent Caenis. 

32  (19)     The  intercalaries  between  the  first  and  second  anal  veins  represented 

by  a  series  of  veinlets,  often  sinuous  or  forking,  extending 
directly  from  the  first  anal  to  the  wing  margin;  costal 
angulation  of  hind  wing  close  to  the  base;  but  two  well- 
developed  caudal  setae,  the  median  one  being  rudimentary 
or  wanting;  basal  joint  of  hind  tarsi  evident  but  not  well 
developed 33 

33  (36)     Median  caudal  seta  a  distinctly  segmented  rudiment  (Fig.  1354);  for- 

ceps of  male  three- jointed;  posterior  prolongation  of  sternum 
of  ninth  segment  of  abdomen  of  female  bifid  at  tip.  .  .     34 

34  (35)     Basal  segment  of  fore  tarsus  of  male  shortest;    claws  of  each  tarsus 

unhke  each  to  each;  hind  wing  with  the  costal  angulation 
acute,  and  the  posterior  fork  of  the  median  vein  occupying 
two- thirds  the  length  of  that  vein Colohurus. 

35  (34)     Basal  segment  of  fore  tarsus  of  the  male  longest;    claws  of  each 

tarsus  alike;  hind  wing  with  the  costal  angulation  obtuse, 
and  the  posterior  division  of  the  median  vein  forked  through 
one-third  its  length Chirotonetes. 

36  (33)     Median  caudal  seta  more  rudimentary  or  wanting;    forceps  of  the 

male  distinctly  four-jointed;  posterior  prolongation  of  the 
sternum  of  the  ninth  abdominal  segment  in  the  female  entire 
at  tip 37 

37  (38)     Claws  of  each  tarsus  alike;  caudal  setae  at  least  one-half  longer  than 

the  body Siphlurus. 

38  (37)     Claws  of  each  tarsus  unlike;  caudal  setae  about  as  long  as  the  body 

in  both  sexes Ameletus. 

39  (18)     Posterior  fork  of  the  median  vein  apparently  simple,  M4  being  de- 

tached and  appearing  as  an  intercalary;  hind  wings  when 
present  at  least  twice  as  long  as  wide,  and  provided  with 
but  1-3  longitudinal  veins 40 


AQUATIC   INSECTS  921 

40  (45)     Hind  wings  present 41 

41  (42)     Fore  wings  with  numerous  costal  cross  veins  before  the  bulla;  hind 

wings  with  a  moderate  number  of  cross  veins .    .   Callibactis. 

42  (41)     Fore  wings  without  costal  cross  veins  before  the  bulla;    hind  wings 

without  cross  veins  or  with  but  1-3  of  them 43 

43  (44)     Marginal  intercalary  veinlets  in  pairs;    hind  wings  oblong,  with  a 

short  costal  angulation Bactis. 

44  (43)     Marginal  intercalary  veinlets  of  the  fore  wing  single;    hind  wings 

linear,  with  a  spur-like  costal  angulation .      .     Centroptilum. 

45  (40)     Hind  wings  absent Clocon. 

Nymphs 

1  (11)     Mandibles  with  an  external  tusk-like  ramus,  visible  from  above;   gills 

on  abdominal  segments  1-7  (often  rudimentary  on  i), 
double,  flattened,  linear,  the  margins  fringed  with  respira- 
tory filaments 2 

2  (9,  10)     Mandibular  tusks  longer  than  the  head  (burrowing  species)   .    .     3 

3  (6)     With  no  frontal  prominence 4 

4  (5)     Legs  increasing  in  length  posteriorly;    gills  of  the  first  abdominal  seg- 

ment simple;  lab  rum  longer  than  wide;  maxillary  palpus 
two-jointed Polymitarcys. 

5  (4)     Legs  decreasing  in  length  posteriorly;   lab  rum  wider  than  long;   maxil- 

lary palpus  three- jointed Euthyplocia. 

6  (3)     With  a  conspicuous  frontal  prominence 7 

7  (8)     Frontal  prominence  rounded Hexagenia. 

8  (7)     Frontal  prominence  bifid  at  tip Ephemera. 

9  (2,  10)     Mandibular  tusks  shorter  than  the  head,  inconspicuous,  only  their 

tips  visible  from  above Potamanthus. 

10  (2,  9)     Unknown Campsurus  and  Pentagenia. 

11  (i)     Mandibles  without  projecting  tusk-like  ramus;    gills  not  as  in  i.     12 
12(13)     Eyes  dorsal;  body  strongly  depressed;  tarsal  claws  with  lateral  teeth; 

dwellers  in  rapid  streams  and  on  wave-beaten  shores  adapted 
to  clinging  to  flat  surfaces  of  rocks,  timbers,  etc. 

Heptagenia. 

13  (12)     Eyes  lateral;  claws  smooth  or  toothed  below 14 

14  (15)     Gills   completely   concealed   under   an   enormously   enlarged,   four- 

spined  dorsal  thoracic  shield Baetisca. 

15  (14)     Gills  exposed;  thoracic  dorsum  normal 16 

16  (31)     Outer  caudal  setae  fringed  on  both  sides 17 

17  (24)     Gills  on  abdominal  segments  1-7  double 18 

18  (21)     Gills  filamentous 19 

19  (20)     Each  a  pair  of  simple  filaments Leptophlchia. 

20  (19)  Each  a  pair  of  clusters  of  slenderer  filaments.     .    .    .     Hahrophlchia. 
21(18)     Gills  lamelliform,  at  least  on  the  middle  segments 22 

22  (23)     Lamellae  of  each  gill  similar Blast  urns. 

23  (22)     Lamellae  of  each  gill  markedly  dififering  in  form  at  tip.     Choroterpes, 


92: 


FRESH-WATER   BIOLOGY 


24  (17)     Gills  absent  from  one  or  more  of  segments  1-7;   one  pair  more  or  less 

elytroid,  covering  those  behind  it 25 

25  (28)     Gills  present  on  the  seventh  abdominal  segment,  elytroid  on  the  third 

or  fourth  segment;    a  pair  of  tubercles  on  the  apical  margin 
of  each  segment  beside  the  middorsal  line 26 

26  (27)     Head  smooth  above Ephemerella. 

27  (26)     Head  armed  above  with  a  pair  of  erect  occipital  tubercles.    Drunella. 

28  (25)     Gills  absent  from  the  seventh  abdominal  segment,  elytroid  on  the 

second  segment;    no  dorsal  abdominal  tubercles.   ...     29 

29  (30)     Elytroid  gill  cover  subquadrate Caenis. 

30  (29)     Elytroid  gill  cover  subtriangular Tricorythus. 

31  (16)     Outer  caudal  setae  fringed  only  on  the  inner  side 32 

32  (37)     Posterolateral  angles  of  the  hinder  abdominal  segments  prolonged 

into  thin,  flat,  sharp  lateral  spines 33 

33  (34)     Fore  legs  conspicuously  fringed  with  long  hairs;    gill  tufts  present 

upon  the  base  of  maxillae  and  front  coxae  and  at  bases  of 

lamellae  on  abdomen Chirotonetes. 

Fore  legs  without  conspicuous  fringes;    no  maxillary  or  coxal  gills; 

no  gill  tufts  at  base  of  lamellae  on  abdomen 35 

Gills  double  on  the  basal  abdominal  segments;   end  of  maxilla  fringed 

with  simple  hairs Siphlurus. 

Gill  lamellae  all  single;  end  of  maxilla  fringed  with  pectinated  hooks. 

Ameletus. 

Posterolateral  angles  of  the  hinder  abdominal  segments  hardly  more 
than  acute  —  not  prolonged  in  thin  flat  lateral  spines.  .     38 

Gill  lamellae  simple 39 

Lamellae  obtuse  at  apex;  maxillary  palpus  rounded  at  the  apex. 

Baetis. 

Lamellae  acute  at  apex;    end  of  maxillary  palpus  truncated. 

Centroptilum. 

Gill  lamellae  double,  at  least  on  some  of  the  anterior  abdominal 
segments 42 

Antennae  shorter  than  the  body;  tracheae  of  gill  lamellae  pinnately 
branched Callibaetis. 

Antennae  longer  than  the  body;  tracheae  of  gill  lamellae  palmately 
branched Cloeon. 


KEY  TO  NORTH  AMERICAN  DRAGONFLIES 

Imagos 

1  (21)     Fore  and  hind  wings  similar,  usually  held  verticaUy  in  repose  (damsel- 

flies) Suborder  Zygoptera     .    .      2 

2  (5)     Quadrangle  (Fig.  1388)  of  the  wings  divided  by  a  number  of  cross  veins; 

antenodal   cross   veins   numerous;     pterostigma   lacking   a 
special  brace  vein;  wings  rather  broad 3 

3  (4)     Basal  space  (space  before  the  arculus)  in  all  wings  free  from  cross  veins. 

Calopteryx. 


34  (33) 

35  (36) 

36  (35) 

37  (32) 

38  (41) 

39  (40) 

40  (39) 

41  (38) 

42  (43) 

43  (42) 

AQUATIC   INSECTS  923 

4  (3)     Basal  space  of  all  wings  traversed  by  cross  veins Hetacrina. 

5  (2)     Quadrangle  without  cross  veins;  antenodal  cross  veins  but  two  in  each 

wing;    pterostigma  with  a  brace  vein  at  its  proximal  end  in 
the  space  behind  vein  Ri;    wings  narrower 6 

6  (9)     Vein  M3  arising  (i.e.,  separating  from  vein  M1+..)  nearer  the  arculus 

than  the  nodus 7 

Fig.  1388.  Wing  venation  in  the  Odonata:  (a)  a  drs.gon?^y,  Cordulef^aster.  (b)  a  damselfly,  Argia; 
(c)  the  region  of  the  stigma,  st,  with  its  brace  vein,  2,  ar,  arculus;  al,  anal  loop;  br,  bridge;  n,  nodus; 
o,  oblique  vein;  t,  triangle;  /',  subtriangle;  g,  quadrangle;  sq,  subquadrangle;  v,  basal  subcostal  cross 
veins;  z,  veins  as  in  Fig.  1386. 

7  (8)     Vein  M2  separating  from  vein  Mi  at  a  distance  of  several  cells  beyond 

the  subnodal  cross  vein Lcstes. 

8  (7)     Vein  M2  separating  from  vein  Mi  close  to  the  subnodal  cross  vein,  less 

than  the  distance  of  one  cell  beyond  it.  Archilestes. 

9  (6)     Vein  M3  arising  nearer  the  nodus  than  the  arculus 10 

10  (11)     Spines  on  the  tibiae  very  long,  twice  as  long  as  the  intervals  between 

them Irgia. 

11  (10)     Spines  of  the  tibiae  hardly  longer  than  the  intervals  between  them.     1 2 

12  (16)     No  pale  postocular  spots  on  the  top  of  the  head;    sexes  similarly 

colored 13 

13  (14,  15)     Colors  of  dorsum  blue  and  black;    yellow  beneath  the  thorax. 

Chromagrion. 

14  (13,  15)     Colors  of  dorsum  red  and  black;  stout  species.    .      Amphiagrion. 

15  (13,  14)     Dorsum   bronzy   green;     slender   species.     .    .    .       Nehallennia. 

16(12)     With  round  or  ovoid  postocular  spots  on  the  head 17 

17  (18)  Sexes  with  a  general  similarity  in  color,  the  female  often  of  a  lighter 
shade;  the  superior  abdominal  appendages  of  the  male 
not  strongly  directed  downward  and  inward.  .    .   Enallagma. 


924 


FRESH-WATER   BIOLOGY 


1 8  (17)     Sexes  strikingly  unlike  in  color;    a  bifid  process  arising  from  the 

apical  margin  of  the  loth  abdominal  segment  in  the  male 
and  the  superior  abdominal  appendages  strongly  directed 
downward  and  inward 19 

19  (20)     Males  chiefly  green  and  black,  with   normal   rhomboidal   stigma; 

females  with  the  orange  of  the  abdomen  covering  something 
less  than  the  three  basal  segments  (becoming  wholly  densely 
pruinose  with  age) Ischnura. 

20  (19)     Males  yellow  or  orange,  with  ovoid  stigma  which  does  not  reach  the 

costal  vein;  females  with  the  four  basal  segments  of  the 
abdomen  yellow  or  orange Anomalagrion. 

21  (i)     Fore   and   hind   wings   dissimilar,    the   latter   broader   at   the   base 

(dragonflies  proper) Suborder  Anisoptera   .    .     22 

22  (49)     Triangle  (Fig.  1388)  about  equally  distant  from  arculus  in  fore  and 

hind  wing;  stigma  with  a  brace  vein  at  its  inner  end  (except 
in  Cordulegaster) 23 

23  (24)     Stigma  unbraced Cordulegaster. 

24  (23)     Stigma  braced  at  its  inner  end  against  an  inclined  cross  vein  in  the 

space  below  it  (Fig.  1362) 25 

25  (36)     Eyes  widely  separated  on  the  top  of  the  head 26 

26  (27)     Basal  subcostal  cross  vein  (Fig.  1388,  h)  present;  a  linear  or  spatulate, 

median,  sternal  process  on  the  first  abdominal  segment; 
legs  very  short,  the  hind  femora  hardly  reaching  the  apex 
of  the  first  abdominal  segment Progomphus. 

27  (26)     Basal   subcostal   cross  vein  usually  wanting;    no  median   sternal 

process  on  the  first  abdominal  segment;  legs  longer,  the 
hind  femora  reaching  or  surpassing  the  middle  of  the  second 
abdominal  segment 28 

28  (31)     Hind  wings  with  a  distinct  anal  loop  (Fig.  1388,  a)  consisting  of  several 

cells 29 

29  (30)     Anal  loop  normally  consisting  of  three  cells;   first  and  fifth  antenodal 

cross  veins  matched  in  position  and  hyper trophied;  stigma 
broad  with  both  sides  convex;  triangles  not  traversed  by 
cross  veins Ophiogomphus. 

30  (29)     Anal  loop  consisting  normally  of  four  cells;  first  and  seventh  antenodal 

cross  veins  matched  in  position  and  hj^Dertrophied;  stigma 
long  and  narrow  with  parallel  sides;  each  triangle  divided 
by  a  cross  vein Hagenius. 

31  (28)     Hind  wings  with  no  distinct  anal  loop,  or  with  one  consisting  of  a 

single  cell 32 

32  (33)     Triangle  of  the  fore  wing  one- third  shorter  than  that  of  the  hind 

wing;  generally  a  single  cell  between  the  bases  of  veins  A2 
and  A3 Lanthus. 

33  (32)     Triangle  of  the  fore  wing  less  than  one-fourth  shorter  than  that  of  the 

hind  wing;  generally,  two  or  more  cells  between  A2  and  A3 
at  their  origin 34 

34  (35)     Hind  femora  naked,  or  with  numerous  short  spines.   .    .     Gomphus. 

35  (34)     Hind  femora  with  five  to  seven  long,  strong  spines.  .   Dromo gomphus. 


AQUATIC  INSECTS  925 

36  (25)     Eyes  approximated  on  the  top  of  the  head 37 

37(42)     The  radial  sector  (/?5,  Fig.  1388,  a)  simple 38 

38  (39)     But  two  cubi to-anal  cross  veins;    vein  M.  undulate;    supratriangle 

without  cross  veins;   but  one  cross  vein  under  the  stigma. 

Gomphacschna. 

39  (38)     With  three  or  more  cubito-anal  cross  veins;    vein  Mo  not  undulate; 

supratriangle  divided  by  cross  veins;  several  cross  veins 
under  the  stigma 40 

40  (41)     Basal  space  traversed  by  cross  veins Boyeria. 

41  (40)     Basal  space  open Basiaeschm. 

42(37)     Radial  sector  bearing  an  apical  fork. 43 

43  (48)     Sectors  of    the  arculus  (veins  Mi_3  and    M4)   separating  from  the 

arculus  at  or  below  its  middle 4_j. 

44  (47)     The  radial  sector  symmetrically  forked:    between  it  and  the  supple- 

mentary vein  below  it,  one  or  two  rows  of  cells 45 

45  (46)     Face  strongly  produced  above,  the  upper  margin  of  the  frons  very 

acute;  the  veins  Mi  and  Mo  parallel  to  the  level  of  the  stigma; 
radial  sector  and  the  supplementary  vein  below  it  separated 
by  a  single  row  of  cells Nasiaeschna. 

46  (45)     Face  vertical,  not  sharply  angulate  at  upper  edge  of  frons;   veins 

Ml  and  M2  approximated  at  the  stigma;  the  radial  sector 
and  the  supplementary  vein  below  it  separated  by  two  rows 
of  cells Epiacschna. 

47  (44)     The  radial  sector  strongly  deflected  toward  the  stigma  at  the  base  of 

its  fork,  unsymmetric;  between  it  and  the  supplementary 
vein  below  it,  three  to  seven  rows  of  cells.      .    .    .     Aeschna. 

48  (43)     Sectors  of  the  arculus  springing  from  above  the  middle  of  the  arcu- 

lus  Anax. 

49  (22)     Triangle  in  the  hind  wing  much  nearer  the  arculus  than  in  the  fore 

wing;  stigma  without  brace  vein 50 

50  (53)     The  triangle  of  the  hind  wing  placed  considerably  beyond  the  arcu- 

lus;   the  anal  loop  well  developed  and  hardly  longer  than 


broad;  more  than  two  cubito-anal  cross  veins. 


51  (52)     Dorsal  surface  of  the  head  with  the  occiput  larger  than  the  vertex; 

subtriangle  of  the  fore  wings  usually  divided  by  a  cross  vein; 
four  to  six  cross  veins  in  the  space  above  the  bridge  (Fig.  13  88) . 

Didymops.  ■ 

52  (51)     Dorsal  surface  of  the  head  with  the  occiput  much  smaller  than  the 

vertex;  subtriangle  of  the  fore  wings  generally  open;  two 
or  three  cross  veins  in  the  space  above  the  bridge. 

Macromia. 

53  (50)     The  triangle  of  the  hind  wing  retracted  to  the  level  of  the  arculus, 

or  even  passing  it  a  little  sometimes;  the  anal  loop,  greatly 
elongated  (except  in  Nannothcmis)  and  becoming  foot- 
shaped;    one  or  two  cubito-anal  cross  veins 54 


926  FRESH-WATER   BIOLOGY 

54  (67)     Sectors  of  the  arculus  (veins  Mi-g  and  M4)  distinctly  separate  at  their 

departure  from  the  arculus;  anal  loop  elongate,  but  not 
distinctly  foot-shaped,  the  toe  part  being  Httle  or  not  at  all 
developed;  the  last  antenodal  cross  vein  extending  from  the 
costal  to  the  radial  veins  (except  in  D.  lintneri,  in  which 
it  generally  extends  only  from  the  costal  to  the  subcostal); 
colors  often  metallic  blue  or  green  on  thorax  and  abdomen.  55 

55  (56)     Veins  M4  and  Cui  in  the  fore  wing  parallel  or  a  little  divergent  apically, 

the  number  of  rows  of  cells  between  them  increasing  toward 
the  margin  of  the  wing Neurocordulia. 

56  (55)     Veins  M4  and  Cui  in  the  fore  wing  approximated  toward  the  margin 

of  the  wing 57 

57  (58)     With  large  brown  spots  on  all  wings  at  nodus  and  apex. 

Epicordulia. 

58  (57)     No  brown  spots  at  nodus  and  apex 59 

59  (60)     Four  (rarely  five)  antenodal  cross  veins  in  the  hind  wing. 

Tetragoneuria. 

60  (59)     Usually  more  than  five  antenodal  cross  veins  in  the  hind  wing.   .     61 

61  (62)     Stigma  very  narrowly  diamond-shaped,  with  the  ends  of  it  meeting 

the  sides  by  an  angle  of  30°  to  35° Helocordulia. 

62  (61)     Stigma  broader,  less  pointed 63 

63  (64)     Triangle  of  fore  wings  open Dorocordulia. 

64  (63)     Triangle  of  fore  wings  divided  by  a  cross  vein 65 

65  (66)  Inferior  appendage  at  end  of  male  abdomen  bifurcated.        Cordulia. 

66  (65)     Inferior  appendage  simple Somatochlora. 

67  (54)  The  sectors  of  the  arculus  in  close  apposition  or  completely  fused  for 

a  little  way  beyond  the  arculus;  anal  loop  generally  dis- 
tinctly foot-shaped,  with  well-developed  ''toe";  the  last 
antenodal  cross  vein  often  discontinuous  at  the  subcostal 
vein 68 

68  (69)     Triangle  of  the  fore  wings  four-sided;  anal  loop  poorly  developed,  not 

foot-shaped Nannothemis. 

69  (68)     Triangle  of  the  fore  wing  fully  differentiated,  three-sided;    anal  loop 

well  developed  and  foot-shaped 70 

70  (71)     Triangle  of  the  fore  wing  with  its  front  and  inner  sides  meeting  by  an 

angle  of  about  100°;  the  subtriangle  without  cross  veins; 
the  vein  which  bisects  the  anal  loop  straight.   .    .   Perithemis. 

71  (70)     Triangle  of  the  fore  wing  with  its  front  and  inner  sides  meeting  by  an 

angle  of  about  90°;  subtriangle  divided  into  three  or  more 
cells;  bisector  of  the  anal  loop  sinuous 72 

72  (89)     Triangle  of  the  fore  wing  not  placed  distinctly  beyond  the  level  of  the 

apex  of  the  triangle  in  the  hind  wing;  pterostigma  with  its 
ends  parallel  or  not  distinctly  divergent. 73 

73  (84)     The  sectors  of  the  arculus  (veins  Mi-g  and  M4)  in  the  fore  wing  more 

or  less  completely  fused  for  a  short  distance  beyond  the 
arculus;  the  triangle  of  the  fore  wing  not  greatly  produced 
posteriorly,  and  (except  in  Celithemis)  normally  containing 
but  a  single  cross  vein,  and  followed  by  two  or  three  rows 
of  cells 74 


AQUATIC   INSECTS  927 

74  (79)     Vein  Cui  of  the  hind  wing  departing  from  the  triangle  at  the  hind 

angle 75 

75  (76)     Sectors  of  the  arculus  (veins  Mi_3  and  M4)  contiguous,  but  incom- 

pletely fused  for  a  distance  beyond  the  arculus;  wings 
generally  conspicuously  spotted  with  yellow  or  reddish  brown. 

Celithemis. 

76  (75)     Sectors  of  the  arculus  in  the  hind  wing  distinctly  fused  for  a  distance 

beyond  the  arculus 77 

77  (78)     Stigma  short  and  thick,  about  twice  as  long  as  wide;  anal  loop  with 

a  big  heel,  there  being  generally  four  cells  between  the  bi- 
sector and  the  heel  point;  face  pure  white.    .    .   Leucorhinia. 

78  (77)     Stigma  more  than  three  times  as  long  as  wide;   anal  loop  generally 

with  but  two  cells  between  the  bisector  and  the  heel  point. 

Sympelrum. 

79  (74)     Vein  Cui  of  the  hind  wing  migrated  a  httle  way  up  the  outer  side  of 

the  triangle,  separating  itself  at  a  distance  from  the  hind 
angle 80 

80  (81)     With  a  single  cross  vein  under  the  stigma,  and  a  long  vacant  space 

before  that  cross  vein Pachydiplax. 

81  (80)     With  two  cross  veins  under  the  stigma  and  the  adjacent  spaces  more 

normal 82 

82  (83)     With  a  single  row  of  cells  between  veins  M2  and  Rg.  .    .    Mesothemis. 
^7,  (82)     With  two  rows  of  cells  for  a  distance  between  veins  M2  and  R^. 

Micralhyria. 

84  (73)     Sectors  of  the  arculus  in  the  fore  wing  contiguous,  but  not  completely 

fused  beyond  the  point  of  their  departure  from  the  arculus; 
radial  sector  distinctly  undulate  (except  in  Ladona) ;  triangle 
of  the  fore  wing  very  much  elongated  posteriorly  and  narrow 
and  generally  traversed  by  two  or  more  parallel  cross  veins, 
and  followed  by  three  to  seven  rows  of  cells 85 

85  (86)     Vein  Mia  arising  under  the  proximal  fourth  of  the  stigma;  fore  wings 

with  the  subtriangle  consisting  of  three  cells,  and  the  tri- 
angle followed  by  three  rows  of  cells Ladona. 

86  (85)     Vein  M^  arising  under  the  middle  of  the  stigma;   fore  wings  with  the 

subtriangle  consisting  of  four  to  eleven  cells,  and  the  triangle 
usually  followed  by  four  to  six  rows  of  cells 87 

87  (88)     Male  with  no  ventral  hooks  on  the  first  abdominal  segment;   female 

with  the  hind  tibia  a  little  longer  than  the  hind  femur;  the 
sexes  alike  in  wing  patterno Libcllula. 

88  (87)     Male  with  a  pair  of  ventral  hooks  on  the  first  abdominal  segment; 

female  with  the  hind  femur  and  tibia  of  equal  length;  wings 
dissimilarly  colored  in  the  two  sexes Plathcmis. 

89  (72)     Triangle  of  the  fore  wing  placed  beyond  the  level  of  the  apex  of  the 

triangle  of  the  hind  wing;  stigma  with  its  inner  end  per- 
pendicular, its  outer  end  very  oblique  to  the  bordering  veins; 
wings  broad  at  base  and  pointed  at  apex 90 

90  (91)     Radial  sector  regularly  curved;  hind  wings  with  a  broad,  basal  colored 

band Tramea. 

91  (90)     Radial  sector  distinctly  undulate;   hind  wings  not  covered  at  base  by 

a  broad  colored  band Pantala. 


928  FRESH-WATER    BIOLOGY 

Nymphs 

1  (22)     Three  large  leaf  like  respiratory  plates  at  the  apex  of  the  slender  abdo- 

men, and  with  the  body  tapering  posteriorly  from  the  head 
(damselflies) Suborder  Zygoptera   .    .       2 

2  (5)     Basal  segment  of  the  antenna  very  large,  as  long  as  the  other  six  to- 

gether; median  lobe  of  the  labium  with  a  very  deep  cleft; 
gills  thick,  the  lateral  ones  triquetral 3 

3  (4)     Median  cleft  of  labium  very  deep,  extending  far  beneath  the  level  of  the 

base  of  the  lateral  lobes Calopteryx. 

4  (3)     Median  cleft  of  the  labium  extending  only  to  the  level  of  the  base  of 

the  lateral  lobes Hetaerina. 

5  (2)     Basal  segment  of  antenna  not  longer  than  succeeding  single  segments; 

labium  with  a  very  shallow  closed  median  cleft  or  no  cleft 
at  all;  gills  thin,  lamelliform 6 

6  (9)     Median  lobe  of  labium  with  a  short,  closed,  median  cleft;   lateral  lobe 

trifid'at  end;  movable  hook  bearing  raptorial  setae;  giUs 
showing  transverse  segmentation 7 

7  (8)     Lateral  lobe  of  the  labium  terminating  in  three  teeth,  between  the 

middle  and  external  of  which  is  situated  a  truncated  and 
serrated  lobe Lestes. 

8  (7)     Three  teeth  only,  terminating  the  lateral  lobe  of  the  labium,  no  trun- 

cated and  serrated  lobe  between  them.      .    .    .     Archilestes. 

9  (6)     Median  lobe  of  labium  entire;    lateral  lobe  bifid  at  end;    hook  naked; 

gills  various 10 

10  (11)     Labium  with  no  raptorial  setae  on  the  mentum  within;  gills  broad, 

thick,  dark  colored,  oval  or  oblong  in  shape  and  obtuse  at 
apex Argia. 

11  (10)     Labium  with  mental  setae;  gills  thinner,  more  pointed  and  nar- 

rower  12 

12(15)     Hind  angles  of  the  head  strongly  angulate 13 

13  (14)     Gills  widest  beyond  the  middle;    body  slender;   head  half  as  long  as 

wide Chromagrion. 

14  (13)     Gills  widest  across  the  middle;   body  stouter;  head  nearly  as  long  as 

wide Amphiagrion. 

15(12)     Hind  angles  of  the  head  rounded 16 

16  (17)     Labium  with  one  mental  seta  (and  a  rudimentary  second  one)  each 

side;  antennae  six- join  ted;  lateral  lobe  of  the  labium  with 
the  distal  end  above  the  end  hook  hardly  denticulated. 

Nehallennia. 

17  (16)     Labium  with  three  to  five  mental  setae  each  side  (one  may  be  smaller 

than  the  others),  and  end  of  lateral  lobe  denticulated  dis- 
tinctly; antennae  seven-jointed  (with  the  possible  exception 
oi  Enallagma  antennatum) 18 

18  (21)     Gills  more  than  half  as  long  as  the  abdomen,  lanceolate;  third  seg- 

ment of  antennae  less  than  a  third  longer  than  the  second .     1 9 

19  (20)     Labium  with  four  to  six  lateral  setae,  generally  with  five,  and  with 

three  (rarely  four)  mental  setae  each  side;  gills  often  with 
a  definite  color  pattern Enallagma. 


AQUATIC  INSECTS 


929 


20  (19)     Labium  with  five  or  six  lateral  setae,  and  with  four  mental  setae  each 

side;  gills  generally  with  no  distinct  pattern.    .    .   Ischnura. 

21  (18)     Gills  less  than  half  as  long  as  the  abdomen,  narrower  and  with  a  long 

tapering  point;    third  segment  of  antenna  more  than  a  third 

longer  than  the  second Anomalagrion. 

Without  external  respiratory  plates,  but  with  a  respiratory  chamber 
inside  the  wide  abdomen;  body  less  slender,  and  not  widest 
across  the  head.     (Dragonflies;    proper.) 

Suborder  Anisoptera   .    .     23 
Labium  flat  or  nearly  so  (the  edges  of  the  lateral  lobes  slightly  up- 
turned in  racAo/^/e^yjc),  without  raptorial  setae 24 

24  (35,  46)  Labium  with  its  median  lobe  entire;  antennae  four- jointed,  the 
fourth  joint  rudimentary;  fore  tarsi  two-jointed:  burrow- 
ing nymphs 25 


(i) 


23  (47) 


Fig.  i38g.  Recognition  characters  of  dragonfly  nymphs.  A,  inner  aspect  of  the  labium;  m,  mentum; 
sm,  submentum;  ml,  median  lobe;  U,  lateral  lobe;  ms,  mental  setae;  \ls,  lateral  setae;  It,  end  hook.  B,  end 
of  the  abdomen  as  seen  from  above:  7,  8,  Q,  10,  abdominal  segments;  d,  dorsal  hooks;  t,  lateral  spines; 
s,  superior  appendage;  /,  paired  lateral  appendages;  c,  inferior  appendages  (cerci). 


25  (26)     Middle  legs  more  approximate  at  the  base  than  are  the  fore  legs; 

fourth  segment  of  the  antenna  slender,  erect,  about  as  long 
as  the  third  segment  is  wide;  the  tenth  abdominal  segment 
about  as  long  as  the  ninth Progomplius. 

26  (25)     Middle  legs  not  more  (usually  less)  approximate  than  the  fore  legs 

at  base;  the  fourth  segment  of  the  antenna  a  mere  rudiment, 
orbicular  or  discoid,  much  shorter  than  the  third  segment 
is  wide;  the  tenth  abdominal  segment  much  shorter  than 
the  ninth 27 

27  (28)     Wing  cases  strongly  divergent  on  the  two  sides;    lateral  lobe  of 

labium  blunt  at  apex Ophiogomphiis. 

28  (27)     Wing  cases  laid  closely  parallel  along  the  back;  lateral  lobe  of  labium 

ending  in  a  sharp,  incurved  hook 29 

29  (30)     Abdomen  very  thin  and  flat,  circular  in  outHne  as  seen  from  above; 

third  segment  of  antenna  flat  and  subcircular.    .    Hagcnius. 

30  (29)     Abdomen  less  depressed,  ovate  to  lanceolate  in  outline,  at  least  twice 

as  long  as  wide 31 

31  (32)     Third  joint  of  antenna  very  flat,  thin,  and  in  outUne  circular  or 

broadly  oval Lanthus. 


930  FRESH-WATER  BIOLOGY 

32  (31)     Third  joint  of  antenna  elongate,  linear,  little  flattened.      .    .    .     33 

33  (34)     Dorsum  of  the  ninth  abdominal  segrnent  rounded,  or  with  a  low, 

obtuse,  median  longitudinal  ridge Gomphus. 

34  {s3)     Ninth  abdominal  segment  with  a  sharp  mid-dorsal  ridge,  ending  in  a 

straight  apical  spine Dromogomphus. 

35  (24,  46)     Labium   with   a    short   median    cleft;    antennae    seven-jointed, 

setaceous;  tarsi  three-jointed;  climbing  nymphs,  with  eyes 
at  sides  of  head 36 

36  (39)     Hind  angles  of  the  head,  viewed  from  above,  sharply  angulate.  .     37 

37  (38)     Lateral  lobe  of  labium  squarely  truncate  on  apex Boyeria. 

38  (37)     Lateral  lobe  of  labium  with  taper-pointed  apex.     .    .    .    Basiaeschna. 

39  (36)     Hind  angles  of  the  head  obtusely  rounded 40 

40  (45)     With  lateral  spines  on  abdominal  segments  4-,  5-,  or  6-9.      .    .     41 

41  (44)     With  lateral  spines  on  segments  4-,  or  5-9 42 

42  (43)     With  dorsal  hooks  on  abdominal  segments  7-9.      .    .  Nasiaeschna. 

43  (42)     With  no  dorsal  hooks  on  abdomen Epiaeschna. 

44  (41)     With  lateral  spines  on  abdominal  segments  6-9 Aeschna. 

45  (40)     With  lateral  spines  on  abdominal  segments  7-9 Anax. 

46  (24,  35)     Labium  with  a  shallow  median  cleft;  antennae  seven-jointed; 

short;  squatting  nymphs,  with  face  vertical,  and  eyes  on 
anterolateral  angles;  depressed;    hairy;  tarsi  three-jointed. 

Tachopteryx. 

47  (23)     Labium  mask-shaped  or  spoon-shaped,  when  closed,   covering  the 

fa-ce  up  to  the  bases  of  the  antennae,  armed  with  raptorial 
setae 4^ 

48  (49)     The  prominent  median  lobe  of  the  labium  cleft  into  two  variously 

formed  teeth  at  apex Cordulegaster. 

49  (48)     The  median  lobe  of  the  labium  entire 50 

50  (53)     Head  with  a  prominent  pyramidal  frontal  horn;     abdomen  flat  and 

almost  circular  in  outhne  as  seen  from  above;  legs  long, 
giving  a  spiderhke  aspect  to  these  big  nymphs;  the  tenth 
abdominal  segment  well  exposed,  not  telescoped  in  the  apex 
of  the  ninth  segment;  teeth  on  the  lateral  lobes  of  the  labium 
with  deep  incisions  between  them 51 

51  (52)     Head  hardly  as  \\dde  across  the  eyes  as  across  the  bulging  hind  angles; 

lateral  spines  not  incurved,  those  of  the  ninth  abdominal 
segment  hardly  surpassed  by  the  tips  of  the  appendages; 
dorsum  of  the  tenth  abdominal  segment  with  no  trace  of  a 
dorsal  hook Didymops. 

52  (51)     Head  widest  across  the  eyes;   spines  of  the  ninth  abdominal  segment 

shorter,  not  nearly  reaching  the  level  of  the  apices  of  the  ap- 
pendages; dorsum  of  the  tenth  segment  with  a  very  rudi- 
mentary dorsal  hook Macromia. 

53  (50)     Head  without  pyramidal  frontal  horn;   abdomen  less  flattened,  more 

elongate;  teeth  on  the  lateral  lobes  of  the  labium  much 
wider  than  high 54 


AQUATIC   INSECTS  931 

54  (65)     Lateral  appendages  of  the  abdomen  more  than  half  as  long  as  the 

inferiors;  hind  femora  longer  than  the  head  is  wide;  when 
the  lateral  spines  are  long,  then  there  is  a  full  series  of  big, 
cultriform  dorsal  hooks  on  the  abdomen 55 

55  (56)     Lateral  setae  four  or  five;   mentum  about  as  long  as  wide. 

Epicordulia. 

56  (55)     Lateral  setae  seven;   mentum  of  labium  longer  than  wide.      .    .     57 

57  (62)     Abdomen  with  large,  laterally  flattened,  generally  cultriform  dorsal 

hooks 58 

58  (59)     Lateral  spines  of  the  ninth  segment  longer  than  half  the  length  of 

that  segment;  dorsal  hooks  on  segments  3-9,  highest  on  6, 
cultriform,  and  sharp \     Tetragoneuria. 

59  (58)     Lateral  spines  of  the  ninth  segment  shorter  than  half  of  that  segment; 

dorsal  hooks  less  developed 60 

60  (61)     Dorsal  hooks  on  segments  4-9  laterally  flattened,  but  not  cultriform. 

Somatochlora. 

61  (60)     Dorsal  hooks  on  segments  6-9,  longest  on  8  and  cultriform. 

Helocordulia. 

62  (57)     Abdomen  with   no   dorsal   hooks,   or  with   these  rudimentary,  not 

flattened  laterally  or  cultriform,  but  small  obtuse  or  pointed 
prominences 63 

63  (64)     Hind  angles  of  the  head  rounded;  lateral  spines  of  the  ninth  abdominal 

segment  one-fifth  as  long  as  that  segment.  .    .    .     CordiiUa. 

64  (63)     Hind  angles  of  the  head  angulate  superiorly;    spines  of  the  ninth 

abdominal  segment  one-third  as  long  as  that  segment. 

Dorocordulia. 

65  (54)     Lateral  abdominal  appendages  generally  less  than  half  the  length  of 

the  inferiors;  hind  femora  generally  as  long  as  the  head  is 
wide;  often  when  the  lateral  spines  of  the  abdomen  are  long 
the  dorsal  hooks  are  wanting  or  reduced 66 

66  (67)     With  large,  cultriform  dorsal  hooks  on  abdominal  segments  3-9;  eyes 

small  and  situated  on  the  mid-lateral  margin  of  the  head  and 
directed  laterally Per  it  hem  is. 

67  (66)     With  no  dorsal  hook  on  the  ninth  abdominal  segment;    eyes  over- 

spreading more  or  less  the  anterolateral  margins  of  the 
head .    .     68 

68  (85)     Basal  segment  of  the  hind  tarsus  more  than  half  as  long  as  the  second 

segment;  lateral  appendages  of  the  abdomen  not  more  than 
half  as  long  as  the  inferiors  (except  in  Libellula  quadri- 
maciilata) ;  superior  abdominal  appendage  regularly  tapering 
to  a  point 69 

69  (70)     Abdominal  appendages  strongly  decurved;    lateral  spines  wanting 

or  extremely  rudimentary Mesothemis. 

70  (69)     Abdominal  appendages  straight  or  very  slightly  declined;    lateral 

spines  evident  on  abdominal  segments  8  and  9 71 

71  (74)     With  no  dorsal  hooks  at  all 72 


932  FRESH-WATER   BIOLOGY 

72  (73)     Abdomen  smooth,  depressed;    head  twice  as  wide  as  long,  with  eyes 

very  prominent  laterally;  lateral  spines  large  and  straight; 
superior  appendage  one-third  shorter  than  the  inferiors. 

Pachydiplax. 

73  (72)     Abdomen  hairy  at  the  apex;    lateral  spines  small  and  sharply  in- 

curved;   superior  appendage  as  long  as  the  inferiors. 

Nannothemis. 

74  (71)     Dorsal  hooks  present,  at  least  on  the  middle  abdominal  segments.    75 

75  (80)     Abdomen  ovate  in  outline,  rather  abruptly  narrowed  to  the  posterior 

end;  hind  margin  of  the  eyes  behind  the  middle  of  the 
head 76 

76  (77)     Lateral  spines  long  and  straight;   abdomen  not  narrowed  posteriorly 

before  the  eighth  segment Celithemis. 

77  (76)     Lateral  spines  shorter  and  more  or  less  incurvate;    the  abdomen 

more  or  less  narrowed  before  the  eighth  segment.  ...     78 

78  (79)     Dorsal  hooks  as  long  as  the  segments  which  bear  them.    Leucorhinia. 

79  (78)     Dorsal  hooks  shorter  than  the  segments  which  bear  them. 

Sympetrum. 

80  (75)     Abdomen  lanceolate  in  outline,   slowly  narrowed   to   the  pointed 

posterior  end;  eyes  capping  the  prominent  anterolateral 
angles  of  the  head,  their  hind  margin  generally  before  the 
middle  of  the  top  of  the  head;    body  generally  hairy.  .     81 

81  (82)     The  tenth  abdominal  segment   with   subcarinate   lateral   margins; 

appendages  very  long;  lateral  setae  0-3 Ladona. 

82  (81)     The  tenth  abdominal  segment  shorter,  cylindric;  appendages  shorter; 

lateral  setae  5-10 ^^ 

^^  (84)     Head  a  little  narrowed  behind  the  eyes;    front  border  of  the  median 
lobe  of  the  labium  entire Libellula. 

84  (83)     Head  not  narrowed  behind  the  eyes  to  the  hind  angles;   front  border 

of  the  median  labial  lobe  crenulate Plathemis. 

85  (68)     Basal  segment  of  the  hind  tarsus  half  as  long  as  the  second  segment; 

lateral  appendages  of  the  abdomen  at  least  three-fourths 
as  long  as  the  inferiors;  lateral  setae  10  or  more;  superior 
appendage  of  the  abdomen  suddenly  contracted  at  its  basal 
third,  the  dorsal  two-thirds  forming  a  long  slender  point.    86 

86  (87)     Movable  hook  of  labium  long  and  slender,  setiform;    teeth  much 

broader  than  high;  spines  of  the  eighth  segment  one-half 
longer  than  the  ninth  segment;  superior  abdominal  append- 
age shorter  than  the  inferiors Tramea, 

87  (86)     Movable  hook  of  the  labium  short,  hardly  longer  than  the  teeth; 

teeth  higher  than  broad;  spines  of  the  eighth  segment  as 
long  as  the  ninth  segment;  superior  appendage  equaling 
the  inferiors Pantala. 


AQUATIC    INSECTS  933 

KEY  TO  AQUATIC  AND  SEMI-AQUATIC  HEMIPTERA 

1  (8)     Antennae  longer  than  the  head,  free.    Forms  that  walk  on  the  water.    2 

2  (5)     Last  segment  of  tarsi  split,  claws  inserted  before  the  apex.      ...     3 

3  (4)     Beak  four-jointed;   intermediate  and  posterior  legs  extremely  long  and 

slender;  body  widest  back  of  the  prothorax. 

Family  Gerridae. 

4  (3)     Beak  three-jointed;   none  of  the  legs  extremely  long  and  slender;   body 

widest  across  the  prothorax Family  Veliidae. 

5  (2)     Last  segment  of  tarsi  entire,  claws  inserted  at  the  apex 6 

6  (7)     Body  linear;   head  as  long  as  thorax;   legs  extremely  long  and  slender; 

beak  not  reaching  anterior  coxae.    Family  Hydrometridae. 

7  (6)     Body  oval ;  head  shorter  than  thorax ;  legs  not  extremely  long  and  slender ; 

beak  reaching  intermediate  coxae.     .   Family  Acanthiidae. 

8(1)     Antennae  shorter  than  the  head,  nearly  or  quite  concealed  beneath  the 

margin  of  the  head,  or  in  a  cavity  beneath  the  eyes.      .     9 

9  (12)     Ocelli  two;  anterior  coxal  cavities  open  behind;  antennae  four-jointed, 

simple.     (Live  near  the  water) 10 

10  (11)     Fore  legs  slender,  fitted  for  running;  eyes  triangular. 

Family  PELOGONroAE. 

11  (10)     Fore  legs  stout,  fitted  for  grasping;    eyes  projecting,  subglobose. 

Family  Nerthrddae. 

12  (9)     Ocelli  none;   anterior  coxal  cavities  open  or  closed  behind;  antennae 

three  or  four-jointed,  simple  or  with  some  of  the  segments 
produced  into  a  lateral  hook.     (Live  in  the  water) .    .    .     13 

13  (32)     Anterior  coxal  cavities  closed  behind;  antennae  four-jointed,  simple 

or  hooked 14 

14  (15)     Antennae  simple;  no  caudal  appendages;  fore  legs  fitted  for  grasping, 

middle  and  hind  legs  for  walking.     .    .   Family  Naucoridae. 

15  (14)     Second  and  third  (sometimes  fourth)  joint  of  antennae  produced  into 

lateral  hooks;  end  of  abdomen  with  a  pair  of  caudal  append- 
ages; fore  legs  fitted  for  grasping,  middle  and  hind  legs  for 
walking  or  swimming 16 

16  (29)     Antennae  four-jointed;  caudal  appendages  short,  strap-shaped,  re- 

tractile; middle  and  hind  legs  flattened,  fitted  for  swimming; 
tarsi  two-jointed.     .    .    .    Family  Belostomatidae  .    .     17 

17  (18)     Fore  tarsus  with  two  claws Hydrocirius. 

18  (17)     Fore  tarsus  with  a  single  claw 19 

19  (22)     Mesothorax  with  a  strong  mid-ventral  keel 20 

20  (21)     An  internal  tooth  borne  upon  both  joints  two  and  three  of  the  an- 

tenna;   all  the  ventral  surface  of  the  body  hairy.    Serphus. 

21  (20)     An  internal  tooth   borne  upon  joints   two,  three   and   four   of   the 

antennae;  venter  hairy  only  in  the  middle.   .    .    .       Abedus. 
22(19)     Mesothorax  without  mid-ventral  keel;  antennae  four-jointed.   .    .     23 

23  (26)     Furrow  of  the  membrane  of  the  fore  wing  regularly  curved;  an  acute 

internal  tooth  on  antennal  segments  two  and  three,  the 
fourth  simple  and  pointed 24 

24  (25)     Membrane  of  the  fore  wing  small;  the  reentrant  angle  seen  at  either 

side  of  the  front  of  the  head  when  viewed  from  above  is 
wholly  in  the  front Fedinocoris. 


934  FRESH-WATER   BIOLOGY 

25  (24)     Membrane  large;    reentrant  angle  bordered  externally  by  the  eye 

itself  {Zaitha  of  most  of  our  literature) ....       Belostoma. 

26  (23)     Furrow  of  wing  membrane   S-shaped;     a  recurved  internal   tooth 

borne  on  antennal  segments  two,  three  and  four.    ...     27 

27  (28)     Front  femora  grooved  internally  for  the  reception  of  the  tibia  {Belos- 

toma oi  most  oi  our  UtersLtuie) Amorgius. 

28  (27)     Front  femora  not  grooved  internally Benacus. 

29  (16)     Antennae  three-jointed;  caudal  appendages  long,  j&hform,  grooved; 

middle  and  hind  legs  fitted  for  walking;  tarsi  one-jointed. 

Family  Nepidae  .    .     30 

30  (31)     Body  oval;    legs  not  extremely  long  and  slender;    prothorax  much 

broader  than  head;  anterior  femora  but  little  longer  than 
tibiae Nepa. 

31  (30)     Body  linear;    legs  extremely  long  and  slender;    prothorax  but  Uttle 

broader  than  head;  anterior  femora  more  than  twice  as 
long  as  tibiae Ranatra. 

32  (13)     Anterior  coxal  cavities  open  behind;  antennae  three  or  four-jointed, 

without  lateral  hooks t,t, 

33  (38)     Head  inserted  in  the  prothorax;  antennae  four-jointed;   beak  three 

or  four-jointed,  not  retractile;  anterior  tarsi  one  or  two- 
jointed,  of  the  usual  form,  with  two  claws. 

Family  NoTONEcrroAE  .   .     34 

34  (37)     Antennae  inserted  in   cavity  beneath   eyes,   second  joint   thickest; 

hind  legs  flattened,  ciliated,  fitted  for  swimming;  abdomen 
keeled  and  hairy.     (Size  larger) 35 

35  (36)     Last  joint  of  antenna  less  than  half  as  long  as  the  third,  which  is 

fringed  with  capitate  hairs.  Hind  tarsi  without  claws. 
(Body  stouter) Notonecta. 

36  (35)     Last  joint  of  antenna  fringed  with  capitate  hairs,  and  many  times 

longer  than  the  third,  which  is  very  small  and  inconspicuous. 
Hind  tarsi  with  claws.     (Body  more  slender).    .     .    Buenoa. 

37  (34)     Antennae  inserted  beneath  the  margin  of  the  head,  third  joint  longest 

and  thickest;  hind  legs  like  the  middle  legs,  tarsi  with 
claws;  abdomen  not  keeled  or  hairy.  (Size  smaller,  not 
over  3  mm.  long) Plea. 

38  {$^)     Head  overlapping  the  prothorax;    antennae  three  or  four- jointed; 

beak  short,  unjointed,  retractile;  anterior  tarsi  one-seg- 
mented, flattened,  with  a  fringe  of  hairs  on  the  edge,  and 
without  claws Family  Corixjdae. 


KEY  TO  NORTH  AMERICAN  AQUATIC  NEUROPTERA 

Adults 

1  (4)     Veins  of  the  wing  disc  all  ending  in  a  succession  of  symmetrical  forks, 

the    terminal   forks   forming    a    distinct    peripheral    zone; 
antennae  moniliform.  .    .     Family  Hemerobiidae      .    .     2 

2  (3)    The  median  vein  repeatedly  forked;   some  of  the  branches  of  vein  Cui 

again  forked.    . Sisyra. 


AQUATIC   INSECTS 


935 


3  (2)     The  median  vein  but  once  forked;  the  branches  of  vein  Cui  all  simple. 

Climacia. 

4  (i)     Veins  of   the  wing  disc   extending  outward  in  straighter  lines,  forks 

fewer  and  less  symmetrical;   antennae  cyHndric  serrate,  or 
pectinate Family  SiALroiDAE   .    .      5 

5  (6)     Fourth  segment  of  the  tarsus  bilobed;    posterior  branch  of  the  radial 

sector  forked.     No  ocelh Sialis. 


Fig.  1390.    Fore  wings  of  two  neuropterous  insects,  Sialis  (above)  and  Climacia  (below),     h,  humeral 
cross- vein;  st,  stigma;  designations  of  principal  veins  as  in  Fig  1386. 

6  (5)     Fourth  segment  of  the  tarsus  simple,  cylindric;  posterior  branch  of  the 

radial  sector  simple.     Three  oceUi 7 

7  (8)     Hind  angles  of  the  head  rounded;    the  median  vein  two-branched; 

antennae  with  segments  enlarged  distally.      .    ,    Chauliodes. 

8  (7)     Hind  angles  of.  the  head  bearing  a  sharp  angulation  or  tooth;    median 

vein  three-branched;    segments  of  the  antennae  cylindric. 

Corydalis. 


1(4) 
2  {3) 


3(2) 

4(1) 
5(6) 


Larvae 

Mouth  parts  adapted  for  piercing  and  sucking,  prolonged  to  half  the 
length  of  the  body;  Hving  on  fresh-water  sponges.      ...   2 

Setae  on  the  dorsum  of  the  thorax  pedunculate  (i.e.,  the  setigerous 
tubercles  elevated  considerably  above  the  level  of  the  integ- 
ument); the  outer  covering  of  the  pupal  case  spun  by  the 
larva  is  of  a  beautiful  hexagonal  mesh Climacia, 

Thoracic  setae  sessile;  the  outer  covering  of  the  pupal  case  is  close  woven. 

Sisyra. 

Mouth  parts  adapted  for  biting 5 

The  last  abdominal  segment  produced  in  a  long,  median,  laterally  fringed 
tail-hke  process;  a  pair  of  lateral  filaments  on  abdominal 
segments  1-7 Sialis. 


Q36  FRESH-WATER  BIOLOGY 

6  (5)     Last  abdominal  segment  bifurcated,  the  fleshy  forks  each  bearing  a 

pair  of  hooks  and  a  minute,  external,  lateral  filament;    con- 
spicuous lateral  filaments  on  abdominal  segments  1-8.  .     7 

7  (8)     Lateral  filaments  with  no  tuft  of  fine  tracheal  gills  at  their  bases. 

Chauliodes. 

8  (7)     Lateral  filaments  each  with  a  tuft  of  fine  tracheal  gills  at  its  base. 

Corydalis. 


KEY  TO  NORTH  AMERICAN  CADDISFLIES 

1  (2)     Micro-caddisflies;   very  small,  mothlike,  hairy,  the  fore  wings  bearing 

numerous  erect  clavate  hairs;  the  marginal  fringe  of  the 
wings  longer  than  their  greatest  breadth;  form  of  wings 
narrowly  lanceolate;  antennae  rather  stout  and  not  longer 
than  fore  wings Family  Hydroptilidae. 

2  (i)     Larger  caddisflies,  with  broader  wings;    marginal  fringes  never  as  long 

as  the  wings  are  broad;  antennae  usually  longer  than  the  fore 
wings 3 

3  (26)     Maxillary  palpus  five-jointed 4 

4  (19)     Last  joint  of  the  maxillary  palpus  simple,  and  not  longer  than  the 

other  joints 5 

5  (10)     Ocelli  present 6 

6  (9)     Front  tibiae  with  two  or  three  spurs,  middle  tibiae  with  four  spurs.     7 

7  (8)     The  first  two  joints  of  the  maxillary  palpus  short  and  thick,  the  third 

joint  much  longer  and  thinner.   .   Family  Rhyacophilidae. 

8  (7)     The  second  joint  of  the  maxillary  palpus  much  longer  than  the  first. 

Females Family  Phryganeidae. 

9  (6)     Front  ribiae  with  a  single  spur,  or  with  none;  middle  tibiae  with  only  two 

or  three  spurs.     Females.       .    .    .   Family  Limnophilidae. 

10  (5)     OceUi  wanting 1 1 

11(12)     A  closed  cell  in  the  principal  fork  of  the  median  vein  in  the  fore  wings. 

Family  Calamoceratidae. 

12(11)  No  closed  cell  in  the  median  fork 13 

13(18)  A  closed  cell  in  the  first  fork  of  the  radial  sector  (i^a) 14 

14(17)  Both  branches  of  the  radial  sector  forked 15 

15  (16)  Veins  Ri  and  R2  confluent  apically  or  connected  by  an  apical  cross 

vein  in  the  fore  wing.    Females.   .   Family  Odontoceridae. 

16  (15)     Veins  Ri  and  R2  not  connected  apically. 

Family  Sericostomatidae. 

17  (14)     Only  the  anterior  branch  of  the  radial  sector  forked. 

Family  Leptoceridae. 

18  (13)     No  closed  cell  in  the  first  fork  of  the  radial  sector. 

Family  Molannidae. 

19  (4)     Last  joint  of  the  maxillary  palpus  usually  much  longer  than  the  others, 

twisted,  and  divided  imperfectly  into  subsegments.    .    .     20 

20  (21)     Ocelli  present Family  Philopotamidae. 


AQUATIC   INSECTS  937 

21  (20)  Ocelli  wanting '. 22 

22  (23)  Front  tibia}  with  three  spurs Family  Polycentropidae. 

23  (22)  Spurs  of  the  front  tibiae  fewer  than  three 24 

24  (25)  Anterior  branch  of  the  radial  sector  in  the  fore  wing  forked. 

Family  Hydropsychidae. 

25  (24)     Anterior  branch  of  the  radial  sector  simple. 

Family  Psychomyiidae. 

2;    CU2      - 

>         'A       ^^2      * 
Fig.  1391.     The  wings  of  a  caddisfly,  Hydropsyche. 

26  (3)     Maxillary  palpi  with  fewer  than  five  joints 27 

27  (28)     Maxillary  palpi  with  four  joints;    ocelli  present.        Males. 

Family  Phryganeidae. 

28  (27)     Maxillary  palpi  with  two  or  three  joints 29 

29  (30)     Maxillary  palpi  filiform  with  cylindric  smooth  joints;  fore  tibiae  with 

a  single  spur.     Males Family  Limnophilidae. 

30  (29)     Maxilary  palpi  hairy  or  scaly,  appressed  against  and  often  covering 

the  face;    fore  tibiae  with  two  spurs.     Males. 

Family  Sericostomatidae. 


KEY  TO  NORTH  AMERICAN  AQUATIC  BEETLES 
Adults 

1  (2)     Hind  tarsi  with  the  antepenultimate  segment  broadly  bilobed,  and 

receiving  the  rudimentary  penultimate  segment  (which  is 
closely  fused  with  the  base  of  the  last  segment)  in  its  apical 
notch Family  Chrysomelidae. 

2  (i)     Hind  tarsi  with  the  last  three  segments  free  and  similar  in  form.  .    .     3 

3  (8)     Hind  legs  shorter  than  the  fore;    eyes  four,  two  above  and  two  on  the 

under  surface  of  the  head.  .    .    .  Family  Gyrinidae   .    .     4 

4  (7)     Last  abdominal  segment  rounded  posteriorly  and  smooth  below.  .    .     5 

5  (6)     Wing  of  the  metasternum  {w,  Fig.  1392)  broadly  triangular.   .     Dineiites. 

6  (5)     Wing  of  the  metasternum  narrow,  elongate,  widened  only  at  its  extreme 

outer  endo Gyrinm* 


938  FRESH-WATER   BIOLOGY 

7  (4)     Last  abdominal  segment  elongate  pyramidal,  and  furnished  with  a  mid- 

ventral  line  of  hairs Gyretes. 

8  (3)     Hind    legs    longer    than    the    fore;    eyes 

two 9 

9  (14)     Base  of  the  hind  legs  covered  by  broad 

overlapping  coxal  plates. 

Famxily  Haliplidae  .    .      10 

10  (1,3)     Coxal   plates  concealing  only  the  three 

basal  segments  of  the  abdomen ; 
last  segment  of  palpi  shorter 
than  the  preceding  segment.    1 1 

11  (12)     Pronotum  widest  before  the  middle. 

Brychius. 

12  (11)     Pronotum  widest  at  the  rear  end. 

Haliplus. 

13  (10)     Coxal  plates  conceaHng  all  but  the  last 

of  the  ventral  abdominal  seg- 
ments; last  segment  of  palpi 
longer  than  the  preceding  seg- 
ment  Peltodytes. 

14(9)     Base  of  the  hind  legs  exposed .    ...     15 

15  (48)     Antennae   shorter   than  the  palpi;   legs 

usually  with  swimming  fringes. 
Family  Hydrophilidae  .    .      16 

16  (23)     Scutellum  wanting  or  indistinct  or  very 

small  and  scalelike.     Posterior 

femora  subcylindrical  and  not 

noticeably  widened  in  the  mid-      pic.1392.  Diagram  of  the  ventral 

die ;  pro  thorax  narrowed  behind,    aspect  of  a  diving  beetle,  Coptotomus 

narrower  than  the  elytra.     The   fX'i^,'c,^ii^1""li'\^°''S:i 

species       are      small,      elongate,     middle  legs;    d,  labial  palpi;    e,  eye; 

roughly  sculptured,  greyish   or  {.rthe'pSfoti^;  5;. 'epipt "'?!," 
nearly  black,  and  usually  tinged   the  wing  cover  (elytron);  f,  pros- 

-  -      -  ,11.  1       temal  process;   /',  metasternal  fork; 

k,  hind  coxa  with  /,  the  inner  lam- 
ina; p,  the  coxal  process  and  q,  the 
coxal  notch;  r,  trochanter  of  the 
hind  leg;  s,  femur;  /,  tibia;  u,  hind 
tarsus  of  five  jcints;  /,  2,  j,  4,  5-  <5, 
ventral  abdominal  segments,  5/^  sf-, 
sP,  sterna  of  pro-,  meso-,  and  meta- 
thoi  ax,  respectively;  u',  wing  of  the 
metasternum;  m,  episternum,  and 
n,  epimeron  of  the  successive  thor- 


with   bronze  and  metalHc    col 
ors 17 

17  (20)  Scutellum  indistinct,  or  apparently  want- 
ing; if  at  all  evident  it  is 
distinctly  triangular  and  acute. 
Species  from  1-2  mm.  long.     18 

18  (iq)     Pronotum  without  striae;  maxillary  palpi   ,., .»_......  „.  -..-  -_-^^    ^  . 

as  long  as  the  head  and  thorax   ^  -^^^  S^rV'nd  ViS 

together,    the   ultimate   segment     the  figure,  and  the  coxal  border  IS  the 

longer  than  the  penultimate;  ^^S^^^\^^%, 
elytra  with  more  than  ten  rows  end  of  the  coxal  line. 
of  punctures.  .    .    .     Hydraena. 

19  (18)     Pronotum  bearing  from  one  to  five  longitudinal  striae  or  abbreviated 

grooves;    the  maxillary  palpi  much  shorter  than  the  head 
and  thorax  together,  the  ultimate  segment  shorter  than  the 
penultimate;   elytra  with  only  ten  rows  of  punctures. 
*^  Octhehius. 


part  of  the  coxal  process,  p,  that  is 
marked  off  laterally  by  the  posterior 


AQUATIC   INSECTS  939 

20  (17)     Scutellum  appearing  as  a  very  small  but  distinct  scale,  shaped  like 

the  last  joint  of  one's  thumb;  the  ultimate  segment  of  labial 
palpus  longer  than  the  penultimate.  Species  from  3-6  mm. 
long 21 

21  (22)     The pronotum  bearing  five  longitudinal  striae;  labial  palpi  moderately- 

large Helophorus. 

22  (21)     The  pronotum  coarsely  punctured  but  without  longitudinal  striae; 

labial  palpi  short Hydrochiis. 

23  (16)     Scutellum   distinct,   moderately   large.     Posterior   femora   flattened 

and  distinctly  widened  at  their  middle;  prothorax  not 
narrowed  posteriorly,  as  wide  as  the  elytra  at  their  base. 
The  species  are  small  or  large,  of  oval,  elliptical  or  even 
hemispherical  form,  with  not  very  coarse  sculpture,  and 
are  commonly  pitchy  black,  often  more  or  less  testaceous, 
very  occasionally  with  metallic  tinges 24 

24  (43)     Metasternum  not  prolonged  into  a  spine;     tarsi  not  compressed. 

The  species  of  this  group  are  all  smaller  than  those  of  the 
next,  less  than  9  mm.  long 25 

25  (26)     Fifth  ventral  segment  w^th  a  deep  notch  in  the  middle  of  its  apical 

border;  middle  and  posterior  tibiae  and  tarsi  bearing  a  close- 
set  fringe  of  long  silky  setae;   scutellum  elongate,  acute. 

Berosus. 

26  (25)     Fifth   ventral   segment   not  notched;   tibiae  and   tarsi   not  fimbri- 

ate  27 

27  (28)     First  two  ventral  segments  concealed  by  whitish  translucent  plates, 

one  on  each  side,  upon  which  are  a  number  of  long  appressed 
setae.  The  species  are  very  convex,  have  a  tendency  to 
partially  roll  up  like  a  sow-bug,  and  are  from  1-2  mm.  in 
length Chaetarthria. 

28  (27)     No  such  plates  over  the  first  ventral  segments 29 

29  (30)     Posterior  tibiae  incurved,  small  at  base  and  considerably  enlarged  at 

their  apex Laccobius. 

30  (29)     Posterior  tibiae  straight;  little  or  not  at  all  thickened  at  their  apex.   31 

31  (32)     Abdomen   with    apparently   eight    ventral    segments.      The    single 

species  is  i^  mm.  long;   of  a  black  color  with  pale  legs. 

Limnebius. 

32  (31)     Abdomen  with  five  ventral  segments,   the  tip  of  the  sixth  often 

visible.     .    .' 33 

S3  (40)     Terminal  segment  of  the  maxillary  palpus  rarely  as  long  as,  usually 
shorter  than,  the  preceding  segment 34 

34  (35)     Elytra  deeply  longitudinally  striate;    tarsi  of  the  middle  and  pos- 

terior legs  with  only  four  segments Helocombus. 

35  (34)     Elytra  not  striate 36 

36  (39)     Mesosternum  with  a  feeble  transverse  carina  or  simple 37 

37  (38)     Mesosternum  with  a  feeble  transverse  carina;    tarsi  of  the  middle 

and  posterior  legs  with  four  segments Cymbiodyta. 

38  (37)     Mesosternum  simple;    all  tarsi  with  five  segments,  the  first  usually 

triangular Helochares. 


940  FRESH-WATER   BIOLOGY 

39  (36)     Mesosternum  with  a  longitudinal  carina;  all  tarsi  with  five  segments, 

the  first  one  small Philhydrus. 

40  {32>)     Terminal   segment   of   maxillary  palpi   distinctly  longer   than   the 

penultimate 41 

41  (42)     Large  species  6.5-8.5  mm.;    the  elytra  distinctly  striate  or  striato- 

punctate Hydrohius. 

42  (41)     Small  species  1.5-3.5  mm.;    the  elytra  not  striate  but  with  confused 

punctuation Creniphilus. 

43  (24)     Metasternum  prolonged  into  an  acute  spine;    tarsi  compressed  so  as 

to  be  oarlike.  The  color  is  always  pitchy  black,  occasion- 
ally with  yellow  margins.  The  size  varies  from  9  to  35 
mm 44 

44  (45)     Metasternum  produced  into  a  short  spine  never  projecting  as  far 

as  the  posterior  margin  of  the  first  ventral  segment.  Pro- 
sternum  acutely  carinate  but  not  grooved  for  the  reception 
of  the  mesosternal  carina Hydrocharis. 

45  (44)     Metatarsal  spine  \try  long  and  acute,  extending  always  beyond  the 

posterior  margin  of  the  first  ventral  segment.  Prosterniun 
with  a  keel-shaped  process  which  is  deeply  grooved  for  the 
reception  of  mesosternal  carina,  thus  locking  pro-  and  meso- 
thorax  together 46 

46  (47)     Length  about  10  mm.     Terminal  segment  of  maxillary  palpi  as  long 

as  or  longer  than  the  preceding;  the  antepenultimate  seg- 
ment straight;  claws  simple Tropisternus. 

47  (46)     Length  about  35  mm.     Terminal  segment  of  maxillary  palpi  much 

shorter  than  the  preceding;  the  antepenultimate  segment 
arcuate;  claws  toothed Hydrophilus. 

48  (15)     Antennae  longer  than  the  palpi  (equahng  them  in  a  few  riffie  beetles). 

49 

49  (90)     Hind  coxae  broadly  flattened  out  and  sohdly  fused  with  the  meta- 

sternum  50 

50  (51)     Metasternum  divided  by  a  transverse  suture  which  separates  a  short 

sclerite  before  the  base  of  the  hind  coxae. 

Family  Amphizoidae. 

A  single  genus  from  western  mountain  streams.     Amphizoa. 

51(50)     Metasternum  not  thus  divided Family  Dytiscidae  .    .     52 

52  (61)     Scutellum  invisible 53 

53  (54)     Third  and  fourth  segments  of  the  fore  and  middle  tarsi  not  greatly 

different  from  the  others;  prosternal  process  acute  posteriorly. 

Laccophilus. 

54  (53)     Third  segment  of  the  fore  and  middle  tarsi  deeply  bilobed,  the  fourth 

segment  rudimentary  or  wanting 55 

55  (56)     Base  of  thorax  united  to  the  elytra  by  a  short  impressed  fine  on  each 

side,  continued  without  interruption  across  the  border  of 
each;  hind  margin  of  the  posterior  coxae  grown  sohdly 
coherent  with  the  first  ventral  segment  of  the  abdomen, 
which  is  considerably  enlarged;   form  elongate;  very  small. 

Bidessus. 

56  (55)     Base  of  thorax  and  elytra  without  a  continuous  impressed  line.  .     57 


AQUATIC    INSECTS  941 

57  (58)     Hind  margin  of  the  posterior  coxae  grown  solidly  coherent  with  the 

first  segment  of  the  abdomen,  which  is  considerably  enlarged; 
form  round  and  very  convex;  shining;  small. 

Desmopachria. 

58  (57)     Hind  margin  of  the  posterior  coxae  overlapping  but  not  coherent 

with  the  first  segment  of  the  abdomen,  which  is  not  espe- 
cially enlarged.  Form  various,  but  never  so  round  and 
convex  as  Desmopachria,  nor  so  small  and  elongate  as 
Bidessus 59 

59  (60)     Hind  coxal  processes  each  divided  by  a  deep  posterior  notch,  the 

inner  ramus  appressed  against  the  first  abdominal  segment. 

Hydrovatus. 

60  (59)     Hind  coxal  process  not  so  formed Hydroporus. 

(In  the  broader  sense,  as  used  here  this  genus  includes 
Coelambus,  Deronectes) 

61  (52)     Scutellum  visible 62 

62  (63)     Clypeal  suture  entire Dytiscus. 

63  (62)     Clypeal  suture  incomplete.      64 

64  (65)     More  than  30  mm.  long;   inferior  spur  of  hind  tibiae  much  dilated, 

bifid,  much  broader  than  other  spur Cyhister. 

65  (64)     Less  than  20  mm.  long;   the  two  spurs  of  the  hind  tibiae  of  equal  or 

nearly  equal  breadth 66 

66  (73)     Distal  margin  of  each  segment  of  the  hind  tarsi  beset  with  a  trans- 

verse row  of  minute  appressed  bristles;  anterior  tarsi  of 
male  with  dilated  segments  forming  a  round  disc.      .    .     67 

67  (68)     Spurs  of  hind  tibiae  acute  at  tip;   claws  of  hind  tarsi  unequal,  the 

inner  one  sometimes  obsolete Uydaticus. 

68  (67)     Spurs  of  hind  tibiae  emarginate  at  tip;  claws  of  hind  tarsi  equal  or 

nearly  so 69 

69  (70)     Elytra  closely  punctate,  usually  f our-sulcate ;  female.       .    .    Acilius. 

70(69)     Elytra  not  punctate,  partly  aciculate  in  female 71 

71  (72)     Middle  femora  beset  with  elongate  setae;  female.     .       Thermonedes. 
72(71)     Middle  femora  beset  with  short  and  stout  setae.      .    .    .     Graphoderes. 

73  (66)     Hind  tarsi  without  such  appressed  bristles;   anterior  tarsi  of  female 

with  dilated  segments  forming  an  oval  disc 74 

74  (79)     A  linear  group  of  minute  setae  present  upon  the  postero-external  angle 

of  the  hind  femora 75 

75  (76)     Claws  of  the  hind  tarsus  unequal;    the  tarsal  segments  produced 

posteriorly  in  overlapping  lobes Ilyhiiis. 

76  (75)     Claws  of  the  hind  tarsus  equal  and  segments  simple 77 

77  (78)     Wing   of   the  metasternum  very  narrow  and   deflexed  around  the 

front  border  of  the  external  lamina  of  the  hind  coxa. 

Ilybiosoma. 

78  (77)     Wing  of  the  metasternum  wedge-shaped,  less  noticeably  deflexed. 

Agabiis. 

79  (74)     No  such  linear  group  of  setae  on  the  postero-external  angle  of  the 

hind  femora ^^ 

80  (81,  82,  83)     Surface  of  the  elytra  reticulate Scutopterus. 


942  FRESH-WATER   BIOLOGY 

81  (80,  82,  83)     Surface  of  the  elytra  transversely  aciculate.    .    .     Colymbetes. 

82  (80,  81,  83)     Surface  of  the  elytra  with  eight  to  ten  longitudinal  striae. 

Copelatus. 
8s  (80,  81,  82)     Surface  of  the  elytra  otherwise  sculptured  or  plain.      .    .     84 

84  (85)     Prosternum  plainly  longitudinally  sulcate;  species  reddish  brown. 

Matus. 

85  (84)     Prosternum  not  sulcate 86 

86  (87)  Apical  segment  of  each  palpus  distinctly  emarginate.     Coptotomus. 

87  (86)     Apical  segments  of  palpi  obtuse  or  truncate 88 

88  (89)     Claws  of  the  hind  tarsus  equal Agabetes. 

89  (88)     Claws  of  the  hind  tarsus  unequal Rhantus. 

90  (49)     Hind  coxae  free 91 

91  (no)     Claws  large;    the  three  basal  ventral  segments  of  the  abdomen 

fused  together,  obhterating  the  sutures. 

Family  Parnidae   .    .     92 

92  (93)     Ventral  abdominal  segments  (see  Fig.  1392)  seven  in  number. 

Psephenus. 

93  (92)     Ventral  abdominal  segments  five  in  number 94 

94  (103)     Fore  coxae  transversely  elongated 95 

95  (102)     Sternum  of  the  prothorax  prolonged  forward  beneath  the  head  in  a 

flat  rounded  lobe;  head  retracted  within  the  front  of  the 
prothorax;  the  two  basal  segments  of  the  antennae  dis- 
tinctly enlarged 96 

96  (97)  Body  rounded  in  outKne Lutrochus. 

97  (96)  Body  oblong,  elongate 98 

98  (99)  Antennae  approximate,  the  terminal  segments  pectinate.     Pelonomus. 

99  (98)  Antennae  distant  at  base 100 

100  (loi)     Antennae  slender Throscinus. 

101  (100)     Antennae  short  and  thick,  the  second  joint  triangularly  dilated,  the 

close-set  distal  segments  lamellate Dryops. 

102  (95)     Sternum  of  prothorax  not  greatly  produced  forward;    head  free; 

antennae  long  and  serrate  (California) Lara. 

103  (94)     Fore  coxae  rounded 104 

104  (109)     Sternum  of  prothorax  produced  forward  in  a  flat  rounded  lobe; 

head  retracted  within  the  front  of  the  prothorax.   ,    .    .   105 

105  (108)     Antennae  eleven- jointed 106 

106  (107)     Fore  tibiae  pubescent  internally Elmis. 

107  (106)     Fore  tibiae  bare  internally Sienelmis. 

108  (105)     Antennae  six-jointed Macronychus. 

109  (104)     Sternum  of  prothorax  not  produced  forward;   head  free. 

Ancyronyx. 
no  (91)     Claws  of  moderate  size;    basal  ventral  segments  free. 

Family  Dascyllidae. 


AQUATIC   INSECTS  943 

Larvae 

1  (4)     Herbivorous  larvae  with  short,  broad  inconspicuous  mandibles. 

Family  Chkysomelidak   .    .       2 

2  (3)     Feeding  exposed  on  the  floating  leaves  of  water  lilies,  etc.;    elongate 

brownish  larvae  of  sluggish  habits Galcrucella. 

3  (2)     Short  arcuate  grublike  larvae,  white  and  translucent,  feeding  on  the 

submerged  roots  of  aquatic  plants Donacia. 

4  (i)     Carnivorous  larvae,  with  prominent  mandibles 5 

5  (12)     Mandibles  sickle-shaped  without  internal  teeth,  but  with  an  internal 

groove  or  perforation  extending  almost  from  base  to  apex.    6 

6  (7)     End  of  the  abdomen  with  two  pairs  of  strong  claws,  and  the  middle 

segments  bearing  single  pairs  of  long  lateral  filaments. 

Family  GYRI^fIDAE, 

7  (6)     No  claws  at  end  of  abdomen 8 

8  (11)     Eyes  in  groups  of  five;   one  claw  on  each  tarsus. 

Family  Haliplidae   .    .     9 

9  (10)     Body  nearly  smooth,  ending  in  a  long  tail Haliplus. 

10  (9)     Body  bearing  numerous  very  long  and    conspicuous   bristlelike  fila- 

ments; no  tail Peltodytes. 

11  (8)     Eyes  in  groups  of  six;    two  claws  on  each  tarsus. 

Family  Dytiscidae. 

12(5)     Mandibles  toothed  internally,  at  base  or  in  the  middle 13 

13  (14)     Tarsi  with  two  claws Amphizoa. 

14(13)     A  single  claw  on  each  tarsus 15 

15  (16)     Antennae  as  long  as  or  longer  than  the  thorax. 

Family  Dascyllidae. 
16(15)     Antennae  shorter  than  the  thorax 17 

17  (18)     Larvae  depressed;    end  of  the  abdomen  with  short  cerci;  gills,  when 

present,  ventral  in  position Family  Parxid.a.e. 

18  (17)     Body  little  depressed;    cerci  wanting;    gills  rarely  present  (and  then 

lateral  in  position,  Berosus).    .    .      Family  Hydrophilidae. 


KEY  TO  NORTH  AMERICAN  AQUATIC  DIPTEROUS  LARVAE 

1  (65)     Head  chitinous,  free,  or  retracted  within  the  front  of  the  prothorax. 

Pupa  usually  free;  when  concealed  in  the  old  larval  skin, 
that  skin  splits  on  emergence  of  the  imago  in  a  longitudioal 
I-  or  T-shaped  cleft.    .    .    .     Suborder  Orthorrhapha  .    .      2 

2  (58)     Mandibles  opposed  to  each  other,  or  inclined  obliquely  downward 

and  opposed  to  a  strongly  chitinized  labial  border. 

Nematocera   .    .     3 

3  (4)     Body  strongly  depressed,  and  with  a  row  of  six  ventral  suckers  for 

attachment  to  the  rock  bed  of  rapid  streams. 

Family  Blepharoceridae 

4  (3)     Body  cylindric,   and  usually  lacking  ventral  suckers;   when  ventral 

suckers  are  developed  they  are  more  than  six 5 


944  FRESH-WATER   BIOLOGY 

5  (6)     Head  imperfectly  chitinized  in  the  rear,  and  wholly  retracted  within 

the  pro  thorax;  posterior  spiracles  situate  upon  a  respiratory 
disc Family  Tipulidae. 

6  (5)     Head  fully  developed  and  usually  free 7 

7  (35)     No  prolegs  developed  upon  the  prothorax 8 

8  (11)     Prolegs  developed  upon  some  of  the  anterior  segments  of  the  ab- 

domen        9 

Q  (10)     The  body  terminates  in  a  very  long  and  conspicuous  respiratory  tube. 

Family  Ptychopteridae. 

10  (0)     Without  respiratory  tube,  body  U-shaped  in  locomotion. 

Family  Ddodae. 

11  (8)     Body  without  prolegs 12 

12  (31)     Thorax  thickened,  the  outUne  of  its  constituent  segments  more  or 

less  confluent;  a  fin  of  swimming  hairs  developed  beneath 
the  end  of  the  abdomen,  and  often  a  respiratory  tube  on 
the  dorsal  side Family  Culicidae   .    .     13 

13  (26)     The  last  abdominal  segment  with  a  single  dorsal  breathing  tube, 

through  which  may  be  seen  a  pair  of  large  tracheae.     .    .     14 

14  (15)     Antennae  fold  back  against  head  and.terminate  in  two  or  three  claws. 

Corethrella. 

15  (14)     Antennae  usually  only  with  a  few  small  erect  bristles  and  one  or  two 

pointed  processes,  or  pendent  and  raptorial 16 

16  (23)     With  brush  of  hairs  projecting  forward  from  the  mouth,  vibratile.     17 

17  (22)     Antennae  not  pendent  and  raptorial 18 

18  (19)     No  ventral  brush  or  rudder  on  last  abdominal  segment  beyond  air 

tube;  small  species,  one  of  which  is  found  in  water  in 
pitcher  plant Wyeo7nyia. 

19  (18)     Last  segment  with  ventral  brush 20 

20  (21)     Head  with  thick  spines;  with  four  blood  gills;    with  stellate  hairs  on 

the  abdomen.     Small  species Uranotaenia. 

21  (20)     Head  without  stout  spines  in  addition  to  the  usual  setae. 

Culex  (sens.  lat.). 

22  (17)     Antennae  pendent  and  raptorial :    .    .    .    .   Mochlonyx. 

23  (16)     Mouth  brush  folded  outward,  raptorial,  not  vibratile 24 

24  (25)     A  plate  on  the  side  of  eighth  abdominal  segment.      .    .  Megarhinus. 

25  (24)     A  patch  of  small  scales  on  the  side  of  the  eighth  abdominal  segment. 

Psorophora. 

26(13)     Last  segment  without  long  breathing  tube 27 

27  (30)     Last  segment  dorsally  with  a  flat  area  in  which  may  be  seen  two 

spiracles 28 

28  (29)     Large  species  with  the  anal  segment  bladderlike.     Mandibles  strongly 

developed Pelorempis. 

29  (28)     Species  of  medium  size  with  anal  segment  cylindrical.    .    .   Anopheles. 


AQUATIC   INSECTS  945 

30  (27)     Last  segment  usually  with   hooks,    no   spiracles   apparent.     Larva 

transparent. Cordlira. 

31  (12)     Body  cyhndric,  or  depressed  fusiform 32 

32  {2>2),  34)     Body  ending  in  two  fleshy  points Family  Rhyphidal. 

2>d>  (32,  34)     Body  ending  in  a  tapering  segment  tipped  with  a  tuft  or  circlet 

of  hairs Ccratopo^oniuc  of  Chiroxomidae. 

34  (32,  33)     Body  ending  in  a  strongly  chitinized  terminal  segment,  usually 

produced  in  chitinous  respiratory  tube.     .    .    Psychodidae. 

35  (7)     Prothorax  with  one  or  two  prolegs 36 

36  (57)     A  pair  of  prolegs  beneath  the  prothorax,  and  another  pajr  at  the  end 

of  the  abdomen Family  Chiroxomidae    .    .     37 

37  (38)     Abdomen  with  prominent  rounded  elevations  or  cushions,  with  rows 

of  teeth  on  the  inferio-anterior  angles  of  the  segments. 

Fsamathiomyia. 

38  (37)     Abdominal  segments  without  cushions 39 

39  (40)     With  retractile  antennae,  the  latter  often  quite  long,  long  sliltlike 

legs,  the  caudal  tufts  of  hair  mounted  on  cylindrical  processes. 

Tuny  pus. 

40  (39)     Not  with  all  the  above  characters 41 

41  (44)     With  the  two  caudal  hair  tufts  mounted  on  cylindrical  projections.    42 

42  (43)     With  blood  gills  on  venter  of  eleventh  segment.    .    .     Hydrohacniis. 

43  (42)     With  blood  gills  only  at  end  of  twelfth  segment.     .    .  Metriocnemus. 

44  (41)     Caudal  tufts  on  small  rounded  papillae 45 

45  (48)     Antennae  elongate,  at  least  one-half  as  long  as  and  often  as  long  as 

or  longer  than  the  head 46 

46  (47)     Antenna  with  one  or  two  sense  organs  at  tip  of  second  segment. 

(Rendered   visible    in   preserved   material    by   soaking   in 
water) Tanytarsiis. 

47  (46)     Antenna  at  most  with  a  seta  at  tip  of  second  segment  at  side  of  the 

third  segment Corynoncura. 

48  (45)     Antennae  short 49 

49  (50)     Larvae  usually  blood  red;  eleventh  body  segment  with  two  pairs  of 

blood  gills C//m);/ow«5  (in  part). 

50(49)     Larvae  greenish,  yellowish,  or  whitish 51 

51  (52)     The  maxilliary  palpus  usually  noticeably  longer  than  broad.     Larva 

in  pools,  pond  water,  or  slow  streams    ....   Chironomiis. 

52  (51)     Palpus  about  as  long  as  broad 53 

53  (54)     Full-grown  larva  not  over  6  mm.  long,  green  or  bluish-green  in  color. 

Anterior  abdominal  segments  of  greater  diameter  than  the 
posterior  ones.  Mandibles  often  transversely  wrinkled; 
the  anterior  prolegs  usually  with  pectinate  setae. 

Cricotopus,  Ortliocladius. 

54  (53)     Full-grown  larva  over  6  mm.  in  length;    mandible  not  transversely 

wrinkled 55 

55  (56)     Labium  with  teeth  all  rounded Diamesa. 

$6  (55)     Labium  with  middle  tooth  broadly  truncate Thalassomyia. 


946  FRESH-WATER   BIOLOGY 

57  (36)     A  single  median  proleg  on  the  prothorax  and  a  terminal  sucking  disc 

upon  the  abdomen,   serving  for  attachment  to  stones  in 
rapid  streams;  abdomen  broadened  posteriorly. 

Family  Simuliidae. 

58  (2)     Mandibles  decurved,  parallel,  their  motion  vertical,  or  nearly  so. 

Brachycera  .    .     59 

59  (64)     Posterior  spiracles  placed  together  within  a  terminal  cleft.  ...     60 

60(63)     Terminal  cleft  vertical;  head  retractile. 

Family  Tab ANIDAE  .    .     61 

61  (62)     Last  antennal  segment  much  longer  than  the  one  preceding;    dorsal 

areas  striated  like  those  of  the  abdomen.      .    .    .     Chrysops. 

62  (61)     Last  antennal  segment  not  longer,  usually  much  shorter,  than  the  one 

preceding;   dorsal  areas  smooth  or  striated,  but  those  of  the 
thorax  nearly  or  quite  free  from  striae Tabanus. 

63  (60)     Terminal  cleft  transverse;    head  not  retractile. 

Family  Stratiomyiidae. 

64  (59)     Posterior  spiracles  separate Family  Leptidae. 

65  (i)     Head   membranous,    very   imperfectly   developed,   often   apparently 

wanting.     Pupa  formed  in  the  hardened  and  contracted 
larval  skin  (puparium),  which  opens  by  a  circular  cap  or  lid. 

Suborder  Cyclorhapha. 
This  group  includes  many  of  the  higher  aquatic  Diptera 
(Syrphujae  SciOMYzmAE,  etc.)  still  too  insufficiently  known  to 
admit  of  the  construction  of  a  satisfactory  key. 

Note:  Acknowledgment  is  hereby  made  of  help  generously  given  in  the  preparation  of  the 
foregoing  keys  in  parts  as  follows:  in  Hemiptera  by  Mr.  C.  R.  Plunkett;  m  Coleoptera  by 
Dr.  J.  C.  Bradley;  in  Diptera  by   Dr.  O.  A.  Johannsen. 

IMPORTANT   REFERENCES   ON   NORTH   AMERICAN 
AQUATIC   INSECTS. 

CoMSTOCK,  J.  H.    1917.    Manual  for  the  Study  of  Insects.     14th  Ed.    Ithaca. 

Kellogg,  V.  L.     1905.     American  Insects.     New  York. 

FoLSOM,  J.  W.     19 13.     Entomology,  with  Reference  to  its   Biological   and 

Economic  Aspects.     2d  Ed.     Philadelphia. 
Howard,  L.  O.     1901.     The  Insect  Book.     New  York. 
Miall,  L.  C.     1903.     Natural  History  of  Aquatic  Insects. 


CHAPTER   XXVIII 
MOSS    ANIMALCULES    (BRYOZOA) 

By  CHARLES  B.  DAVENPORT 

Director  of  the  Station  for  Experimental  Evolution,  Cold  Spring  Harbor,  Long  Island,  N.Y. 

Prominent  among  the  animals  commonly  discovered  in  fresh 
water  are  the  Bryozoa,  or  moss  animalcules,  also  called  Polyzoa. 
They  are  forms  of  exceedingly  dehcate  and  attractive  appearance, 
often  so  transparent  that  under  favorable  circumstances  the  entire 
structure  may  be  made  out  under  the  microscope.  Almost  all 
species  form  colonies  composed  of  many  individual  animals  (zooids) 
united  together  and  the  whole  mass  is  not  only  easily  visible  but 
often  conspicuous,  whereas  the  separate  zooids  are  so  minute  that 
they  can  ordinarily  be  detected  only  with  a  hand  lens.  These 
colonies  take  the  form  of  branching  threads  spread  on  the  surface 
of  stones,  sticks,  submerged  plants  or  other  objects  in  the  water. 
Others  produce  a  thick  crust,  while  still  others  form  soHd  jelly-like 
masses  which  in  one  species  reach  the  size  of  the  closed  fist  and  not 
infrequently  surpass  that  (Fig.  1401).  The  bulk  of  this  mass  con- 
sists of  transparent  or  faintly  tinged  gelatinous  material  from 
which  the  individual  zooids  project  into  the  water  as  they  also 
do  from  the  filamentous  colonies  previously  mentioned.  The 
expanded  "head"  (lophophore)  of  the  zooid  with  its  crown  of 
tentacles  is  difficult  to  see  since  the  animals  are  exceedingly  timid 
and  respond  to  the  slightest  disturbance  by  retreating  instantly 
within  their  protective  covers  where 
they  remain  even  long  after  the  water 
has  become  quiet  again.     Continuous 

study   of    the    colony   in    a    dish    of    fresh        Fig.  1393.    CristalcUa  mucedo;  colony, 

.  natural  size.     (After  Allman.) 

water  is  rewarded  by  the  appearance  of 

the  spreading  disks  or  heads,  until  the  surface  of  the  colony  blossoms 

with  abundant  groups  of  delicate  tentacles.      (Fig.  1393.) 

All  are  essentially  sessile,  but  a  few,  like  Cristatella  and  Pectina- 
tella,  have  the  capacity  for  a  sHght  movement  of  the  colony  on 

947 


948  FRESH-WATER   BIOLOGY 

the  substratum.  The  nature  of  the  colony  formation  is  variable: 
sometimes  close,  forming  a  corm  of  zooids  fused  into  one  mass,  as  in 
Cristatella;  sometimes  loose,  each  zooid  being  distinct,  as  in  Urnatella. 
Each  zooid  has  a  structure  not  unlike  that  of  a  rotifer.  It 
secretes  a  resistant  outer  covering.  This  is  calcareous  in  some  of 
the  marine  forms,  but  is  generally  chitinous  or  gelatinous  in  those 
of  fresh  water.  So  prominent  and  variable  is  this  cuticula  (con- 
stituting the  "zooecium, "  or  "cell")  that  its  form  is  frequently 
used  as  a  means  of  distinguishing  species.  The  body  wall  is  very 
thin,  having  reh'nquished  its  protective  function  in  favor  of  the 
cuticula.  It  is  separated  from  the  viscera  by  a  relatively  enor- 
mous body  cavity.  In  the  case  of  species  whose  zooids  are  fused 
together  the  body  cavities  are  confluent.  The  ahmentary  tract  is 
relatively  simple.  It  consists  of  a  U-shaped  tube  whose  only 
glands  are  localized  in  the  epithehum  of  its  walls.  The  mouth 
end  of  the  tube  is  furm'shed  with  a  corona  of  numerous  ciliated 
tentacles  which  create  a  vortex  at  the  mouth.  The  mouth  is,  in 
one  order  of  fresh-water  species  (Phylactolaemata),  provided  with 
an  "epistome"  or  protecting  flap.  A  long  esophagus  leads  to  the 
capacious  stomach  and  this  to  the  flask-shaped  rectum.  The 
anus  lies  near  the  mouth  either  outside  or  inside  the  corona  of 
tentacles.  For  protection,  the  tentacles  can  be  retracted  quickly 
under  the  shelter  of  the  body  cuticula  like  the  proboscis  of  certain 
polychaetes.  There  are  numerous  long  slender  muscles  effecting 
the  retraction.  The  nervous  system  is  simple.  A  brain  Hes  between 
esophagus  and  rectum  and  sends  nerves  to  tentacles  and  ahmentary 
tract.  Circulation  is  effected  by  the  general  fluid  of  the  body 
cavity.  Well  defined  excretory  tubules  seem  to  be  missing  if  we 
except  the  doubtful  case  of  certain  Phylactolaemata.  In  the 
Gymnolaemata  the  viscera  periodically  degenerate  into  a  brownish 
mass,  a  new  ahmentary  tract  regenerates,  and  the  degenerated 
mass  passes  through  the  wall  of  the  gut  and  is  expelled  by  the  anus. 
Eggs  are  formed  on  the  body  wall  and,  in  Phylactolaemata,  the 
sperm  on  the  mesentery  ("funiculus").  In  the  marine  species  the 
embryos  early  become  free-swimming,  but  in  Phylactolaemata  they 
develop  in  a  sort  of  uterus  until  they  are  young  colonies.^    These 

1  The  fresh-water  form,  Pectinatella  magnifica,  produces  a  small  free  swimming  spherical  larva  which 
settles  to  the  bottom  almost  immediately  and  there  by  budding  gives  rise  to  a  colony. 


MOSS    ANIMALCULES    (BRYOZOA)  949 

are  then  set  free,  and,  after  a  time,  settle  and  affix  themselves. 
Like  other  sessile  forms,  Bryozoa  have  gained  a  variety  of  methods 
of  reproduction.  Ordinary  sexual  reproduction  and  budding  have 
been  already  mentioned.  In  some  Phylactolaemata  —  Peciinatella 
and  Cristatella  —  the  colonies  occasionally  undergo  fission  and 
move  apart,  and  the  same  process  occurs  regularly  in  Urnatella. 
Statoblast  formation,  which  occurs  on  the  funiculus  in  Phylacto- 
laemata, is  mentioned  below. 

The  fresh-water  Bryozoa  do  not  constitute  a  natural  group  of 
animals,  but  have  descended  from  ancestors  belonging  to  widely 
distinct  families.  There  can  be  no  question  that  these  ancestors 
were  marine  animals.  Excepting  the  suborder  Phylactolaemata, 
all  fresh- water  Bryozoa  belong  to  groups  most  of  whose  representa- 
tives are  marine.  The  fresh-water  forms  seem  to  have  made  their 
way  up  estuaries  and  rivers  to  lakes  and  ponds.  Here  they  acquired 
the  capacity  of  forming  statoblasts  or  hibernacula,  by  virtue  of 
which  the  species  was  enabled,  on  the  one  hand,  to  survive  the 
winter  and,  on  the  other,  to  be  carried  by  waterfowl  and  winds 
over  divides  from  one  drainage  basin  to  another.  Thus  the  fresh- 
water species  have  become  nearly  cosmopolitan.  Plumatella 
prince ps  has  been  found  in  North  and  South  America,  through- 
out Europe,  in  Molucca,  Japan,  and  Australia — i.e.,  in  all  but  one 
of  the  great  geographical  divisions  of  the  land  areas  of  the  globe. 

The  fresh-water  Bryozoa  live  in  all  kinds  of  fresh  waters  and  are 
indeed  among  the  most  ubiquitous  of  aquatic  animals.  They  are 
found  in  stagnant  pools  and  in  rushing  rivers,  although  particular 
species  favor  special  habitats.  The  different  species  of  Pluma- 
tella occur  in  varied  habitats.  Paludicella  and  Peciinatella  favor 
running  water  and  Lophopus,  Cristatella.  and  Plumatella  polymorpha 
favor  quiet  ponds.  The  fresh-water  Bryozoa  feed  on  microscopic 
organisms  which  are  caught  in  the  vortex  created  by  their  ciUated 
tentacles.  Diatoms  are  especially  conspicuous  objects  in  their 
alimentary  tracts.  Since  diatoms  require  Hght  for  their  construc- 
tive metaboHsm,  they  are  found  chiefly  in  the  upper  strata  of  the 
water,  and  consequently  Bryozoa  are  usually  not  found  at  great 
depths.  However,  in  a  mass  of  material  dredged  by  Professor  H. 
B.  Ward  from  the  Middle  Ground,  Traverse  Bay,  Lake  Michigan, 


950  FRESH-WATER  BIOLOGY 

at  a  depth  of  23  to  36  meters,  Paludicella  ehrenhergii  and  Frederi- 
cella  sultana  were  abundant.  Although  Cristatella  is  usually  found 
on  the  underside  of  floating  Hly  pads  or  in  other  situations  near 
the  surface,  I  have  obtained  it  from  the  still  waters  of  Trinity 
Lake,  Westchester  County,  New  York,  at  a  depth  of  2  to  3  meters. 
Asper  records  dredging  Fredericella  sultana  in  certain  Swiss  lakes 
at  a  depth  of  50  to  80  meters.  Little  light  penetrates  to  such  a 
depth,  and  we  may  conclude  that  hght  is  not  at  all  directly  neces- 
sary for  the  development  of  fresh-water  Bryozoa.  Indeed,  masses 
of  Paludicella  are  sometimes  obtained  from  water  pipes  where  they 
flourish  to  an  alarming  extent. 

The  Bryozoa  have  become  adapted  to  Hfe  in  ponds  by  forming 
statoblasts  at  certain  seasons  of  the  year.  The  entire  significance 
of  the  statoblasts  has  not  been  determined.  Typically,  they  winter 
over  and  one  may  find  the  shores  strewn  with  them  in  the  early 
spring.  They  hatch  out  in  New  England  late  in  May  or  early  in 
June.  So  the  statoblasts  have  come  to  be  regarded  as  winter  buds, 
or  adaptations  to  preserve  the  race  from  being  killed  ofT  by  freezing 
of  the  water.  They  often  begin  to  develop  early  in  the  summer, 
and  I  have  observed  what  has  been  seen  by  European  observers, 
that  some  statoblasts  hatch  in  nature  even  in  September.  Also 
Fr.  Miiller  has  informed  Kraepehn  that  the  fresh-water  Bryozoa 
of  Blumenbau,  Brazil,  which  experience  no  winters,  nevertheless 
form  statoblasts.  It  seems  fair  to  conclude  that  there  are  other 
functions  performed  by  the  statoblasts  than  resistance  to  winter. 
For  instance,  they  serve  to  maintain  the  species  during  drought, 
or  they  aid  in  distribution  by  clinging  to  the  waterfowl  or  resisting 
the  action  of  digestive  fluids.  The  wide  distribution  of  the  species 
of  fresh-water  Bryozoa  indicates  the  value  of  the  statoblast  in  the 
process  of  dispersion.  For  a  detailed  account  of  the  distribution 
of  the  fresh-water  species  in  the  United  States  see  Davenport  (1904). 

Preserving.  —  The  chief  difficulties  in  the  way  of  preserving 
fresh-water  Bryozoa  arise,  first,  from  the  rapid  contraction  of  the 
polypides  into  the  corm,  and,  secondly,  in  the  case  of  the  gelatin- 
ous forms,  from  the  large  amount  of  water  in  the  body;  for,  if  the 
specific  gravity  of  the  killing  or  preserving  medium  is  very  differ- 
ent from  that  of  the  water,  distortion  will  occur. 


MOSS    ANIMALCULES    (BRYOZOA) 


951 


To  kill  expanded  it  is  necessary  first  to  narcotize.  Chloral 
hydrate  is  used,  added  slowly  in  crystals  until  the  polypides  do  not 
react  to  touch.  To  preserve  in  the  natural  form,  the  animals  may  be 
plunged  directly  into  4  per  cent  formaldehyde  (formahn,  10  per  cent). 

The  classification  of  fresh- water  Bryozoa  has  been  in  a  state  of 
great  confusion  owing  to  the  great  variability  in  the  form  of  the 
colony.  The  form  of  the  colony  depends  very  largely  upon  external 
factors,  such  as  food  supply,  form  of  substratum,  and  crowding. 
The  statoblast  has  a  form  that  is  quite  independent  of  external 
factors,  and  upon  it,  consequently,  great  stress  is  laid  in  systematic 
work.  The  form  of  the  statoblast  is,  however,  not  wholly  uncor- 
related  with  that  of  the  stock,  so  the  form  of  the  stock  is  to  be 
considered.  In  the  following  classification  that  proposed  by 
Kraepelin  has  been  adopted  entire. 

KEY  TO  NORTH  AMERICAN  FRESH-WATER  BRYOZOA 

I  (2)     Anus  opening   inside   the   tentacular  corona;    tentacles  incapable  of 

complete  retraction Subclass  Endoprocta. 

Only  one  species  known  in  North  America. 

Urnatella  gracilis  Leidy  185 1. 

Stock  consisting  of  a  basal  plate,  from  which 
there  usually  arise  two  segmented  stems  termi- 
nating in  the  polypide.  More  rarely  one  or 
more  than  two  stems  arise  from  the  disk. 
Habit,  running  water.  From  Schuylkill  River, 
Pa.;  Scioto  River,  O.;  Illinois  River,  111. 


Fig.  1394.  Urnatella  gracilis,  (a)  Colony  from 
Illinois  River  at  Havana.  X13.  (After  Daven- 
port.)    {b)  Single  polyp.     (After  Leidy.) 


2  (i)     Anus  opening  outside  the  tentacular  corona,  which  is  capable  of  being 

retracted Subclass  Ectoprocta   .    .   3 

3  (6)     Zooecia  sharply  separated  from  each  other;   no  epistome. 

Order  Gymnolaemata   .    .  4 

4  (5)     Stock  consists  of  stolons  from  which  at  intervals  an  erect  cylindrical, 
hyahne  single  zooid  arises,  having  a  terminal  aperture. 

Pottsiella  erccta  Potts  1884. 


Lophophore  circular,  20  (10  to  21)  tentacles.  Habitat, 
photophil;  on  upper  surface  of  stones  in  rapids;  sometimes 
penetrating  incrusting  sponges  (Ephydatia  leidyi).  From 
Tacony  Creek,  Montgomery  Co.,  Pennsylvania. 


Fig.  1395. 


Pottsiella  erecta.    X  25.     (From  Kraepelin's  figure  of  a 
Pennsylvania  specimen.) 


952 


FRESH-WATER    BIOLOGY 


5(4) 


Stock  composed  of  zooids  that  are  sharply  separated  from  one  another 
by  partitions;  sparsely,  usually  oppositely  branched;  with 
a  chitinous  cuticula.  The  zooids  are  club-shaped  and  have 
a  lateral,  quadrangular  aperture  near  the  larger,  distal  end. 
..-y.J  ,H..  Faludicella  ehrenhergii  van  Beneden  1848. 

Zooids  about  2  mm.  long;  lateral  buds  partly  repent, 
partly  erect;  about  16  tentacles.  Habitat,  flowing  streams; 
occasionally  in  water  pipes.  From  Massachusetts,  Penn- 
sylvania, Illinois,  and  Lake  Michigan. 

Fig.  1396.     Paludicella  ehrenbergii.    (a)  Colony,  half  natural  size. 
{b)  Portion  of  same  enlarged.     X  5-     (After  Kraepelin.) 


6  (3)     Zooecia  confluent;     epistome    present.     .   Order  Phylactolacmata.    .      7 

7  (14,  15)     Statoblasts  without  hooks,  rounded  at  ends 8 


8  (9)  Stock  branched  in  form  of  antlers;  more  rarely  massed  with  recumbent 
and  elevated  tubes;  mostly  brown  or  incrusted  with  algae 
and  grains  of  sand;   rarely  hyaline. 

Fredericella  sultana  Blumenbach  1774. 


Tubes  cylindrical,  the  older  ones  mostly  keeled. 
Without  complete  dissepiments.  Apertures  terminal 
at  the  broadened  or  bifid  ends  of  tubes.  Polypide 
very  long  and  slender;  tentacles  arranged  in  a  nearly 
circular  corona.  Few  tentacles,  not  exceeding  24. 
Statoblasts  dark  brown,  bean-shaped  or  eUiptical, 
without  float,  and  with  smooth  upper  surface. 
Habitat  on  wood,  stones  and  water  plants  in  standing 
and  slowly  flowing  waters.  From  Maine  to  Penn- 
sylvania, westward  to  Wisconsin  and  even  Flathead 
Lake,  Montana.     Common  in  the  Great  Lakes. 


Fig.  1397.     Fredericella  sultana,     (a)  Portion  of  branch, 
natural  size,     (b)  Polyp  magnified.     (After  Hyatt.)    (c) 
^vV;^         Statoblast.     (After  Kraepelin.) 


9  (8)  Colonies  consist  of  cylindrical  tubes,  which  are  either  branched  or  form 
massive  clumps  or  run  over  the  substratum  as  hyahne, 
lobed  tubes Plumatella  Lamarck.    .      10 

Partitions  rudimentary  or  absent,  cuticula  brown  to  hyaline,  often  incrusted.  Tentacular 
corona  markedly  horseshoe-shaped,  with  40  to  60  tentacles.  Intertentacular  membrane  present. 
Statoblasts  without  hooks;  either  free,  elliptical,  with  broad  float,  or  (in  the  horizontal  tubes) 
without  float,  of  large  size  and  irregular  shape. 

The  commonest  genus  of  our  fresh-water  Bryozoa.  Has'been  reported  from  all  continents  ex- 
cept Africa.    Lives  in  the  most  diverse  habitats,  in  ponds  or  streams,  usually  not  in  the  light. 


10  (13)     Colony  with  vertical  as  well  as  horizontal  branches 11 


MOSS    ANIMALCULES    (BRYOZOA) 


953 


II  (12)     Cuticula  thick  and  brown,  with  a  keel  that  broadens  at  aperture. 

Free  statoblasts  elongated;    proportions  i  :  1.53  to  i  :  2.8. 

Plumatella  princeps  Kraepelin  1887. 


Tubes  openly  branched,  repent, 
with  short  lateral  branches,  antler- 
like  Var.  a,  emarginata. 

Colony  robust,  branched  often  ris- 
ing from  subtratum.  Keel  little  de- 
veloped.    Statoblasts  elongated. 

Var.  /3,  friUicosa. 

Vertical  branches  predominate, 
forming  an  intertwined  mass. 

Var.  7,  mucosa. 

Vertical  tubes  fused  into  a  mass 
from  which  only  the  aperture  rises 
free.      .....   Var.  5,  spongiosa. 


Fig.  1398.  Plumatella  princeps,  var.  a.  (a)  Portion 
of  colony,  two-thirds  natural  size,  {b)  Branch  much 
magnified.     (After  Kraepelin.) 


12  (11)     Cuticula  rarely  browned  or  keeled.     Free  statoblasts  nearly  circular, 
I  :  I  to  I  :  1.5.     .    .   Plumatella  polymorpha  Kraepelin  1887. 


Tubes  creeping  with  short  vertical  side 
branches.  Cuticula  semi-transparent;  but 
variable;  keel  not  evident. 

Var.  a,  repcns  {  =  P .-arcthusa  Hyatt). 

Tubes  repent,  branching  or  thickly  inter- 
twined, covering  the  substratum.  Few  or  no 
vertical  branches.  Cuticula  lightly  colored  to 
transparent Var.  jS,  opprcssa. 

Tubes  repent,  with  many  elongated  and 
branched  vertical  rami.  Cuticula  semi-opaque, 
no  evident  keel Var.  7,  cacspitosa. 

Tubes  repent.  Vertical  branches  close  to- 
gether, even  fused,  forming  great  solidncss. 
Cuticula  brown,  aperture  hyaline,  slightly 
elongated Var.  b,  Jiuigosa. 


Fig.  i?99.  PlumaleUa  polymorpha,  vnr.  a.  (a)  Young  colony,  two- 
thirds  natural  size,  (b)  Branch  much  magni6ed.  (c)  Statoblast, 
X  40.     (After  Kraepelin.) 


954 


FRESH-WATER   BIOLOGY 


13  (10)     Horizontal    branches    only.     Cuticula    delicate,    colorless,    hyaline. 

Elevated    aperture-cone    wrinkled    and    besprinkled    with 
white.     Free  statoblasts  nearly  circular. 

Plumatella  punctata  Hancock  1850. 
Stock  repent  and  open, 
forming  long  hyaline  tubes 
that  give  rise  to  only  a  few, 
likewise  repent,  lateral 
tubes.  .  .  .  Var.  a,  prostrata. 
From  Maine,  Pennsylvania, 
Illinois,  and  Lake  Erie. 

Stock  repent,  very  thickly 
branched,  completely  cover- 
ing the  substratum,  which 
seems  enveloped  in  thick 
layer  of  gelatinous  vesicles. 
Var.  /3,  densa. 

Fig.  1400.  Plumatella  punctata, 
var.  a.  (a)  Colony  two-thirds 
natural  size,  (b)  Branch  much 
magnified.  (c)  Statoblast. 
X  40.     (After  Kraepelin.) 

14  (7)     Statoblasts  large,  elliptical,  but  at  each  end  drawn  out  into  a  sharp  apex ; 

broad  float,  hooks  absent.  Lophopiis  cristallinus  Pallas  1766. 
Colony  shaped  like  a  sack;  erect,  sometimes  more  or  less  lobed  by  indentations  of  margin, 
looking  then  sometimes  hke  a  glove.  Outer  cuticula  layer  delicate  and  hyaline,  more  incrusted 
at  base.  Polypides  scattered,  a  group  of  them  rising  from  each  lobe.  Lophophores  with  about 
60  tentacles.  The  colony  may  divide  along  the  constrictions  between  the  lobes.  Habitat, 
chiefly  standing  water,  such  as  pools,  or,  rarely,  slowly  flowing  water.  Chiefly  attached  to 
plant  stems.     From  Schuylkill  and  Illinois  rivers. 

15  (7)     Statoblasts  with  hooks 16 

16  (17)     Colonies  hyahne,  in  the  form  of  a  rosette,  lobed,  with  horizontal 

tubes  only Pectinatella  Leidy  .    .     17 

They  secrete  a  great  gelatinous  base  which  is  common  to  many  colonies.  Aperture  slightly 
elevated  above  common  coenecium.  Statoblasts  large  and  circular  to  subrectangular,  with 
broad  bent  float  and  one  marginal  row  of  anchor-shaped  hooks. 

1 7  Pol)^ides  scattered  or  in  double  row  along  each  lobe ,  the  gelatinous  base  often 

10  to  20  centimeters  thick.     Pectinatella  magnifica  Leidy  1851. 

Tentacles  60  to  84  in  number.     Statoblasts  about  i  mm.  in  diameter,  provided  with  11  to  22 

hooks  from  0.15  to  0.25  mm.  long.     Habitat,  submerged  branches  or  twigs  of  trees,  wooden 

stakes,  gates  of  dams,  walls  of  reservoirs  or  stones  in  brooks.     Shady  situations,  such  as  south 

walls  of  reservoirs,  or  wood-covered  streams.    From  Maine  to  Mississippi. 


Fig.  1401.     Pectinatella  magnifica.    (a)  Young  colony,  natural  size,     (b)  Section  highly  magnified,    (c) 
Statoblast,  ventral  view,    (d)  Statoblast  in  profile.   X  iS-  (e)  Colony  on  plant  stem.  X  |.  (After  Kraepelin.) 


MOSS    ANIMALCULES    (BRYOZOA) 


955 


i8  (i6)     Colony  unbranched,  gelatinous,  with  a  flat  ''sole." 

Cristatella  mucedo  Cuvier  1798. 

External  cuticula  lacking,  or  developed  merely  as  a  thin  gelatinous  layer  under  the  sole. 
All  polypides  contract  into  a  common  cavity.  Statoblast  large,  circular,  with  float  and  a  cir- 
clet of  hooks  on  both  sides.  Young  corm  of  circular  form  later  elongated,  worm-like,  attaining 
a  length  of  2  to  5  cm.  in  summer,  to  28  cm.  in  autumn.  Colonics  often  gregarious  in  a  common 
gelatinous  substance.  Eighty  to  ninety  tentacles.  Statoblasts  with  10  to  .54  dorsal  hooks,  20 
to  so  ventral  hooks.  Habitat,  in  standing  or  slow-flowing  water,  on  submerged  branches  of 
dead  trees,  under  side  of  Hly-pads,  and  on  other  aquatic  plants. 

Statoblasts  less  than  i  mm.  in  diameter;  hooks  on  dorsal  side  10  to  22;  on  ventral  side 

20  to  37 Var.  a,  genuina  (  =  C.  ophidea  Hyatt  1868). 

From  Maine,  Massachusetts,  New  York,  Illinois,  and  Lake  Erie. 
Statoblasts  over  i  mm.;   hooks  on  dorsal  side  20-34;  on  ventral  side  38-5°- 

Var.  /3,  idae  (  =  C.  idac  Leidy  1858;   C.  tacustris  Potts  1884). 
From  Rhode  Island  and  Pennsylvania. 


f^W//. 


Fig.  1402.    Cristatella  mucedo.    (a)  Colony  much  enlarged.    (6)  Statoblast  ventral  aspect,  (c)  Statoblast 
in  profile.    X  25.     (After  Allman.) 


IMPORTANT   REFERENCES   ON    FRESH-WATER   BRYOZOA 

Allman,  J.     1856.     A  Monograph  of  the  Fresh-water  Polyzoa.    London. 
Davenport,  C.  B.     1890.     Cristatella:   The  Origin  and  Development  of  the 

Individual  in  the  Colony.     Bull.  Mus.  Comp.  Zool.,  Harvard  College,  20: 

101-152. 
1891.     Budding   in   Paludicella   and   other   Bryozoa.     Bull.    Mus.    Comp. 

Zool.,  Harvard  College,  22:  1-114. 
1904.     Report  on  the  Fresh-water  Bryozoa  of  the  United   States.     Proc. 

U.  S.  Nat.  Mus.,  27:  211-221. 
Hyatt,  A.     1866-68.     Obvervations  on  Polyzoa,  Suborder  Phylactolacmata. 

Communications  Essex  Institute,  4'.  167-228;    5:  97-112,  145-160,  193- 

232. 


956  FRESH-WATER  BIOLOGY 

Kraepelin,  K.  1887.  Die  Deutschen  Siisswasser-Bryozoen.  Eine  Mono- 
graphic. I,  Anatomisch-Systematischer  Teil.  Abhandl.  Naturw.  Verein, 
Hamburg,  10:  1-168. 

Landacre,  F.  1901.  Sponges  and  Bryozoa  of  Sandusky  Bay.  Ohio  Nat., 
i:  96-7. 

Leidy,  J.     1883.    Urnatella  graciHs.    Jour.  Acad.  Nat.  Sci.,  Phila.,  9:  5-16. 


CHAPTER   XXIX 
THE    MOLLUSCA 

By  BRYANT  WALKER,  Detroit,  Mich. 

For  the  purposes  of  this  treatise  and  in  order  to  differentiate  the 
group  from  the  other  great  phyla  of  the  animal  kingdom  repre- 
sented in  our  fresh-water  fauna,  the  Mollusca  may  be  defined  as 
animals  with  a  soft  body  encased  in  a  hard  shell,  which  may  be 
either  in  one  piece  (univalve)  or  in  two  pieces  (bivalve).  In  the 
univalve  mollusca  or  Gastropoda,  commonly  called  snails,  the  shell 
may  be  coiled  either  obliquely  or  horizontally  or  may  be  a  simple 
uncoiled,  conical,  tent-shaped  secretion  on  the  back  of  the  animal. 
In  this  class,  the  animal  possesses  a  distinct  head,  with  a  pair  of 
contractile  tentacles,  at  the  base  of  which  are  placed  the  eyes. 
On  the  lower  side  of  the  head,  between  the  tentacles,  is  the  mouth, 
which,  on  its  inner,  upper  margin,  is  usually  provided  with  a  chi- 
tinous  jaw  of  from  one  to  three  pieces.  In  the  lower  part  of  the 
mouth  is  the  radula,  a  muscular  ribbon  covered  with  minute  teeth. 

The  fresh-water  Gastropoda  are  divided  into  two  main  groups  or 
subclasses  according  as  they  breathe  the  free  air  by  means  of  a 
lung  or  are  provided  with  a  gill  for  subaqueous  respiration.  As 
the  name  implies,  these  animals  progress  by  crawling  on  the  ven- 
tral surface  of  the  body,  which  is  modified  to  form  a  flat,  muscular 
disk  called  the  foot. 

The  bivalve  mollusca  or  Lamellibranchia,  usually  known  as  clams 
or  mussels,  have  the  body  protected  by  two  symmetrical,  opposing 
valves,  which  are  united  above  by  an  elastic  tissue  called  the 
ligament.  They  have  no  head  and  have,  accordingly,  been  called 
the  Acephala.  They  have  no  tentacles,  eyes,  jaws,  or  radula. 
The  mouth  is  simply  an  orifice  at  the  anterior  end  of  the  body,  on 
each  side  of  which  is  a  flap  or  palpus,  which  assists  in  guiding  the 
food  to  the  mouth.  The  foot  is  an  axe-shaped  mass  of  muscular 
tissue  (hence  the  name  of  Pelecypoda  often  used  for  the  class), 
which  may  be  extended  from  the  anterior  portion  of  the  shell  and, 

957 


958  FRESH-WATER   BIOLOGY 

by  effecting  a  lodgment  in  the  bottom,  drag  the  animal  slowly- 
forward.  The  lamelHbranchs  breathe  by  means  of  two  gills  sus- 
pended on  each  side  of  the  body,  which  are  divided  into  a  series  of 
water  tubes  by  septa  or  lamellae,  through  which  the  water  circu- 
lates by  means  of  cilia.  The  whole  body  is  enclosed  in  a  soft 
mantle,  which  secretes  the  shell  along  its  outer  margins.  Poste- 
riorly the  mantle  has  two  openings,  through  the  lower  of  which 
the  water  enters  the  shell,  passes  forward,  aerating  the  gills  and 
carrying  food  to  the  mouth,  and  then  flows  out  through  the  upper 
opening. 

A  more  detailed  account  of  the  structure  of  the  two  classes  rep- 
resented in  our  fauna  will  be  found  under  the  head  of  classification. 

The  North  American  Fauna 

As  would  naturally  be  expected  from  the  vast  extent  of  the  ter- 
ritory included  in  the  United  States  and  British  America  and  the 
great  diversity  both  in  the  climatic  and  physical  conditions  prev- 
alent in  different  portions  of  the  continent,  the  fresh-water  fauna 
of  North  America  is  not  only  one  of  great  abundance,  both  in 
species  and  individuals,  but  also  of  great  diversity  in  character;  and 
a  very  large  proportion  of  the  genera  represented  are  pecuHar  to 
it.  While  but  one  of  the  eighteen  famihes  represented  in  our  fauna 
is  peculiar  to  the  continent,  that  one,  the  Pleuroceratidae,  is  extraor- 
dinarily developed  both  in  genera  and  species  and,  where  found, 
its  members  usually  occur  in  great  abundance. 

On  the  other  hand,  of  the  eighty-six  genera  recognized  at  the 
present  time,  no  less  than  forty-nine,  or  five-ninths,  are  peculiar 
to  North  America,  while  of  the  many  hundred  of  described  species, 
it  is  safe  to  say  that  more  than  ninety  per  cent  are  not  found  else- 
where. Indeed,  barring  the  comparatively  small  number  of  cir- 
cumpolar  species  in  the  north,  and  the  somewhat  larger  represen- 
tation of  tropical  or  subtropical  forms  found  on  our  southern  borders, 
practically  the  whole  of  our  molluscan  fauna  may  be  said  to  be 
distinctively  North  American. 

The  distribution  of  the  various  families,  genera,  and  species 
represented  in  our  fauna  varies  greatly  in  the  different  sections  of 
the  continent. 


THE  MOLLUSCA  959 

Most  of  the  families  have  representatives  in  all  portions  of  the 
country  where  suitable  conditions  of  environment  are  to  be  found. 
But  there  are  some  notable  exceptions.  Thus  the  Viviparidae, 
which  form  one  of  the  most  conspicuous  elements  of  the  fauna  of 
the  Eastern  States,  are  not  found  west  of  the  Mississippi  Valley. 
The  AmpuUaridae,  which  replace  the  Viviparidae  in  the  tropics,  are 
only  found  in  Florida  and  Southern  Georgia;  while  the  great 
family  of  the  Pleuroceratidae,  the  one  family  peculiar  to  our  fauna, 
is  not  found  west  of  the  Mississippi  Valley  drainage,  except  for  a 
few  isolated  species  that  occur  in  the  northern  Pacific  states. 

Many  of  the  genera  have  a  general  distribution  in  all  parts  of 
the  continent.  That  is,  some  representatives  of  such  genera  will 
be  found  practically  every  place  where  suitable  conditions  obtain. 
But  it  is  to  be  borne  in  mind  that  comparatively  few  species  have 
a  general  distribution.  Many  of  them  have,  so  far  as  known,  a 
very  limited  habitat,  while  others  range  over  a  large  extent  of 
territory.  Many  of  the  genera  are  likewise  restricted  to  certain 
portions  of  the  continent  and  particularly  to  certain  drainage 
systems,  while  others  are  confined  to  a  very  limited  area.  The 
Coosa  River  in  Alabama,  in  this  respect,  has  a  most  remarkable 
fauna.  No  less  than  six  genera  and  very  many  species  are  known 
to  occur  only  in  it  and  its  tributaries. 

But  while,  in  a  general  way,  it  is  true  that  our  fauna  as  a  whole 
is  well  known,  and  its  distinctive  characters  recognized,  yet  the 
sum  total  of  our  present  knowledge,  large  as  it  may  seem,  is  very 
small  and  inadequate  when  compared  with  what  we  might  and 
would  like  to  know  about  it. 

But  a  very  small  portion  of  the  continent  has  been  collected  over 
with  any  sort  of  thoroughness,  and  there  are  undoubtedly  very 
many  new  types,  both  generic  and  specific,  yet  to  be  discovered. 
While,  of  course,  the  mere  description  of  new  species  is  the  least 
important  part  of  the  work  of  the  conchologist,  yet  the  accurate 
knowledge  of  all  the  species  found  within  our  borders  is  the  basis 
for  the  solution  of  the  larger  problems  of  distribution  and  evolution, 
which  are  of  great  importance.  The  exact  range  of  very  few,  if 
any,  even  of  our  most  common  species  is  exactly  known.  It  is 
very    desirable  that  lists  of  the  species  occurring  in  all  the  states 


960  FRESH-WATER   BIOLOGY 

and  counties  of  the  country  should  be  compiled.  Such  local  Hsts, 
when  the  specimens  are  correctly  determined,  are  of  great  value 
and  interest  and  are  always  acceptable  contributions  to  scientific 
hterature.^ 

The  life  history  and  habits  of  the  different  species  form  a  subject 
of  great  interest,  and  as  yet  but  httle  is  known  about  them.  Then, 
too,  very  little  is  known  of  the  internal  anatomy  of  our  species, 
much  less,  indeed,  than  of  the  land  mollusca.  In  all  these  lines 
of  work  and  study  there  is  a  fruitful  and  unreaped  field  of  investi- 
gation, which  cannot  fail  to  yield  both  pleasure  and  profit  to  the 
student  who  will  undertake  to  study  the  common  forms  of  mollus- 
can  fife,  which  are  to  be  found  so  abundantly  in  all  parts  of  our 
country. 

Collection  and  Preparation  of  Specimens 

Nearly  every  permanent  body  of  water  has  its  mollusks,  varying 
according  to  its  character.  Some  species  are  found  only  in  rapidly 
flowing  water,  and  others  only  in  ponds  and  still  water.  Ditches 
and  other  stagnant  waters  are  usually  good  collecting  ground  for 
Pisidia  and  other  small  species.  The  low  places  in  the  woods, 
which  dry  up  in  the  summer  time,  have  a  number  of  species  that 
are  not  found  elsewhere,  and  which  bury  themselves  in  the  mud 
when  the  water  disappears.  Sand  banks  in  rivers  and  lakes  are 
favorite  resorts  of  many  of  the  smaller  species.  The  under  side 
of  the  Hly  pads  should  be  scrutinized,  while  the  Ancyli  should  be 
looked  for  on  stones  and  dead  clam  shells. 

The  distribution  of  the  different  species  in  all  the  states  and 
territories  being  of  prime  importance,  the  collector  should  always 
bear  in  mind: 

First,  that  a  dead  shell  is  better  than  none  at  all; 

Second,  that  dead  shells  should  not  be  taken,  if  five  ones  can 
be  had,  and  that  careful  search  will  usually  discover  them  in  the 
immediate  vicinity. 

Third,  that  all  the  species  are  extremely  variable  in  their  abun- 
dance from  year  to  year,  and  so  it  is  a  safe  rule,  "when  you're 
getting,  to  get  a  plenty." 

1  The  writer  will  gladly  aid  students  in  the  identification  of  their  specimens  without 
charge.    Address  45  Alfred  St.,  Detroit,  Mich. 


THE   MOLLUSCA  961 

The  apparatus  for  collecting  is  very  simple. 

It  is  necessary  to  have  a  dipper  and,  if  possible,  a  small  dredge. 
The  dipper  is  made  from  an  ordinary  tin  one  by  removing  the 
bottom  and  substituting  one  of  fine  wire  cloth.  By  removing  the 
end  of  the  handle,  the  dipper  can  be  slipped  on  the  end  of  a  cane 
or  pole  when  in  use.  This  is  useful  not  only  for  reaching  the  larger 
specimens  from  the  shore  or  boat,  but  especially  for  sifting  the  mud 
and  sand  from  the  bottom,  where  a  multitude  of  small  species  live, 
which  otherwise  would  not  be  found.  It  will  be  found  more  con- 
venient to  empty  the  contents  of  the  dipper,  when  thoroughly 
washed  out,  into  a  pail  or  small  bag,  and  carry  the  whole  mass 
home  before  undertaking  to  pick  out  the  shells.  If  attempted  in 
the  field,  many  of  the  smaller  and  more  desirable  things  are  apt  to 
be  overlooked.  By  spreading  the  mass  out  in  the  sun  for  a  short 
time,  it  will  become  dry  and  friable  so  that  the  shells  can  be  easily 
separated  and  picked  out.  An  ordinary  reading  glass  is  very  useful 
for  the  detection  of  the  more  minute  forms  in  sorting  over  such 
material. 

Many  desirable  species  live  in  water  too  deep  for  the  convenient 
use  of  the  dipper,  and  for  these  it  is  necessary  to  have  a  small 
dredge.  One  with  an  aperture  of  9  by  6  inches  is  as  large  as  can 
be  used  satisfactorily  by  a  single  person  in  a  boat. 

Several  small  bags  and  a  number  of  wide-mouthed  bottles  and 
small  vials  should  be  carried,  so  that  the  specimens  from  different 
localities  may  be  kept  separate.  Care  must  be  taken  to  keep  the 
more  fragile  species  separate  from  the  heavier  ones,  otherwise  they 
are  likely  to  be  damaged  in  moving  about.  For  the  same  reason 
it  is  better  to  fill  the  bottles  partially  with  water  while  in  the  field, 
as  the  mollusks  then  attach  themselves  to  the  glass  and  are  less 
likely  to  be  broken.  It  is  not  necessary  to  take  alcohol  into  the 
field. 

Specimens  to  be  kept  for  anatomical  purposes  may  be  preserved 
in  alcohol,  which  at  first  should  be  greatly  diluted,  not  stronger 
than  25  per  cent;  after  a  day  or  two  the  specimens  should  be  re- 
moved to  50  per  cent  alcohol,  and  later  to  the  undiluted.  Formal- 
dehyde, 2  per  cent  dilution,  is  an  admirable  preservative  for  ma- 
terial of  this  kind.     It  should  not,  however,  be  used  when  it  is 


962  FRESH-WATER   BIOLOGY 

desired  to  keep  the  shells  as  specimens,  as  it  destroys  those  left  in 
it  any  length  of  time. 

With  the  exception  of  the  larger  species  of  Planorbis,  which  are 
more  easily  cleaned  by  boiling,  it  is  practically  immaterial  whether 
the  fluviatile  univalves  are  boiled,  or  put  directly  into  diluted  alco- 
hol for  a  day  or  two.  In  either  case  there  is  no  difficulty  in  ex- 
tracting the  animals.  The  curved  points  of  the  collecting  forceps 
are  convenient  for  this  purpose,  and  hooks  of  various  sizes  can  be 
made  from  safety  pins.  By  tying  these  on  small  wooden  handles 
very  effective  instruments  can  be  made.  Small  hooks  or  ''probes" 
of  various  sizes  fitting  into  an  adjustable  handle  are  most  convenient 
and  can  be  obtained  from  any  dealer  in  dental  instruments.  A 
small,  fine-pointed  dental  syringe  is  indispensable  for  this  work. 
When  the  animal  is  completely  extracted,  the  interior  of  the  shell 
should  be  thoroughly  washed  out  with  the  syringe.  A  small  piece 
of  sponge  on  the  end  of  a  fine  copper  wire,  which  can  be  bent  in  any 
direction,  is  very  useful  for  removing  the  mucus,  which  is  apt  to 
adhere  to  the  interior.  This  should  always  be  carefully  attended 
to;  if  not  it  will  greatly  disfigure  the  specimen  when  dried.  The 
exterior  should  then  be  thoroughly  scrubbed  with  a  soft  tooth  or 
nail  brush.  When  perfectly  clean,  inside  and  out,  the  water  should 
be  carefully  emptied  out  and  the  shell  put  aside  in  the  air,  but  not 
in  the  sun,  to  dry. 

It  is  not  desirable  to  attempt  to  clean  the  minute  species  by 
removing  the  animal.  They  should  be  put  directly  into  25  per  cent 
alcohol  for  a  day  or  two.  If  to  be  left  longer  in  the  alcohol,  the 
strength  should  be  increased.  Twenty-four  hours,  however,  in  the 
alcohol  is  all  that  is  necessary.  Then  they  can  be  dried  in  the  air 
without  leaving  any  offensive  odor.  Either  before  or  after  drying 
they  can  be  cleaned,  if  necessary,  by  putting  them  in  a  bottle  of 
water,  with  some  fine,  clean  sand,  and  shaking  them  together  until 
all  the  dirt  has  been  removed  by  the  sand.  Jn  the  operculate 
species,  it  is  desirable  to  retain  the  opercula  of,  at  least,  part  of  the 
specimens.  While  it  adds  to  the  labor,  it  increases  the  value  of 
the  specimen  if  it  is  always  done.  These  are  easily  removed  from 
the  animal  and,  after  being  cleaned,  should  be  put  inside  the  shell 
and  the  aperture  plugged  with  cotton.     All  the  foreign  matter  both 


THE   MOLLUSCA  963 

inside  and  outside  of  the  shell  should  be  removed  by  thorough 
washing.  All  the  water  species  are  apt  to  be  more  or  less  incrusted 
with  deposits  of  lime  or  oxide  of  iron.  These  can  be  removed  by 
immersing  them  in  oxalic  acid.  Care  should  be  taken  not  to  pro- 
long the  operation,  or  the  texture  of  the  shell  may  be  injured. 
Elbow  grease  is  the  most  effective  agent  for  making  good  specimens. 
When  that  fails,  use  the  acid.  The  Ancyli  are  always  more  or  less 
coated  in  this  way,  and  can  easily  be  cleaned  by  floating  them  for 
a  few  minutes  on  the  acid,  upside  down,  and  then  gently  brushing 
them  off  with  a  soft  brush  while  held  on  the  tip  of  the  finger. 

The  larger  bivalves  should  be  well  washed  and,  if  necessary, 
scraped  off  with  the  knife  as  soon  as  taken,  care  being  taken  not 
to  injure  the  epidermis. 

They  can  be  boiled,  if  desired,  when  the  shells  will  open  and  the 
animals  easily  removed.  But,  as  a  rule,  it  is  more  convenient, 
unless  collected  in  large  quantities,  to  cut  the  muscles,  which  hold 
the  valves  together,  with  a  thin-bladed  knife  and  scrape  the  animal 
out.  Care  should  be  taken  not  to  break  the  edge  of  the  fragile 
species  when  inserting  the  knife.  All  traces  of  the  animal  matter 
should  be  removed,  and  after  a  thorough  washing  the  valves  tied 
together  with  a  string  until  thoroughly  dried.  Never  use  colored 
twine  for  this  purpose,  as  it  is  apt  to  stain  the  shells.  Any  surface 
incrustation  can  be  removed  either  with  oxalic  or  muriatic  acid. 
The  latter  is  more  convenient  for  the  larger  species,  and  can  be 
applied  with  a  small  brush.  To  avoid  trouble,  it  is  safer  to  wear 
rubber  gloves,  if  a  large  quantity  of  material  is  to  be  cleaned.  Care 
must  be  exercised  in  using  the  acid  and  the  specimens  frequently 
washed,  lest  damage  be  done  to  the  shell.  The  smaller  bivalves, 
the  Sphaeria  and  Pisidia,  are  best  treated  by  putting  into  diluted 
alcohol  for  a  day  or  two  and  then  drying  them.  If  left  too  long 
the  shells  are  apt  to  open,  which  interferes  with  the  looks  of  the 
specimens.  The  larger  species  of  Sphaerium  are  better  with  the 
animal  removed.  This  can  be  done  after  boiling,  or  a  few  days 
in  alcohol.  As  these  are  usually  too  small  to  be  easily  tied  together 
to  keep  the  valves  from  gaping,  each  specimen,  while  the  hinge  is 
flexible,  should  be  closely  wrapped  up  in  a  small  piece  of  tissue 
paper  until  completely  dry. 


964  FRESH-WATER  BIOLOGY 

While  it  is  not  usually  desirable  to  keep  ''dead"  shells  for  the 
cabinet,  occasionally  it  is  necessary.  In  such  cases,  the  color  can 
be  in  some  measure  restored  by  applying  a  solution  of  paraffin 
and  gasoline  (a  cubic  inch  of  the  former  in  half  a  pint  of  the  latter). 
*'Dead"  Unionidae  can  be  improved  in  appearance  and  the  bril- 
liancy of  the  nacre  measurably  restored  by  applying  muriatic  acid. 

A  good  collection  is  characterized  by  two  essentials: 

First,  the  careful  selection  and  preparation  of  the  specimens 
themselves; 

Second,  absolute  accuracy  in  the  matter  of  the  localities  from 
which  they  came. 

There  is  Httle  excuse  for  having  poor  and  ill-cleaned  specimens. 
There  is  none  at  all  for  failure  to  keep  accurate  records  of  the  col- 
lector's fieldwork.  A  drawer  of  any  common  species,  without  any 
indication  of  whence  they  came,  even  if  well  cleaned,  would  be 
absolutely  without  value.  Such  a  drawer  of  any  of  our  species 
from  fifty  or  one  hundred  different  localities,  definitely  indicated, 
would  be  a  valuable  contribution  to  the  conchology  of  any  state. 
Specific  names  can  be  suppHed  or  corrected  any  time,  but  a  mis- 
taken or  erroneous  locality  can  never  be  corrected.  The  collector, 
therefore,  should  be  careful  never  to  trust  to  memory  for  facts  of 
this  kind.  Both  in  collecting  and  cleaning,  the  specimens  from 
each  locality  should  be  kept  carefully  separated  and  labeled.  Too 
much  importance  cannot  be  given  to  this  point.  The  study  of  the 
geographical  distribution  of  the  mollusca  is  one  of  the  most  im- 
portant branches  of  conchological  work,  and,  to  be  of  any  value, 
this  must  be  based  on  absolutely  accurate  work  on  the  part  of  the 
collector. 

The  manner  of  casing  and  arranging  the  collection  is  largely  one 
of  individual  preference.  A  catalogue,  however,  is  essential,  and 
it  is  better  to  begin  systematically  in  this  particular  and  thus  avoid 
the  necessity  of  doing  it  all  over  again  when  the  collection  begins 
to  assume  considerable  size.  There  should  be  a  serial  catalogue 
and  a  card  catalogue.  Each  addition  to  the  collection  should  be 
numbered  as  soon  as  received  and  entered  in  the  serial  catalogue, 
which  should  be  a  book  ruled  in  as  many  columns  as  the  collector 
desires. 


THE   MOLLUSC  A  965 

The  card  catalogue  is  convenient  in  a  small  collection.  It  be- 
comes absolutely  necessary  in  a  large  one.  The  cards  should  be 
of  uniform  size  for  convenience  in  handling.  If  it  is  desired  to 
have  a  card  for  every  entry,  they  can  be  smaller  than  if  it  is  desir- 
able for  economy  of  space  to  have  as  many  entries  as  possible  on 
one  card.  In  the  latter  case  a  convenient  size  is  that  of  the  ordinary 
library  card,  which  can  be  ruled  to  hold  twenty  entries.  The  name 
of  the  species  is  written  on  the  top,  and  the  number  of  each  entry 
of  that  species  and  the  locality  are  entered  below.  Such  a  card  as 
this  enables  the  collector  to  see  at  a  glance  not  only  whether  any 
given  species  is  represented  in  his  collection,  but  also  from  what 
localities,  and  saves  a  large  amount  of  time  which  would  otherwise 
be  spent  in  turning  over  the  leaves  of  a  serial  catalogue.  The 
cards  can  be  kept  in  drawers  or  boxes  of  proper  size  and  can  be 
arranged  alphabetically  under  the  different  genera  and  families. 
Guide  cards  slightly  higher  than  the  ordinary  card,  indicating  the 
genera,  can  be  inserted  in  their  proper  places. 

In  collections  intended  for  pubUc  exhibition,  it  is  usually  neces- 
sary to  have  the  specimens  mounted  on  cards  or  blocks.  But  in 
private  collections  such  an  arrangement  is  a  mistake,  not  only 
on  account  of  the  greater  room  required  for  the  collection,  but 
particularly  because  it  prevents  the  handling  of  the  specimens  for 
purposes  of  study. 

Specimens  under  an  inch  in  diameter  are  most  conveniently 
kept  in  glass  vials.  These  can  be  obtained  from  any  wholesale 
druggist.  They  should  be  without  a  neck  and  of  standard  sizes. 
The  length  will  depend  upon  the  standard  size  of  the  tray  adopted. 
For  my  own  collection  I  use  three  sizes,  i,  |,  |  inch  in  diameter. 
As  these  vials  are  rather  fragile,  the  pressure  of  the  cork  is  apt  to 
break  them.  The  cork  should  therefore  be  softened  by  rolling  or 
crushing.  A  pair  of  plumber's  burner  pliers  is  useful  for  this 
purpose.  The  serial  number  should  be  put  on  the  cork  or  on  a 
small  piece  of  paper  inside.  Specimens  too  large  for  the  vials 
should  have  the  number  on  the  shell  in  ink.  Then,  if  a  drawer 
happens  to  be  overturned,  the  specimens  can  be  sorted  out  again 
without  difl&culty. 

When  numbered,  the  vials  and  specimens  should  be  placed  in 


966  FRESH-WATER  BIOLOGY 

trays.  For  these  a  standard  size  should  be  adopted,  so  that  they 
will  conveniently  fit  into  the  drawers  of  the  cabinet.  In  the 
National  Museum  at  Washington,  the  unit  is  i  by  2  inches,  and 
the  larger  sizes  are  all  multiples  of  that  unit.  In  the  Academy  of 
Natural  Sciences  at  Philadelphia,  the  unit  is  ij  by  3.  There  is 
one  advantage  in  the  use  of  the  larger  unit  where  space  is  a  serious 
question.  For  the  small  species  the  vials  may  be  used  only  ij 
inches  in  length,  and  two  vials  can  be  put  into  one  tray,  thus  dou- 
bling the  capacity  of  the  drawer.  The  trays  should  be  of  the  same 
depth.  One-half  inch  is  sufficient  for  most  of  the  univalve  species. 
For  the  larger  species,  such  as  the  Unionidae,  requiring  trays  of 
good  size,  f  inch  is  better.  These  trays  can  be  had  of  any  paper- 
box  manufacturer,  or  can  be  easily  cut  out  of  cardboard  by  the 
collector,  the  corners  being  fastened  together  by  strips  of  gummed 
paper.  The  character  of  the  cases  for  a  collection  is  determined 
by  the  means  and  incHnation  of  the  collector.  Any  case  of  shallow 
drawers  will  do.  If,  however,  cases  are  to  be  made,  they  should 
be  made  of  a  standard  size  with  interchangeable  drawers.  Each 
tray  should  have  a  neat  label  giving  the  serial  number,  the  name, 
and  the  locality  of  the  specimens  it  contains.  A  box,  bottom 
side  up,  can  be  used  for  separating  the  genera  and  species  in  every 
drawer.  Small  labels  of  convenient  size  for  designating  them  can 
be  had,  already  gummed,  at  any  bookseller's. 

In  packing  shells,  small  specimens  should  not  be  mixed  with 
large  ones,  as  they  are  apt  to  get  lost;  nor  should  fragile  shells  be 
put  in  with  stronger  ones,  as  they  are  likely  to  be  broken.  The 
minute  specimens  can  be  put  into  gelatin  capsules,  small  vials, 
quills,  or  paper  tubes  made  by  rolling  writing  paper  around  a  lead 
pencil,  gumming  down  the  edge  and  stopping  the  ends  with  cotton. 
Do  not  mix  shells  from  different  locahties.  Write  the  locality  on 
a  label  and  wrap  it  up  with  each  vial  or  package.  Use  plenty  of 
cotton  in  packing  fragile  shells.  Pill  boxes  and  match  boxes  are 
convenient  for  packing  purposes.  Wrap  up  each  vial  or  box  sepa- 
rately, then,  if  a  smash  does  occur,  there  is  a  fair  chance  of  saving 
some  of  the  specimens  and  no  danger  of  mixing  the  contents  of 
different  packages.  Do  not  send  paper  boxes  by  mail.  Pack  in 
a  wooden  box. 


THE   MOLLUSC  A  967 

For  purposes  of  dissection  either  fresh  or  alcoholic  specimens 
may  be  used.  Live  specimens  may  be  killed  by  plunging  them 
into  boiling  water  for  a  few  seconds.  The  animal  can  thus  be 
removed  from  the  shell  in  the  usual  way,  using  great  care  not  to 
mutilate  it  with  the  hook;  or  the  shell,  if  not  too  heavy,  can  be 
carefully  broken  away  with  the  forceps.  Preserved  specimens  are 
frequently  difficult  to  extract  from  the  shell,  in  which  case  the  shell 
must  be  removed  either  by  breaking  or,  if  too  thick,  by  dissolving 
it  in  muriatic  acid. 

^'Two  pairs  of  fine  scissors  will  be  necessary,  one  pair  with  straight 
points,  the  other  with  curved  points;  one  or  more  fine  scalpels,  and 
two  pairs  of  fine  forceps,  one  straight  and  the  other  curved.  Dis- 
secting needles  are  also  necessary.  These  can  be  made  by  forcing 
the  heads  of  fine  needles,  by  means  of  a  pair  of  pliers,  into  the  end 
of  a  round  stick  of  small  diameter.  The  point  of  one  of  these 
needles  should  be  bent  so  as  to  form  a  hook,  first  heating  the  end 
of  the  needle  to  a  white  heat." 

*'In  dissecting  the  animal,  a  circular  china  dish  about  4  inches 
in  diameter  and  2  in  depth  will  be  necessary;  also  a  piece  of  sheet 
cork  as  large  as  will  lie  at  the  bottom  of  the  dish,  fastened  to  a 
thin  sheet  of  lead  with  either  string  or  rubber  bands.  It  is  best 
to  have  the  lead  of  the  same  size  as  the  cork.  This  leaded  cork 
is  to  be  placed  in  the  bottom  of  the  dish,  and  the  dish  filled  with 
alcohol.  If  the  animal  has  once  been  placed  in  alcohol,  all  dissec- 
tions should  be  made  in  alcohol,  but  freshly  killed  specimens  may 
be  dissected  in  water,  and  many  of  the  organs  at  this  time  present 
a  much  more  natural  appearance  than  when  acted  on  by  alcohol. 
Place  the  animal  on  the  cork  and  fasten  it  down  with  small  pins, 
or  better  yet,  with  very  fine,  short  needles  inserted  through  the 
margin  of  the  foot.  Then  with  a  fine  pair  of  scissors,  commencing 
at  the  head,  cut  through  the  integument  along  the  center  of  the 
back,  taking  care  not  to  injure  any  of  the  organs  below.  The 
integument  is  now  to  be  removed  from  the  dorsal  part,  turned 
back  and  fastened  to  the  cork,  removing  the  needles  from  the 
margin  of  the  foot  and  putting  them  through  the  edges  of  the 
integument.     All  the  organs  of  the  anterior  part  of  the  snail  are 


968  FRESH-WATER   BIOLOGY 

thus  brought  into  view,  and  further  dissection  of  the  organs  can 
be  inteUigently  made."-^ 

The  method  of  preparing  the  jaws  and  hngual  membrane  for 
examination  is  as  follows: 

''On  opening  the  head  (of  the  snail)  from  above,  one  readily 
notices  at  the  extreme  anterior  part,  close  against  the  outer  integu- 
ment, a  prominent,  oval  body.  This  is  called  the  buccal  mass.  It 
is  easily  cut  away  from  the  animal,  and  will  be  found  to  contain 
both  jaw  and  lingual  membrane.  These  can  be  removed  by  fine 
scissors  or  knives  from  the  buccal  mass  in  the  larger  species,  but 
in  the  smaller  species,  the  method  usually  employed  is  putting 
the  whole  buccal  mass  in  a  watch  crystal,  full  of  a  strong  solution 
of  caustic  potash.  Allowing  it  to  remain  for  several  hours,  the 
potash  will  destroy  all  of  the  buccal  mass,  and  leave  the  jaw  and 
lingual  membrane  perfectly  clean  and  ready  for  examination. 
They  must  be  well  rinsed  in  clean  water,  in  another  watch  crystal, 
before  examination.  Another  more  expeditious  process,  is  to  place 
the  whole  buccal  mass  in  a  test  tube  with  the  solution  of  potash, 
and  boil  it  for  a  few  seconds  over  a  spirit  lamp.  Pouring  the  con- 
tents of  the  tube  into  a  watch  crystal,  the  lingual  membrane  at- 
tached to  the  jaw  will  be  readily  seen  by  a  pocket  lens.  If  the 
species  be  small,  its  whole  body  may  be  thrown  into  the  solution. 
Still  more  minute  species,  may  be  treated  in  this  way;  crush  the 
whole  shell  between  the  glass  sHdes;  wash  the  particles  of  broken 
shell  in  a  few  drops  of  water,  still  keeping  the  body  of  the  animal 
on  the  slide;  when  clean,  drop  on  it  the  caustic  potash  and  boil  it 
by  holding  the  sHde  itself  over  the  spirit  lamp. 

"For  purpose  of  examination,  the  jaw  and  Ungual  membrane 
may  be  simply  mounted  in  water  and  covered  with  thin  glass.  One 
must  be  sure  in  spreading  out  the  lingual  membrane  not  to  have 
its  upper  side  down,  and  it  is  well  to  cut  it  transversely  in  several 

^  No  detailed  instructions  for  the  dissection  of  the  fresh-water  moliusks  have  been 
published  in  this  country.  For  an  admirable,  fully  illustrated  paper  on  the  dissection 
of  the  land  snail,  which  can  be  easily  adapted  for  the  use  of  the  student,  see  Simpson, 
Bull.  N.  Y.  State  Museum,  viii,  p.  241  (1901;.  The  same  author  has  published  an 
excellent  study,  fully  illustrated,  of  the  anatomy  of  Anodonta,  which  should  be  in  the 
hands  of  every  student.     See  Rep.  N.  Y.,  State  Mus.  of  Nat.  Hist.,  35,  p.  169. 


THE   MOLLUSCA 


969 


places,  as  the  teeth  are  beautifully  shown  and  often  stand  detached 
on  the  edges  of  the  cut. 

''For  preservation  for  future  study,  the  glycerin  preparations 
sold  by  the  opticians  will  be  found  useful,  though  they  have  the 
great  disadvantages  of  deKquescing  in  warm  weather."  ^ 

The  radula  may  also  be  mounted  in  Canada  balsam.  In  this 
case  it  should  be  stained  with  carmine  or  chromic  acid,  as  otherwise 
the  specimens  will  in  time  become  transparent. 

Measurement  and  Descriptive  Terms 

The  length  or  height  of  a  univalve  shell  is  the  distance  from  the 
apex  to  the  basal  edge  of  the  lip,  measured  along  a  line  drawn 
through  the  axis. 

The  greater  diameter  is  the  greatest  width,  including  the  lip, 
measured  on  a  line  drawn  at  right  angles  to  the  axis. 

The  lesser  diameter  is  measured  on  the  same  plane,  but  on  a  line 
at  right  angles  to  the  greater  diameter. 

Shells  are  dextral  or  sinistral,  accordingly  as  the  aperture  is  on 
the  right  or  left  of  the  axis,  when 
held,   apex  uppermost,  with   the 
aperture  facing  the  observer. 

In  bivalve  shells,  the  length  is 
the  distance  from  the  anterior 
to  the  posterior  extremity;  the 
height  is  the  distance  at  right 
angles  between  two  parallel  lines 
so  drawn  as  to  touch  the  highest 
dorsal  and  lowest  basal  points; 
the  width  is  the  greatest  diameter 
measured  in  a  line  at  right  angles 
to  the  basal  line. 

The  remainder  of  the  terms  in 
common  use  are  sufficiently  indi- 
cated  on   the    following    diagrams.  7-9.   Greatest  diameter. 

1  W.  G.  Binney,  Man.  Am.  Land  Shells,  p.  44-  For  full  insLruclions  in  regard  to 
the  preparation  ot  the  radulae  of  the  minute  species,  see  Beecher,  Journal  X  Y.  Micro- 
scopical Society,  1888,  p.  7. 


.-5 


Fig.  1403.    Th 

1.  Apex. 

2.  Spire. 

3.  Operculum. 

4.  Lip. 


6.    Umbilicus. 
8.    Suture, 
o.   Columella. 
-5.    Height. 


970 


FRESH-WATER  BIOLOGY 


Fig.  1404.    The  shell  of  a  bivalve. 


1.  Hinge. 

2.  Beak. 

3.  Pseudo-cardinals. 

4.  Scar  of  anterior  retractor. 

5.  Scar  of  anterior  adductor. 


6.  Scar  of  protractor  pedis. 

7.  Pallial  line. 

8.  Scar  of  posterior  adductor. 

9.  Scar  of  posterior  retractor. 
10.   Lateral  teeth. 


Classification 

Of  the  several  classes  into  which  the  subkingdom  of  the  Mollusca 
is  divided,  but  two,  the  Gastropoda  and  Lamellibranchia,  are 
represented  in  the  fresh-water  fauna  of  North  America.  The  for- 
mer includes  all  the  univalve  species  commonly  called  snails  or 
periwinkles,  and  the  latter,  all  the  bivalve  forms  usually  known  as 
clams  or  mussels. 

The  class  Gastropoda,  as  the  name  implies,  are  mollusks  in  which 
the  ventral  portion  of  the  body  is  developed  into  a  fleshy,  more 
or  less  expanded,  creeping  disk,  called  the  foot,  by  the  muscular 
contractions  of  which  the  animal  progresses. 

When  fully  expanded,  the  animal  is  seen  to  have  a  distinct  head, 
with  a  pair  of  tentacles,  at  the  base  of  which  are  placed  the  eyes. 
In  the  center  of  the  head,  below  and  between  the  tentacles,  is  the 
mouth,  in  which,  on  the  upper  surface,  are  situated  the  jaws,  from 
one  to  three,  and,  on  the  lower  side,  the  lingual  ribbon  or  radula, 


THE  MOLLUSCA 


971 


the  surface  of  which  is  covered  with  numerous  rows  of  small  chitin- 
ous  teeth. 

The  Gastropoda  are  either  ovo viviparous  or  oviparous.  The  sexes 
are  separate  in  some  groups  (Dioecia)  and  united  in  the  same  indi- 
vidual in  others  (Monoecia).  All  of  the  fresh- water  gastropods  are 
provided  with  an  external  shell,  which  covers  the  animal  completely 
when  retracted,  and  which  is  spiral,  discoidal,  or  conical  in  shape. 

Owing  to  the  torsion  of  the  body,  caused  by  the  spiral  shape  of  the 
shell,  the  animal  of  all  the  fresh-water  gastropods,  while  externally 
bilaterally  symmetrical,  is  internally  asymmetrical.  There  is  but 
one  lung  or  one  functional  gill,  as  the  case  may  be,  and  the  termina- 
tions of  the  digestive  and  genital  systems,  instead  of  being  posterior 
and  central,  corresponding  to  the  mouth,  are  on  the  side  near  the 
respiratory  chamber. 

The  Gastropoda  are  further  divided  into  subclasses,  accordingly 
as  the  torsion  of  the  viscera  has  or  has  not  been  accompanied  by  a 
similar  twisting  of  the  visceral  nerve  loop.  In  the  Euthyneura, 
the  visceral  nerve  loop  lies  beneath  the  intestinal  canal,  and  was 
consequently  not  affected  by  the  torsion  to  which  that  organ  was 
subjected,  while  in  the  Streptoneura,  the  visceral  nerve  loop  lies 
above  the  intestines  and  became  involved  in  the  twisting  of  the 
viscera  and  was  consequently  made  to  assume  the  form  of  the  figure 
8.  The  aquatic  Euthyneura,  which  comprise  practically  all  our 
air-breathing  or  pulmoniferous  fluviatile  mollusks,  are  included 
in  the  order  Pulmonata;  while  the  Streptoneura  comprise  all  the 
gill-breathing  or  branchiferous  species,  which  are  furnished  with 
a  pecuUar  chitinous  or  calcareous  structure  attached  to  the  upper 
surface  of  the  posterior  extremity  called  the  operculum,  and  which, 
when  the  animal  retires  within  the  shell,  completely  closes  the 
aperture.  Species  thus  provided  are  termed  operculate.  The 
Pulmonata,  on  the  other  hand,  have  no  operculum,  and  are  there- 
fore called  inoperculate. 

The  Pulmonata  are  divided  into  two  suborders:  the  Stylomma- 
tophora,  in  which  the  eyes  are  borne  on  the  extremities  of  retractile 
tentacles,  and  which  are  all  terrestrial  species;  and  the  Basom- 
matophora,  in  which  the  eyes  are  placed  at  the  base  of  contractile 
tentacles,  and  which  are  aquatic  or  amphibious  in  habit. 


972  FRESH- WATER  BIOLOGY 

The  Basommatophora  are  subdivided  ijito  three  superfamilies 
based  mainly  on  the  general  character  of  their  habitat: 

I.  Terrestrial  or  semiamphibious,  living  in  damp  places  or  near 
the  margin  of  the  sea,  but  not  in  the  water,  —  Akteophila. 

II.  Aquatic,  living  in  fresh  water  and  usually  coming  occasionally 
to  the  surface  for  air,  —  Limnophila. 

III.  Aquatic,  living  in  salt  or  brackish  water  along  the  seashore 
in  the  littoral  zone,  —  Petrophila. 

The  Streptoneura  are  divided  into  two  orders: 

I.  The  Aspidobranchia,  in  which  the  nerve  centers  are  not 
closely  concentrated,  and  the  original  bilateral  symmetry  has  not 
wholly  disappeared,  there  being  two  auricles  to  the  heart  and  two 
kidneys. 

II.  The  Pectinibranchia,  in  which  all  trace  of  bilateral  symmetry 
in  the  circulatory,  respiratory,  and  execretory  systems  has  disap- 
peared and  the  nervous  system  is  more  concentrated. 

The  fresh-water  aspidobranchs  all  belong  to  the  suborder  Rhipido- 
glossa,  in  which  the  radula  has  very  numerous  marginal  teeth 
arranged  like  the  sticks  of  a  fan. 

The  Pectinibranchia  are  divided  into  two  suborders,  of  which 
only  one,  the  Taenioglossa,  in  which  the  radula  has  but  one  lateral 
and  two  marginal  teeth  on  each  side  of  the  central  tooth,  is  repre- 
sented in  our  fluviatile  fauna.  The  fresh-water  Taenioglossae  are 
all  included  in  the  superfamily  Platypoda,  in  which  the  foot  is  flat- 
tened ventrally  for  creeping  purposes. 

The  several  superfamilies  of  the  Euthyneura  and  Streptoneura 
are  subdivided  into  families,  of  which  thirteen  are  represented  in 
the  North  American  fauna. 

The  class  Lamellibranchia,  so  called  from  the  form  of  the  gills, 
comprises  all  the  fresh-water  bivalve  shells  commonly  called  clams 
or  mussels.  The  name  Pelecypoda  is  frequently  applied  to 
this  class  from  the  hatchet-like  shape  of  the  foot.  The  lameUi- 
branchs  are  aquatic  mollusks,  without  a  distinct  head  and  with 
the  mantle  divided  into  two  lobes,  which  secrete  a  bivalve  shell 
united  by  a  ligament,  which  covers  the  entire  animal.  The  lobes 
of  the  mantle  are  united  by  one  or  two  transverse  muscles,  which 
are  attached  to  the  inner  surface  of  the  valves  and  by  their  con- 


THE   MOLLUSCA 


973 


traction  close  the  shell.  They  are  destitute  of  jaws  or  radula,  and 
the  cephalic  region  is  furnished  only  with  a  pair  of  labial  palps  on 
each  side.  They  feed  by  ciliary  action  and  breathe  by  gills  sus- 
pended on  each  side  of  the  body.  The  digestive  system  consists 
of  a  stomach,  a  liver,  and  a  more  or  less  convoluted  intestinal  canal 
with  its  oral  and  anal  extremities  at  the  opposite  ends  of  the  body. 
The  edges  of  the  mantle  lobes  in  the  fresh-water  forms  are  usually 
united  between  exhalent  and  inhalent  orifices,  and  in  some  famihes 
the  posterior  margins  are  extended  in  one  or  two  siphons.  The 
foot  is  ventral,  usually  compressed,  hatchet-shaped,  and  adapted 
for  burrowing.  The  nervous  system  consists  of  three  principal 
groups  of  ganglia  (cerebral,  pedal,  and  visceral),  united  by  nerves. 
They  are  monoecious  or  dioecious. 

The  following  diagram  represents  the  classification  of  the  fresh- 
water Gastropoda  as  thus  briefly  outlined. 


Class 


GASTROPODA 


Subclass 


Streptoneura. 


Order  Pectinibranchia  Aspidobranchia 

Suborder        Taenioglossa       Rhipidoglossa 


Superfamily     Platypoda 


Euthyneura. 
Pulmonata. 

I 

Basommatophora. 


Limnophila  Petrophila  Akteophila. 


•*■ \ 


Viviparidae  Neritidac     Lymnaeidae     Siphonariidae      Auriculidae. 

Ampullariidae  Planorbidae     Gadiniidae 

Valvatidae  Ancylidae 

Assimeniidae  Physidae 

Amnicolidae 

Pleuroceratidae 


The  Radula 

As  the  radula  of  the  gastropod  mollusca  is  very  important  as  a 
basis  for  classification,  the  following  series  of  t>^ical  forms  is  given, 
which  should  be  used  in  connection  with  the  key. 


974 


FRESH-WATER   BIOLOGY 


AURICULIDAE 


^^^n^n^ 


Fig.  1.    Carychium  exiguum  Say. 


SiPHONARIIDAE 


29  27  17  15  13  11 


'*^ 

^ 


Fig.  II.    Siphonaria  alternata  Say. 


Gadiniidae 


Fig.  III.    Gadinia  reticulata  Say. 


Lymnaeidae 


(VWl^^'^ 


Fig.  IV.    Lymnaea  stagnalis  L. 


Planorbidae 


C  1-8  U 

Fig.  V.    Planorbis  irivolvis  Say. 


THE   MOLLUSCA 
Physidae 


Fig.  VI.    Physa  humerosa  GId. 

Ancylidae 


Fig.  VII.    Gundlachia  meekiana  Stimp. 


Ampullariidae 


Fig.  VIII.    Ampullaria  paludosa  Say. 


975 


C 


Fig.  IX.     Viviparus  inlertextus  Say. 


Valvatidae 


r\ 


Fig.  X.     Vdlvata  tricarinata  Say. 


976 


FRESH-WATER  BIOLOGY 


ASSIMENIIDAE 


Fig.  XI.    Assimenia  grayana  Leach. 


Amnicolidae 


■^^H 


o 

« 


Fig.  XII.    Amnicola,  porata  Say. 


PLEUROCERAXroAE 


Fig.  XIII.    Anculosa  dissimilis  Say. 


Neritidae 


Fig.  XIV.    Neritina  reclivata  Say. 


The  classification  of  the  Lamellibranchia  is  based  primarily  on 
the  structure  of  the  gill.  Each  gill  consists  of  "a,  hollow  vascular 
axis  bearing  on  each  face  a  row  of  more  or  less  flattened  filaments 
which  are  nothing  more  than  simple  expansions  of  the  axis."  The 
LamelHbranchia  are  divided  into  four  orders,  according  as  these 
filaments  are  flat  and  non-reflected  (Protobranchia)  or  parallel, 
ventrally  directed  and  reflected  (Filibranchia),  or  are  united  at 


THE   MOLLUSCA  977 

regular  intervals  by  vascular  junctions  (Eulamellibranchia) ,  or  are 
entirely  absent  (Septibranchia). 

All  of  the  North  American  fresh-water  lamellibranchs  belong  to 
the  order  Eulamellibranchia.  This  order  is  divided  into  nine  sub- 
orders, of  which  only  one  is  represented  in  our  fauna.  The  suborder 
Submytilacea  consists  of  ''Eulamellibranchia,  in  which  the  mantle 
is  only  slightly  closed,  generally  there  is  only  a  single  suture. 
Siphons  absent  or  very  short.  Gills  smooth.  Nearly  always  dimy- 
arian  (with  two  adductor  muscles).  Shell  equivalve  with  an  exter- 
nal ligament." 

The  Submytilacea  are  divided  into  a  large  number  of  families 
of  which  seven  are  represented  in  the  North  American  fauna: 

Margaritinidae  Sphaeriidae 

Unionidae  Cyrenidae 

Dreissensiidae  Cyrenellidae 
Rangiidae. 


KEY  TO  NORTH  AMERICAN  FRESH-  AND  BRACKISH-WATER 

MOLLUSCA. 

1  (103)     Animal  with  a  distinct  head,  bearing,  usually,  contractile  tentacles. 

Shell  univalve Class  Gastropoda  .    .     2 

2  (63, 100)     Animal  inoperculate,  pulmoniferous.    .  Order  Pulmonata  .    .     3 

3  (17,22)     Animal  terrestrial   or   semiamphibious.      Shell   spiral,    columella 

plicate  at  the  base;  outer  lip  usually  dentate  or  Urate. 

Family  Auriculidae   .    .     4 

4  (9)     Foot  entire,  not  divided  transversely.   .  Subfamily  Auriculinae  .    .     5 

5  (6,  7)     Shell  minute,  pupaeform,  outer  lip  thickened,  reflected,  or  expanded. 

Carychium  M  tiller. 

A  group  of  small  species  of  general  distribution  from  the  Atlantic  to  the  Pacific. 
The  only  genus  in  the  family  found  at  a  distance  from  the  seashore.  Found  in 
damp  places  under  dead  leaves,  pieces  of  bark,  etc.  They  are  usually  included 
among  the  terrestrial  species  and  are  included  here  rather  on  account  of  their 
systematic  position  than  as  belonging  strictly  to  the  fresh-water  fauna.  Example, 
C.  exiguum  Say,  (Fig.  1405;  X  10),  from  the  Eastern  States. 
Fig.  1405 

1  Unless  otherwise  indicated,  the  figures  are  of  natural  size.  In  other  cases,  the 
amount  of  enlargement  or  reduction  is  indicated.  To  obtain  the  actual  size  of  any 
species,  divide  the  length  of  the  figure  in  millimeters  by  the  index. 


978 


FRESH-WATER   BIOLOGY 


6  (5,  7) 


Fig.  1406. 
7  (5,  6) 


Shell  oval;  lip  thickened  but  not  reflected;  smooth  within;  no  callous 
deposit Auricula  Lamarck. 


The  typical  Auriculae  are  not  represented  in  our  fauna.  A  single  species,  A . 
pellucens  Mke.  (Fig.  1406),  belonging  to  the  subgenus  Auriculastrum  Fischer,  is 
found  along  the  southern  Florida  coast  and  keys. 


Shell  oval;  lip  thickened,  with  a  single  strong  ridge  revolving  longi- 
tudinally into  the  aperture Tralia  Gray   .    .     8 

A  single  species,  T.  pusilla  Gmel.,  (Fig.  1407;  X  itd),  found  along  the  Florida 
coast  and  "easily  recognized  by  its  pure  brown  color,  three  plaits  and  the  single 
ridge  on  the  inside  of  the  impressed  outer  lip"  (Dall.). 


Fig.  1407. 

8    Shell  oblong-ovate;  lip  thickened  by  a  ridge  of  callus,  simple  or  denticulate, 
within  the  edge;  no  lirae  or  longitudinal  ridges. 

Subgenus  Phytia  Gray. 

This  group  has  been  usually  knowTi  as  Alexia  Gray,  but  that  name  is  preoccupied 
and  inadmissible.  A  single  species,  T.  mysotis  Dr.,  (Fig.  1408;  X  2|),  locally  intro- 
duced from  Europe  on  both  the  Atlantic  and  Pacific  coasts.  The  west  coast  form 
is  usually  known  as  Alexia  setifer  Cooper. 

Fig.  1408. 

9(4)     Foot  divided  transversely  by  a  sulcus.     Subfamily  Melampinae   .    .    10 

10  (11,  16)     Shell  globose-conic;  lip  sharp,  with  a  dentate  or  nodulous  callus 
within Pedipes  Adanson. 


Several  species  are  found  on  the  southern  Floridan  and  Californian  coasts 
and  are  easily  distinguished  by  their  globular  form  and  unusually  large  parietal 
tooth.     Example,  P.  unisulcatus  Cpr.,  (Fig.  1409;  X  22)  from  CaUfomia. 


Shell  ovate-conic,  oblong,  or  subfusiform;  outer  lip  sharp,  usually 
Urate  within Melampus  Montfort  .    .     la 

Four  subgenera:  12,  13,  14,  15. 

12  (13)     Shell   ovate-conoid;   spire   short;    body-whorl   very   large,  broadest 
above  and  tapering  to  the  base;  lip  Urate  within. 

Subgenus  Melampus  s.s. 

The  species  of  this  group  are  abundantly  found  in  the  salt  marshes  and 
brackish  water  of  both  the  eastern  and  western  coasts.  The  shape  of  the  shell 
and  the  apertural  armature  are  eminently  characteristic.  Example,  M.lineatus 
Say,  (Fig.  14 10;  X  i,).  from  the  Atlantic  coast. 

Fio.  1410. 


THE   MOLLUSCA 


979 


13  (14)     Shell  ovate-oblong;   spire  produced,   pointed;   outer  lip   thickened, 
sometimes  with  one  denticle  on  the  callus. 

Subgenus  Ovatella  Bivona. 

A  single  European  s^Qcits,  Melamptis  bidenlata  Mont.,  (Fig.  141 1;  X  2  j),  intro- 
duced on  the  coast  of  New  England.  "The  shell,  except  for  its  smoother  epidermis 
and  obsolete  parietal  denticle,  is  almost  exactly  like  the  lighter-colored  forms 
of  Tralia  tnysotis,  a  fact  which  has  led  to  much  confusion  "  (Dall.)-  In  living 
examples,  this  species  is  easily  distinguished  by  the  transversely  divided  foot. 
Fig.  1411. 

14  (15)     Shell  elongated,  solid,  rounded  to  a  point  at  both  ends;  outer  lip 
Urate  within Subgenus  Dctracia  Gray. 


A  single  species,  Melampus  buUoides  Mont.,  (Fig.  1412;  X  2,),  is  found  along 
the  Florida  coast  and  keys. 


Fig.  141 2. 

15  (12)  Shell  small,  thin,  subfusiform;  spire  elevated;  columella  twisted  to 
form  one  strong,  spiral  ridge  entering  the  volutions;  outer 
lip  thin,  sharp,  without  internal  lirae,  thickening  or  denticu- 
lations Subgenus  Sayella  Dall. 

Only  two  minute  species  are  known,  both  of  which  occur  on  the  Florida  coast. 
Example,  Melampus  hemphilli  Dall.     (Fig.  1413;  X  5.) 

Fig.  1413- 

16  (10,  11)     Shell  small,  sinistral,   elongate;  lip  slightly   thickened,   smooth 
within Blauneria  Shuttleworth. 


A  single  species,  5.  heteroclita  Mont.,  (Fig.  1414;  X  3 i),  occurs  on  the  Florida 
coast.     It  is  easily  distinguished  by  its  sinistral  shape. 


Fig.  1414. 

17  (3,  22)     Animals  marine  or  semi-amphibious,  living  on  rocks  where  they  are 

immersed  at  high  tide.     Head  without  tentacles.  ...      18 

18  (21)     Shell  patelliform,  with  a  subcentral  apex.     Animal  with  a  jaw  and 

both  lung  and  gill Family  SiPHONARnDAE. 

Only  one  genus Siphonaria  Sowerby   .    .     19 

19  (20)     Shell  solid,  porcellanous;  surface  with  more  or  less  elevated  ribs  ex- 
l^®k  tending  to  the  margin Subgenus  Siphonaria  s.s. 

Two  species  only,  found  on  the  east  coast  of  Florida,      Example,  5.  dter- 
y<^        nata  Say,  (Fig.  1415)- 


Fig.  1415. 


q8o  fresh-water  biology 

20  (19)     Shell  thin,  horny,  smooth,  or  with  fine  radiating  lines,  which  do  not 

interrupt  the  margin Subgenus  Liriola  Dall. 

Two  species  are  represented  on  the  west  coast.      Example,  Siphonaria 
peltoides  Cpr.,  (Fig.  1416;  X  li). 

Fig.  1416. 

21  (18)     Shell  patelliform,  obliquely  conical.     Animal  with  a  lung  only;  no 

gill;  no  jaw Family  Gadiniidae. 

Only  one  genus Gadinia  Gray. 

Two  species  occur  on  the  southern  California  coast.      Another,  de- 
scribed from  Cuba,  may  be  looked  for  on  the  Florida  keys.      Example, 
G.  reticulata  Sby.,  (Fig.  1417-) 
Fig.  1417. 

22(3,17)     Animal  aquatic,  inhabiting  fresh  water 23 

Four  families:  23,  32,  50,  53- 

23  (32)     Shell  spiral,  dextral;  spire  more  or  less  elongated;  tentacles  flattened, 

triangular Family  Lymnaeidae. 

Only  one  genus Lytnnaca  Lamarck  .    .     24 

Eight  subgenera:  24,  25,  26,  27,  28,  29,  30,31. 

24  (25)     Shell  large,  thin;  spire  slender  and  acute;  body-whorl  large,  inflated; 
columella  strongly  twisted;  axis  pervious. 

\]]  Subgenus  Lymnaea  s.s. 

V!  it 

The  typical  species,  L.  stagnalis  L.,  is  circumboreal,  but  the  typical  form  is 
not  found  in  America.  The  common  American  form  is  known  as  L.  stagnalis 
oppressa  Say,  (Fig.  1418;  Xf). 

.-./  ji  ' 

Fig.  1418. 

25  (26)     Shell  large,  solid,  bulimiform;  spire  short;  body-whorl  large,  inflated; 

axis  impervious Subgenus  Bulimnaea  Haldeman. 

I   '     ^  \    \<K  The  typical  and  only  species,  Lymnaea  megasoma  Say,  (Fig.  1419;  X  i), 

\  yy\\        inhabits  the    northern   United  States  and  Canada,  west  to  Manitoba, 
\\\^^^^^</      '  ^       Minnesota  and  Iowa. 


Fig.  1419. 


THE   MOLLUSCA 


98 


26  (27)     Shell  thin;  spire  short,  acute;  body-whorl  large,  inflated;  lip  expanded. 

Subgenus  Radix  Montfort. 


The  typical  species,  Lymnaea  auricularia  L.  (Fig.  1420),  is  European, 
but  has  been  locally  introduced  in  several  of  the  Eastern  States. 


Fig.  1420. 

27  (28)     Shell  thin;  spire  short;  body-whorl  large,  elongated,  not  inflated;  sur- 
face sculptured  with  spiral  incised  lines. 

Subgenus  Pseudosiiccinea  Baker. 


The  typical  species,  Lymnaea  columella  Say,  (Fig.  142 1 ),  has  a  general  distribu- 
tion throughout  the  eastern  United  States  and  Canada. 


Fig.  1421. 
28  (2q)     Shell  very  long  and  slender;  spire  elongated,  acute;  body-whorl  long 
and  narrow;  columella  smooth.    Subgenus  Acella  Haldeman, 


A  single  species,  Lymnaea  haldemani  "Desh."  W.  G.  Binn.,  (Fig.  1422),  occurs 
in  the  St.  Lawrence  drainage  system  and  the  upper  part  of  the  Mississippi  River. 


Fig.  1422. 

29  (30)  Shell  varying  from  elongate  to  short  ovate;  outer  lip  (usually)  some- 
what thickened  within;  columella  somewhat  twisted  and 
phcate;  surface  with  strong,  spirally  impressed  hues. 

Subgenus  Stagnicola  Leach. 


The  typical  species,  Lymnaea  palustris  Mull.,  (Fig.  1423),  is  a  circum- 
boreal  and  is  usually  the  most  common  species  in  the  Northern  States  and 
Canada. 


Fig.  1423. 

30  (31)     Shell  as  in  Stagnicola,  but  with  the  surface  longitudinally  costate. 

Subgenus  Polyrhytis  Meek. 


The  only  recent  species  known,  Lymnaea  utahensis  Call.,  (Fig.  1424)1  is  from 
Utah. 


Fig.  1424. 


982  FRESH-WATER  BIOLOaY 

31  (24)  Shell  small,  turreted;  spire  somewhat  elevated;  spiral  sculpture 
wanting  or  subobsolete;  columella  not  twisted;  inner  lip 
usually  reflected  over  the  umbilicus. 

/\\\Y]  Subgenus  Galba  Schrank. 

This  group  of  small  species  has  a  wide  range  from  the  Atlantic  to  the  Pacific. 
The  example,  Lymnaea  obrussa  Say,  (Fig.  1425;  X  15),  is  a  common  species  in  the 
Eastern  States. 

Fig.  1425. 

32  (50)     Shell  discoidal,  sinistral,  or  dextral,  or  spiral  with  a  very  low  spire. 

Animal  sinistral;  tentacles  cylindrical. 

Family  Planorbidae  .    .     33 

The  dextral  species  of  this  family  present  the  apparent  anomaly  of  a  sinistral  animal  with  a 
dextrally-coiled  shell.  Such  shells  are  not  true  dextral  shells,  but  represent  the  condition  of 
hypertrophy,  so  called,  in  which  the  spiral  growth  of  the  shell,  instead  of  being  from  the  apex 
downward,  as  is  usually  the  case,  is,  as  it  were,  from  the  apex  upward,  the  result  being  an  appar- 
ently dextral  shell  with  a  sinistral  animal.  Such  shells  are  also  called  ultradextral.  In  the 
formation  of  the  key  to  the  subdivisions  of  the  family,  the  shells  are  treated  with  reference  to 
their  apparent  mode  of  spiral  growth. 

33  (47)     Shell  discoidal Subfamily  Planorbinae  .    .     34 

34  (46)     Aperture  edentate PlanorUs  Miiller  .    .     35 

Six  subgenera:  35,  36,  39.  40,  41  >  42. 

35  (36)     Shell  sinistral,  large;  whorls  rounded  above  and  below,  gradually  in- 

creasing;  aperture  but  slightly  expanded;  lip  simple  and 
sharp Subgenus  Planorbis  s.s. 

^  '^^^^Ajrr^  ^  single,  characteristic  species,  P.  glabratus  Say,  (Fig.  1426;  X  s),  is 

'V^e'      Jh-'  found  in  Florida. 


Fig.  1426. 

36  (39)     Shell  dextral  or  sinistral,  few  whorled;  the  whorls  carinate  above  and 

rapidly   enlarging;   base   funicular;   aperture   suddenly   ex- 
panded and  lip  thickened. 

Subgenus  Helisoma  Swainson   .    .     37 

37  (38)     Shell  dextral,  carina  ted  above  and  below;  spire  and  base  funicular. 

Section  Helisoma  s.s. 


The  typical  species,  Planorbis  antrosus  Con.,  (Fig.  1427;  X  i^),hasa 
general  distribution  east  of  the  Rocky  Mountains  and  rarely  on  the 
Pacific  coast. 


Fig.  1427- 


THE  MOLLUSCA 


983 


38  (37)     Shell  sinistral;  early  whorls  flattened  and  carinate  above;  base  funic- 
ular       Section  Pierosoma  Dall. 


This  group  includes  nearly  all  the  larger  North  American  Planorbes 
and  is  represented  by  numerous  species  found  in  all  parts  of  the  country. 
Type,  Flanorbis  Irivolvis  Say,  (Fig.  1428). 


Fig.  1428. 

39  (40)     Shell  sinistral;  aperture  campanulate;  Hp  thickened. 

Subgenus  Planorhella  Haldeman. 

The  typical  form,  Planorbis  campanulatus  Say,  (Fig.  1429;  X  li),  is  of 
common  occurrence  and  wide  distribution  in  eastern  Canada  and  the 
United  States  north  of  Tennessee. 

Fig.  1429. 

40  (41)     Shell  dextral,  much  depressed;  upper  surface  convex,  base  flattened; 
body-whorl  carinate;  lip  simple. 

Subgenus  Tropidiscus  Stein. 


A  single  species,  Planorbis    cultratus  Orb..   (Fig.  1430;  X  2),  of  this  (in 
America)  tropical  group  has  been  collected  in  Texas  and  Florida. 

Fig.  1430. 

41  (42)     Shell   small,   dextral;   periphery   carinated;   base   convex;   aperture 
oblique ;  lip  simple Subgenus  Hippuetis  Agassiz. 


A  group  of  small  species  of  general  distribution  through  the  Northern 
States  and  Canada.  All  of  our  species  belong  to  the  section  Menetus  H. 
&  A.  Adams,  of  which  the  type  is  Planorbis  opercularis  Gld.,  (Fig.  1431; 
X  3),  from  Cahfornia. 


Fig.  143 I. 


42  (35)     SheU  smaU,  depressed;  body- whorl  rounded  or  obtusely  angulated; 
lip  simple Subgenus  Gyraulus  Agassiz  .    .     43 


43  (44,  45)     Surface  spirally  striate  and  hispid. 


.    .    Section  Gyraulus  s.s. 


A  few,  small  species,  not  uncommon  in  the  eastern  Northern  States 
and  Canada.  The  group  is  not  represented  on  the  Pacific  coast.  Ex- 
ample, Planorbis  hirsutus  Gld.,  (Fig.  1432;  X3)- 


984  FRESH-WATER   BIOLOGY 

44  (43,  45)     Surface  smooth  or  finely  striate Section  Torquis  Dall. 

^■^^ 

This  group  of  small  species  is  o\  general  distribution  from  the  At- 
.7i:*5^  /--^  lantic  to  the  Pacific.    Type,  Planorbis  parvus  Say,  (Fig.  1433;  X  45)- 

Fig. 1433- 

45  (43,  44)     Shell  minute;  surface  costate.      .    .     Section  Armiger  Hartmann. 

A  The  typical  species  only,  Planorbis  crista  L.,  (Fig.  1434;  X  7),  repre- 

sents this  group  in  our  fauna  and  has  been  recorded  from  Maine  to  Illi- 
nois and  northward. 

Fig.  1434- 

46  (34)     Aperture  with  one  or  more  sets  of  laminae  or  teeth  behind  the  margin. 

Segmentina  Fleming. 

The  typical  Segmentinae  are  not  represented  in  our  fauna.  All  of  the 
American  species  belong  to  the  subgenus  Planorbula  Haldeman.  The  type 
5.  armiger  a  Say,  (Fig.  1435;  X  2)  is  common  in  the  northern  Eastern  States 
and  Canada. 

Fig.  1435. 

47  (33)     Shell  spiral,  dextral,  flattened  above  and  convex  below;  body-whorl 

very  large Subfamily  Pompholiginae  .    .     48 

48  (49)     Shell  imperforate Pompholyx  Lea. 

'i|  \  Two  or  three  species  only  are  known  from  California.     Type,  P.  effusa 

•))       Lea.,  (Fig.  1436;  X  2i). 

Fig.  1436. 

49  (48)     Shell  deeply  umbilicate Carinifex  W.  G.  Binney. 

A\'  \\l//  )  '^^^  typical  species,  C.  newberryi  Lea.,  (Fig.  1437)1  is. from  Cali- 

\V^ijjg;  /  fomia. 

Fig.  1437. 

50  (53)     Shell  spiral,  sinistral.    Animal  sinistral;  tentacles  slender,  cylindrical. 

Family  Physidae   .    .     51 


THE  MOLLUSCA 


985 


ei  (52)     Shell  with  body-whorl  usually  inflated.     Inner  edge  of  mantle  digitate 
or  lobed,  extending  partly  over  the  shell. 

Physa  Draparnaud. 


T  The  species  of  this  genus  are  very  numerous  and  extremely  variable,  so  that 
many  more  species  have  been  described  than  really  exist.  The  Physae  are  found 
in  all  parts  of  the  country,  but  the  majority  of  the  species  are  inhabitants  of  the 
Northern  States  and  Canada.    Example,  P.  gyrina  Say,  (Fig.  143^;  X  li). 


Fig.  1438. 

52  (51)     Shell  slender,  elongated.     Inner  edge  of  mantle  simple,  not  extending 

over  the  shell Aplexa  Fleming. 

The  typical  species,  .4.  hypnorum  L.,  (Fig.  1439;  X  li),  is  circumboreal  and  has  a 
'),l      general  distribution  through  the  Northern  States  and  Canada  from  the  Atlantic 

'\\W'.vy/       to  the  Pacific. 

Fig.  1439. 

53  (23)     Shell  patelliform  or  depressed,  dextrally  spiral,  neritiform  or  planorbi- 

form.     Animal  sinistral  or  dextral;  tentacles  short,  blunt, 

cylindrical Family  Ancylidae  .    .      54 

Five  genera:  54,  59,  60,  61,  62. 

54  (59)     Shell  patelliform,  small,  thin;  apex  posterior,  slightly  inclined  to  one 

side Ancyliis  Miiller  .    .      55 

55  (58)    Apex  inclined  to  the  right Subgenus  Ancylus  s.s  .    .     56 

56  (57)     Apex  subacute,  radially  striate Section  Ferrissia  Walker. 

Numerous  species  and  of  general  distribution,  usually  found  adhering  to 
stones,  etc.,  in  running  water.    Type,  Ancylus  rividaris  Say,  (Fig.  1440;  X  3)- 
Fic.  1440. 

57  (56)     Apex  depressed,  smooth.  ........     Section  Laevapex  Walker. 

The  species  of  this  group  are  usually  found  in  quiet  water  and  are.  as 
a  rule,  larger,  thinner,  and  more  depressed  than  the  Ferrissias.    Type, 
Ancylus  diaphanus  Hald.,  (Fig.  1441;  X  2J). 
Fig.  1441. 

58  (55)     Apex  inclined  to  the  left Subgenus  Acroloxus  Beck. 


Only  one  American  species,  Ancylus  nutlallii  Hald.,  (Fig.  144^;  X  2), 
from  Oregon,  has  been  referred  to  this  group,  but  its  anatomy  is  un- 
known and  its  generic  position  is  very  doubtful. 


Fig.  1442. 


986  FRESH-WATER  BIOLOGY 

59  (60)     Shell  large,  thick  and  solid;  apex  smooth. 


La7ix  Clessin. 


This  genus  is  restricted  to  the  Pacific  coast  and  is  distinguished  by 
the  large  size  and  thick  sohd  shells.  Type,  L.  newberryi  Lea.  (Fig. 
1443)- 


Fig.  i44i 


60  (61)     Shell  ancyliform,  small,  thin,  with  a  septum  across  the  apical  portion 

of  the  interior Gundlachia  Pfeiffer. 

f5.v^  This  very  remarkable  and  peculiar  genus  has 'a  general  but  very  local 

K/Mllf        distribution  from  the  Atlantic  to  the  Pacific.      Example,  G.  meekiana 
Stimp.,  (Fig.  1444;  X  6),  from  the  Eastern  States. 

FlG^  1444- 

61  (62)  Shell  small,  spiral,  dextral,  neritoid,  or  crepidula-like,  with  a  broad, 
thin,  columellar  plate  projecting  across  the  end  of  the  aper- 
ture next  to  the  spire Amphigyra  Pilsbry. 


Only  a  single  species,  A.  alabamensis  Pils.,  (Fig.  1445;  X  10),  from  the 
Coosa  River,  Alabama,  is  known. 


FiC.  1445- 


62  (54)     Shell  very  minute,  dextral,  spiral,  subdiscoidal;  columellar  margin 
broadly  dilated Neoplanorhis  Pilsbry. 


Four  species  of  this  genus  have  been  recently  described  from  the  Coosa 
River,  Alabama,  and  are  among  the  smallest  mollusks  known  in  our 
faima.    Type,  N.  tantillus  Pils.,  (Fig.  1446;  X  10). 


Fig.  1446. 

63  (2,  100)     Animal  operculate,  branchiferous   (except  Assimenia).     Radula 

with  seven  rows  of  teeth. 

Order  Pectinibranchiata.     .   Suborder  Taenioglossa  .    .     64 
Six  families:  64,  65,  66,  71,  72,  90. 

64  (65)     Shell  small,  spiral,  dextral,  conical;  operculum  spiral.    Animal  pul- 
moniferous Family  Assimeniidae. 

Only  a  single  genus Assimenia  Leach. 

The  Assimenias  live  in  brackish  water  in  the  upper  part  of  the  littoral  zone. 
Two  species  occur  on  the  Florida  keys  and  two  on  the  coast  of  California.  Ex- 
ample, A.  calif ornica  Try  on,  (Fig.  1447;  X  4). 

Fig.  1447. 


THE   MOLLUSCA 


987 


65  (66)  Shell  large,  globose-turbinate;  umbilicate;  operculum  corneus,  con- 
centric. Animal  with  the  respiratory  chamber  divided  into 
two  parts,  one  being  the  lung  and  the  other  containing  a  gill. 

Family  Amplllakiidae. 
Only  a  single  genus A  mpullar ia  LamnTck. 


The  Ampullarias  are  the  largest  of  our  fresh- 
water snails.  Two  or  three  species  occur  in 
Georgia  and  Florida.  Example,  A.  paludosa 
Say,  (Fig.  1448). 


Fig.  1448. 


66  (71)     Shell  of  moderate  size,  dextral,  turbinate,  imperforate,  or  subperforate; 
operculum  corneus.     Animal  branchiferous. 

Family  Viviparidae   .    .     67 
Four  genera:  67,  68,  69,  70 


67  (68)  Shell  rather  thin;  operculum  concentric,  inner  margin  simple.  Animal 
with  foot  of  moderate  size,  not  produced  beyond  the  snout. 
Teeth  of  the  radula  multicuspid.      .    .    Vivipariis  ^\ontioxi. 


Several  species  are  found  in  the  Mississippi  Valley  and 
from  Ohio  and  Indiana  south  to  the  Gulf.  They  arc 
usually  to  be  distinguished  from  the  Campelomae  by  the 
thinner  and  more  globose  shells  and  convex  whorls.  Ex- 
ample, V.intcrtextus  Say,  (Fig.  1449;  X  li). 


Fig.  1449- 


988 


FRESH-WATER  BIOLOGY 


68  (69)  Shell  thick  and  solid;  operculum  concentric,  inner  edge  simple.  Animal 
with  the  foot  very  large,  much  produced  beyond  the  snout. 
Teeth  of  the  radula  simple  or  only  minutely  crenulate. 

Catnpeloma  Rafinesque. 


This  genus  is  peculiar  to  North  America  and  the  several 
species  are  usually  very  abxmdant,  when  found.  Though  norm- 
ally dextral,  sinistral  examples  are  not  uncommon.  They  range 
from  the  Mississippi  Valley  east  to  the  Atlantic  and  from  the  St. 
Lawrence  Valley  south  to  the  Gulf.  Example,  C.  subsolida  Anth., 
(Fig.  1450). 


Fig.  1450. 

69  (70)     Shell  turreted;  operculum  with  a  subspiral  nucleus. 

Lioplax  Troschel. 


This  genus  is  also  peculiar  to  this  country.  The  several  species  are  restricted 
to  the  states  east  of  the  Mississippi  and  south  of  Ohio  and  New  Jersey.  Type, 
L.  subcarinata  Say,  (Fig.  1451)- 


Fig.  145 1. 

70  (67)  Shell  (typically)  large,  solid,  imperforate;  spire  elevated;  operculum 
concentric,  with  the  inner  margin  reflected,  forming  an  ele- 
vated, marginal  fold Tulotoma  Haldeman. 


This  genus  is  peculiar  to  North  America  and  is  restricted  to  the 
Alabama  River  and  its  tributaries  in  Alabama.  The  two  leading 
species  are  remarkable  for  their  heavy,  nodulous,  or  tuberculated 
shell.     Type,  T.  magnifica  Con.,  (Fig.  1452). 


Fig.  1452. 

71  (72)     Shell  small,  spiral,  dextral,  turbinate,  or  subdiscoidal;  aperture  entire, 

circular;  operculum  round,  multispiral.     No  basal  denticles 

on  the  central  tooth  of  the  radula.    .   Family  Valvatidae. 

Only  one  genus Valvata  Miiller. 


The  several  species  of  this  genus  are  usually  found  in  great  numbers  and 
are  of  general  distribution.    Example,  V.  tricarinata  Say,  (Fig.  1453 ;  X  4). 


Fig.  1453. 


THE    MOLLUSCA 


989 


72  (90)     Shell  small,  spiral,  dextral.     Central  tooth  of  the  radula  with  one  or 

more  basal  denticles.    .  .    .    Family  Amxicolidak  .    .      73 
Five  subfamilies:  73,  74,  82.  88,  89. 

73  (74)     Operculum  calcareous,  concentric Subfamily  Bythininae. 

Only  one  genus Bythinia  Gray. 


A  sinRle  European  species,  B.  tentaculala  L.,  (Fig.  1454;  X  2),  has  been  intro- 
duced by  commerce  from  the  Hudson  River,  along  the  line  of  the  Erie  Canal, 
and  into  the  Great  Lakes  as  far  west  as  Chicago. 


Fig.  1454- 

74  (82)     Operculum  corneus,  paucispiral.     Shell  thin;  columella  not  thickened. 

Foot  simple Subfamily  Amnicolinae  .     .     75 

Six  genera:  75,  77,  78,  79,  80,  81. 

75  (76)     Shell  smooth,  usually  subglobose.     Central  tooth  of  the  radula  multi- 

cuspid, with  a  tongue-shaped  process  projecting  on  the  ante- 
rior surface  and  beyond  the  base  and  with  several  basal 
denticles Amnicola  Gould  and  Haldeman   .  .     76 


Very  numerous  both  in  species  and  individuals.  In  shell  characters  some  of 
the  more  elongate  species  approach  Paludestrina,  but  as  a  rule  the  shell  is  more 
globose,  with  a  shorter  spire.     Type,  A.  limosa  Say,  (Fig.  1455;  X  4)- 


Radula  more  minute  and  the  denticulations  of  the  cusps  of  the  teeth 
finer  and  sharper Subgenus  Cincinnatta  Pilsbry. 

This  subdivision  is  based  wholly  on  the  character  of  the  lingual  teeth.  The 
shell  characters  are  those  of  Amnicola.  Type,  Amnicola  cmcinnatiensis  Anth., 
(Fig.  1456;  X2i). 


Shell  similar  to  Amnicola,  but  more  slender  and  elongated.  Central 
tooth  of  the  radula  with  but  one  basal  denticle  on  each  side 
and  without  the  tongue-shaped  process. 

Paludestrina  Orbigny. 

The  species  of  this  genus  are  numerous  and  range  from  the  Atlantic  to  the  Pa- 
cific.    Example,  P.  nickliniana  Lea,  (Fig.    i457;  X  6). 


Shell  elongated,  turreted,  longitudinally  ribbed  or  pHcate. 

Trvonia  Stimpson. 


Fig.  14s 5 


76 


Fig.  1456. 

77  (78) 


Fig. 1457- 
78  (77) 


The  type  and  only  species,  T.  ./a//,ra/.  Stimp..  (Fig.  145S;  X  2i),  is  found  fossU 
M  W        in  southern  California  and  living  in  Nevada. 


Fig.  1458. 


990 


FRESH-WATER  BIOLOGY 


79  (80)     Shell  elongated,  strongly  carinated  on  the  periphery. 

Pyrgulopsis  Call  and  Pilsbry. 


^ .  The  typical  species,  P.  nevadensis  Stearns  (Fig.  1459;  X  3),  is  from  Nevada.   Others 

AVa  \.^J^       have  been  described  from  the  Mississippi  and  Tennessee  valleys. 


80  (81)     Shell  ovate-conic;  whorls  shouldered  and  usually  coronated  with 
spines Potamopyrgus  Stimpson. 


Two  species  from  Florida  and  Texas,  respectively,  are  represented  in  our 
fauna.  Typically  spinose,  all  the  species  are  dimorphic,  having  both  an  angu- 
late,  spinose  form  and  a  smooth,  ecarinate  one.  Example,  P.  coronatus  Pfr. 
(Fig.  1460;  X3l). 


Fig.  1460. 

81  (75)     Shell  subpyramidal,  rather  sohd,  smooth;  body- whorl  subangulated 
at  the  periphery.    .    .    .     Littoridina  Eydoux  and  Souleyet. 


A  South  American  genus.      A   single  species  from  Florida,  L.  monroensis, 
Frfld.  (Fig.  1461;  X  7),  has  been  doubtfully  assigned  to  it. 


Fig.  1461. 

82  (88)     Shell  with  a  large  body- whorl  and  short  spire;  columella  usually 

callously   thickened;   operculum   corneus,   subspiral.     Foot 
simple.     Central   tooth   of   the   radula  with   several   basal 

denticles Subfamily  Lythoglyphinae  .    .     83 

Five  genera:  83,  84,  85,  86,  87. 

83  (84)     Shell  depressed-conic;  base  concave,  widely  and  deeply  umbilicated. 

Cochliopa  Stimpson- 


A  Central  American  genus,  of  which  one  species,  C.  riograndensis  P.  and 
F.  (Fig.  1462;  X  6),  has  been  found  in  Texas  and  another  (doubtfully)  in 
California. 


Fig.  1462. 


84  (85)  Shell  minute,  globose-turbinate,  narrowly  but  deeply  umbilicated; 
columellar  lip  thin;  operculurr  corneus,  paucispiral;  nuclear 
whorls  large,  slowly  and  regularly  increasing. 

Clappia  Walker. 

Only  a  single  species,  C.  clappii  Walker  (Fig.  1463;  X  6^),  from  the  Coosa 
River,  Alabama,  is  known.  It  somewhat  resembles  Somatogyrus  in  shape, 
but  can  be  easily  distinguished  by  its  deep  umbilicus  and  peculiar  operculum. 

Fig.  1463. 


THE   MOLLUSCA 


991 


85  (86)  Shell  obliquely  ovate,  thick,  solid,  imperforate;  columella  flattened 
and  calloused;  lip  sinuous,  effuse,  and  projecting  anteriorly. 
Verge  winged Fluminicola  Stimpson. 

A  characteristic  west  coast  genus.  In  shell  characters,  it  is  quite  simi- 
lar to  Somatogyrus,  but  differs  radically  in  anatomical  details  and  is  widely 
separated  in  range.     Type,  F.  nuttalliana  Lea  (Fig.  1464;  X  2). 

Fig.  1464. 

86  (87)  Shell  usually  thick  and  soHd,  imperforate  or  narrowly  perforate; 
body-whorl  large;  columella  callously  thickened;  spire  usu- 
ally short;  aperture  very  obUquc,  lip  projecting  above;  oper- 
culum subspiral,  nuclear  whorls  small,  rapidly  increasing. 

Somatogyrus  Gill. 

A  group  of  small  species  found,  mainly,  south  of  the  Ohio  and  east  of  the 

Mississippi.     The  thickened  columella  is  characteristic  and  enables  the  species 

to  be  easily  separated  from   the  associated  genera.      Example,  S.  subglobosus 

Say  (Fig.  1465;  X2). 

87  (86)  Shell  not  very  thick,  imperforate;  body-whorl  large;  spire  short; 
peritreme  continuous  in  the  same  plane;  columella  scarcely 
thickened.     Verge  simple Gillia  Stimpson. 


This  genus  is  restricted  to  the  Atlantic  coast  states,  ranging  from  New  Jer- 
sey to  South  Carolina.    Type,  G.  altilis  Lea  (Fig.  1466;  X  2). 


Fig.  1466. 

88  (89)     Shell  as  in  Amnicolinae,  very  small;  operculum  circular,  multispiral. 

Foot  simple Subfamily  Lyogyrinae. 

Only  one  genus Lyogyrus  Gill. 


A  peculiar  genus  of  minute  species  restricted  to  the  Atlantic  coast  states. 
Easily  distinguished  by  its  operculum.     Type,  L.  pupoideus  Gld.  (Fig.  1467;  X6). 


Fig.  1465. 


Fig.  1467. 


89  (88) 


Shell  elevated,  turreted;  operculum  subspiral.     Foot  divided  by  a 

transverse  sulcus Subfamily  Pom.atiopsinae. 

Only  one  genus Pomatiopsis  Tryon. 

The  species  of  this  group  are  terrestrial  or  rather  semiamphibious  in  habit, 
being  always  found  near  but  not  in  the  water.  The  divided  foot  is  very  pe- 
culiar. The  animal,  aided  by  its  long  snout,  progresses  by  a  series  of  steps. 
Type,  P.  lapidaria  Say  (Fig.  1468;  X  4)- 


90  (72)  Shell  dextral,  spiral,  thick,  soHd,  globose,  or  elongated;  operculum 
corneus,  subspiral.  Animal  without  an  external  verge.  Cen- 
tral tooth  of  the  radula  without  basal  denticles. 

Family  Pleuroceratidae  .   .     91 
Seven  genera:  91,  92,  94,  95,  97.  98,  99- 


992 


FRESH-WATER   BIOLOGY 


91  (92)     Shell  large,  fusiform;  base  of  aperture  prolonged  in  a  long  canal. 

lo  Lea. 


This  group  of  large,  striking  species  is  confined  to  the  rivers  of  east- 
ern Tennessee.  They  are  found  only  in  very  rapidly  running  water. 
Example,  /.  spinosa  Lea  (Fig.  1469). 


Shell  globose-conic;  columella  callously  thickened  above  and  below; 
aperture  shortly  channeled  below. 

Lithasia  Haledman  .    .     93 


The  Lithasiae  form  a  very  distinct  group  characterized  by  the  colu- 
mella thickened  by  deposits  of  callus  above  and  below  and  the  short  canal 
at  its  base.  With  the  exception  of  three  species,  which  extend  as  far 
north  as  the  Wabash  River,  Indiana,  the  group  is  restricted  to  Ken- 
tucky, Tennessee,  and  Alabama.     Type,  L.  geniculata  Con.  (Fig.  147c). 


Fig.  1470. 
93  Shell  similar  to  Lithasia,  but  with  the  basal  canal  more  produced. 

Section  Angitrema  Haledman. 


This  group  connects  Lithasia  with  lo.      Type,  Lithasia   armigera   Say 
(Fig.  I 471). 


Fig.  1471. 
94  (95)     Shell  obovate,  thick,  solid;  spire  short;  body-whorl  large;  columella 
callously  thickened  above,  incurved  below  and  subtruncate. 

Eurycaelon  Lea. 


This  genus,  when  restricted  to  the  species  grouping  about  the  t3TDe,  is 
confined  to  the  rivers  of  the  Tennessee  drainage  system.  Type,  E.  anthonyi 
Budd  (Fig.  1472). 


Fig.  1472. 


THE   MOLLUSCA 


993 


95  (97)  Shell  elongated,  conic,  or  cerithiform;  aperture  subrhomboidal,  pro- 
longed into  a  short  canal  below;  columella  twisted,  not 
callously  thickened.    .   .    .     Pleurocera  Rafinesque   .    .     96 


Exceedingly  abundant  and  of  great  variety.  Numerous  species  have 
been  described  from  the  rivers  of  Kentucky,  Tennessee,  and  Alabama.  A 
few  species  extend  north  to  the  Great  Lakes  and  west  to  the  Mississippi 
Valley.  The  species  vary  greatly  in  contour,  ranging  from  long,  slender, 
and  rather  thin  to  large,  heavy,  and  broadly  conic.  Example,  P.  canalicu- 
latum  Say  (Fig.  1473). 


Fig.  1473. 

96  Shell  smooth;  spire  obtusely  conical;  body- whorl  subcyUndrical ;  aper- 

ture subquadrate;  columella  thickened  below,  twisted  and 
drawn  back,  base  subcanahculate;  lip  very  sinuous. 
Vv  Section  Strephobasis  Lea. 


A  niunber  of  nominal  species  have  been  described  from  Tennessee  and 
northern  Alabama.    Type,  Pleurocera  plena  Anth.  (Fig.  1474). 


Shell  ovate-conic  to  elongate;  smooth,  plicate,  striate,  or  tuberculate; 
aperture  subrhomboidal,  subangular  at  the  base,  but  not 
canaliculate;  columella  simple,  smooth.   .    .    Gofiiobasis  \^t^. 


This  genus  comprises  about  three-fifths  of  all  the  species  of  the  family 
and  is  enormously  developed  in  the  rivers  of  Tennessee  and  Alabama.  A 
few  species  extend  north  to  the  St.  Lawrence  Valley  and  west  to  Texas  and 
the  western  tributaries  of  the  Mississippi.  A  small  group  of  species  is  also 
found  on  the  Pacific  coast  and  is  the  only  genus  of  the  family  represented  in 
that  region.  Example,  G.  virginica  Gmel.  (Fig.  1475),  from  the  Atlantic 
states. 


Fig.  1474. 
97  (98) 


Fig.  1475- 


98  (99)     Shell  conical  or  globose-ovate;  aperture  with  a  slit  along  the  suture, 
entire  below Gyrotoma  Shuttleworth. 


This  remarkable  genus  is  confined  to  the  Coosa  River,  Alabama,  where 
it  is  represented  by  a  considerable  number  of  described  species.  The 
sutural  sHt  is  characteristic  and  is  either  direct,  narrow,  and  deep,  or  ob- 
lique, short,  and  wide.     Example,  G.  demissum  Lea  (Fig.  1476). 


Fig.  1476 


994 


FRESH-WATER   BIOLOGY 


99  (91) 


Shell  thick,  solid,  subglobose,  with  a  very  short  spire,  or  thinner  and 
conical;  aperture  oval  or  subcircular,  entire  below;  columella 
callously  thickened.      . Anculosa  Say. 

This  group  differs  from  all  of  the  genera  of  the  family  by  the  entire  aperture. 
The  heavy,  subglobose  species  range  from  the  Ohio  River  south  into  Alabama  and 
Georgia  but  are  not  found  in  the  northern  Atlantic  States  nor  in  the  Mississippi 
Valley.  The  thin,  conical  species  are  characteristic  of  the  Atlantic  drainage 
from  New  York  southward.    Type,  A.  praerosa  Say  (Fig.  1477) • 

Pig.  1477. 

100  (2,  63)  Radula  with  numerous  rows  of  teeth,  consisting  of  a  central 
tooth,  2-5  laterals,  and  numerous  marginals  arranged  like  the 
sticks  of  a  fan. 

Order  Aspidobranchia      .    .      Suborder  Rhipidoglossa. 
Represented  by  a  single  family.  .    .      Neritidae     .    .    loi 


loi  (102) 


Fig.  1478. 


Shell  globose,  imperforate,  very  thick  and  solid;  aperture  semi- 
ovate,  columellar  region  expanded,  flattened,  and  thick- 
ened; operculum  calcareous,  edge  with  projecting  processes 
(apophyses),  articulating  with  the  columella. 

Neritina  Lamarck. 

A  few  species  of  this  characteristic  tropical  genus  are  found  in  the  fresh  and 
brackish  waters  of  Florida  and  the  Gulf  coast.  Example,  N.  reclivata  Say  (Fig. 
1478). 


102  (loi)     Shell  small,  thin,  corneus;  columella  concavely  flattened,  calloused; 
operculum  corneus,  paucispiral,  without  apophyses. 

Lepyrium  Dall. 


This  genus  was  created  for  a  single  small  species,  known  only  from  the 
Coosa  and  Cahawba  rivers  in  Alabama  and  is  peculiar  in  the  character  of 
the  operculum.     Type,  L.  showalteri  Lea  (Fig.  1479;  X35). 


Fig.  1479. 

103  (i)     Anunal  acephalous.     Shell  consisting  of  two  opposing,  symmetrical 
valves  united  by  a  ligament.    Class  Lamellibranchia   .    .    104 

Represented  by  a  single  order,  Eulamellibranchia     .    .    104 
Seven  families:  105,  106,  166,  167,  i73,  i74;  in  two  groups;  104,  165. 


104  (165)     Shell  equivalve;  interior  nacreous;  ligament  external;  hinge  with 

or  without  teeth,  but  never  with  true  cardinal  teeth;  when 

present,  the  modified  anterior  lateral  teeth  are  known  as 

pseudocardinals  and  the  posterior  teeth  as  laterals.  .    .      105 

Two  families:  105,  io6. 


THE   MOLLUSCA 


995 


105  (106)  Shell  elongated,  laterally  compressed;  hinge  with  usually  only 
pscudocardinals;  laterals,  when  present,  very  obscure.  Gills 
without  water  tubes  and  with  scattered  interlamellar  con- 
nections, which  in  certain  places  form  irregular  diagonal  rows. 

Family  jMargaritanidae. 
Only  one  genus Margaritana  Schumacher. 

The  typical  species,  M  .margaritiJera'L.  (Fig.  1480;  X?),  is  circumboreal,  but  in  this  country  is 
found  only  in  the  northern  Atlantic  and  Pacific  states,  being  unknown,  with  one  possible  excep- 
tion, from  the  whole  interior  portion  of  the  continent.  Another  species  is  found  in  the  Ten- 
nessee and  Ohio  drainage  systems,  and  two  more  have  been  described  from  the  Gulf  drainage. 


Fig.  1480. 


106  (105)  Shell  subcircular,  oval,  subtriangular,  or  elongated ;  hinge  edentulous 
or  with  pscudocardinals  only  or  with  both  pscudocardinals 
and  laterals.  Gills  with  water  tubes  and  distinct,  contin- 
uous interlamellar  septa,  running  parallel  to  the  filaments. 

Family  Unionidae   .    .      107 


107  (121,  140)  Marsupium  formed  by  all  four  gills  or  by  the  outer  gills  only; 
edge  of  marsupium  always  sharp  and  not  distending;  water 
tubes  simple  in  the  gravid  female. 

Subfamily  Unioninae   .    .     108 


Five  genera:  108, 


13,  114.  115,  117 


108  (113)  All  four  gills  serving  as  marsupia.  Shell  alike  in  both  sexes,  tri- 
angular, quadrate  or  rhomboidal,  solid,  inflated,  beaks 
usually  prominent,  sculptured  with  a  few  coarse,  subparallel 
ridges,  which  are  inflated  where  they  cross  the  posterior 
ridge;  posterior  ridge  ordinarily  well  developed;  hinge  com- 
plete, with  strong  teeth;  hinge  plate  wide;  berjk  cavities  deep 
and  compressed Quadrula  Rafinesque    .    .      109 

Four  sections:  109,  no,  in,  112. 


996 


FRESH-WATER   BIOLOGY 


109(110)     Surface  plicate Section  Crenodonta  SchXnteT. 

The  species  of  this  group,  characterized  by  the  heavy,  plicate  sculpture  of  the  valves,  are 
among  the  largest  and  heaviest  of  the  American  Unionidae.  They  are  very  abundant  throughout 
the  Southern  States  from  Georgia  to  Texas.  Two  species  range  north  into  the  St.  Lawrence 
drainage,  the  headwaters  of  the  Mississippi,  and  to  Lake  Winnipeg.  Type,  Quadrula  plicata 
Say  (Fig.  1481;  Xi). 


Fig.  1481. 


no  (in)  Surface  pustulose,  with  a  radial  furrow  above  the  posterior  ridge, 
usually  painted  with  triangular  spots  or  chevron-shaped 
Unes Section  Quadrula  s.s. 

The  typical  species,  Q.  cylindrica  Say  (Fig.  1482;  X  5),  ranges  through  the  entire  Ohio, 
Cumberland,  and  Tennessee  river  systems  and  west  to  Arkansas.  A  few  other,  less  elongated, 
species  are  found  in  Tennessee  and  Alabama. 


Fig.  1482. 


THE   MOLLUSCA 


997 


III  (112)     Surface  pustulose;   no  radial  furrow  above   the  posterior  ridge; 
unicolored  or  rayed,  never  painted  as  in  Quadnda  s.s. 

Section  Theliderma  Swainson. 

This  section  comprises  three  well-marked  groups:  first,  that  of  the  typical  species,  Quadrula 
lachrymosa  Lea  (Fig.  1483),  having  a  quadrate  or  rhomboid  shell  with  a  wide,  shallow  radial 
furrow  in  front  of  the  posterior  ridge;  second,  that  of  Q.  piislulosa  Lea,  with  a  rounded,  quad- 
rate shell  with  no  radial  furrow;  third,  two  small  species  from  Georgia  and  Florida,  rounded- 
rhomboid  in  shape,  without  the  furrow  and  with  the  surface  covered  with  zigzag  corrugations. 
Most  of  the  species  are  found  only  in  the  Southern  States,  but  the  first  two  groups  have  repre- 
sentatives ranging  north  to  Michigan  and  Minnesota. 


Fig.  1483. 


112(109)     Surface  smooth StciionFiisconaia  Simpson. 


While  the  majority  of  the  species  of  this 
section  are  found  in  the  Southern  States,  it  is 
well  represented  as  far  north  as  Michigan  and 
the  upper  Mississippi.  Type,  Quadrula  un- 
data  Bar.  (Fig.  1484)- 


Fig.  1484. 


998 


FRESH-WATER   BIOLOGY 


113  (114)  All  four  gills  serving  as  marsupia.  Shell  large,  solid,  rhomboid, 
truncated  posteriorly  in  the  male,  elongated,  with  a  strong 
posterior  ridge,  sexes  dissimilar  in  shape,  the  posterior  region 
being  rounded  and  subcompressed  in  the  female;  hinge  com-  ^| 
plete;  surface  pustulose,  except  on  the  extended  portion  of 
the  female Tritigonia  Agassiz. 

The  type,  T.  tuber culata  Bar .  (Fig.  1485;  X  i),  is  very  common  in  the  Mississippi  drainage  and 
in  the  Southern  States  from  Alabama  to  Texas. 


Fig.  1485. 


THE  MOLLUSCA 


999 


114  (115)  Outer  gills  only  serving  as  marsupia.  Shell  rounded;  beaks  sculp- 
tured with  numerous  line  irregular  corrugations;  hinge  com- 
plete; nacre  violet Rotundaria  RatVncsque. 

The  type,  R.  luberculata  Raf.  (Fig.  i486),  ranges  from  southern  Michigan  through  the  Ohio 
Tennessee,  and  Mississippi  systems,  south  to  Texas.  Another  species  ranges  from  Kentucky 
and  Tennessee  to  Iowa. 


Fig.  i486. 


115  (117) 


Outer  gills  only  serving  as  marsupia.  Shell  alike  in  both  sexes; 
triangular  to  rhomboid,  usually  with  a  prominent  umbonal 
region;  beaks  at  or  near  the  anterior  end;  beak  cavities  shal- 
low; hinge  complete;  surface  smooth,  brown  to  yellow, 
usually  not  very  dark,  frequently  rayed. 

Pleurobema  Rafmesque   .    .     116 


This  is  a  large  group,  of  which 
more  than  seventy  species  are 
known.  With  the  exception  of  a 
few  species  found  in  the  Ohio  and 
Mississippi  drainage,  it  is  confined 
to  the  streams  of  the  Southeastern 
States  from  Tennessee  and  Georgia 
to  the  Mississippi.  The  shells  of 
this  genus  are  easily  distinguished 
from  the  Quadrulac,  which  they 
often  resemble  by  the  uniformly 
shallow  beak  cavities.  Type,  P. 
cldva  Lam.  (Fig.  1487). 


Fig.  1487. 


ICX)0 


FRESH-WATER   BIOLOGY 


ii6  Shell  large,  irregularly  oval,  inflated;  surface  with  a  number  of 

large,  scattered  tubercles.  .    .     Section  Plethohasus  Simpson. 

This  section  contains  only  two  species,  inhabiting  the  Ohio  and  Tennessee  drainage  areas. 
The  type,  Pleurobema  aesophus  Green  (Fig.  1488;  X  i),  extends  west  into  Missouri  and  Minnesota. 


Fig.  1488. 


117  (108)     Outer  gills  only  serving  as  marsupia.     Shell  alike  in  both  sexes; 

ovate  to  elongate,  rounded  in  front,  pointed  or  biangulate 
behind;  beaks  nearer  to  the  middle  than  to  the  anterior  end; 
hinge  complete;  surface  usually  smooth,  dark  brown  to  black, 
often  indistinctly  rayed Z^^;z/o  Retzius  .    .     118 

118  (119,  120)     Shell  elongated,  rhomboid  or  oval,  more  or  less  biangulated 

behind;  surface  smooth  or  feebly  corrugated;  beak  sculpture 
consisting  of  a  few  rather  strong  ridges,  which  are  nearly 
parallel  to  the  growth  lines  or  slightly  double-looped. 

Section  Elliptio  Rafinesque. 

The  typical  section  of  this  genus  is  restricted  to  the  Old  World.  The  section  Elliptio  is  the 
largest  group  of  Unionidae  represented  in  our  fauna.  More  than  ninety  species  are  recognized. 
The  metropoHs  of  the  genus  is  in  the  Southeastern  States,  but  representatives  are  found  in  all 
of  the  Eastern,  Southern,  and  Central  States.      Type,  Unio  crassidens  Lam.  (Fig.  1489;  X  5). 


Fig.  1489. 


THE   MOLLUSCA  lOOl 

119  (118,  120)     Shell  spinose Section  Canlhyria  Swainson 


The  typical  and  only  species, 
Unio  spinosus  Lea  (Fif,'.  141^0; 
X  3 ),  is  confined  to  the  Altamaha 
River,  (JeorKia,  and  is  one  of  the 
most  remarkable  Unios  known. 
In  the  extraordinary  develop- 
ment of  the  spines,  it  is  unique. 


Fig.  1490. 

120  (ii8,  119)     Shell  smooth;  beaks  sculptured  with  concentric  ridges. 

Section  Uniomcrus  Conrad. 


The  typical  species,  Unio  tclralasmus 
Say  (Fig.  1491;  Xj),  has  a  wide  range 
from  Ohio  south  to  Alabama  and  Texas. 
A  few  other  species  are  found  in  Georgia 
and  Florida. 


Fig.  1491. 

121  (107,  140)     Marsupium  formed  by  the  entire  outer  gills,  distending  trans- 

versely, when  charged;  water  tubes  in  the  gravid  female 
divided  longitudinally  into  three  tubes,  of  which  only  the 
center  one  is  used  as  an  ovisac.  Hinge  rarely  complete,  the 
laterals  or  both  the  pseudocardinals  and  laterals  being  often 
entirely  wanting;  sexual  differences  in  the  shell  very  rarely 

present Subfamily  Anodontixae   .    .     122 

Eleven  genera:  122,  123,  124,  125,  126,  127,  128,  129,  130,  134,  139. 

122  (123)     Hinge  with  lateral  teeth  wanting  and  only  rudimentary  pseudo- 

cardinals;  beak  sculpture  consisting  of  a  few  strong,  con- 
centric ridges.  Ovisac  of  each  water  tube  subdivided  into 
a  number  of  compartments  running  crosswise  to  the  gill. 

Strophitus  Ratinesque. 


Only  a  few  species  are  known,  most 
of  them  coming  from  the  Southeast- 
ern States.  The  species  figured,  S. 
cdcntulus  Say  (Fig.  1402;  Xi),  has  a 
wide  range  from  New  England  to 
North  Carolina  and  west  to  Minne- 
sota and  Tennessee. 


Fig.  1492. 


I002 


FRESH-WATER  BIOLOGY 


123  (124)  Shell  thin;  hinge  edentulous;  beak  sculpture  consisting  of  several 
more  or  less  doubly-looped  parallel  ridges,  often  slightly  nod- 
ulous on  the  loops Anodonta  Lamarck. 

This  genus  is  the  only  one  of  the  North  American  Naiades  that  has  a  general  distribution 
from  the  Atlantic  to  the  Pacific.  Numerous  species  are  recognized.  They  are  easily  distin- 
guished by  the  edentulous  hinge  and  double  loop  of  the  beak  sculpture.  Example,  A .  grandis 
Say  (Fig.  1493;  X5). 


Fig.  1493. 

124  (125)  Shell  smooth,  elongated,  rather  thin,  inequilateral,  compressed; 
epidermis  shining,  often  rayed;  a  single,  imperfect  pseudo- 
cardinal  in  each  valve  and  sometimes  vestiges  of  laterals. 

Lastena  Rafinesque. 


Only  a  single  species  is 
known,  L.  lata  Raf.  (Fig. 
1494;  X  1),  and  is  found  in  the 
Ohio,  Cumberland,  and  Ten- 
nessee river  systems. 


Fig. 1494. 

125  (126)  Shell  smooth,  elongated,  subtriangular,  with  usually  a  high,  sharp 
posterior  ridge;  hinge  with  a  rudimentary  pseudocardinal 
and  lateral  in  each  valve Gonidea  Conrad. 


This  genus,  represented 
by  a  single  species,  G.  ati- 
gw/a/a  Lea  (Fig.  1495;  x|), 
as  usually  found,  is  remark- 
able for  the  sharp  posterior 
ridge  and  more  or  less 
flattened  posterior  region. 
It  is  a  characteristic  west 
coast  species  and  ranges 
from  central  California 
north  to  British  Columbia, 
and  east  to  Idaho. 


Fig.  1495. 


THE   MOLLUSCA 


lOO 


126  (127)     Shell  smooth,  elliptical;  hinge  edentulous;  beak  sculpture  consisting 
of  a  few  fine,  concentric  ridges.    .    .     Anodontoides  Simpson. 


The  type,  A.  ferussaciana 
Lea  (Fig.  1496;  x  1),  is  of 
general  distribution  in  the  St. 
Lawrence,  Ohio,  and  Mis- 
sissippi drainage  areas.  The 
concentric  undulations  of  the 
beaks  are  characteristic. 


Fig  1496. 


127  (128)  Shell  small,  solid,  thick  in  front,  with  two  radial  ridges  extending 
from  the  beaks  to  the  biangulated  posterior  end.  Pseudo- 
cardinals  solid;  laterals  wanting Pegias  Simpson. 


A  single  species,  P.fahula  Lea  (Fig.  1497),  from  the  Cum- 
berland and  Tennessee  river  systems,  is  the  only  one  known. 


Fig.  1497 


128  (129)  Shell  large,  inflated,  subrhomboidal,  with  two  radiating  rows  of 
knobs;  beak  sculpture  coarse,  continuous  with  that  of  the 
surface  which  consists  of  oblique  folds  and  wrinkles;  pseudo- 
cardinals  large;  laterals  short  and  blurred. 

Arcidens  Simpson. 

The  typical  and  only  species,  ^ .  confragosa  Say  (Fig.  1498;  X  j).  is  common  throughout  the 
Ohio  and  Mississippi  drainage  systems  and  southwest  to  Texas. 


Fig.  1498. 


I004 


FRESH-WATER   BIOLOGY 


129  (130)  Shell  large,  solid,  inflated,  subrotund;  beak  sculpture  weak,  not 
continuous  with  the  surface  sculpture,  which  consists  of 
oblique  folds;  hinge  strong  and  complete. 

Arkansia  Ortmann  and  Walker. 

The  t5T5e  and  only  species  known.  A.  wheeleri  O.  and  W.  (Fig.  1499;  XI),  has  recently  been 
discovered  in  the  Old  River,  Arkadelphia,  Ark. 


Fig.  1499. 

130  (134)     Shell  eUiptic-rhomboid,  compressed ;  pseudocardinals  well  developed; 
laterals  more  or  less  imperfect  or  subobsolete. 

Symphynota  Lea  .    .      131 


131  (132, 133)     Shell  smooth,  shining,  rayed;  teeth  delicate;  laterals  moderately 
developed Subgenus  Symphynota  s.s. 

The  type,  S.compressa  Lea  (Fig.  1 500;  X  t),  is  one  of  the  common  species  of  the  Northern  States, 
ranging  from  New  York  west  to  Nebraska  and  south  to  Arkansas.  Several  other  species  are 
found  in  the  Atlantic  drainage  from  New  York  to  South  CaroUna  and  in  eastern  Tennessee  and 
northern  Alabama. 


Fig.  1500. 


THE  MOLLUSCA 


lOO: 


132  (131,  133)     Shell  subrhomboid,  compressed,  posterior  slope  corrugated; 
lateral  teeth  subobsolete.     Subgenus  Lasmigona  Rafinesque. 

The  type  and  only  species,  Symphynota  costata  Raf.  (Fig,  1501;  X  i),  is  common  in  the  St. 
Lawrence  and  Mississippi  drainage  systems. 


133  (131,  132)     Shell  large,  ovate-rhomboid,  subcompressed,  smooth;  hinge 
very  heavy;  lateral  teeth  imperfectly  developed. 

Subgenus  Pterosygna  Rafinesque. 

Only  one  species,  Symphynota  complanata  Bar.   (Fig.   1502;  Xi),  which  has  a  wide  range 
from  the  Great  Lakes  and  the  upper  Mississippi  south  into  Alabama  and  Arkansas. 


Fig.  1502 


134  (139)     Shell  rhomboidal,  inflated,  with  a  wcll-dcvclopcd  posterior  ndge; 
pseudocardinals    well    developed;    laterals    subobsolete    or 

wanting Alasmidonta  Say   .    .     13 5 

Four  subgenera:  135,  136,  137,  138. 


ioo6 


FRESH-WATER   BIOLOGY 


135  (136) 


Shell  ovate-rhomboid,  solid,  inflated;  beak  sculpture  very  coarse 
and  heavy;  pseudocardinals  large,  solid;  laterals  very  im- 
perfect or  wanting Subgenus  Alasmidonta  s.s. 


The  type  and  only  species,  A.  undulata 
Say  (Fig.  1503;  X  1),  is  a  characteristic  shell 
of  the  Atlantic  states  south  to  North  Caro- 
lina, but  is  not  found  west  of  central  New 
York. 


Fig.  1503. 


136  (137)     Shell  small,  decidedly  rhomboid;  beak  sculpture  sUghtly  corrugated; 
teeth  compressed Subgenus  Pressodon  Simpson. 

The  typical  species,  Alasmidonta  calceola  Lea  (Fig.  1504), 
has  a  wide  distribution  through  the  Northern  States  from  the 
Mississippi  eastward.  Several  other  species  occur  in  the 
Atlantic  and  Southeastern  States.  One  species,  A .  collina 
Con.,  is  remarkable  for  having  one  or  more  small  spines 
near  the  center  of  each  valve. 

Fig.  1504. 


137  (138)     Shell  elongated,  rhomboid,  inflated,  posterior  slope  sHghtly  corru- 
gated; pseudocardinals  imperfect;  laterals  wanting. 

Subgenus  Rugifera  Simpson. 

The  type,  Alasmidonta  marginata  Say  (Fig.  1505),  ranges  from  New  York  and  South  Caro- 
lina west  to  the  Mississippi  Valley.  Another  species  is  found  only  in  the  Tennessee  and  Cum- 
berland river  systems. 


Fig.  1505. 


THE   MOLLUSCA 


1007 


138  (135)  Shell  thin,  triangular,  greatly  inllated,  with  a  high,  sharp  posterior 
ridge;  pseudocardinals  compressed,  reflcxed;  laterals  want- 
ing  Subgenus  Bidlclla  Simpson. 

This  group  is  composed  of  two  very  peculiar  species  found  only  in  South  Carolina  and  Georgia. 
Type,  Alasmidonta  arcula  Lea  (Fig.  1506;  X  S). 


139  (122) 


I'lG.   1506. 


Shell  small,  thin,  elongate-elliptical;  beak  sculpture  consisting  of 
fine  parallel  ridges,  looped  up  in  the  middle;  a  high,  irregular, 
compressed  pseudocardinal  in  each  valve;  laterals  nearly 
or  quite  lacking Hemilastena  Agassiz. 


The  type  and  only  species,  H.  ambigna  Say 
(Fig.  1507),  occurs  in  the  Ohio  river  system, 


1  the  Ohio  river  system, 
rangmg  norm  to  i\Iichigan,  west  to  Iowa, 
south  to  Arkansas,  and  east  to  Tennessee. 


Fig.  1507. 


140  (107,  121)  Marsupium  formed  from  the  outer  gill  alone  and  usually  from 
the  posterior  portion  only;  edge  of  marsupium,  when  charged, 
distending  and  bulging  out  beyond  the  original  edge  of  the 
gill;  water  tubes  simple  in  the  gravid  female.  Hinge  com- 
plete; male  and  female  shells  usually  quite  different. 

Subfamily  Lampsilinae   .    .     141 
Twelve  genera:  141,  146,  151,  152,  iS3.  is6,  i59.  i6o,  161,  162,  163,  164. 


ioo8 


FRESH-WATER   BIOLOGY 


141  (146)  Male  and  female  shells  different;  female  shell  with  a  decided  infla- 
tion in  the  post-basal  region,  which  is  thinner  than  the  rest 
of  the  shell,  of  different  texture,  often  toothed,  and  usually 
radiately  sculptured;  hinge  complete;  marsupium  occupying 
the  posterior  part  of  the  gill  only. 

Truncilla  Rafinesque  .   .     142 
Four  subgenera:  142,  143,  144,  i45- 


142  (143)     Male  shell  smooth,  no  radial  groove  in  front  of  the  posterior  ridge. 
Female  with  a  high  posterior  ridge,  posterior  slope  flattened. 

Subgenus  Truncilla  s.s. 

The  type,  T.  triquetra  Raf.  (Fig.  1508),  occurs  from  western  New  York  to  Nebraska  and  south 
to  Kansas  and  northern  Alabama.     Five  other  species  are  found  in  Tennessee  and  Alabama. 


Fig.  1S08. 


143  (144)  Male  shell  with  a  wide,  radiating,  shallow  depression  in  front  of  the 
posterior  ridge.  Female  with  a  small,  rounded,  well-defined 
radial  post-basal  swelling.   .    .   Subgenus  Scalenaria  Agassiz. 

The  type,  Truncilla  sulcata  Lea  (Fig.  1509),  ranges  from   the   Tennessee  River  north  to 
southern  Michigan.    Two  other  species  occur  in  Tennessee  and  Georgia. 


Fig.  1509. 


THE   MOLLUSCA 


1009 


144  (145)  Male  shell  with  a  posterior  and  central  radiating  ridge  with  a 
furrow  between.  Female  with  a  greatly  produced  inflation 
a  little  behind  the  center  of  the  base. 

Subgenus  Dysnoynia  Agassiz. 

This  is  one  of  the  most  remarkable  groups  of  the  genus  and  is  represented  by  three  species 
from  the  Ohio,  Cumberland,  and  Tennessee  rivers.  Type,  Truncitla  Joliata  Hild.  (Fig.  15 10; 
X  h)' 


Fig.  1510. 


145  (142)  Male  shell  with  a  wide,  shallow,  radiating  depression  in  front  of 
the  posterior  ridge.  Female  with  a  rounded,  fohaceous 
swelling  at  the  posterior  base.    .    .    Subgenus  Pilea  Simpson. 

Eight  species,  found  mostly  in  the  Tennessee  drainage,  but  ranging  north  to  southern  Michigan 
and  west  to  Arkansas.     Type,  Truncilla  personata  Lea  (Fig.  151 1). 


Fig.  151 


146  (151)  Male  and  female  shell  different.  Shell  ovate  to  elliptical,  smooth; 
hinge  complete.  Female  shell  more  or  less  expanded  in 
the  post-basal  region,  but  the  expansion  docs  not  differ  in 
texture  from  the  rest  of  the  shell.  Marsupium  occupying 
the  posterior  part  of  the  outer  gill. 

Lampsilis  Rafinesque   .    .      147 


lOIO 


FRESH-WATER   BIOLOGY 


147  (150)     Beak  sculpture  consisting  of  coarse  parallel' ridges,  scarcely  looped 
or  fine  and  doubly  looped. 

Subgenus  Lampsilis  s.s.    .    .      148 


148  (149)  Shell  often  very  large,  usually  rather  thin,  inflated,  shining,  fre- 
quently rayed.  Beak  sculpture  consisting  of  coarse  parallel 
ridges,  scarcely  looped Section  Lampsilis  s.s. 

This  group  includes  some  of  the  largest  of  the  Unionidae.     Found  in  all  of  the  Eastern  States 
from  New  England  to  Georgia  and  west  to  Arkansas.     Type,  L.  ovata  Say  (Fig.  1512;  X  I). 


Fig.  1512. 


THE    MOLLUSC  A 


Toil 


149  (148)     Shell  oval  to  oblong;    beak  sculpture  consisting   of   fine,   doubly 
looped  ridges Section  Eurynia  Rafinesque. 

This  group  has  many  species  and  is  of  general  distribution  from  Manitoba  to  Texas  and 
eastward.     Type,  Lampsilis  recta  Lam.  (Fig.  151,^;  X  2). 


Fig.  1513. 


150  (147)  Shell  small,  inflated,  oval  to  obovate;  male  usually  more  or  less 
pointed  posteriorly;  female  truncated  obliquely  on  the  post- 
base;  beak  sculpture  consisting  of  rather  strong  concentric 
ridges Subgenus  CarimciiUna  Simpson. 

A  well-marked  group  of  small,  dark-colored  species  easily  distinguished  by  the  pecuHar  beak 
sculpture.  Most  of  the  species  are  confined  to  the  Southern  States  from  Georgia  to  Texa.s,  but 
two  or  three  range  north  to  Illinois  and  southern  Michigan.  Type,  Lampsilis  tcxasensis  Lea 
(Fig.  i5i4;Xl). 


Fig.  15 14. 


IOI2 


FRESH-WATER   BIOLOGY 


151  (152)  Male  and  female  shells  alike.  Whole  outer  gill  serving  as  marsu- 
pium,  its  edge  thrown  into  a  number  of  folds.  Shell  elon- 
gate-triangular, solid  and  thick;  hinge  complete;  hinge  plate 
wide  and  flat Ptychohranchus  Simpson. 

The  typical  species,  P.phaseolus  Hild.  (Fig.  1515;  X  I),  is  common,  ranging  from  Michigan 
south  to  Alabama  and  Louisiana.  Five  other  species  are  known,  four  in  Alabama  and  one  in 
Arkansas. 


Fig.  1515. 

152  (153)  Male  and  female  shells  alike.  Marsupium  occupying  nearly  the 
whole  of  the  outer  gill  and,  when  fully  developed,  folded. 
Shell  solid,  round- triangular;  hinge  complete;  hinge  plate 
wide  and  flat;  surface  sculptured  by  irregular  ridges  and 
humps,  painted  with  undulating,  radiating,  broken  hair- 
Unes  or  maculations Dromus  Simpson. 

Only  two  species  are  known,  both  from  the  Tennessee  and  Cumberland  river  systems.    Type, 
D.  dramas  Lea  (Fig.  1516;  Xs). 


Fig. 1516. 


153  (156)  Male  and  female  shells  different,  the  latter  being  slightly  inflated 
in  the  post-basal  region.  Shell  short  oval,  rounded,  or  retuse. 
Marsupium  occupying  the  posterior  portion  of  the  outer 
gills  and  projecting  far  below  the  rest  of  the  branchiae, 
dolabriform  or  kidney-shaped.    ObovariaRa,^esq\ie  .    .    154 


THE   MOLLUSCA 


1013 


154  (155)     Shell  retrorse  to  short  oval;  beaks  high  and  central. 

Subgenus  Obovaria  s.s. 

A  small  group  of  species  mostly  found  in  the  Southern  States  from  Alabama  to  Arkansas. 
The  type,  O.  retusa  Lam.  (Fig.  15 17),  occurs  in  the  Ohio,  Tennessee,  and  Cumberland  systems, 
and  another  species  ranges  north  to  southern  Michigan. 


Fig. 1517. 


155  (154)     Shell  elliptical;  beaks  anterior. 


Subgenus  Pseudoon  Simpson. 


Two  species  only.  The  tyY>e,  Ohovaria  ellipsis  Lea  (Fig.  1518;  X  i),  ranges  from  the  upper 
Mississippi  and  lower  Great  Lakes  south  to  Tennessee  and  Arkansas.  The  other  is  found  from 
Arkansas  to  Louisiana  and  east  to  Alabama. 


^^.. 


^^ 


Fig.  1518. 


156  (159)  Male  and  female  shells  different,  the  latter  being  more  or  less 
inflated  in  the  post-basal  region.  Shell  triangular  ovate, 
with  a  distinct,  often  sharp  posterior  ridge;  hinge  complete. 
Marsupium  kidney -shaped,  occupying  the  posterior  portion 
of  the  outer  gills,  but  not  extending  quite  to  the  hinder  end. 

Plagiola  Agassiz   .   .      157 


I 


idi4 


FRESH-WATER   BIOLOGY 


157  (158)     Hinge  heavy  and  strong;  hinge  plate  wide  and  flat. 

Subgenus  Plagiola  s.s. 

The  type  and  only  species,  P.  securis  Lea  (Fig.  1519;  X  h),  occurs  abundantly  in  the  Ohio  and 
Mississippi  systems  and  south  to  Alabama. 


Fig.  I sic 

58  (157)     Hinge  delicate;  hinge  plate  narrow. 

Subgenus  Amygdalonaias  Crosse  and  Fischer. 


A  group  of  only  three  species  character- 
ized by  the  sharp  posterior  ridge  and  arrow- 
shaped  pattern  of  the  epidermis.  Two  of 
them  occupy  the  Mississippi  drainage,  ex- 
tending into  southern  Michigan  and  south  to 
Alabama  and  Texas.  The  third  is  pecuHar 
to  Texas.  Example,  Plagiola  elegans  Lea 
(Fig.  1520;  XI). 


Fig.  1520. 

159  (160)     Male  and  female  shells  alike;  oval-solid,  inflated,  with  a  row  of 

large  knobs  running  from  the  beaks  to  the  center  of  the 

base;  hinge  complete.     Marsupium  consisting  of  a  few  dis- 

^  tinctly  marked  ovisacs  situated  just  behind  the  center  of  the 

'  outer  gill  and  projecting  far  below  the  rest  of  the  branchiae. 

Obliquaria  Rafinesque. 


The  typical  and  only  species,  0.  reflexa 
Raf.  (Fig.  152 1 ),  ranges  from  Michigan 
south  to  Alabama  and  Texas. 


Fig.  1521. 


THE   MOLLUSCA 


lOl 


i6o  (i6i)  Male  and  female  shells  alike ;  very  thick  and  solid,  inflated,  rounded- 
triangular;  surface  nodular,  radiately  wrinkled,  or  lachry- 
nious;  epidermis  painted  with  delicate  green  mottling  on  a 
light  ground.  Marsupium  consisting  of  several  long  purple 
ovisacs  pendent  from  near  the  central  base  of  the  outer 
gills  and  formed  into  a  close  coil  with  the  ends  turned  inward. 

Cy progenia  Agassiz. 

The  typical  species,  C.  irrorata  Lea  (Fig.  1522),  is  common  in  the  Ohio,  Cumberland,  and 
Tennessee  river  systems.  One  other  species  occurs  in  the  states  west  of  the  Mississippi,  from 
Missouri  to  Oklahoma. 


Fic.  1522. 


161  (162)  Male  and  female  shells  different,  that  of  the  latter  being  slightly 
swollen  behind  the  middle  of  the  base.  Shell  rather  small, 
elongated,  dorsal  slope  plicately  or  nodulously  wrinkled; 
hinge  complete.  Marsupium  occupying  the  central  portion 
of  the  outer  gill Mai  ion  id  us  Simpson. 

A  small  group  of  species  characterized  by  their  elongate  shape  and  plicate  dorsal  slope.  It 
is  restricted  to  the  waters  of  Tennessee,  Alabama,  Georgia,  and  Florida.  Type,  M.  conradicus 
Lea  (Fig.  1523)- 


Fig.  1523. 


ioi6 


FRESH-WATER   BIOLOGY 


162  (163)  Male  and  female  shells  much  alike,  but  the  latter  is  usually  some- 
what inflated  in  the  post-basal  region.  Shell  large,  ovate, 
usually  rather  thin,  but  in  some  species  quite  solid,  gaping 
at  the  anterior  edge  and  on  the  dorsal  slope ;  normally  winged 
on  the  dorsal  slope,  but  the  wing  is  often  lost  in  the  adult; 
hinge  complete.  Marsupium  occupying  the  posterior  portion 
of  the  outer  gills.  Glochidia  celt-shaped,  with  two  spines  on 
each  valve  and  with  gaping  margins  .  .  Pro/>/em  Rafinesque. 
This  group  is  well  characterized  by  the  large,  usually  thin  shell,  which  is  more  or  less  alate  in 

the  dorsal  region.     It  occurs  throughout  the  St.  Lawrence  and  Mississippi  systems  and  extends 

south  to  Texas  and  Alabama.     Type,  P.  data  Say  (Fig.  1524;  X  i). 


Fig.  1524. 


THE   MOLLUSCA 


1017 


163  (164)  Male  and  female  shells  not  greatly  different,  the  latter  being  some- 
what more  inflated  and  expanded  in  the  post-basal  region. 
Shell  thin,  rather  compressed,  and  winged  on  the  dorsal 
slope;  hinge  complete,  but  the  pseudocardinals  are  reduced 
to  mere  tubercles  often  nearly  wanting.  Marsupium  as 
in  Froptera.  Glochidia  semicircular,  very  small,  without 
spines Paraptera  Ortmann. 

This  genus  in  shell  characters  is  very  like  the  preceding,  but  has  been  separated  on  account 
of  the  great  difference  in  the  shape  of  the  glochidia.  The  type,  and  only  species  yet  known  to 
belong  to  it,  P.  gracilis  Bar.  (Fig.  1525;  X  |),  has  a  wide  range  from  the  Great  Lakes  south  to 
Alabama  and  west  to  the  Mississippi  Valley. 


164  (141)  Male  and  female  shells  different,  the  latter  being  swollen  in  the 
post-basal  region.  Marsupial  characters  unknown.  Shell 
short-elliptical,  solid,  much  inflated;  pseudocardinals  divided 
into  irregularly  radiating,  granular  laminae;  hinge  plate 
reduced  to  a  mere  rounded  line  behind  the  pseudocardinals. 

Glchuld  Conrad. 

The  type  and  only  species,  G.  rotundata  Lam.  (Fig.  1526;  X  h),  ranges  from  Florida  to  eastern 
Texas.  Conchologically  very  distinct  by  reason  of  its  peculiar  hinge,  little  is  known  of  its 
anatomical  characters  and  further  information  is  greatly  to  be  desired,  especially  in  regard  to 
the  gravid  female. 


iiJ'V 


Fig.  1526. 


ioi8 


FRESH-WATER   BIOLOGY 


165  (104)     Interior  of  shell  non-nacreous  or  porcellanous,  or  the  whole  shell 

of  a  prevailing  prismatic  substance 166 

Five  families:  166,  167,  168,  173,  i74- 

166  (167)     Shell  of  a  prevailing  prismatic  substance,   mytiliform,  very  in- 

equilateral; beaks  compressed,  terminal;  Ugament  subinter- 
nal;  anterior  adductor  and  pedal  protractor  muscles  inserted 
on  a  septum  in  the  beak.     Byssiferous. 

Family  Dreissensiidae. 
Only  one  genus Congeria  Partsch. 


Represented  in  our  fauna  by  two  species.  Example,  C. 
leucophaeata  Con.  (Fig.  1527;  X  2),  found  on  the  Atlantic 
coast  from  Maryland  to  Florida. 


Fig.  1527. 


167  (168)  Shell  porcellanous,  subtrigonal,  thick,  and  solid;  ligament  external; 
hinge  with  true  cardinal  teeth  and  with  both  anterior  and 
posterior  laterals;  pallial  line  with  a  distinct  sinus. 

Family  Cyrenidae. 
Only  a  single  genus Cyrena  Lamarck. 


Represented  in  our  fresh-water  fauna  by  a  single  species,  C. 
carolinensis  Bosc  (Fig.  1528),  found  in  streams  and  brackish  water 
near  the  coast  from  South  Carolina  to  Texas. 


Fig.  1528. 

168  (173)     Shell  non-nacreous,  usually  small  and  thin;  hinge  with  cardinal  and 

both  anterior  and  posterior  lateral  teeth;  no  hinge  plate; 
pallial  Hne  simple.     .    .    .     Family  Sphaeriidae    .    .     169 
Four  genera:  169,  170,  171,  172. 

169  (170)     Shell  oval,  equilateral;  beaks  nearly  subcentral;  nepeonic  valves 

not  distinctly  separated  from  the  subsequent  growth  of  the 
shell;  cardinal  teeth  two  in  each  valve.   .  Sphaerium  ^co^oM. 


This  group  contains  the  largest  species  of  the 
family  and  is  easily  distinguished  from  Musculium  by 
the  thicker,  striate  shell  and  noncalyculate  beaks. 
The  species  are  numerous  and  of  general  distribution. 
Example,  S.  simile  Say  (Fig.  1529;  X  if). 


Fig.  1529. 


THE   MOLLUSCA 


1019 


170  (171)  Shell  thin  and  delicate,  suborbicular  to  oblong;  beaks  prominent, 
usually  retaining  the  nepeonic  valves;  cardinal  teeth  minute^ 
often  obsolete;  anterior  and  posterior  laterals  present. 

Miisciiliiim  Link. 


This  group  has  a  general  distribution.  The  prominent  beaks  with 
the  distinctly  marlved  nepeonic  shell  are  the  distinctive  feature,  but  in 
some  species  these  are  lacking.  The  thin,  rounded,  polished  shell  is, 
however,  quite  characteristic.  Example,  M.  partumeium  Say  (Fig. 
i5oo;  X2). 


Fig.  1530. 


171  (172)     Shell  subrhomboidal,  thin,  moderately  inflated,  with  the  posterior 
side  longer;  cardinal  teeth  feeble,  only  one  in  each  valve. 

Eiipera  Bourguignat. 

A  tropical  group,  of  which  two  or  three  species  occur  in  Florida,  Ala- 
bama, and  Texas.  The  rhomboidal  shape  is  characteristic.  The  shells 
appear  to  be  mottled  and  are  usually  so  described,  but  according  to 
Dr.  W.  H.  Dall  these  "spots"  are  caused  by  a  parasitic  infusorian  that 
attacks  the  interior  of  the  shell.    Example,  E.  singleyi  Pils.  (Fig.  1531; 

X3). 
Fig.  1531. 


172  (169)  Shell  small,  rounded,  oval,  or  obliquely  cuneiform,  inequilateral, 
anterior  side  longer;  beaks  subterminal;  cardinal  teeth 
double  in  each  valve Pisidium  C.  Pfeiffer. 


The  Pisidia  are  of  general  distribution  and  a  great  number  of  species 
have  been  described.  They  are  easily  distinguished  from  the  allied 
genera  by  the  very  inequilateral  shell,  the  hinge  being  on  the  shorter 
side.     Example,  P.  virginicum  Bgt.  (Fig.  1532;  X  2). 


Fig. 1532. 


173  (174)  Shell  rounded,  inflated,  thin;  beaks  forward;  surface  smooth  or 
slightly  concentrically  sculptured;  cardinal  teeth,  two  in 
the  right  and  one  in  the  left  valve;  no  lateral  teeth. 

Family  Cyrenellid.\e. 
Only  one  genus Cyrcnclla  Deshayes. 


Represented  in  our  fauna  by  a  single  species,  C.  floridana  Dall  (Fig. 
1533;  X  1 5),  from  Florida.  It  is  easily  distinguished  by  the  lack  of  lateral 
teeth. 


Fig.  1533. 


I020  FRESH-WATER   BIOLOGY 

174  (166)  Shell  thick,  oval,  subtrigonal,  ventricose,  smooth;  beaks  prominent; 
ligament  inclosed  in  a  pit  and  invisible  externally;  hinge 
with  cardinal  and  both  anterior  and  posterior  lateral  teeth; 

pallial  line  sinuous Family  Rangiidae. 

Only  one  genus Rangia  Des  Moulins. 


The  typical  species,  R.  cuneata  Gray  (Fig.  1534; 
X  12),  is  found  in  great  abundance  in  the  brackish 
waters  of  the  Gulf  coast  from  Alabama  to  Mexico. 


Fig.  1534. 

IMPORTANT   PAPERS   ON   FRESH-WATER   MOLLUSCA. 

Baker,  F.  C.     1898.     The  Mollusca  of  the  Chicago  Area.     Part  I,  Pelecypoda. 
1902.     Part  II,  Gastropoda. 

191 1.  The  Lymnaeidae  of  North  and  Middle  America. 

BiNNEY,  W.  G.     1865.     Land  and  Fresh-water  Shells  of  North  America,  Part 

II.     Smithsonian  Misc.  CoU.,  v.  7,  No.  143,  172  pp.     Part  III,  No.  144, 

128  pp. 
Haldeman,  S.  S.     1842.     Monograph  of  the  Fresh-water  Univalve  Mollusca 

of  the  United  States.     Continued  by  G.  W.  Tyron,  Jr.,  1870. 
Ortmann,   a.   E.     191 1.     A   Monograph   of  the  Najades  of  Pennsylvania. 

Mem.  Carnegie  Mus.,  4  :  279-347. 

191 2.  Notes  upon  the  FamiHes  and  Genera  of  the  Najades.     Ann.  Car- 
negie Mus.,  8  :  222-364. 

Prime,  Temple.  1865.  Monograph  of  American  Corbiculidae.  Smithsonian 
Misc.  Coll.,  V.  7,  No.  145,  192  pp. 

Simpson,  C.  T.  19 14.  A  Descriptive  Catalogue  of  the  Naiades  or  Pearly  Fresh- 
water Mussels.     Printed  by  Bryant  Walker,  Detroit,  Mich.     1540  pp. 

Stimpson,  William.  1865.  Researches  upon  the  Hydrobiinae  and  Allied 
Forms.     Smithsonian  Misc.  Coll.,  v.  7,  No.  201,  64  pp. 

Tryon,  G.  W.,  Jr.  1873.  Land  and  Fresh-water  Shells  of  North  America. 
Part  IV,  Strepomatidae.     Smithsonian  Misc.  Coll.,  v.  16,  No.  253,  435  pp. 


CHAPTER   XXX 
THE    AQUATIC    VERTEBRATES 

By  C.  H.  EIGENMANN 

Professor  of  Zoology  in  Indiatta  University,  and  Curator  of  Fishes  in  the  Carnegie  Museum,  Pittsburgh,  Pa. 


INTRODUCTORY 

The  chief  object  in  the  life  of  any  animal  is  to  leave  another 
like  it  in  its  place  when  it  dies.  To  accomplish  this  object  it  must 
find  a  range  in  which  it  may  secure  its  food  and  itself  escape  be- 
coming food;  it  must  secure  a  mate  and  a  home  in  which  its  young 
may  be  reared  to  the  point  of  self-dependence.  The  world  con- 
tains a  great  variety  of  animals  adapted  to  all  possible  environ- 
ments. Either  the  greatly  diverse  characters  of  these  animals 
have  arisen  to  adapt  them  to  their  different  ranges  and  homes,  or 
the  greatly  diverse  environments  have  been  selected  because  they 
were  adapted  to  the  otherwise  and  elsewhere  acquired  characters 
of  different  animals.  Certainly  when  new  water  or  land  areas  arise 
the  latter  will  be  the  origin  of  its  adopted  fauna. 

The  vast  territory  containing  the  majority  of  the  innumerable 
lakes  and  streams  with  whose  fauna  and  flora  we  are  concerned, 
extending  from  the  Arctic  regions  south  to  the  region  of  the  Ohio 
River,  was  a  few  thousand  years  ago  covered  with  a  continuous 
sheet  of  ice.  The  fauna  and  flora  of  this  area  are  composed 
of  immigrants,  of  animals  and  plants  that  moved  in  as  the  ice 
moved  out  and  selected  the  places  adapted  to  their  requirements. 
While  no  doubt  many  of  them  have  become  modified  since  their 
advent  into  this  area,  there  can  be  no  doubt  that  their  fundamental 
adaptations  were  elsewhere  acquired  and  that  in  their  case  it  has 
been  a  selection  of  environments  to  suit  these  adaptations. 

Fresh  waters  may  be  and  are  used  first,  for  ranges;  second,  for 
homes;  or  third,  for  both  purposes  by  various  animals.  One  finds 
animals  which  breed  on  land  but  are  adapted  to  utilize  fresh  waters 


I02  2  FRESH-WATER   BIOLOGY 

daily  or  seasonally  for  ranges;  others  that  range  on  land  but  visit 
the  water  during  breeding  seasons  to  make  therein  their  homes  and 
to  enable  their  young  to  grow  up  in  it.  Still  other  animals  utiHze 
fresh  waters  both  as  a  range  and  a  home,  —  rarely,  or  never,  leave 
it  or  even  are  incapable  of  leaving  it.  Roughly  speaking,  mam- 
mals, birds,  and  reptiles,  in  so  far  as  they  are  aquatic,  belong  to 
the  first  of  this  ecological  group.  Batrachians  belong  to  the  sec- 
ond, a  few  batrachians  and  all  fishes  to  the  third. 

The  first  of  these  groups  is  composed  of  more  or  less  perfect 
readaptations  of  land  animals  to  water.  The  second  is  composed 
of  originally  aquatic  animals  as  yet  imperfectly  adapted  to  the 
land,  while  the  members  of  the  third  group  are,  and  at  all  times 
have  been,  the  aquatic  animals  par  excellence.  While  the  visitors 
or  inhabitants  of  fresh  water  may  be  sharply  distinguished  from 
the  non-aquatic,  the  relations  and  adaptations  of  aquatic  animals 
to  the  different  regions  of  the  water  are  very  diverse. 

Mammals 

The  aquatic  mammals  are  but  imperfectly  adjusted  to  some 
part  of  the  aquatic  habitat  and  confine  themselves  to  shallow 
water  and  the  shore.  None  of  them  could  five  in  an  enclosed  space 
filled  with  water.  The  number  of  truly  aquatic  mammals  is  small. 
Most  mammals  only  visit  the  water  to  drink.  Others,  as  the  moose, 
seek  the  water  to  browse  on  the  marginal  vegetation  or  to  escape 
enemies.  Others  less  inclined  to  enter  water  secure  part  of  their 
food  from  it.  The  raccoon  fishes  along  the  margins  of  streams 
for  crayfishes.  A  dexterous  tomcat,  proverbially  wary  of  wetting 
his  feet,  one  memorable  night  neatly  cleaned  out  two  aquaria,  one 
stocked  with  rare  blind  fishes  and  one  with  still  rarer  axolotls. 
None  of  the  above  dive. 

The  mink  secures  most  of  its  food  on  land  but  it  catches  both 
fishes  and  muskrats  in  the  water  into  which  it  does  not  hesitate 
to  dive  to  escape  an  enemy  or  to  secure  food. 

The  more  distinctly  aquatic  mammals  are  the  star-nosed  mole, 
the  muskrat,  the  beaver,  and  the  otter.  All  of  these  use  the  water 
as  a  range,  making  their  homes  in  very  close  proximity  to  the 
water  if  not  actually  in  it.     Of  these  the  otter  is  a  carnivore,  the 


THE   AQUATIC   VERTEBRATES  1023 

rest  plant  feeders,  though  sometimes  eating  animal  food.  They 
have  been  so  reduced  in  numbers,  —  in  some  places  entirely  exter- 
minated, —  that  they  have  become  almost  a  neghgible  part  of  the 
aquatic  vertebrate  fauna.  Only  the  muskrat  must  be  considered 
as  an  ecological  element  in  all  eastern  fresh  waters. 

The  muskrat  is  abundant  along  most  of  the  eastern  streams  and 
lakes.  It  is  a  shallow-water  animal  and  affects  its  environment  in 
a  specific  way.  It  builds  lodges  of  sod  and  cat-tail  stalks,  twigs 
and  vegetable  debris.  It  gathers  Hly  roots,  on  which  it  feeds,  but 
its  most  specific  action  is  on  various  mussels.  The  muskrat  lodge 
is  always  surrounded  by  shells  of  dead  bivalves,  and  at  Winona 
Lake  it  has  been  found  by  Headlee  that  the  muskrat  sets  a  bound- 
ary to  the  shoreward  migration  of  mussels  as  the  soft  bottom  of 
the  pelagic  area  sets  a  hmit  to  their  migration  toward  deep  water. 
The  activities  of  the  muskrat  are  more  restricted  in  winter  than  in 
summer,  but  they  do  not  hibernate. 

Beavers  have  disappeared  from  thickly-settled  regions.  They 
are,  in  some  of  their  habits,  larger  editions  of  the  muskrat.  They 
build  lodges  not  unhke  those  of  the  muskrat.  They  cut  and 
gather  twigs  and  stems  for  food  but  the  action  for  which  beavers 
are  conspicuous,  is  the  building  of  dams,  and  creating  of  ponds. 
They  thus  add  to  the  extent  of  the  aquatic  en\ironment. 

The  seal-Hke  otter  is  no  longer  a  part  of  the  aquatic  en\ironment 
in  well  settled  parts  of  America.  They  are  the  most  aquatic  of 
the  fresh-water  mammals.  As  swimmers,  they  are  more  expert  than 
fishes,  which  they  catch  and  eat.  They  also  prey  upon  muskrats 
and  aquatic  birds. 

Of  the  star-nosed  mole.  Stone  says:  "The  star-nosed  mole  is  a 
creature  almost  as  well  fitted  for  a  partially  aquatic  life  as  the 
otter  and  mink,  and,  as  a  matter  of  fact,  does  pass  most  of  its  time 
about  the  water;  pushing  extensive  tunnels  through  the  black, 
peaty  soil  of  swamps  and  along  the  borders  of  httle  brooks  and 
ponds.  The  soft,  black  loam  is  thrown  up  in  frequent  heaps  a 
foot,  more  or  less,  in  diameter;  the  opening  of  the  burrow  being 
under  the  bank,  and  as  often  beneath  the  water  as  above.  The 
tunnel  itself  must  frequently  be  flooded  to  the  great  discomfort 
of  its  inmates. 


I024  FRESH-WATER    BIOLOGY 

''But  the  old  ones  show  no  fear  of  the  water;  I  have  frequently 
seen  them  swimming  both  under  water  and  on  the  surface,  even 
where  the  current  was  pretty  strong,  and  have  always  observed 
them  to  be  perfectly  confident  and  unfrightened  at  such  times." 

Birds 

In  cold  and  temperate  regions  birds  are  seasonal,  robbing,  \isi- 
tors  of  the  water.  Only  one-fourth  to  one-fifth  of  our  entire  bird 
fauna  is  in  any  sense  aquatic.^ 

The  passerine  birds  are  dominant  now  and  of  this  group  none 
are  strictly  aquatic.  One  hundred  and  twenty-nine  of  the  215 
species  of  birds  of  Monroe  County,  Indiana,  are  passerine.  Of 
these  only  the  red-winged  blackbird,  the  six  species  of  swallows, 
the  water  thrushes,  and  the  long-billed  marsh  wren  are,  even  re- 
motely, related  to  the  water.  Taking  all  the  birds  that  range  in 
or  about  the  water  —  for  none  of  them  can  be  said  to  home  in  the 
water  —  one  finds  a  graduated  series,  from  those  more  to  those 
less  aquatic  in  their  habits.  More  than  this,  birds  show  the  most 
complete  series  of  adaptations  to  different  aquatic  zones. 

The  swallows  must,  by  courtesy,  be  mentioned  as  forming  the 
first  of  this  series  of  ecological  groups.  They  are  never  found 
upon  or  in  the  water,  but  skim  over  its  surface,  occasionally  just 
touching  it  in  their  search  for  food.  Mosquitoes  and  other  minute 
aquatic  insects  are  the  attraction  for  them  and  they  are,  therefore, 
very  definitely  related  to  the  aquatic  fauna.  They  remain  in  the 
latitude  of  the  Ohio  River  from  early  April  to  September. 

A  second  ecological  group  is  formed  by  the  kingfisher,  the  terns, 
gulls,  and  (for  fresh  waters  rarely)  the  pelicans.  The  kingfisher, 
from  his  perch  over  a  stream,  dives  into  the  water  beneath  him  for 
fishes.  He  is  largely  a  shore  fisher.  The  terns,  gulls,  and  pelicans 
dive  from  an  aerial  poise  into  the  pelagic  region  of  the  lake  and 
secure  fishes  near  the  surface.  The  terns  and  gulls  also  alight  to 
pick  the  refuse  floating  on  the  surface  for  they  are  scavengers  as 

^  Out  of  99  birds  observed  during  the  summer  about  one  of  the  northern  Indiana 
lakes,  19  are  more  or  less  related  to  the  water.  Out  of  215  birds  observed  at  all 
seasons  of  the  year  about  Bloomington,  Indiana,  55  are  related  to  the  water. 


THE   AQUATIC  VERTEBRATES  1025 

well  as  robbers.  The  kingfisher  is  a  poor  swimmer,  but  the  terns, 
gulls,  and  pelicans  rest  gracefully  on  the  surface.  In  the  latitude 
of  the  Ohio  the  kingfisher  is  found  between  early  March  and  No- 
vember, rarely  even  in  December.  The  terns  migrate  to  the 
northern  lakes  in  summer  and  the  pelicans  are  but  stray  visitors. 
The  terns,  gulls,  and  pelicans  have  certainly  acquired  the  adapta- 
tion to  the  water  at  the  ocean. 

The  third  ecological  group  is  formed  by  the  grebes  and  loons. 
They  are  pelagic  birds,  swimmers  par  excellence,  both  upon  the 
surface  and  in  the  water.  The  term  diving  ought  not  to  be  ap- 
plied to  the  performance  of  both  kingfisher  and  loon. 

The  fourth  ecological  group  is  formed  by  the  bottom-feeding 
ducks,  the  mudhen,  geese,  and  swans.  They  are  littoral  or  abys- 
mal forms  securing  their  food  in  the  mud  at  the  bottom,  largely 
about  the  margins  of  ponds  or  lakes  in  water  not  too  deep  to  pre- 
vent them  from  reaching  the  bottom  when  "tipping."  Many 
of  the  ducks  are  good  swimmers  under  water,  and  the  bay  and 
sea  ducks  are  said  to  reach  the  bottom  at  a  depth  of  100  to  150 
feet. 

The  fifth  ecological  group  is  formed  by  the  herons,  cranes,  and 
bitterns.  These  range  in  much  the  same  zone  as  most  of  the  ducks, 
but  their  food,  for  the  most  part,  is  different.  They  stalk  cau- 
tiously, without  jerk  or  sudden  motion,  or  stand  in  water  of  a 
depth  not  too  great  for  their  long  legs.  Their  spearlike  bill  im- 
pales fish  or  frog. 

The  sixth  and  last  of  the  ecological  groups  of  aquatic  forms  con- 
tains the  rails  and  snipes.  These  are  shore  birds,  wading  in  the 
shallowest  water  or  along  the  wet  shores,  frequently  moving  with 
the  advancing  and  retreating  waves,  picking  the  stranded  animals 
from  the  surface  or  probing  for  their  prey  in  the  soft  beaches. 

All  of  the  groups  except  the  first,  the  swallows,  nest  as  near  the 
water  as  possible.  Less  strictly  aquatic  are  the  swamp  black- 
bird and  long-tailed  marsh  wren  which  build  their  nests  in  cat  tails; 
Ukewise  the  song  and  marsh  sparrows,  so  abundant  along  margins 
of  stream  or  pond.  From  the  nature  of  the  case  the  waters  of 
northern  and  temperate  zones  are  a  closed  book  to  all  the  birds  in 
winter.    Hence,  birds  are  not  perennial  elements  of  the  aquatic 


I026  FRESH-WATER   BIOLOGY 

fauna.  Birds  derive  their  food  from  the  water.  The  few  that,  as 
carrion,  serve  as  food  for  other  aquatic  animals  or  that  may  be 
captured  by  fish,  otter,  or  alligator  are  a  negligible  quantity. 

Reptiles 

Reptiles,  like  mammals,  are  shallow-water  and  littoral  forms, 
largely  in  summer.  As  with  mammals,  a  gradual  gradation  is 
found  from  species  living  exclusively  on  land,  —  Hke  the  turtles  and 
snakes  of  the  Mojave  desert  or  the  land  tortoise  and  green  snakes 
of  the  Mississippi  valley,  —  through  those  which  do  not  ordinarily  go 
into  the  water  but  will  enter  it  without  hesitation  if  circumstances 
demand,  — like  the  black  snake  and  garter  snake,  —  to  such  as  the 
water  snakes,  leather  snakes,  geographic  turtle,  painted  turtle, 
and  snapping  turtle  that  bask  on  the  margins  of  lakes  and  streams 
but  take  to  the  water  for  food  or  at  the  slightest  sign  of  danger; 
and  lastly,  to  the  alhgators,  musk  turtles,  and  soft-shelled  turtles 
which  give  the  final  gradation  to  adaptations  for  Ufe  in  water.  Of 
these,  the  soft-shelled  turtle,  which  can  utilize  the  oxygen  dis- 
solved in  the  water,  has  probably  reached  the  highest  adjustment 
to  aquatic  existence.  But  no  hard  and  fast  line  can  be  drawn. 
The  habits  of  different  species  overlap  so  neatly  that  one  finds  a 
shading  from  reptiles  with  a  purely  aquatic  range  to  those  with  an 
entirely  terrestrial  range.  All  of  them  have  their  homes  on  land 
in  so  far  as  they  have  homes  at  all.  Some  secure  only  a  part, 
others  all  of  their  food  from  the  water.  Of  those  that  obtain  it 
from  the  water  some  feed  on  fishes  (purely  aquatic  food) ;  others 
like  the  alligators,  which  catch  water  birds,  utilize  the  water  to 
secure  terrestrial  visitors  in  part.  Others  may  seek  both  sorts 
of  food.  Snakes  take  to  the  margin  of  water  in  part  for  fishes, 
in  part  for  frogs,  etc. 

The  water  snakes  give  birth  to  living  young.  Since  the  young 
may  be  liberated  in  the  water  these  snakes,  in  one  sense,  are  the 
most  aquaric  of  the  reptiles.  But  since  they  cannot  utilize  the 
oxygen  in  the  water  the  soft-shelled  turtles  exceed  them  in  adap- 
tation to  an  aquatic  existence  in  this  respect.  All  the  turtles,  as 
well  as  the  alligators,  are  compelled  to  make  their  homes  or  nests  on 


THE   AQUATIC   VERTEBRATES  1027 

land.  The  soft-shelled  turtles  usually  lay  their  eggs  in  sandy  beaches, 
sometimes  in  harder  banks  near  the  water.  The  painted  turtles 
and  snapping  turtles  dig  holes  more  remote  from  the  water's  edge. 
The  musk  turtles  lay  their  eggs  in  muck,  in  decaying  stumps  or 
logs,  or  accumulations  of  decaying  weeds  on  the  margins  of  lakes. 

No  one  would  seriously  doubt  that  the  mammalian  and  rep- 
tilian faunas  of  fresh  waters  have  both  been  derived  from  terres- 
trial ancestors.  The  adjustment  to  water  conditions  consists  largely 
in  an  adaptation  of  the  limbs  and  tail  to  swimming  and  diving. 
Both  are  organs  primarily  used  for  land  progression.  Further 
adaptations  in  reptiles,  such  as  the  utilization  of  the  oxygen  in 
the  water  by  the  turtles,  are  much  more  rare,  and  found  only  in 
extreme  adaptations  to  an  aquatic  sojourn. 

The  paths  of  turtles  may  readily  be  seen  among  fields  of  Chara 
in  shallow  water.  A  painted,  geographic,  or  a  musk  turtle  may 
be  seen  basking  in  the  sun  on  the  surface,  the  neck  curved  up,  the 
nose  out  of  water.  If  disturbed  it  dives  into  the  Chara  and  soon 
disappears  in  one  of  its  innumerable  paths.  A  curious  commen- 
salism  is  reported  between  the  soft-shelled  turtle  and  the  black 
bass.  The  bass  is  said  to  follow  the  turtle,  which,  nosing  about 
under  rocks  and  in  crannies  scares  out  some  of  the  crayfishes  and 
other  denizens  of  such  places.  These  are  then  easily  captured  by 
the  attending  black  bass.  There  is  a  peculiar  correlation  between 
the  disposition  of  turtles  and  the  degree  of  their  armature.  The  soft- 
shelled  turtle  is  the  least  protected  by  bony  plates.  Next  in  order 
comes  the  snapping  turtle,  with  only  a  cross-shaped,  ventral  plate, 
most  of  the  ventral  surface  being  open  to  attack.  This  is  followed 
by  the  musk  turtle,  the  painted  and  the  geographic  turtle,  Bland- 
ing's  turtle  and  finally  the  box  turtle.  The  highest  degree  of  pro- 
tection is  found  in  the  terrestrial  box  turtle,  whose  plastron  is 
hinged  and  can  be  closed  in  front  and  behind.  Correlated  with 
the  defective  armature  in  the  soft-shelled  turtle  we  find  the  extreme 
of  pugnacity.  A  soft-shelled  turtle  will  snap  and  bite  on  suspicion 
from  the  time  it  is  half  way  out  of  its  shell.  The  disposition  of 
the  snapping  turtle,  with  exposed  ventral  surface,  is  proverbial. 
The  musk  turtle  will  bite,  as  anyone  who  has  collected  their  eggs 
can  testify.     On  the  other  hand,  the  well-protected  painted,  geo- 


I028  FRESH-WATER    BIOLOGY 

graphic,  and  Blanding's  turtles,  and  above  all,  the  terrestrial  and 
perfectly-armored  box  turtle,  are  the  gentlest  of  creatures  which  no 
amount  of  provocation  will  induce  to  bite.  Although  the  correla- 
tion between  armature  and  disposition  is  very  striking  there  may 
be  no  causal  relation  between  the  two.  The  character  of  the  food 
may  be  the  cause  of  the  disposition. 

Batrachians 

The  batrachians,  as  a  group,  are  aquatic  to  a  much  greater 
degree  than  the  mammals  or  reptiles.  In  North  America  they  are 
summer  and  especially  spring  members  of  the  aquatic  fauna. 
Some  of  them,  with  all  their  ancestry,  have  been  strictly  aquatic. 
They  are  autochthons,  products  of  evolution  in  fresh  water.  Such 
aquatic  forms  have  gills  and  a  tail  throughout  life.  The  Siren  and 
the  mud  puppy,  of  deadly  repute,  belong  to  this  group  and  so  does 
the  blind  salamander  of  Texas.  Whereas  in  the  reptiles  and  the 
mammals  gradations  from  pure  terrestrials  to  less  or  more  aquatics 
have  been  noted,  in  the  batrachians  one  finds  gradations  from  the 
purely  aquatic  to  the  more  or  less  terrestrial,  and  none  have  reached 
the  possibiKty  of  living  in  deserts  in  dry  places.  So  many  of  the 
batrachians  lay  their  eggs  in  water  that  those  that  do  not  are 
accounted  remarkable.  In  a  small  pond  near  Indiana  University, 
which  has  been  examined  at  all  seasons  of  the  year,  it  has  been 
found  that  a  salamander,  AmUy stoma  jefersonianum,  begins  to  lay 
as  soon  as  the  ice  disappears  after  December.  Sometimes  this 
happens  early  in  January  or  it  may  not  until  March.  After  the 
spawning  of  jeffersonianum  comes  that  of  Amhly stoma  punctatum. 
Both  deposit  their  eggs  in  jellylike  clumps.  Hyla  pickeringii  and 
Acris  gryllus  spawn  in  the  same  pond  between  early  March  and  late 
May.  During  late  spring  and  early  summer  the  newt,  Diemictylus 
viridescens,  spawns  here.  Very  frequently  this  pond  dries  up  in 
summer,  and  then  there  is  an  opportunity  to  see  how  any  of  the 
aquatic  batrachians  may  become  terrestrial.  Late  in  summer  Am- 
blystoma  opacum  spawns  in  this  pond.  Usually  the  pond  is  dry  at 
the  time,  whereupon  the  salamander  lays  its  eggs  under  leaves  or 
under  a  board,  coiling  itself  about  the  eggs.     The  hatching  of  such 


THE  AQUATIC   VERTEBRATES  IO29 

eggs  may  be  delayed  much  beyond  the  normal  time  and  will  then 
occur  at  once  with  the  first  rain.  The  young  still  require  a  pond 
for  their  growth  from  hatching  to  the  metamorphosis.  Toads  and 
frogs  have  evidently  become  adapted  to  range  on  land  without 
losing  their  ancestral  habit  of  making  their  home  in  water.  Whether 
their  webbed  toes  and  swimming  legs  are  in  their  original  condi- 
tion, or  whether  they  are  readaptations  to  water  may  be  left  in 
abeyance. 

The  batrachians  play  an  important  part  in  the  economy  of  small 
pools,  a  less  important  one  in  small  streams,  and  are  a  negligible 
quantity  in  waters  of  any  size.  To  the  rule  that  their  abundance 
is  in  inverse  proportion  to  the  size  of  the  body  of  water,  the  perenni- 
branchs  form  the  only  exception.  In  early  spring  nearly  every 
puddle  contains  hundreds  or  thousands  of  toad  eggs  and  larvae. 
The  tadpoles  act  as  scavengers  for  a  short  time  and  then  pass  out 
of  the  life  of  the  puddle.  Every  pond  of  greater  permanence 
serves  the  frogs  as  the  puddles  and  ponds  do  the  toad.  Frog  tad- 
poles are  scavengers  and  mud  eaters,  with  elongate,  aUmentary 
canal.  They  remain  in  the  water  much  longer  than  young  toads 
and  when  they  become  adult  may  pass  out  of  the  Ufe  of  the  puddle 
or  pond  as  completely  as  the  adult  toad,  or  may  remain  more  or 
less  closely  identified  with  the  birthplace.  When  the  adult  frogs 
remain  about  the  water,  they  bear  a  different  relation  to  the 
aquatic  Kfe  from  the  young.  The  ahmentary  canal  has  become 
shortened  and  the  frog  is  an  eater  of  live  food,  insects,  and  fishes. 
In  its  turn  the  frog  serves  as  food  for  fishes,  snakes,  and  birds. 

Fishes 

The  chief  and  perennial  vertebrate  elements  of  the  aquatic  fauna 
are  the  fishes.  They,  with  a  few  batrachians  and  possibly  a  turtle, 
are  the  only  members  of  the  fauna  that  have  both  their  home  and 
their  range  in  the  water.  They  alone  of  the  vertebrates  are  so 
adjusted  to  an  aquatic  existence  that  they  could  be  hermetically 
Bealed  in  a  balanced  aquarium. 

There  are  fishes,  big  and  little,  thick  and  thin,  long  and  short, 
deep,  and  of  Httle  elevation,  sharp-nosed  and  blunt-snouted,  tooth- 


I030 


FRESH-WATER   BIOLOGY 


Fig.  1535.    Red-Eye  or  Goggle-Eye,  Ambloplites  rupestris  (Rafinesque).    Actual  size,  32 
115  mm.  and  183  mm.  long  respectively. 


THE   AQUATIC   VERTEBRATES 


1031 


less  and  fanged,  naked  and  scaled,  barbelcd  and  not,  noctun.al 
and  diurnal,  bottom  sitters  and  top  skimmers,  riffle  inhabitants  and 
pool  dwellers,  mud-puddlers  and  mountaineers,  round-bellied  and 
serrate-edged.  They  are  adapted,  in  short,  to  all  conditions  of 
possible  Jish  environment.     The  same  gamut  of  size,  shape,  and 


Fig.  1536.     Long-Eared  Sunfish,  Lepomis  megalolis  (Rafinesque).     Actual  size,  90  mm.  long. 

habit  is  found  in  the  fresh  waters  of  South^ America  and  North 
America  though  the  twc  continents  have  no  fishes  in  common. 
The  members  of  different  families  have  thus  independently  become 
convergently  and  divergently  adapted. 

Fresh-water  fishes  do  not  form  a  group  by  themselves.     \'arious 


Fig.  1537.    Little  Pickerel,  Lucius  vermiculatus  (Le  Sueur).    Actual  size.  119  mm.  lonp. 

marine  famiUes  have  contributed  to  the  fauna.  But  the  larger 
per  cent  of  the  fresh-water  fishes  belong  to  the  single  superorder 
Ostariophysi.  Of  the  600  fresh-water  species  of  North  America, 
307,  or  over  half,  belong  to  this  group. 


1 032  FRESH-WATER  BIOLOGY 

The  fresh- water  fishes  of  North  America,  exclusive  of  Mexico, 
are  distributed  among  the  following  families,  of  which  those  of 
undoubted  recent  marine  origin  are  printed  in  italics. 

Lamprey  1 8      Salmon 28      Sunfish ; 37 

Paddlefish i      Trout  perch i      Perch 72 

Sturgeon 7      Blindfish 8      Bass 4 

Garpike 3      Killifish 52      Drum i 

Bowfin I      Mud  minnow 2      Surf  fish i 

Characini i      Pike 5      Cichlid  2 2 

Carp 230      Alaska  Blackfish i      Goby 6 

Sucker 51      Eel i      Sculpin 21 

Catfish 25      Stickleback 7      Cod i 

Mooneye 3      Silver  side 2      Sole i 

Herring 5      Pirate  perch 2 

Gizzard  shad i      Elassoma 2  . 

Few  localities,  even  among  the  most  favored,  contain  more  than 
50  species  of  the  600  found  in  North  America.  The  entire  Missis- 
sippi basin  harbors  about  200  species,  the  Great  Lakes  with  their 
tributaries,  152,^  the  state  of  Indiana,  163.  Eel  River  in  Indiana 
(85  miles  long),  with  all  of  its  tributary  lakes  and  streams,  harbors 
76  species.  White  River  of  Arkansas,  84;  the  Maumee  basin,  87. 
Bean  Blossom  Creek,  about  25  miles  long,  harbors  44  species  in 
less  than  two  miles  near  its  middle.  Lake  Ontario  with  all  of  its 
tributaries  is  inhabited  by  73  species;  Lake  Champlain  and  its 
tributaries  by  54;  Lake  Chautauqua  with  its  tributaries  by  31; 
the  Winnipeg  System,  Canada,  by  44;  the  St.  Lawrence  River,  by 
63  and  8  marine.  Winona  Lake  of  Kosciusko  County,  Indiana, 
exclusive  of  its  tributaries,  harbors  23  species,  Turkey  Lake  with- 
out its  tributaries,  29  species.  The  outlet  of  Turkey  Lake,  for  a 
mile  of  its  length,  harbors  an  equal  number. 

There  is  a  vast  difference  in  the  number  of  species  found  in 
equal  areas  of  streams  and  lakes.  Other  things  equal  a  given 
area  of  surface  water  or  a  given  cubic  quantity  of  water  of  a  small 
stream  harbors  more  individuals  and  greater  diversity  of  species 
than  the  same  area  and  bulk  of  either  a  large  river  or  lake.  The 
places  in  America  from  which  the  greatest  diversity  of  fish  life  has 
been  reported  are : 

1  These  are  fully  described  and  many  of  them  figured  in  Jordan  and  Evermann's 
Fishes  of  North  and  Middle  America,  Bull.  U.  S.  Fish  Com.,  and  also  in  Jordan's 
"  Guide  to  the  Study  of  Fishes,"  Henry  Holt  and  Co. 

2  Immigrants  from  South  America. 

3  Of  these  27  are  peculiar  to  the  Great  Lakes  basin. 


THE  AQUATIC   VERTEBRATES  1033 

Saline  and  Washita,  ^  mile  above  Arkadelphia,  Arkansas 47 ' 

Fort  Smith  and  neighborhood 50 

Bean  Blossom  Creek,  Indiana 44 

Cypress  Creek,  Alabama 42 

Obeys  River,  Tennessee 39 

Tuscaloosa,  Alabama 32 

Mammoth  Spring,  Arkansas 37 

Washita,  Arkansas 36 

In  contrast  with  these  the  following  poor  faunas  arc  recorded: 

Connecticut  River 18 

Clear  Lake,  California 13 

Klamath  basin,  California 15 

The  entire  Yellowstone  Park' 10 

San  Luis  River,  California 4 

Kicking  Horse  River,  Canada 2 

Salt  Lake  basin 14 

Sevier  River,  Utah ^ 7 

Columbia  River  System 37 

Colorado  basin 33 

Pennamaguan  Lake,  Washington  County,  Maine 10 

Meddybemp  Lake  and  Dennys  River,  Washington  County,  Maine 9 

Western  Grand  Lake  System,  Washington  County,  Maine 14 

St.  Croix  River  basin,  Washington  County,  Maine 8 

Perkins  Lake,  Idaho 7 

Alturas  Lake,  Idaho 4 

San  Diego  County,  California 4 

Of  these  the  Connecticut,  Klamath,  Yellowstone,  San  Luis,  the 
Maine  lakes  and  streams,  and  Alturas  Lake  each  have  entirely 
distinct  faunas  and  the  Columbia  and  Colorado  have  only  a  few 
species  each  in  common  with  the  Salt  Lake  basin.  It  is  quite  evi- 
dent from  an  inspection  of  these  lists,  that  a  general  consideration 
of  the  fresh-water  fauna  of  North  America  applicable  to  all  cases 
is  quite  out  of  the  question.  There  are  a  number  of  quite  distinct 
faunas.  A  few  general  observations  may  be  supplemented  with 
an  analysis  of  a  few  typical  localities  to  get  at  the  nature  of  the 
fish  fauna. 

Jordan  2  summarizes  a  long  experience  of  gathermg  fishes  in 
many  waters  of  North  America  as  follows: 

''Some  of  the  conditions  most  favorable  to  the  existence  in  any 
stream  of  a  large  number  of  species  of  fishes  are  the  following,  the 
most  important  of  which  is  the  one  mentioned  first:  Connection 
with  a  large  hydrographic  basin;  a  warm  climate;  clear  water;  a 
moderate  current;  a  bottom  of  gravel,  preferably  covered  by  a 

1  Two  localities  are  included  in  this  and  several  in  the  total  of  50  in  the  next. 
>  "A  Guide  to  the  Study  of  Fishes,"  p.  307. 


I034  FRESH-WATER   BIOLOGY 

growth  of  weeds;  little  fluctuation  during  the  year  in  the  volume 
of  the  stream  or  in  the  character  of  the  water. 

"Limestone  streams  usually  yield  more  species  than  streams 
flowing  over  sandstone,  and  either  more  than  the  streams  of  regions 
having  metamorphic  rocks.  Sandy  bottoms  usually  are  not  favor- 
able to  fishes.  In  general,  glacial  drift  makes  a  suitable  river 
bottom,  but  the  higher  temperature  usual  in  regions  beyond  the 
limits  of  the  drift  gives  to  certain  southern  streams  conditions 
still  more  favorable.  These  conditions  are  all  well  reahzed  in  the 
Washita  River  in  Arkansas,  and  in  various  tributaries  of  the  Ten- 
nessee, Cumberland,  and  Ohio;  and  in  these,  among  American 
streams,  the  greatest  number  of  species  has  been  recorded. 

''The  isolation  and  the  low  temperature  of  the  rivers  of  New 
England  have  given  to  them  a  very  scanty  fish  fauna  as  compared 
with  the  rivers  of  the  South  and  West." 

Agassiz  says  concerning  New  England:  "In  this  isolated  region  of 
North  America,  in  this  zoological  island  of  New  England,  as  we 
may  call  it,  we  find  neither  Lepidosteus,  nor  Amia,  nor  Poliodon, 
nor  Amblodon,  nor  Grystes,  nor  Centrarchus,  nor  Pomoxis,  nor 
Ambloplites,  nor  C alliums,  nor  Carpiodes,  nor  Hyodon,  nor  indeed 
any  of  the  characteristic  forms  of  North  American  fishes  so  com- 
mon everywhere  else,  with  the  exception  of  two  Pomotis,  one 
Boleosoma,  and  a  few  Catostomus.^'' 

Continuing,  Jordan  says: 

"Of  the  six  hundred  species  of  fishes  found  in  the  rivers  of  the 
United  States,  about  two  hundred  have  been  recorded  from  the 
basin  of  the  Mississippi.  From  fifty  to  one  hundred  of  these 
species  can  be  found  in  any  one  of  the  tributary  streams  of  the 
size,  say,  of  the  Housatonic  River  or  the  Charles.  In  the  Connecti- 
cut River  there  are  but  eighteen  species  permanently  resident;  and 
the  number  found  in  the  streams  of  Texas  is  not  much  larger.** 

"The  waters  of  the  Great  Basin  are  not  rich  in  fishes,  the  species 
now  found  being  evidently  an  overflow  from  the  Snake  River  when 
in  late  glacial  times  it  drained  Lake  Bonneville.  This  postglacial 
lake  once  filled  the  present  basin  of  the  Great  Salt  Lake  and  Utah 
Lake,  its  outlet  flowing  northwest  from  Ogden  into  Snake  River. 
The  same  fishes  are  now  found  in  the  upper  Snake  River  and  the 


THE   AQUATIC   VERTEBRATES  1035 

basins  of  Utah  Lake  and  of  Sevier  Lake.  In  the  same  fashion 
Lake  Lahonton  once  occupied  the  basin  of  Nevada,  the  Humboldt 
and  Carson  sinks,  with  Pyramid  Lake.  Its  drainage  fell  also  into 
the  Snake  [Klamath?]  River,  and  its  former  Umits  are  shown  in 
the  present  range  of  species.  These  have  almost  nothing  in  com- 
mon with  the  group  of  species  inhabiting  the  former  drainage  of 
Lake  Bonneville.  Another  postglacial  body  of  water,  Lake  Idaho, 
once  united  the  lakes  of  southeastern  Oregon.  The  fauna  of  Lake 
Idaho,  and  of  the  lakes  Malheur,  Warner,  Goose,  etc.,  which  have 
replaced  it,  is  also  isolated  and  distinctive.  The  number  of  species 
now  known  from  this  region  of  these  ancient  lakes  is  about  125. 
This  list  is  composed  almost  entirely  of  a  few  genera  of  suckers, 
minnows,  and  trout.  None  of  the  catfishes,  perch,  darters,  or 
sunfishes,  moon-eyes,  pike,  killifishes,  and  none  of  the  ordinary 
eastern  types  of  minnows  have  passed  the  barrier  of  the  Rocky 
Mountains. 

"  West  of  the  Sierra  Nevada  the  fauna  is  still  more  scanty,  only 
about  seventy  species  being  enumerated.  This  fauna,  except  for 
certain  immigrants  from  the  sea,  is  of  the  same  general  character 
as  that  of  the  Great  Basin,  though  most  of  the  species  are  different. 
.  .  .  The  rivers  of  Alaska  contain  but  few  species,  bareh'  a  dozen 
in  all,  most  of  these  being  found  also  in  Siberia  and  Kamchatka. 
In  the  scantiness  of  its  faunal  Hst,  the  Yukon  agrees  with  the  Mac- 
kenzie River,  and  with  Arctic  rivers  generally." 

The  fauna  of  the  Great  Lakes  and  of  the  Red  River  of  the  north 
is  essentially  Hke  that  of  the  Mississippi  Valley. 

The  Origin  of  the  Fresh-water  Fishes.  —  Many  of  the  fresh-water 
fishes  of  North  America  have  been  more  remotely  or  more  recently 
derived  from  the  sea.  Some  of  them,  as  the  eel,  still  come  from 
the  sea  during  each  generation,  to  find  in  fresh  water  their  range; 
others  are  but  seasonal  visitors,  entering  the  fresh  waters  from  the 
ocean  as  the  salamanders  enter  them  from  the  land,  to  find  homes. 
These  various  anadromous  fishes  will  be  considered  later.^     Still 

1  The  anaclromous  habit  may  be  of  double  origin.  The  various  salmons,  many  of 
whose  relatives  live  in  fresh  water,  may  be  fresh-water  species  contributed  to  the  ocean. 
The  shad  and  striped  perch,  on  the  other  hand,  whose  relatives  live  in  the  ocean,  have 
become  anadromous  through  the  general  habit  of  many  oceanic  fishes  to  seek  the  shore 
and  shallow  water  as  the  breeding  season  approaches. 


1036  FRESH-WATER   BIOLOGY 

others,  with  both  range  and  home  in  fresh  water,  belong  to  present 
marine  families  and  have  evidently  comparatively  recently  become 
members  of  the  fresh-water  fauna. 

A  notable  example  of  a  fish  comparatively  recently  contributed 
by  the  sea  to  fresh  water  is  Hysterocarpus  traski  Gibbons.  It  is  a 
viviparous  fish  of  the  rivers  of  central  California.  All  of  its  rela- 
tives live  in  the  Pacific  Ocean  from  which  it  is  an  undoubted 
immigrant. 

The  sea  basses  furnish  several  illustrative  examples.  The  striped 
bass,  Roccus  lineatus,  is  an  oceanic  fish  entering  rivers  to  spawn, 
while  its  nearest  relative,  Roccus  chrysops,  the  white  bass,  is  con- 
fined to  the  Great  Lakes  and  upper  Mississippi  Valley.  Closely 
related  to  these  are  the  yellow  bass,  Morone  interrupta,  of  the  lower 
Mississippi  Valley,  and  the  white  perch,  Morone  americana,  in 
salt  and  fresh  water  from  Nova  Scotia  to  South  Carolina.  The 
ninety  other  American  members  of  this  family  are  all  marine. 

Various  species  of  Rohalos  (Centropomus)  enter  fresh  water. 

The  Mugilidae  have  added  various  species  to  the  fresh  waters 
south  of  the  United  States.  The  Atherinidae  have  contributed  the 
skipjack  to  our  rivers  and  lakes,  and  south  of  us  this  marine  family, 
whose  eggs  are  provided  with  threads,  has  contributed  and  is  con- 
tributing to  the  fresh  waters  all  the  way  from  Mexico  to  Patagonia. 


Fig.  1538.     Skipjack,  Labidestes  siculus  (Cope).     Actual  size,  95  mm.  long. 

The  sticklebacks  and  kilHfishes  help  to  bridge  the  gap,  if  such 
exists,  between  the  fresh  waters  and  the  ocean.  Even  the  pipe- 
fishes and  flounders  have  a  tendency  to  colonize  fresh  waters,  and 
the  flounders  at  least  have  succeeded  in  South  America. 

The  Sciaenidae,  a  marine  family,  has  contributed  the  thunder- 
pumper  or  white  perch  to  the  Great  Lakes  and  Mississippi  Valley, 
and  several  other  species  to  the  streams  of  South  America.  Some 
of  its  marine  species  occasionally  run  up  streams. 

The  large  family  of  the  Cottidae  has  added  the  miller's-thumb. 


THE  AQUATIC   VERTEBRATKS  1037 

Others  of  undoubted  marine  origin  have  entered  fresh  water  at 
such  remote  periods  that  they  have  set  up  distinct  fresh-water 
families,  as  the  suntishes,  the  perches,  and  the  CichHdac. 

Finally,  we  have  the  dominant  fresh-water  groups  of  characins, 
minnows,  carps,  suckers,  and  catfishes  whose  origin  from  the 
sea  is  so  remote  that  the  orders  and  superorders  embracing  all  of 
these  dominant  members  of  the  fresh-water  fauna,  with  the  excep- 
tion of  Arius  and  related  genera,  are  peculiar  to  fresh  water. 


Fig.  1539.    Miller's  Thumb,  Coitus  ictalops  (Rafinesque). 

Dispersal  of  Fresh-water  Fishes.  —  No  fishes  have  been  or  are 
bemg  permanently  contributed  to  the  land.  The  eel  is  capable 
of  moving  over  short  stretches  of  land,  and  Periophthalmus  may 
leave  the  water  in  search  of  food.  In  the  South  American  fresh 
waters  a  relative  of  the  catfish  is  said  to  be  able  to  move  from 
pond  to  pond,  and  in  the  Congo  and  in  South  American  rivers 
live  fishes  that  temporarily  fly  over  the  water.  But  all  these  spe- 
cies are  adapted  to  the  water  and  can  live  for  longer  periods  only 
in  connection  with  it. 

The  two  factors  that  more  than  others  are  responsible  for  the 
abundance  or  paucity  of  the  faunas  are  accessibility  and  tempera- 
ture. The  latter  will  be  considered  more  at  length  later.  Acces- 
sibihty  demands  some  attention  now. 

A  locality  is  accessible  to  fishes  if  it  is  connected  with  an  inhab- 
ited locality  by  a  permanent  or  seasonal  waterway.  There  are 
fishes  that  apparently  defy  tliis  general  rule  and  that  skip  or  have 


1038  FRESH-WATER   BIOLOGY 

skipped  in  a  tantalizing  way,  from  mountain  stream  to  mountain 
stream,  appearing  wherever  conditions  are  favorable.  Here,  as 
elsewhere,  the  mystery  will  probably  dissolve  when  all  the  facts 
are  in.  The  catfishes  and  darters  have  not  been  able  to  cross  to 
the  Pacific  slope  in  the  United  States,  but  in  Mexico  they  have 
accompUshed  this  feat.  A  tilting  of  the  land,  or  change  in  relative 
rainfall,  or  some  other  reason  has  enabled  some  of  the  Pacific 
slope  streams  to  capture  some  of  the  former  tributaries  of  the  Rio 
Grande.  With  the  tributary  went  the  darters,  the  catfishes,  and 
other  fishes  it  contained.  A  freshet  or  a  cave-stream  may  some- 
times be  responsible  for  an  apparently  mysterious  distribution. 
Salt  water  is  sometimes  a  barrier  to  the  migration  of  fresh-water 
fishes.  Jordan  ^  says  of  the  streams  of  San  Luis  Obispo  County, 
California,  of  which  the  San  Luis  Creek  mentioned  before  is  one: 

'^The  county  of  San  Luis  Obispo  lies  along  the  coast  of  Califor- 
nia, midway  between  Monterey  and  Santa  Barbara.  It  is  com- 
posed of  two  or  three  isolated  valleys  opening  out  to  the  sea,  and 
surrounded  on  all  sides  by  high  and  barren  mountains.  These 
mountains  have  served  as  a  barrier,  shutting  off  all  access  of  fishes 
to  the  streams  of  the  region  from  the  larger  basins  of  the  north  and 
east.  The  valleys  of  San  Luis  Obispo  are  traversed  by  clear, 
swift,  cold  streams  rising  in  mountain  springs.  In  these  streams 
very  few  species  of  fishes  are  found,  and  these  few,  except  in  one 
case  (Agosia  nubila),  are  species  which  have  come  into  the  fresh 
waters  by  way  of  the  sea.  None  of  the  characteristic  types  of 
the  San  Joaquin  and  Sacramento  valleys  are  found  in  San  Luis 
Obispo  County.  This  is  evidently  not  due  to  any  character  of  the 
waters,  but  simply  to  the  fact  that  these  fishes  cannot  reach  San 
Luis  Obispo  except  by  descent  to  the  sea." 

But  there  is  also  evidence  that  the  ocean  is  not  invariably  a 
barrier.     To  quote  again  from  Jordan :  ^ 

"The  passage  of  species  from  stream  to  stream  along  the  Atlantic 
slope  deserves  a  moment's  notice.  It  is  under  present  conditions 
impossible  for  any  mountain  or  upland  fish,  as  the  trout  or  the 
miller's  thumb,  to  cross  from  the  Potomac  River  to  the  James,  or 

1  Bull.  U.  S.  Fish  Com.  for  1894,  p.  141. 

'  "Guide  to  the  Study  of  Fishes,"  pp.  312  and  313. 


THE   AQUATIC   VERTEBRATES  IO39 

from  the  Neuse  to  the  Santee,  by  descending  to  the  lower  courses 
of  the  rivers,  and  thence  passing  along  either  through  the  swamps 
or  by  way  of  the  sea.  The  lower  courses  of  these  streams,  warm 
and  muddy,  are  uninhabitable  by  such  fishes.  Such  transfers  are, 
however,  possible  farther  north.  From  the  rivers  of  Canada  and 
from  many  rivers  of  New  England  the  trout  does  descend  to  the 
sea  and  into  the  sea,  and  farther  north  the  white  fish  does  this  also. 
Thus  these  fishes  readily  pass  from  one  river  basin  to  another.  As 
this  is  the  case  now  every^where  in  the  north,  it  may  have  been  the 
case  farther  south  in  the  time  of  the  glacial  cold.  We  may,  I 
think,  imagine  a  condition  of  things  in  which  the  snow  fields  of 
the  Allegheny  chain  might  have  played  some  part  in  aiding  the 
diffusion  of  cold-loving  fishes.  A  permanent  snow  field  on  the 
Blue  Ridge  in  western  North  CaroHna  might  render  almost  any 
stream  in  the  Carolinas  suitable  for  trout,  from  its  source  to  its 
mouth.  An  increased  volume  of  colder  water  might  carry  the 
trout  of  the  head  streams  of  the  Catawba  and  the  Savannah  as 
far  down  as  the  sea.  We  can  even  imagine  that  the  trout  reached 
these  streams  in  the  first  place  through  such  agencies,  though  of 
this  there  is  no  positive  evidence.  For  the  presence  of  trout  in 
the  upper  Chattahoochee  we  must  account  in  some  other  way  .... 

"With  the  lowland  species  of  the  southern  rivers  it  is  different. 
Few  of  these  are  confined  within  narrow  limits.  The  streams  of 
the  whole  South  Atlantic  and  Gulf  Coast  flow  into  shallow  bays, 
mostly  bounded  by  sand  pits  or  sand  bars  which  the  rivers  them- 
selves have  brought  down.  In  these  bays  the  waters  are  often 
neither  fresh  nor  salt;  or,  rather,  they  are  alternately  fresh  and 
salt,  the  former  condition  being  that  of  the  winter  and  spring. 
Many  species  descend  into  these  bays,  thus  finding  every  facility 
for  transfer  from  river  to  river.  There  is  a  continuous  inland 
passage  in  fresh  or  brackish  waters,  traversable  b>'  such  fishes, 
from  Chesapeake  Bay  nearly  to  Cape  Fear;  and  similar  con- 
ditions exist  on  the  coasts  of  Louisiana,  Texas,  and  much  of 
Florida." 

Adaptations  to  the  Main  Object  id  I z/r.  —  Fishes  either  lay 
eggs  that  are  fertilized  in  the  water,  retain  eggs  that  have  been 
internally  fertilized  to  the  time  of  hatching  or  in  a  few  species  give 


I040  FRESH-WATER   BIOLOGY 

birth  to  living  young   which   have  been  carried  far  beyond  the 
*'  hatching  "  point. 

A.  Migration.  As  the  spawning  season  approaches,  fishes  under- 
take a  general  inigratory  movement.  The  migration  may  be  of 
great  or  very  Hmited  extent.  The  movement  is  in  general  one  of 
going  upstream  to  small  brooks  and  shoreward  to  shallow  water. 
In  some  cases  the  migration  may  mean  the  movement  for  a  few 
feet  only.  Some  minnows  and  darters  move  to  a  favorably-placed 
rock  or  weed.  The  skipjack  in  our  small  lakes  moves  to  the  zone 
of  pickerel  weeds  near  shore.  The  sunfishes,  black  bass,  and  many 
others  move  shoreward  to  shallow  water.     Some  minnows  move  to 


Fig.  1540.     bucKer,  Catostonius  commersoni  i,Lacept;de).     Acluul  size,  232  mm.  long. 

riffles  from  neighboring  pools.  The  upstream  movement  of  suckers 
is  powerful  in  CaHfornia,  and  has  become  proverbial  in  IlUnois  and 
neighboring  waters. 

The  limit  in  the  extent  of  migratory  movements  upstream  is 
reached  by  the  Pacific  coast  salmons.  The  quinnat  salmon  of  the 
Pacific  coast  is  the  king  of  the  migrants.  It  enters  the  Columbia 
River  at  the  age  of  four  years,  in  March  and  April.  The  entire 
summer  is  taken  up,  without  food,  in  ascending  to  its  spawning 
grounds.  It  spawns  a  thousand  miles  and  more  from  the  ocean, 
or  in  Alaska  two  thousand  miles  from  the  sea,  in  shallow  riffles  of 
small  streams  at  the  headwaters  of  the  streams  it  ascends.  Alturas 
Lake,  near  one  of  its  spawning  places,  has  an  elevation  of  7,335 
feet.  After  spawning  the  adult  dies.  It  never  succeeds  in  regaining 
the  ocean.  The  Atlantic  slope  salmon  {Salmo  salar)  ascends  from 
the  ocean  to  the  headwaters  of  streams  north  of  Cape  Cod.  The 
relative  of  the  salmons,  the  cisco  of  Tippecanoe  Lake,  in  December 
ascends  its  tributary  streams  to  spawn.  The  marine  lamprey  as- 
cends streams  from  the  Atlantic  Ocean.  The  landlocked  lamprey 
(Petromyzon  marinus  unicolor)  of  central  New  York  migrates  eight 


THE   AQUATIC    VERTEBRATES  104I 

to  ten  miles  from  Cayuga  Lake  up  the  streams  to  spawn.  The 
silver  lamprey  of  the  Mississippi  Valley  ascends  small  brooks  in 
the  spring.  On  the  Pacific  slope  the  Pacific  lamprey  ascends 
streams  in  large  numbers.  At  La  Grange,  Idaho,  I  found  very 
many  congregated  below  a  milldam  which  they  had  not  been  able 
to  ascend.  The  sturgeons,  for  the  most  part  living  in  the  sea,  also 
ascend  streams  to  spawn. 

While  many  species  of  fishes  have  the  habit  of  entering  fresh 
water  when  they  approach  ripeness,  the  eel  alone,  of  the  fishes  of 
the  northern  hemisphere,  has  the  reverse  habit  of  taking  to  salt 
water  when  the  reproductive  period  approaches.  It  has  been  well 
known  for  many  years  that  during  winter  and  early  spring  the 
young  of  the  eel  enter  the  mouths  of  streams  in  enormous  numbers. 
Redi  records  the  entrance  of  young  eels  into  the  Arno  in  1667,  and 
says  that  at  Pisa  three  million  pounds  of  young  eels  30-120  mm. 
were  taken  in  five  hours.  They  find  their  way  for  hundreds  of 
miles  from  the  ocean.  ''Young  individuals  three  to  five  inches 
long  ascend  rivers  in  incredible  numbers,  overcoming  all  obstacles, 
ascending  vertical  walls  or  floodgates,  entering  every  large  and 
swollen  tributary,  and  making  their  way  even  over  terra  firma  to 
waters  shut  off  from  all  communications  with  rivers." 

The  American  eel,  which  is  closely  related  to  the  European  eel, 
is  found  in  afl  fresh  waters  emptying  from  the  Gulf  of  St.  Lawrence 
to  Mexico.  Eels  have  been  seen  in  Colorado  1500  miles  from  the 
Gulf  of  Mexico,  at  an  elevation  of  7200  feet.  Only  the  females 
ascend  such  distances,  the  males  remaining  near  the  coast.  While 
in  fresh  water  they  feed  on  everything  eatable.  When  the>'  ap- 
proach their  full  size,  in  about  four  years,  they  descend  the  streams 
to  the  ocean  in  autumn.  They  are  lost  sight  of  beyond  a  distance 
of  a  mile  from  shore,  but  about  six  months  after  they  have  entered 
the  sea,  eel  eggs  have  been  found  floating  on  the  surface.  Hiey 
are  large  eggs,  with  a  very  large  peri\dtelline  space,  and  vesicular 
yolk.  They  hatch  into  larvae  quite  unlike  eels.  These  become 
gradually  greatly  modified,  but  not  in  the  direction  of  becoming 
eel-Hke.  It  is  not  until  the  larvae  are  about  a  year  old  that  they 
are  metamorphosed  into  young  eels  which  ascend  streams  such  as 
their  parents  have  descended  two  years  previously.     Like  all  fishes, 


I042  FRESH-WATER  BIOLOGY 

such  as  the  lampreys  and  salmon,  which  make  very  elaborate 
preparations  to  produce  their  young  at  a  great  distance  from 
their  range,  the  eels  never  regain  their  range,  and  probably  all 
die  after  the  first  reproductive  period.  It  is  not  improbable  that 
in  some  landlocked  lakes  eels  mature  and  reproduce  in  fresh  water, 
but  no  eels  with  ripe  eggs,  nor  eggs,  nor  larval  eels,  have  been  found 
in  fresh  water. 

Homes  of  Fishes.  —  Emphasis  has  been  laid  on  the  fact  that 
the  ultimate  fate  of  all  fresh  water  is  locomotion,  and  that  usually 
currents  exist  between  fresh-water  lakes  and  the  ocean.  All  fresh- 
water fishes  are  adapted  to  this  condition  and  make  provision  to 
anchor  their  eggs  or  give  birth  to  living  young.  There  is  but  one 
fresh-water  fish  known  to  me  that  has  pelagic  eggs,  the  eel.  It 
has  not  become  adapted  to  rear  its  yoimg  in  fresh  water,  but  enters 
the  sea  before  the  reproductive  period.  This  suggests  that  the 
adaptation  of  fresh-water  fishes  to  resist  currents  did  not  arise 
after  they  had  entered  the  fresh  water,  but  that  such  oceanic 
candidates  for  fresh-water  existence  as  had  eggs  adapted  to  resist 
the  currents  gained  a  permanent  lodgment;  while,  on  the  contrary, 
none  of  those  with  pelagic  eggs  have  been  able  to  estabHsh  perma- 
nent homes  in  fresh  waters.  All  anadromous  and  fresh- water 
fishes  either  have  eggs  heavier  than  water  which  lodge  in  gravel,  or 
produce  attachable  eggs.  Many  marine  fishes  have  pelagic  eggs, 
and  none  of  these  have  become  permanent  residents  in  fresh  water. 
Others  have  adhesive  eggs,  that  at  the  moment  of  being  laid  will 
adhere  to  foreign  substances;  others  have  cohesive  eggs  that  will 
become  attached  to  each  other,  but  not  to  foreign  substances.  Of 
the  adhesive  eggs  some  are  simply  sticky  all  over  and  others  have 
mushroom-shaped  processes  that  have  sticky  heads  (stickleback). 
The  eggs  of  still  other  fishes  have  filaments  that  coil  about  foreign 
substances.  All  of  these  types  are  found  in  fresh  waters.  The 
fundamental  adaptation,  that  to  flowing  water,  was  acquired  by 
the  ancestors  of  fresh-water  fishes  before  they  were  able  to  leave 
the  ocean. 

Along  with  this  adaptation  against  currents,  we  have  in  the 
fresh-water  fishes  elaborate  brooding  habits  that  in  part,  at  least, 
are  an  adaptation  to  another  fresh- water  condition,  i.e.,  the  settling 


THE  AQUATIC   VERTEBRATES  1043 

of  sediment.     A  very  brief  survey  of  the  nature  of  the  eggs  and 
the  brooding  habits  as  far  as  known  is  instructive. 

Amia,  the  sunfishes,  and  the  black  bass  build  their  nests  in 
shallow  water  with  little  or  no  current.  The  nest  is  either  pre- 
pared in  weed-covered  patches  or  on  the  sand.  Afnia  prefers 
weed-covered  patches  but  is  not  exclusive  in  its  selections.  The 
nest,  prepared  by  the  male  with  the  snout  and  fins,  consists  simply 
of  an  area  from  which  the  vegetation  has  largely  been  removed, 
or  it  may  be  but  a  saucer-shaped  pit  in  sand.  The  eggs  of  Amia 
are  adhesive  and  are  attached  to  the  sides  and  bottoms  of  the 
nest.     The  male  remains  over  or  near  the  nest  until  the  eggs  hatch, 


Fig.  1541.    Large-mouthed  Black  Bass,  Micropterus  salmoides  (Lacepede). 

occasionally  fanning  away  sediment,  and  always  while  near  the  nest 
ready  to  drive  out  intruders.  The  male  accompanies  the  school  of 
young  until  they  reach  a  length  of  100  mm. 

The  sunfishes  and  black  bass  build  their  nests  preferably  in  gravel 
or  sand,  but  not  to  the  entire  exclusion  of  the  locahties  preferred 
by  Amia.  Their  eggs  are  quite  small  and  also  adhesive,  and  are 
found  at  the  sides  or  bottom  of  a  nest. 

The  male  of  the  small-mouthed  black  bass  builds  the  nest. 
There  are  no  secondary  sexual  characters.  "  Each  ^  male  tests  the 
bottom  in  several  places  by  rooting  into  it  with  his  snout  and  fan- 
ning away  the  overlying  mud  or  sand  with  his  tail.  If  he  does  not 
find  gravel  after  going  down  three  or  four  inches,  he  seeks  another 
place.  Having  found  a  suitable  place,  he  cleans  the  sand  and  mud 
from  the  gravel  by  sweeping  it  with  his  tail.  He  then  turns  over 
the  stones  with  his  snout  and  continues  sweeping  until  the  gravel 
over  a  circular  spot,  some  two  feet  in  diameter,  is  clean.  The  sand 
is  swept  toward  the  edge  of  the  nest  and  there  forms  a  few  inches 
^  From  Lydell,  Bull.  U.  S.  Fish  Com.,  22:  39. 


I044  FRESH-WATER   BIOLOGY 

high,  leaving  the  center  of  the  nest  concave  like  a  saucer.  The 
nest  is  usually  located  near  a  log  or  large  rock  so  as  to  be  shielded 
from  one  side.  If  the  bank  is  sheer  and  the  water  deep  enough, 
the  nest  may  be  built  directly  against  the  bank."  .  .  . 

After  spawning  the  male  drives  the  female  away.  "The  male, 
and  the  male  only,  now  continues  to  guard  the  nest,  fanning  sedi- 
ment from  the  eggs  and  repelling  enemies.  At  66°  F.  the  eggs 
hatch  in  five  days  and  the  young  fishes  swarm  up  from  the  bottom 
in  twelve  to  thirteen  days  from  the  day  of  hatching. 

"  Shortly  after  the  young  small-mouthed  bass  rise  from  the  nest 
they  scatter  out  over  a  space  four  or  five  rods  across  —  not  in  a 
definite  school  with  all  the  fish  moving  together,  but  as  a  loose 
swarm,  moving  independently  or  in  small  groups.  The  fry  may 
be  at  the  surface  or  on  the  bottom,  in  weeds  or  clear  water,  and  are 
attended  by  the  male  until  they  are  i|  inches  long.  The  swarm 
then  gradually  disperses  and  the  young  fry,  which  were  previ- 
ously black,  take  on  the  color  of  the  old  fish." 

Other  fishes  having  adhesive  eggs  attach  them  to  the  lower 
surfaces  of  rocks  and  boards.  Several  of  our  darters  have  this 
habit,  as  well  as  several  minnows.  The  eggs  of  some  species  of 
darters  are  attached  to  the  upper  surfaces  of  rocks.  Other  fishes 
suspend  their  eggs  from  aquatic  plants,  with  or  without  nest 
building.  The  goldfish,  which  has  adhesive  eggs,  attaches  them 
singly  to  aquatic  plants,  as  the  fish  swims  about.  The  skipjack 
probably  does  the  same,  though  in  this  species,  as  in  the  case  of 
its  marine  relatives,  the  egg  is  suppHed  with  long,  thread-Kke  fila- 
ments. I  have  seen  pairs  of  these  fishes  wind  in  and  out  near 
the  surface  among  water  plants,  and  once  saw  a  pair  of  gar  pikes 
late  in  June  going  through  the  same  performance.  The  yellow 
perch  provides  similarly  for  its  eggs.  They  are  laid  in  long  strings 
which  are  suspended  from  aquatic  plants.  The  eggs  of  the  stickle- 
backs have  mushroom-shaped  processes  that  are  adhesive. 

The  lampreys,  salmon,  trout,  some  suckers,  and  some  minnows 
have  eggs  which  are  heavier  than  water.  These  fishes  deposit 
their  eggs  among  the  gravel  of  swift-flowing  water  where  Kttle 
sediment  falls.  Some  of  our  catfishes  and  the  miller's-thumb 
have  cohesive,  agglutinating  eggs.     These  are  laid  under  boards 


THE   AQUATIC   VERTEBRATES  1045 

or  in  other  protected  places  and  guarded  by  the  male.  The  male 
Noturus  not  infrequently  proceeds  to  swallow  the  eggs  he  guards 
when  they  are  uncovered. 

''Both^  parents  of  the  yellow  catfish  are  a  pale  yellow  color, 
the  number  of  eggs  deposited  was  estimated  at  two  thousand. 
The  incubatory  period  was  five  days  in  a  mean  water  temperature 
of  77°  F.,  the  lowest  temperature  being  75  degrees  and  the  highest 
80  degrees. 

''During  the  entire  hatching  period  both  parents  were  incessant 
in  their  efforts  to  prevent  the  smothering  of  the  eggs,  to  keep  them 
clean,  and  to  guard  against  intruders.  The  eggs  were  kept  con- 
stantly agitated  and  aerated  by  a  gentle  fanning  motion  of  the 
lower  fins,  and  foreign  particles,  either  on  the  bottom  of  the  nest 
or  floating  near  the  eggs,  were  removed  in  the  mouth  or  by  the 
fins.  The  most  striking  act  in  the  care  of  the  eggs  was  the  sucking 
of  the  egg  masses  into  the  mouth  and  the  blowing  of  them  out, 
this  being  repeated  several  times  with  each  cluster  before  another 
lot  was  treated. 

''The  male  was  particularly  active  in  watching  for  intruders, 
and  savagely  attacked  the  hands  of  the  attendant  who  brought 
food;  he  also  rushed  at  sticks  or  other  objects  introduced  into  the 
aquarium.  Practically  the  entire  work  of  defence  was  assumed 
by  the  male,  although  the  female  occasionally  participated. 

"During  the  time  the  fry  were  on  the  bottom  the  attentions  of 
the  parents  were  unrelaxed,  and,  in  fact,  were  increased,  for  the 
tendency  of  the  different  lots  to  become  scattered  had  to  be  cor- 
rected, and  the  dense  packing  of  the  young  in  the  corners  seemed 
to  occasion  much  concern.  The  masses  of  fry  were  constantly 
stirred,  as  the  eggs  had  been,  by  a  flirt  of  the  fins,  wliich  often 
sent  dozens  of  them  three  or  four  inches  upward,  to  fall  back  on 
the  pile. 

"The  very  young  fry  were  also  taken  into  the  mouths  of  the 
parents  and  blown  out,  especially  those  which  became  separated 
from  the  main  lot  and  were  found  in  the  sand  and  sediment.  The 
old  fish  would  take  in  a  mouthful  of  fry  and  foreign  particles, 
retain  them  for  a  moment,  and  expel  them  with  some  force.  After 
^  From  Smith  &  Harron,  liull.  U.  S.  Fish  Com.,  22:  151. 


1046  FRESH-WATER   BIOLOGY 

the  young  began  to  swim  and  became  scattered,  the  parents  con- 
tinued to  suck  them  in  and  mouth  them,  and,  as  subsequently- 
developed,  did  not  always  blow  them  out. 

*'An  interesting  habit  of  the  parents,  more  especially  the  male, 
observed  during  the  first  few  days  after  hatching,  was  the  mixing  and 
stirring  of  the  masses  of  young  by  means  of  the  barbels.  With  the 
chin  on  the  bottom,  the  old  fish  approached  the  corners  where  the 
fishes  were  banked,  and  with  the  barbels  all  directed  forward  and 
flexed  where  they  touched  the  bottom,  thoroughly  agitated  the 
mass  of  fry,  bringing  the  deepest  individuals  to  the  surface.  This 
act  was  usually  repeated  several  times  in  quick  succession.  The 
care  of  the  young  may  be  said  to  have  ceased  when  they  began  to 
swim  freely,  although  both  parents  continued  to  show  solicitude 
when  the  attendant  approached  the  aquarium  from  the  rear." 

In  contrast  to  the  nest-building  habits  are  the  habits  of  those  fishes 
seeking  a  definite  sort  of  locaHty  where  to  deposit  their  eggs.  The 
dace  (Semotilus),  stone  roller  {Campostoma),  and  rainbow  darter 
{Ethesostoma  caeruleum)  select  gravelly  bottom  on  shallow  riffles 
above  a  pool.  The  habits  of  the  darter  have  recently  been  made 
the  subject  of  exhaustive  study  by  Miss  Cora  D.  Reeves.^  These 
fishes  spawn  when  the  temperature  reaches  about  60°  F.  The 
males  select  holdings  which  they  guard  and  from  which  they  drive 
rival  males  by  a  display  of  color  and  by  blows  delivered  with  head 
and  tail.  The  female  buries  herself  partly  in  the  gravel,  the  male 
taking  a  position  over  her,  other  males  crowding  in.  A  few  eggs 
and  milt  are  extruded  at  a  time  and  the  spawning  act  oft  repeated. 
The  eggs  are  adhesive  and  stick  to  the  gravel. 

The  adaptation  to  currents  in  fresh  water  thus  consists  in  various 
devices  to  anchor  the  eggs.  The  adaptation  against  sediment  is 
found  in  the  guarding  and  fanning  habit  of  the  male,  the  deposit 
of  eggs  to  the  lower  surface  of  rocks  or  boards  and  on  riffles,  and 
the  suspension  of  eggs  from  water  weeds.  To  these  groups  of 
more  or  less  adaptive  habits  we  must  add  the  peculiar  brooding 
habits  of  some  catfishes,  Cichlids,  and  the  blind  fishes,  and  Cyprin- 
odonts.  Some  of  the  South  American  catfishes  have  the  habit  of 
carrying  their  eggs  in  the  mouth.     Some  of  them,  Aspredo,  carry 

1  Biol.  Bull.,  14J  35. 


THE   AQUATIC    VKRTKKRATKS 


104; 


them  attached  to  the  ventral  surface.  Several  African  and  South 
American  Cichlids  carry  the  eggs  and  young  in  their  mouths  and 
gill  chambers.  The  so-called  myth,  that  a  given  fish  leads  about 
his  brood  and  guards  them  in  his  mouth  when  danger  approaches, 
is  not  a  myth  for  some  of  these  species. 

The  blind  fishes  of  North  America  carry  their  eg«,^s  in  I  heir  gill 
chambers.     In  these  fishes  the  oviduct  has  moved  forward  so  that  it 


--^ 


Fig.  1542.     Rainbow  Barter,  Etheosloma  caeruleum  Storer,   $  . 

opens  just  behind  the  isthmus.  The  young  are  carried  for  a  month 
or  two  until  they  have  reached  a  length  of  10  mm.  In  a  group  of 
Cyprinodonts  reaching  as  far  as  Indiana,  but  increasing  in  diver- 
sity of  species  and  numbers  of  individuals  southward,  the  eggs  are 
retained  by  the  female  until  the  yolk  is  absorbed  by  the  growing 
young  fish,   and   sometimes   for   a  much   longer  period.     In    the 


Fig. 


Rainbow  Darter,  Etheosloma  cacruleum  Storer,   9  •     Actual  size,  50  mr 


blind  fishes  of  Cuba  the  young  are  about  an  inch  in  length  at  the 
time  of  birth  and  in  the  Cahfornia  surf-perch  thc\-  may  be  twice 
as  long. 

Secondary  Sexual  Characters.  —  Such  features  consist  in  size, 
disposition,  color,  or  structure.  Large  differences  in  all  of  these 
are  found  in  the  kilUfishes.  In  some  of  these  species  the  male 
is  minute  and  provided  with  an  anal  fin  modified  into  a  lance- 


1048  FRESH-WATER   BIOLOGY 

like  blade.  This  is  not  an  intromittent  organ  but  is  apparently 
used  as  a  momentary  clasper  as  the  male  darts  at  the  female  with 
the  lance  directed  forward  and  upward,  Kberating  the  spermatozoa 
in  spermatophores  as  the  tip  of  the  lance  comes  in  contact  with 
the  female.  A  single  impregnation  may  furnish  the  female  with 
spermatozoa  for  several  broods  of  young. 

The  male  of  Amia  has  a  caudal  ocellus.  In  Rivulus  it  is  the 
female  that  possesses  the  caudal  ocellus. 

The  differences  in  disposition  in  the  black  bass,  in  which  no 
other  secondary  sexual  differences  exist,  are  mentioned  elsewhere. 


Fig.  1544.     Blunt-Nosed  Minnow,  Pimephales  notatus  (Rafinesque),  $  .     Actual  size,  73  mm.  long. 

The  greatest  display  of  secondary  sexual  colors  is  seen  in  the  sun- 
fishes  and  especially  in  the  little  darters  and  in  Chrosomus  whose 
brilliant  coloration  is  scarcely  surpassed  by  that  of  the  humming 
birds.  The  greatest  display  of  secondary  sexual  color  takes  place 
just  before  the  breeding  season.  It  may  be  used  as  a  sex  recog- 
nition mark,  a  battle  flag,  as  in  the  rainbow  darter,  or  as  a  lure  to 
the  female. 

In  many  males  small  excrescences  appear  on  the  sides,  on  the 
fins,  or  on  the  head  during  the  breeding  season.  The  anal  fin  is 
often  provided  with  booklets  in  suckers.  The  male  of  Campostoma 
becomes  covered  with  tubercles.  Pimephales  develops  short,  warty 
horns  on  the  head  and  the  horned  dace  (Semotilus  atromaculatus) 
large,  long  ones.  Some  of  these  are  used  as  excitants  for  the  fe- 
male, others  undoubtedly  to  enable  the  male  to  cling  to  the  female 
during  the  spawning  act. 

Physical  Environment  and  Adaptations  to  it.  With  the  excep- 
tions noted,  fishes  are  always  found  in  water.  The  character  of 
the  water,  i.e.,  the  per  cent  of  salt  and  other  chemicals  in  solution, 
determines  the  three  major  ecological  divisions  of  fishes:  I,  the 
marine  fishes;  II,  the  brackish  water  fishes;  and  III.  the  inland, 


THE  AQUATIC  VERTEBRATES  1 049 

fresh- water  fishes.     The  first  two  groups  are  beyond  the  scope  of 
this  chapter. 

The  inland  fishes,  according  to  the  physical  character  of  the 
environments  selected  by  them,  may  be  divided  into  the  following 
groups,  in  part  suggested  by  Cope  and  Jordan. 

1.  Lowland  fishes:  the  bowfin,  pirate  perch,  large-mouthed  black 
bass,  sunfishes,  mud-minnow,  and  some  catfishes. 

2.  Channel  fishes,  ranging  from  lowland  to  upland:  the  channel 
catfish,  the  moon-eye,  gar  pike,  buffalo  fishes,  and  drum. 

3.  Upland  fishes:  many  of  the  darters,  shiners,  and  suckers,  and 
the  small-mouthed  black  bass. 

4.  Mountain  fishes:  the  brook  trout,  and  many  of  the  darters 
and  minnows. 

5.  Lake  fishes,  inhabiting  only  waters  which  are  deep,  clear, 
and  cold:  the  various  species  of  whitefish  and  the  Great  Lake 
trout. 

6.  Anadromous  fishes,  or  those  which  run  up  from  the  sea  to 
spawn  in  the  fresh  water:  the  salmon,  sturgeon,  shad,  and  striped 
bass. 

7.  Catadromous  fishes,  that  descend  to  the  ocean  to  spawn:  the 
eel. 

8.  Cave  fishes,  found  exclusively  in  cave  streams:  the  Ambly- 
opsidae. 

Many  of  the  species  are  found  in  more  than  one  of  the  areas 
mentioned. 

Liland  waters  vary  greatly  in  the  amount  of  the  solids  in  solu- 
tion or  suspension.  In  the  Great  Salt  Lake  and  the  alkali  lakes  of 
the  west  the  amount  of  solids  in  solution  is  prohibitive  to  fish  life. 
In  all  other  waters,  however  small,  if  accessible,  fishes  are  found. 
Even  temporary  ponds  are  colonized  by  catfishes  and  sunfishes  if 
they  are  at  all  accessible.  Sediment  is  present  in  variable  amounts 
and  some  fishes,  depending  exclusively  upon  sight  to  detect  their 
prey,  are  found  only  in  water  free  from  sediment. 

Under  given  conditions  in  moving  water,  the  amount  of  o.xxgcn  in 
solution  is  tolerably  constant.  When  a  body  of  fresh  water  freezes 
over,  or  after  the  summer  thermocline  is  formed,  the  oxygen  may 
become  reduced  in  quantity  or  disappear  altogether  in  the  deeper 


I050  FRESH-WATER   BIOLOGY 

portions  of  a  lake.  Through  the  reduction  in  oxygen  fishes  may 
be  either  killed  in  large  numbers  or  compelled  to  emigrate.  Fishes 
being  exclusive  water  animals  are  especially  adapted  to  utilize  the 
oxygen  in  the  water.  The  gills  are  the  universally  present  res- 
piratory organs  but  in  special  cases  the  fins  and  part  of  the  ah- 
mentary  canal  may  be  forced  into  service.  In  the  gar-pike  the 
air-bladder  serves  as  a  lung,  at  least  for  the  ehmination  of  CO2. 
Various  other  fishes  have  cellular  air-bladders  connected  with  the 
aUmentary  canal  that  suggest  respiration.  Tower  found  that  in 
fishes  dying  of  asphyxiation  the  ratio  of  CO2  to  O  in  the  air- 
bladder  increases. 

During  the  breeding  season  when  the  gill  chambers  are  full  of 
eggs  much  of  the  respiration  of  the  blindfishes  is  probably  forced 
on  the  fins  and  general  surface.  In  the  surf -fish,  to  which  the  Sac- 
ramento Hysterocarpus  belongs,  the  young  are  born  fully  devel- 
oped.^ In  their  earliest  development  in  the  oyary  the  general 
surface  of  the  larva  must  act  as  a  respiratory  organ,  later  the  ali- 
mentary canal  functions  as  such.  A  continuous  stream  of  ovarian 
fluid  passes  in  at  the  gill-opening  and  out  at  the  anus  at  this  time. 
Finally  the  fins  become  hypertrophied  into  enormous  sheets  super- 
abundantly suppKed  with  blood  vessels.  In  the  Cuban  blindfishes, 
in  which  the  young  reach  a  length  of  an  inch  at  the  time  of  birth, 
vascular  lobes  are  developed  in  the  ovary,  which  the  young  take 
into  their  mouths  and  to  which  they  cling,  possibly  both  for  food 
and  oxygen.  It  is  very  probable  that  those  fishes  that  are  capable 
of  living  out  of  water  for  a  time  carry  on  respiration  through  their 
moist  skin. 

Temperature  and  Adjustment  to  it.  —  In  nearly  all  fresh  waters 
of  the  temperate  region  there  is  a  fluctuation  in  the  water  be- 
tween 32°  to  80°  F.  The  extreme  fluctuation  is  found  only  on 
the  surface  of  the  water.  In  the  bottom  of  lakes  eighty  feet  deep, 
the  annual  fluctuation  ranges  perhaps  between  39°  and  60°  F. 
Fishes  can  always  escape  the  extreme  fluctuations  by  seeking  deeper 
water.  That  they  are  adjusted  to  live  through  extreme  cold  is 
shown  by  the  fact  that  some  species  may  be  frozen  in  ice  and  re- 

1  The  life  history  of  this  species  has  not  been  traced,  but  that  of  some  of  its 
marine  relations  has. 


THE   AQUATIC   VERTEBRATES  1051 

vive  when  thawed  out.  The  adjustment  in  this  respect  probably 
increases  as  one  goes  northward.  Turner  says  of  the  Alaskan 
Dallia:  "When  taken  from  the  traps  the  fish  are  immediately  put 
into  these  baskets  and  taken  to  the  village,  where  the  baskets  of 
fish  are  placed  on  stages  out  of  the  way  of  dogs.  The  mass  of  fish 
in  each  basket  is  frozen  in  a  few  minutes,  and  when  required  to 
take  them  out  they  have  to  be  chopped  out  with  an  axe  or  beaten 
with  a  club  to  divide  them  into  pieces  of  sufhcient  size  to  feed  the 
dogs. 

''The  vitaUty  of  these  fish  is  astonishing.  They  will  remain  in 
those  grass  baskets  for  weeks,  and  when  brought  into  the  house 
and  thawed  out  they  will  be  as  lively  as  ever.  The  pieces  which 
are  thrown  to  the  ravenous  dogs  are  eagerly  swallowed,  the  ani- 
mal heat  of  the  dog's  stomach  thaws  the  fish  out,  whereupon  its 
movements  cause  the  dog  to  vomit  it  up  alive." 

The  lower  temperature  hmit  is  set  to  fish  Kfe  by  the  freezing 
point  of  the  medium,  32°  F.  for  fresh  water,  below  this  for  salt 
water.  The  upper  observed  Hmit  in  ponds  is  somewhere  near 
100  degrees.^  If  the  water  is  suddenly  raised  to  this  point,  fishes 
survive  but  a  few  seconds.  While  the  upper  limit  may  be  set  by 
the  effect  of  the  increased  heat  on  the  protoplasm,  its  effect  may 
be  indirect  and  operate  through  the  reduction  in  the  amount  of  0 
held  in  suspension  by  the  warm  as  compared  with  the  cold  water. 
That  fishes  will  attempt  any  temperature  is  evidenced  by  the 
fact  that  they  occasionally  enter  water  in  the  National  Park  hot 
enough  to  boil  them. 

The  adaptabihty  of  fishes  to  different  temperatures  is  well  shown 
by  Rhinichthys  dulcis  wliich  is  found  in  the  streams  coming  from 
the  warm  springs  at  Banff  in  the  Canadian  National  Park,  and 
also  in  the  icy  waters  of  Vermilion  Creek  at  the  same  place.  The 
same  individuals  are  adjustable  within  wide  limits,  and  the  same 
species  is  sometimes  found  over  a  long  north  and  south  range. 
Nevertheless,  temperature  has  doubtless  played  an  important 
part  in  setting  a  northern  Hmit  to  the  migration  of  species,  as 
they  followed  the  retreating  ice  of  the  glacial  period.     In  North 

1  Jordan  and  Richardson  (Proc.  U.  S.  Xat.  Mus.,  2>3>  •  3i9-3-^0  record  Lucania  browni 
from  a  hot  spring  with  a  temperature  of  128°  F. 


I052  FRESH-WATER   BIOLOGY 

America  a  southward  migration  has  probably  not  taken  place  since 
that  time. 

Fishes  of  cold  waters  are  primarily  members  of  the  families  of 
salmon  and  trout,  whitefish,  miller's- thumb,  and  blackfishes.  The 
check  by  cold  has  not  been  placed  on  any  individual  migration  or 
limits  set  to  the  adult.  Rhinichthys  dulcis  and  the  many  species 
adapted  to  the  great  range  of  variation  in  the  temperature  in  any 
of  our  temperate  lakes  shows  this.  The  temperature  factor  de- 
termining distribution  is  set  rather  by  the  adaptation  of  the  eggs 
to  warm  or  cold  water.  Our  trout,  salmon,  and  whitefishes  breed 
largely  in  winter  when  the  temxperature  is  low.  The  rate  of  de- 
velopment of  their  eggs,  like  that  of  all  cold-water  eggs,  is  slow. 
The  warm-water  species  are  warm-water  species  not  because  their 
individuals  are  incapable  of  entering  cold  water,  for  many  of  them 
do,  but  because  their  eggs  will  not  develop  in  anything  but  water 
much  warmer  than  that  in  which  the  eggs  of  cold-water  species 
develop.  Their  eggs  are  of  rapid  development.  They  are  ad- 
justed to  fluctuations  in  temperature  and  they  respond  to  such 
fluctuations  in  temperature  by  hastening  or  slowing  their  rate  of 
development.^  The  point  of  attack  of  temperatures  is  on  the  eggs 
and  young,  not  on  the  adult,  and  temperature  controls  distribu- 
tion through  its  influence  on  the  eggs. 

In  all  cold  waters  of  the  United  States  accessible  to  them,  trout, 
salmon,  and  whitefish  are  found.  Some  of  them,  the  brook  trout, 
Rocky  mountain  whitefish,  Coulter's  whitefish  and  salmon,  are 
adjusted  to  swift  currents;  others,  the  lake  trout  and  many  white 
fishes,  to  the  stagnant  waters  of  lakes.  Some  of  the  latter  are 
littoral  or  abysmal  or  pelagic,  depending  on  the  nature  of  their 
food.  The  elevation  of  a  stream  has  probably  primarily  nothing 
to  do  with  the  distribution  of  its  inhabitants,  but  because  elevated 
waters  are  usually  cold  (and  frequently  swift)  ah  accessible  moun- 
tain waters  are  inhabited  by  cold-water  species.  The  number  of 
species  adjusted  to  cold  waters  is  not  as  great  and  their  afiinities 

^  The  cod  eggs  which  hatch  in  thirty  days  at  a  temperature  of  from  0.0-2°  C. 
hatch  in  thirteen  days  in  a  temperature  of  6-7.9°.  Herring  eggs  which  require  forty 
days  at  a  temperature  of  2-3.9°  C  hatch  in  eleven  at  a  temperature  of  10-11.9°;  the 
shad  which  hatches  in  eleven  days  at  a  temperature  of  13.5°  hatches  in  three  to  five 
days  in  a  temperature  of  from  20-23°. 


I 


THE   AQUATIC   VERTEBRATES  IO53 

are  not  as  varied  as  those  adjusted  to  the  warmer,  more  accessible 
waters  of  the  central  and  southern  lowlands.  The  latter  are  the 
homes  of  the  black  bass,  sunfishes,  catfishes,  gar  pikes,  and  others. 

So  called  warm-water  species  are  capable  of  a  wide  range  of 
adjustment  to  differing  climates.  Wherever  a  north  and  south 
river  connects  warmer  with  colder  areas  in  which  the  species  are 
otherwise  different,  the  easy  route  of  migration  induces  some  sj)ecies 
to  extend  their  range  into  otherwise  shunned  areas.  The  Missis- 
sippi has  induced  a  southward  migration  of  several  species  beyond 
their  normal  range,  the  Nile  has  extended  the  equatorial  African 
fauna  to  its  mouth.  But  the  most  notable  example  is  offered"  by 
the  Madeira  and  Tapajos  to  Paraguay  and  La  Plata  waterway. 
It  extends  from  the  equator  south  to  a  latitude  equal  to  that  of 
Memphis.  Nearly  all  of  the  fishes  of  Buenos  Aires  belong  to  Ama- 
zonian genera  or  even  species.  Only  one  or  two  Amazonian  genera 
have  succeeded  in  reaching  the  borders  of  the  United  States. 
Fifty  Amazonian  genera  have  reached  the  La  Plata  basin  that  have 
not  succeeded  in  going  an  equal  distance  south  on  the  Atlantic 
coast  where  they  did  not  have  the  facilities  or  inducement  of  a 
continuous  waterway. 

Current  and  Adjustment  to  It.  —  The  major  adaptation  of  all 
fresh-water  fishes  is  to  the  locomotion  of  water.  Most  fishes 
stand  head  upstream,  a  position  that  makes  the  respiratory  move- 
ment easiest  in  a  current.  Different  fishes,  and  in  some  cases  the 
same  fishes  at  different  seasons  of  the  year,  are  adjusted  to  the 
entire  range  of  variation  in  the  intensity  of  the  locomotion.  Water- 
falls only  are  not  inhabited  by  fishes,  but  even  these  are  ascended 
or  descended  if  not  too  high.  Different  species  of  the  Salmonidae 
give  us  examples  of  the  entire  range  of  adjustment  to  currents. 
Some  of  them  five  only  in  the  stagnant  water  of  deep  lakes.  Others 
live  only  in  swift  mountain  brooks.  The  members  of  the  genus 
Coregonus  usually  live  in  the  stagnant  waters  of  lakes,  but  Core- 
gonus  coulteri  is  found  in  a  mountain  torrent,  and  the  Tippecanoe 
Cisco,  which  lives  in  the  stagnant  water  of  the  lake  during  the 
greater  part  of  the  year,  runs  up  the  tributaries  in  December. 
Other  whitefishes  and  trout  have  the  same  habit.  Difi'crent  fishes 
are  even  adjusted  to  the  differences  in  the  same  small  stream  in 


I054 


FRESH- WATER   BIOLOGY 


which  quiet  pools  alternate  with  swift-flowing  ripples.  In  the 
Mississippi  Valley  the  riffles  are  occupied  by  darters,  in  Cuba  by 
gobies,  in  South  America  by  characins,  and,  although  belonging 
to  widely  different  famiHes,  they  greatly  resemble  each  other. 

Light  and  Adjustments  to  It.  —  In  the  shallower  parts  of  clear 
water  the  fluctuations  in  hght  from  day  to  night  are  but  little  less 
than  in   the   air.     Various  fishes  are  variously  adjusted   to   the 


Fig.  1545.    Hog  Sucker,  Calostomus  nigricans  Le  Sueur.    Actual  size,  305  mm.  long. 

light.  Some  are  nocturnal,  remaining  hidden  during  the  day,  as 
the  common  catfish.  Some  combine  stereotropism  with  their  neg- 
ative hehotropism,  and  take  shelter  in  crevices  and  under  rocks. 
The  Hght-shunning  habit  on  the  part  of  their  ancestors  doubtless 
accounts  for  the  cave-inhabiting  blindfishes  of  to-day.  Some 
diurnal  fishes  habitually  stay  in  the  shade  of  some  tree,  or  log,  or 
pier,  while  others  are  found  in  the  open.  There  seems  to  be  a 
complete  gradation  between  the  bhndfishes,  which  always  live  in 


Fig.  1546.    Hog  Sucker,  Catostomus  nigricans  Le  iiueur.    Actual  size,  81  mm.  long. 


total  darkness,  and  those  fishes,  Hke  some  sunfishes,  that  five  in 
total  hght,  as  far  as  this  exists. 

The  eye  is  not  the  only  Kght-perceiving  organ  of  aquatic  verte- 
brates. The  skin  is  sensitive  to  Hght  in  many  cases.  The  blind- 
fishes,  whose  eyes  are  not  functional  and  may  be  entirely  removed, 
nevertheless  appreciate  the  difference  between  light  and  dark. 
The  young  after  having  their  eyes  removed  are  as  sensitive  to 


THE  AQUATIC  VERTEBRATES  105  5 

light  as  those  with  eyes,  and  the  entire  skin  seems  equally  sensitive 
to  light.  The  sight  of  the  nocturnal  fishes  is  worse  than  that  of 
owls,  and  their  eyes  are  but  Uttle  used.  The  sight  of  the  posi- 
tively heliotropic  fishes,  on  the  other  hand,  is  good,  their  eyes  are 
large  and  they  depend  on  their  eyesight  for  food.  They  capture 
living  food  and  are  frequently  pelagic  in  habit.  Small-mouthed 
fishes  depending  on  their  eyes  for  food  will  not  take  food  that  is 
at  rest.  Small  fragments  of  meat  falling  through  the  water  will 
readily  be  seized  but  will  not  be  picked  up  from  the  bottom.  The 
great  variety  of  artificial  flies  and  gyrating  baits  are  man's  adapta- 
tions to  the  fact  that  some  large-mouthed  fishes  also  select  their 
food  by  sight. 

Depth  and  the  Bottom,  and  Adjustments  to  Them.  —  No  system- 
atic study  of  the  bottoms  of  our  lakes  has  been  made  and  it  is 
hence  unknown  how  extensive  the  abysmal  fauna  is.  In  fishes 
ranging  in  deep  water  the  adjustment  is  probably  due  not  so  much 
to  the  depth  itself,  as  to  the  things  that  go  with  depth.  Pressure 
increases  one  atmosphere  with  each  thirty  feet  in  depth,  plants 
disappear  beyond  a  few  feet,  and  with  the  plants  necessarily  disap- 
pear all  the  animals  (fish  food  for  the  most  part),  that  are  associ- 
ated with  the  plants. 

The  character  of  the  bottom  is  not  a  simple  element  like  tem- 
perature, Hght,  or  current.  There  is  a  graduation  from  mud  to 
gravel  and  rock  and  each  of  these  may  be  weed-covered  or  bare. 
But  whether  the  bottom  is  mud,  gravel  or  rock  depends  on  cur- 
rent. That  certain  species  are  found  principally  on  one  bottom  or 
another  is  certain,  but  that  the  adjustment  is  to  the  character  of 
the  bottom  and  not  to  the  current  and  food  that  go  with  it  is 
doubtful. 

The  Biological  Environment  and  Adjustment  to  It.  —  Food  is  the 
controlling  factor  in  the  local  distribution  of  fishes  within  any 
unit,  as  chemical  composition  and  temperature  are  controlling 
factors  in  the  geographical  distribution  among  the  dift"erent 
units.  Food  itself  is  dependent  on  other  food  and  this  ultimately 
on  depth,  nature  of  bottom,  current,  and  the  other  elements  of  the 
physical  environment.  For  the  most  part  the  food  of  the  young  is 
essentially  different  from  the  food  of  the  adult  of  the  same  species, 


1056  FRESH-WATER   BIOLOGY 

and  consists  of  the  organisms  composing  the  plankton,  largely 
Entomostraca.  The  members  of  a  local  fish  fauna  are  distrib- 
uted in  the  following  ecological  groups:  pelagic,  littoral  (bottom 
fishes,  all  predacious  fishes),  and  nocturnal. 

To  these  should  be  added  abysmal  fishes,  but  nothing  is  known 
of  these  in  America  except  that  Triglopsis  is  found  in  deeper  water 
of  the  Great  Lakes. 

Pelagic,  abysmal,  littoral,  and  nocturnal  forms  are  such  as  find 
their  food  in  those  regions  or  times.  Their  adaptations  are  but 
secondary  adjustments  to  the  region  in  which  their  food  is  found. 
Everything  eatable  is  food  for  some  fishes  though  few  have  such 
omnivorous  tastes  as  to  take  the  entire  bill  of  fare.  The  skipjack 
{Lapidestes)  is  a  surface  ranger  and  occupies  as  definite  a  position 
under  the  surface  of  the  pelagic  area  of  our  lakes  as  the  swallows 
do  over  it.  Insects  and  all  other  minute  terrestrial  organic  mat- 
ters reaching  the  surface  of  the  water  find  a  lodgment  in  their 
stomachs.  Frequently  the  fish  darts  out  of  the  water  as  the 
swallow  dips  into  it  to  secure  its  food.  Its  food  is  not  confined  to 
terrestrial  strays,  but  it  also  takes  Entomostraca  and  Chironomus 
larvae.  Zygonectes  and  Fundulus  also  range  near  the  surface  but 
nearer  the  shores.  In  the  mountain  lakes  in  which  the  skipjack 
is  not  found,  the  half-grown  whitefish  (Coregonus  williamsoni)  occu- 
pies the  same  ecological  niche.  In  Lake  Tahoe  on  June  evenings 
individuals  nine  inches  long  rise  to  gnats  blown  into  the  lake,  and 
they  can  then  be  caught  with  a  minute  hook  baited  with  a  fly. 

In  the  American  tropics  a  killifish  with  half  its  eyes  adapted  to 
seeing  in  air  and  the  other  half  adapted  to  seeing  in  water  also 
ranges  on  the  surface.  Larger  objects  reaching  the  surface  of  the 
water  are  secured  by  black  bass,  trout,  and  other  fishes  that  range 
and  poise  in  deeper  water  and  ''rise"  to  their  prey  near  the  sur- 
face as  the  kingfisher  dives  for  his.  All  fishes  that  rise  to  arti- 
ficial bait,  grasshoppers,  etc.,  belong  to  this  group.  Some  trout 
rise  more  readily  to  a  mouse  but  for  esthetic  reasons  this  cannot  be 
recommended  for  bait. 

Another  series  of  pelagic  fishes  is  formed  by  the  plankton  feeders. 
There  are  several  sorts  of  these.  The  young  of  most  fishes,  the 
sunfishes  and  minnows  and   some  whitefishes,  see    their  minute 


THE   AQUATIC   VERTEBRATES  IO57 

prey  and  deliberately  pick  it  from  the  water.  Such  are  pro\'ided 
with  teeth  either  in  their  mouths  or  in  their  gullets.  AniAher 
series  probably  including  the  spoonbill  catfish  take  in  large  quanti- 
ties of  water  and  strain  the  plankton  from  it.  They  have  weak 
teeth  or  none  and  specially-adapted  gill  rakers  for  straining  the 
water. 

The  various  darters,  a  pecuHar  American  product,  are  all  lit- 
toral. They  rest  on  their  pectorals  on  the  bottom,  in  shallow 
water.  With  head  erect  and  eyes  protruding  they  are  ready  for 
anything  that  moves  within  their  range  of  \ision.  They  are  found 
among  weeds  and  gravel,  chiefly  in  flowing  water  so  shallow  that 


Fig.  1547.    Johnny  Darter,  Boleosotna  nigrum  Rafinesque.    Actual  size,  55  mm.  long. 

the  surface  is  rippled.  Associated  with  them,  or  in  places  similar 
to  these,  in  favorable  locahties,  are  miller's-thumbs.  The  pirate 
perch  and  trout  perch  should  probably  also  be  placed  here. 

Other  bottom  fishes  with  sucker  mouth  and  elongate  alimentary 
canal  are  found  over  mud  bottoms.  These  include  Campostoma, 
suckers,  carp,  and  sturgeon  in  North  America.  In  tropical  America 
their  place  is  taken  by  peculiar  armored  relatives  of  the  catfishes, 
the  Loricariidae.  Lastly,  the  large,  predacious  fishes  treat  the 
smaller  fishes  as  they  in  their  turn  treat  the  plankton.  Here  be- 
long the  muscalonge,  the  pickerels,  salmon  trout,  and  the  basses. 
Our  nocturnal  catfishes  and  the  ubiquitous  eel  are  omnivorous. 
They  take  what  they  can.  Everything  that  tastes  or  moves  and 
is  within  reach  is  food  for  the  nocturnal  catfish.  Some  blindfishes 
planted  in  a  pool  had  a  way  of  disappearing  that  was  mysterious, 
until  the  pool  was  drained  and  the  sardonic  catfish,  lurking  under  a 
rock  and  found  in  possession  of  the  last  bhndfish  partly  digested, 
solved  the  mystery. 

Fishes  are  adapted  to  their  food  in  structure  as  well  as  habit. 


1058  FRESH-WATER   BIOLOGY 

The  dentition  varies  from  none  at.  all  to  the  crushing  apparatus  of 
the  white  perch,  the  cutting  incisors  of  some  of  the  killifishes  and 
the  raspHke  patches  of  the  teeth  of  the  muscalonge.  The  mouth 
varies  in  position,  shape,  and  size  according  to  the  food,  from  the 
ventrally-placed  sucker  mouth  to  the  upward-pointing  mouth  of 
Zygonectes;  from  the  small  mouth  of  the  cisco  to  the  capacious  maw 
of  the  muscalonge.  The  gill-rakers  vary  from  none  to  the  com- 
pHcated  strainers  of  the  spoonbill  catfish.  The  aHmentary  canal 
also  varies  with  the  food  from  the  short  canal  of  the  flesh  eaters 
to  the  convoluted  tube  many  times  as  long  as  the  fish  in  the  mud 
eaters.  That  fishes  are  a  very  adaptable  group  is  shown  by  the 
fact  that  in  South  America  a  single  family,  the  characins,  have 
the  widest  range  of  adaptation  in  the  alimentary  canal  to  different 
food.  Forbes  has  pointed  out  that  the  minnows  of  North  America 
are  adjusted  to  a  great  variety  of  food.  He  distinguishes  four 
groups:  (i)  Intestine  two  to  nine  times  as  long  as  the  fish,  pharyn- 
geal teeth  not  hooked,  with  grinding  surface.  (2)  Intestine  one  to  one 
and  two-thirds  times  as  long  as  the  fish,  pharyngeal  teeth  hooked, 
with  grinding  surface.  (3)  Intestine  somewhat  shorter  than  the  fish, 
teeth  hooked,  with  grinding  surface.  (4)  Intestine  usually  shorter 
than  the  head  and  body,  teeth  hooked,  without  grinding  surface. 
Concerning  the  relation  of  these  structures  Forbes  says: 
*'It  is  consequently  from  a  comparison  of  the  ratios  of  these 
groups  that  we  shall  derive  the  most  interesting  facts  relating  to 
the  correspondence  of  food  and  structure.  The  most  conspicuous 
result  is  the  great  preponderance  of  mud  in  the  intestines  of  the 
fishes  of  the  first  group,  characterized  by  an  extraordinarily  elon- 
gate intestine,  and  by  pharyngeal  teeth  destitute  of  hooks  and  pro- 
vided with  a  broad  grinding  surface.  Here,  as  already  noted, 
mud,  sand,  and  gravel  amount  to  about  three-fourths  of  the  mat- 
ter ingested,  while  in  the  third  and  fourth  groups  only  trivial  and 
accidental  quantities  occurred.  In  the  second  group,  on  the  other 
hand,  with  intestines  intermediate  in  length,  mud  was  still  abundant, 
but  much  less  so  than  in  the  first,  averaging  less  than  half  the 
whole.  If  we  exclude  this  indigestible  matter,  however,  we  shall 
find  the  first  group  still  further  distinguished  by  the  predominance 
of  vegetation  as  compared  with  animal  matter,  the  latter  being 


THE   AQUATIC   VERTEBRATKS  1059 

only  about  one-third  the  former,  while  in  groups  three  and  four, 
on  the  other  hand,  vegetation  amounts  to  about  one-third  the 
animal  food.  The  groups  last  mentioned,  distinguished  from  each 
other  as  they  are  only  by  the  presence  of  a  masticatory  surface 
on  the  pharyngeal  teeth  in  the  first,  and  its  absence  in  the  second, 
differ  scarcely  at  all  in  their  general  food  characters,  and  this 
structural  feature  seems  therefore  to  be  of  little  significance.  In 
both  the  animal  ratio  amounts  to  seventy-five  per  cent,  and  vege- 
tation stands  in  each  at  twenty-five;  while  insects  are  respectively 
fifty  and  sixty-one." 

Recently  Putter  has  maintained  that  fishes  absorb  food  in  solu- 
tion in  the  water.  He  found  that  a  goldfish  lived  for  forty-one 
days  in  tap  water  which  contained  no  organized  food  and  the 
oxygen  consumed  substantially  accounted  for  the  loss  in  weight. 
When  organic  substances  were  dissolved  in  the  tap  water,  the  goldfish 
survived  for  seventy-eight  days,  and  the  oxygen  consumed  greatly 
exceeded  the  amount  that  would  account  for  the  loss  in  weight. 

Food  according  to  its  nature  may  be  detected  by  sight,  perception 
of  vibrations,  touch,  smell,  or  taste. 

Food  is  detected  by  sight  in  most  fishes.  Many  fishes  will 
seize  an  object  that  is  in  motion  without  discrimination  as  to 
what  it  is  provided  it  is  the  right  size.  If  it  is  suitable  for  food 
that  fact  is  discovered  by  touch  or  taste,  or  both,  in  the  mouth 
and  the  object  is  swallowed.  If  it  is  not  fit  for  food  it  is  rejected. 
It  is  evident  that  in  such  cases  sight  only  locates  the  moving 
object,  other  senses  distinguish  its  nature. 

Neither  friend  nor  foe  of  the  fishes  discloses  his  presence  by 
sound,  but  frequently  does  so  by  vibrations  of  lower  frequency. 
It  is  extremely  doubtful  whether  any  sound  produced  over  water 
is  heard  by  fishes  in  the  water.  The  sounds  of  the  air  are  scarcely 
capable  of  passing  the  surface  of  the  water  to  an  extent  to  be  per- 
ceived by  an  ear  under  water  as  highly  developed  as  that  of  man. 
The  ears  of  fishes  are  much  more  simple  than  those  of  man.  The 
ability  on  the  part  of  fishes  to  hear  at  all  has  been  disputed,  but 
Parker  ^  has  recently  made  experiments  that  show  conclusively 
that  fishes  hear  sounds  produced  under  water. 

1  Bull.  U.  S.  Fish  Com.,  22  :  45-64. 


Io6o  FRESH-WATER   BIOLOGY 

In  over  half  of  our  fresh-water  fishes  the  air  bladder  is  connected 
by  a  chain  of  ossicles  with  the  ear.  In  some  of  them  the  air 
bladder  comes  in  contact  with  the  skin  in  an  area  just  behind  the 
head.  The  intercostal  muscles  are  not  developed  at  this  place  and 
a  form  of  tympanum  is  thus  produced.  It  has  been  suggested  that 
this  Weberian  apparatus,  as  it  is  called,  is  in  reahty  an  auditory 
organ ;  that  it  is  a  static  apparatus  controlling  the  rising  and  sink- 
ing of  the  fish  in  water;  that  it  is  a  manometer  acquainting  the 
fish  with  the  degree  of  pressure  that  is  exerted  by  the  gases  in  the 
air  bladder  against  its  walls;  that  it  is  a  barometer  acquainting 
the  fish  with  the  variations  in  the  atmospheric  pressure;  that  it  is 
a  sound  producer.  Judged  by  its  structure  alone,  in  some  forms 
the  air  bladder  is  divided  into  two  small  lateral  parts  connected 
with  the  ossicles,  the  rest  of  the  air  bladder  having  disappeared,  it 
seems  more  than  probable  that  it  is  an  organ  for  the  perception  of 
sound. 

Vibrations  of  lower  frequency  than  those  producing  sound,  such 
as  may  be  produced  by  waves  or  bodies  falling  into  the  water,  are 
perceived  by  the  lateral  line  organs  of  fishes.  The  lateral  fine 
organs  of  the  head  of  the  blindfishes  are  greatly  exaggerated  and 
their  ability  to  perceive  vibrations  enables  these  fishes  to  secure 
Hving  prey  with  precision.  The  lateral  line  organs  of  the  head 
take  the  place  of  the  eyes  of  pelagic  fishes  in  detecting  food.  Fer- 
nandus  Payne  succeeded  in  getting  an  Amhlyopsis  to  respond  to 
the  water  dripping  into  its  aquarium.  It  would  rise  to  the  point 
where  the  drop  of  water  struck  and  would  try  to  seize  it  by  snap- 
ping at  it.  Perception  of  vibrations  by  the  lateral  line  organs  of 
the  head  enabled  it  to  locate  the  point  of  impact  of  the  water. 
Touch,  taste,  or  smell  could  have  nothing  to  do  with  it.  These 
fishes  may  touch  recently-crushed  amphipods  on  which  they  feed 
without  paying  any  attention  to  them  unless  a  stray  leg  is  still 
moving.  They  will  readily  take  meat  attached  to  a  string  held  in 
the  hand  to  give  it  motion. 

Many  fishes  are  conscious  of  the  presence  of  food  by  perceiving 
it  either  through  the  sense  of  smell,  touch,  or  taste.  Parker  has 
demonstrated  that  the  catfish  can  detect  minced  earthworms  by 
its  sense  of  smell.     The  elaborate  experiments  of  Herrick  with 


THE   AQUATIC    VERTEBRATES  lo6l 

codfishes  have  shown  that  their  sense  of  smell  gives  them  but 
vague  information,  while  the  senses  of  touch  and  taste,  whose  organs 
are  found  over  the  entire  body,  enable  the  catfish  to  detect  and 
secure  any  food  coming  in  contact  with  any  part  of  the  body.  In 
contrast  to  the  bhndfishes  (Amblyopsis)  of  the  Ohio  Valley  caves, 
the  Point  Loma  blindfish  secures  its  food  through  touch  and  taste. 
A  hungry  Point  Loma  blindfish  with  a  stroke  of  the  fins  brings 
the  mouth  in  position  for  operations  as  soon  as  any  portion  of  its 
skin,  especially  of  the  head,  comes  in  contact  with  food. 

Fish  Enemies.  —  The  enemies  of  fishes  are  the  mink,  otter,  an 
occasional  raccoon  and  cat  among  the  mammals;  the  kingfisher, 
herons,  ducks,  loons,  and  terns  among  birds;  an  occasional  bull- 
frog and  possibly  Necturus  among  batrachians;  several  snakes, 
and  many  fishes,  spawn  eaters,  fry  catchers,  lampreys,  and  adult- 
eating,  predacious  fishes. 

The  otter  as  a  fish  enemy  has  been  practically  eliminated.  71ie 
occasional  fish  caught  by  the  mink  and  raccoon  will  form  but  a 
small  annual  total.  In  fact,  by  the  changes  incident  to  advancing 
civilization,  all  but  the  aquatic  enemies  of  the  fishes  have  been 
reduced  to  a  point  where  their  depredations  can  have  but  little 
selective  value. 

Fishes  evidently  could  avoid  terns  and  kingfishers  by  living  below 
the  few  inches  penetrated  by  these  divers.  But  the  advantages  of 
food  near  the  surface  evidently  outweigh  the  danger  of  being 
caught,  as  long  as  a  sudden  dive  or  a  dart  forward  will  enable  the 
fish  to  escape. 

Herons  and  ducks  are  avoided  by  selecting  water  too  deep  for 
these  enemies.  Color  and  swiftness  are  probably  other  adapta- 
tions to  the  same  enemies.  The  darter  sits  with  outspread  pec- 
torals on  the  bottom  of  a  stream  or  lake  within  easy  reach  of  a 
heron.  A  sudden  motion  of  the  powerful  pectorals  and  he  sits  as 
composedly  somewhere  else.  The  dart-like  motion  which  gives  the 
darter  its  name  is  an  adaptation  to  secure  food  and  avoid  enemies. 
Swiftness,  inconspicuousness,  or  ability  to  enter  retreats  are  the 
means  of  defense  against  the  loon  and  his  ilk.  Howe\or,  none 
of  the  devices  are  always  efficient. 

The  greatest  enemy  of   fishes  is  the  spawn   stealer.     At  Lake 


lo62  FRESH-WATER  BIOLOGY 

Tahoe  the  dead  trout  eggs  from  the  hatchery  were  daily  thrown 
into  the  lake.  Wliile  no  fish  might  be  in  evidence  a  handful 
of  trout  eggs  was  sure  to  bring  a  bullhead  {Cottus  heldingi)  from 
under  every  rock.  The  same  thing  happened  when  the  young 
trout  fry  were  planted  in  the  brooks.  The  adaptations  of  the 
black  bass,  sunfish,  and  Amia  against  depredations  in  their  nests 
have  already  been  given.  No  doubt  many  young  fishes  are  eaten 
by  minnows  and  sunfishes.  A  half-starved  sunfish  captured  in  a 
cave  began  to  pick  out  the  larval  bhndfishes  in  his  pail,  with  neat- 
ness and  dispatch,  as  soon  as  there  was  light  enough  for  it  to  see 
them.  The  herding  or  schooling  of  their  young  by  many  fishes,  as 
an  adaptation  against  enemies,  has  been  described  before.  Against 
their  predacious  neighbors  strength,  agility,  endurance,  and  color 
are  the  adjustments.  The  dispersal  of  a  school  and  the  leap  out 
of  the  water,  reaching  its  maximum  in  the  fhght  of  the  flying  fish, 
are  all  adaptations  to  escape  specific  attacks.  Aside  from  these 
general  adaptations  in  the  habit,  structural  adaptations  against 
fish-eating  enemies  are  also  found. 

The  stickleback  has  divergent,  erectile  spines  that  can  be  locked 
when  erected.  This  arrangement  is  altruistic  rather  than  egoistic. 
While  it  does  not  prevent  a  duck  or  other  animal  from  eating  an 
occasional  stickleback  the  duck  is  not  Ukely  to  be  tempted  by  a 
second  stickleback.  More  effective  weapons  are  the  erectile  dorsal 
and  pectoral  spines  of  the  catfishes.  In  the  stone  cats  the  spine 
is  surrounded  by  glandular  tissue  producing  poison.  The  spine  in 
entering  an  opponent  pierces  the  gland  and  carries  some  of  the 
poison  into  the  wound. 

Color  must  be  looked  upon  as  an  adjustment  to  light  in  the 
presence  of  enemies.  The  amount  of  color  on  the  surface  of  a 
fish  is  proportionate  to  the  intensity  of  the  light  in  the  environment. 
The  arrangement  of  the  color  is  conditioned  by  the  surroundings. 
Its  presence  is  an  adaptation  to  the  physical  environment  and  its 
arrangement  is  an  adaptation  to  the  biological  environment.  All 
animals  living  for  generations  in  caves  become  bleached  and  finally 
lose  all  pigment.  Nocturnal  fishes  are  in  large  measure  black. 
Bottom  fishes,  like  the  darters,  hog  sucker,  miller's-thumb,  are 
mottled  and  crossbarred.     Weed-inhabiting  species  are  barred  (yel- 


I 


THE  AQUATIC   VERTEBRATES  T065 

low  perch),  striped  (black  bass),  or  mottled  (pickerels,  sunfishes, 
etc.).  Large  size  and  strength  are  the  best  adaptations  against 
existing  fish  enemies.  Small  size  and  insignificance  are  advan- 
tageous for  other  reasons.  Between  these,  alertness,  with  power 
of  quick  movement,  and  protective  color  are  the  most  efi'icient 
means  of  escaping  enemies. 

But  all  of  these  adaptations  are  not  always  sufiicient.  The 
most  insidious  of  the  fish  enemies  is  the  lami)rey.  So  perfect  is 
its  means  of  attachment  to  its  prey,  that  such  a  hard-scaled  and 
vigorous  fish  as  Amia  calva  can  rarely  prevent  the  attachment 
and  adhesion,  although  the  most  violent  efforts  be^made.  If  a 
lamprey  is  attached  to  a  stone  of  moderate  size,  the  stone  is  fre- 
quently brought  out  with  the  fish  if  the  animal  is  jerked  up  sud- 
denly. In  letting  go  its  hold  all  that  is  necessary  is  to  fill  the  disc 
with  water  from  the  respiratory  bronchus,  whereupon  suction 
ceases  and  the  animal  is  free.  In  feeding,  the  sharp  teeth  pressed 
against  the  skin  of  the  animal  to  which  it  is  attached  naturally 
call  the  blood  to  the  place.  This  hyperaemia  is  caused  even  more 
by  the  suction.  At  the  same  time  the  piston-Uke  tongue  with  its 
powerful  muscles  and  the  saw-Hke  teeth  soon  rasp  a  hole  through 
the  skin.  The  blood  is  then  sucked  from  the  fish  and  swallowed. 
The  whole  operation  is  something  Hke  the  extraction  of  blood  by  a 
leech.  The  lamprey  may  remain  upon  a  fish  so  long  as  the  latter 
supplies  sufficient  nutriment.  Sometimes  the  fish  becomes  ex- 
ceedingly pale  and  weak  so  that  it  floats  near  the  surface.  In 
such  a  case,  the  fishermen  know  immediately  that  there  is  a  lam- 
prey attached  to  the  fish,  and,  with  a  dip  net,  usually  have  no  great 
trouble  in  catching  both.  The  birds  of  prey  also  make  this  their 
opportunity  and  frequently  carry  oft"  the  floating  fish,  the  lamprey 
sometimes  remaining  attached  until  it  has  been  carried  a  consid- 
erable distance  into  the  air. 

That  the  injury  to  the  food  fishes  is  very  great  may  be  inferred 
from  the  fact  that  sometimes  out  of  fifteen  catfish  caught  on  a  set 
line  in  one  night,  ten  to  twelve  have  great  raw  sores  where  lampreys 
have  attacked  them.  In  the  spring,  too,  when  the  suckers  {Catosto- 
mus)  run  up  to  spawn,  very  many  of  them  carry  a  lamprey,  and 
naturally  by  the  great  drain  of  blood  it  causes,  the  fish  must  be 


1064  FRESH-WATER   BIOLOGY 

weakened,  so  that  obstacles  on  the  way  to  the  spawning  ground 
are  less  Uable  to  be  surmounted  than  if  the  fish  were  in  full  vigor. 
In  South  America  small  catfishes  Uve  in  the  gills  of  larger  catfishes. 

Origin  of  Adapted  Faunas.  —  It  has  been  shown  that  the  major 
adaptations  of  fresh-water  fishes  were  acquired  by  their  ancestors 
before  they  were  ehgible  to  a  fresh-water  existence. 

The  origin  and  modification  of  the  cave  fauna  gives  us  a  con- 
crete example  of  the  change  of  location,  resulting  from  predestined 
adaptation  and  of  subsequent  minor  adaptations.  Caves  are  at  the 
present  time  being  colonized  by  the  immigration  of  salamanders  of 
the  genus  Sprier  pes  and  other  animals  that  have  become  adapted 
to  a  cave  existence  through  their  habit  of  living  in  the  dark  under 
rocks,  bark,  and  other  similar  places.  The  adaptation  to  the  con- 
ditions of  cave  existence  in  this  case  determines  the  change  of 
location  when  the  opportunity  arises. 

That  minor  adaptations  will  occur  in  these  after  they  have 
become  exclusively  cave  forms,  is  shown  by  the  structure  of  the 
permanent  cave  salamanders  of  Missouri  and  Texas.  These  have 
in  large  measure  lost  their  color  and  have  degenerate  eyes. 

A  somewhat  more  complex  example  is  furnished  by  the  history  of 
the  Horse  Cave  River.  At  Horse  Cave,  Kentucky,  a  wide  valley 
extends  north  and  south.  Tributary  valleys  come  from  the  east  and 
west.  The  hills  bordering  these  valleys  are  limestone  capped  with 
sandstone.  The  north  and  south  valley  was  formed  by  the  Horse 
Cave  River  that  originally  flowed  over  sandstone  like  that  capping 
the  bordering  hills.  No  doubt  it  had  a  fauna  as  varied  as  that  of 
any  surface  stream.  The  stream  cut  first  through  the  sandstone, 
then  through  the  limestone.  When  it  had  reached  the  easily  dis- 
solving limestone  of  the  Kentucky  caves  and  Green  River  had  cut 
some  distance  below  the  surface. of  this,  some  part  of  its  water, 
later  more  and  more,  found  its  way  to  the  Green  River  by  under- 
ground channels.  To-day  not  a  sign  is  seen  on  the  surface  of  the 
streams  that  are  responsible  for  the  valley  about  Horse  Cave.  At 
least  one  of  them  rushes  through  lofty  chambers  one  hundred 
eighty-five  feet  beneath  the  streets  of  Horse  Cave  City.  With 
this  change  in  the  environment,  with  the  disappearance  of  Horse 


THE   AQUATIC   VERTEBRATES  1065 

Cave  River  from  the  surface,  its  inliabitants  had  to  migrate. 
They  moved  in  two  directions  to  adapted  environments.  The 
shore  fishes  and  channel  fishes  moved  out  to  the  Green  River 
where  their  descendants  five  to  the  present  day.  The  negatively 
heliotropic,  nocturnal,  or  stereotropic  fishes  moved  into  the  holes 
dissolved  in  the  bottom  of  the  river.  Hieir  descendants  live,  at 
the  present  time,  in  the  stream  below  or  within  the  valle\-.  They 
are  colorless  and  all  but  eyeless,  and  have,  no  doubt,  acc^uired  this 
exaggerated  adaptation  to  their  present  abode  since  their  immi- 
gration. But  the  major  adaptation  to  the  cave  existence  they 
possessed  before  the  formation  of  the  caves,  and  it  was  responsible 
for  their  migration  to  their  present  habitat. 

As  was  pointed  out  in  the  opening  paragraphs,  the  fauna  of  the 
glaciated  region  of  North  America  has  similarly  been  derived  by 
immigration  from  the  south  and  possibly  the  ocean  and  Siberia  to 
the  north  and  west.  The  Great  Lake  Basin  has  but  twenty-seven 
of  its  one  hundred  fifty-two  species  peculiar  to  itself;  five  are  but 
varieties  of  more  southern  species  and  the  remaining  twenty-one 
more  than  represent  the  extent  to  which  its  fauna  has  become 
adapted  in  this  area  for  some  of  them  (eight  Salmonidae  and  eight 
Cottidae)  are  cold-water  species  that  may  have  been  crowded  out  of 
the  region  south  of  the  basin  by  the  encroaching  heat  after  the 
passing  of  the  glacial  epoch. 

The  selective  migration  to  adapted  locations  must  be  added  to 
the  factors  contributing  to  the  origin  of  adapted  faunas.  This 
factor,  ''change  of  location,"  is  as  important  to  the  origin  of 
adapted  faunas  as  the  ''change  of  function"  to  the  origin  of 
adaptive  structures.  Innumerable  minor  adaptations  to  heat, 
sediment,  light,  food,  and  to  the  peculiar  coml)inations  found  in 
each  selected  locality  have  no  doubt  arisen  in  such  localities. 


io66  FRESH-WATER   BIOLOGY 

IMPORTANT  WORKS   ON  AQUATIC   VERTEBRATES 

General 
Cambridge   Natural    History,   edit,   by  S.  F.  Harmer  and   A.  E.   Shipley. 
Volumes:  vn,  Fishes;  vni,  Amphibia;  v,  Reptilia;  rx,  Birds;   x,  Mam- 
mals.    London. 
ScHARFF,  R.  F.     191 2.     Distribution  and  Origin  of  Life  in  America.     New 
York. 
Bulletin  of  the  U.  S.  Bureau  of  Fisheries;  Washington,  D.  C. 

(Contains  many  articles  on  Fishes,  Birds,  and  Reptiles.) 

Mammals 
Ingersoll,  Ernest.     1907.     The  Life  of  Animals.     The  Mammals.     New 

York. 
Seton,  E.  T.     1909.    Life  Histories  of  Northern  Animals.    2  vols.    New  York. 
Stone,  Witmer,  and  Cram.     1902.     American  Animals.     New  York. 

Birds 
Chapman,  F.  M.     191 2.     Birds  of  Eastern  North  America.     New  York. 
CouES,  Elliott.     1903.     Key  to  North  American  Birds.     Boston. 
RiDGWAY,  Robert.     Birds  of  North  and  Middle  America.     Bulletin  U.  S.  Nat. 

Mus.,  No.  50.     Part  I,  1901;  Part  II,  1902;  Part  III,  1904;  Part  IV, 

1907;  Part  V,  1911. 

Reptiles 
Cope,  E.  D.     1898.     Crocodilians,  Lizards,  and  Snakes  of  North  America. 

Ann.  Rep.  Smithsonian  Inst.,  pp.  153-1270. 
DiTMARS,  R.  L.     1907.     Reptile  Book.     New  York. 

Amphibia 

C0PE,E.  D.    1889.    The  Batrachia  of  North  America.    Bull.  U.  S.  Nat.  Mus., 

34:  1-525- 
DiCKERSON,  Mary  C.     1906.     Frog  Book.     New  York. 

Fishes 
Jordan,  D.  S.     1905.     Guide  to  the  Study  of  Fishes.     New  York. 
Jordan,  D.  S.,  and  Evermann,  B.  W.     i 896-1 900.     The  Fishes  of  North  and 
Middle  America.    Bull.  U.  S.  Nat.  Mus.,  No.  47.    4  Parts. 
1902.    American  Food  and  Game  Fishes.     New  York. 

A  number  of  admirable  state  lists  have  been  published  on  Mammals,  Birds,  and  Fishes.    Nominally 
confined  to  a  single  state,  they  are  useful  over  a  much  wider  territory. 


CHAPTER   XXXI 
TECHNICAL    AND    SANITARY    PROBLEMS 

By  GEORGE   C.  WHIPPLE 

Professor  of  Sanitary  Engineering,  Harvard  University 

There  are  several  very  practical  problems  of  fresh-water  biology 
which  deserve  consideration,  and  which  will  be  treated  briefly  in 
this  chapter.  They  relate  chiefly  to  some  of  the  smallest  organisms 
found  in  fresh  water,  —  the  bacteria  and  the  plankton.  There  are 
other  problems,  to  be  sure,  which  have  to  do  with  larger  organisms, 
but  most  of  these  have  been  referred  to  in  the  various  chapters 
which  have  gone  before. 

First  and  foremost  is  the  problem  of  disease  transmission.  Patho- 
genic bacteria  are  not  normally  present  in  natural  fresh  waters, 
but  rivers  and  lakes  in  inhabited  regions  are  subject  to  pollution 
with  the  excrement  of  animals  and  human  beings  and  such  excre- 
mentitious  substances  are  liable  to  contain  the  germs  of  disease. 
The  adoption  of  the  water  carriage  system  of  sewerage  about  the 
middle  of  the  nineteenth  century  greatly  increased  these  chances 
of  fresh-water  contamination.  Water  which  contains  excrementi- 
tious  matter  or  bacteria  of  fecal  origin  may  be  said  to  be  con- 
taminated; if  bacteria  are  actually  present  the  water  is  said  to  be 
infected.  The  most  noteworthy  diseases  which  are  water-borne 
are  typhoid  fever,  Asiatic  cholera,  and  dysentery,  but  there  are 
other  water-borne  diseases,  for  contaminated  water  may  contain  the 
spores  of  other  bacteria,  molds,  and  the  ova  of  parasitic  worms. 
Fresh  water  also  may  serve  as  a  medium  within  which  mosquito 
larvae  grow  and  from  which  mosquitoes  emerge.  Special  kinds  of 
mosquitoes  play  an  important  part  in  the  transmission  of  yellow 
fever  and  certain  other  diseases.  Then  there  may  be  indirect  as 
well  as  direct  relations  between  man  and  the  microorganisms  found 
in  water. 

Microscopic  organisms  form  the  basis  of  the  food  supply  of 
fishes  and  thus  indirectly  contribute  to  human  sustenance.     Oysters 

1067 


I068  FRESH-WATER   BIOLOGY 

feed  chiefly  upon  diatoms.  The  smaller  Crustacea  feed  upon 
bacteria  and  minute  algae  and  protozoa,  and  are,  in  turn,  devoured 
by  larger  organisms. 

In  the  public  water  supplies  the  appearance  of  algae  and  proto- 
zoa in  large  numbers  is  the  occasion  of  complaint  by  the  water 
consumers,  for  these  organisms  make  the  water  unsightly  and  ill 
smelling.  They  also  clog  filters  and  increase  the  cost  of  water 
purification. 

Water  as  a  Conveyor  of  Disease  Germs.  There  are  few  if  any 
bacteria  pathogenic  to  human  beings  which  are  naturally  found  in 
fresh  waters.  Trouble  comes  only  when  waters  become  infected 
with  pathogenic  bacteria  derived  from  other  human  beings  or  from 
animals.  Such  bacteria  do  not  thrive  and  multiply  in  natural 
waters  so  far  as  is  now  known  but  are  merely  mechanically  trans- 
ported by  water.  Furthermore,  instead  of  multiplying  in  water 
pathogenic  bacteria  tend  to  decrease  in  numbers  after  the  time  of 
infection.  This  is  an  important  practical  matter  as  it  greatly 
affects  the  safety  of  all  pubUc  water  suppHes.  For  example,  a 
rapidly  flowing  stream  may  convey  infection  for  long  distances  in 
a  short  time,  while,  on  the  other  hand,  a  lake  or  pubHc  reservoir 
may  store  the  water  for  so  long  a  time  that  there  is  opportunity  for 
dangerous  bacteria  to  die. 

The  longevity  of  pathogenic  bacteria  in  water  depends  upon 
many  things  among  which  may  be  included  the  original  character 
of  the  bacteria  themselves,  the  temperature  of  the  water,  the  oppor- 
tunities for  sedimentation  and  destruction  by  other  organisms,  the 
effect  of  sunlight,  etc.  Using  general  figures  it  may  be  said  that 
under  average  conditions  about  70  per  cent  of  typhoid  fever  bac- 
teria will  disappear  the  first  week,  90  per  cent  during  the  first  two 
weeks,  and  99  per  cent  during  six  weeks.  They  will  live  longer 
in  cold  water  than  in  warm  water.  That  is  why  most  of  the 
water-borne  typhoid  fever  epidemics  have  occurred  during  the  cold 
months  of  the  year.  The  spirillum  of  Asiatic  cholera  is  known  to 
behave  in  a  similar  manner  but  less  is  known  in  regard  to  the  rate 
at  which  it  dies.  There  is  some  reason  to  believe  that  it  has  a 
shorter  life  in  water  than  the  typhoid  fever  bacillus.  There  is 
a  group  of  bacteria  presumably  of  intestinal  origin  which  give 


TECHNICAL   AND   SANITARY   PROBLEMS  1069 

rise  to  dysentery  and  various  diarrhoeal  disturbances.  Presumably 
these  bacteria  behave  in  the  same  manner  as  the  typhoid  fever 
bacillus. 

The  routine  methods  of  bacteriology  at  the  present  time  do  not 
permit  of  a  trustworthy  determination  of  the  above-mentioned 
pathogenic  bacteria.  It  is  true  that  in  some  instances  such  have 
been  isolated  from  water  but  the  process  is  a  difficult  one  and  nega- 
tive results  are  of  Httle  value.  This  being  the  case,  modern  sani- 
tarians do  not  attempt  to  determine  the  safety  of  water  by  searching 
for  these  pathogenic  organisms.  Instead  they  make  tests  to 
determine  the  presence  and  abundance  of  an  organism  which  is 
commonly  found  in  the  intestines  of  man  and  warm  blooded  animals 
generally  known  as  bacillus  coH.  This  test  can  be  made  with  a 
fair  degree  of  reliability  and  it  is  much  used. 

B.  Coli  as  an  Index  of  Contamination.  Unpolluted  ground  waters 
contain  practically  no  B.  coli  but  in  proportion  as  waters  are  subject 
to  contamination  with  excremental  substances  the  numbers  of  B. 
coK  increase.  All  surface  waters  are  likely  to  contain  these  germs, 
but  in  unpolluted  sources,  such  as  uninhabited  woodland  areas,  the 
numbers  are  very  small  indeed.  Even  the  broad  waters  of  the 
Great  Lakes  contain  B.  coh  in  small  numbers  though  very  often 
they  are  absent  from  the  quantities  usually  used  in  the  test.  Rivers 
which  drain  farm  lands  contain  B.  coli  in  larger  numbers;  streams 
and  fresh  waters  which  receive  sewage  contain  them  in  still  larger 
numbers.  B.  coli,  therefore,  may  be  fairly  regarded  as  a  valuable 
index  of  fecal  contamination.  This  is  so  far  true  that  the  U.  S. 
government  has  established  bacteriological  standards  for  drinking 
water  served  by  interstate  carriers  which  includes  a  permissible 
Hmit  for  the  number  of  B.  coli.  As  stated  by  the  U.  S.  Public 
Health  Service,  waters  in  which  B.  coli  are  absent  from  two  out 
of  five  portions  of  10  cc.  may  be  used,  but  waters  in  which  B.  coli 
is  found  in  three  or  more  out  of  live  10  cc.  portions  would  be  con- 
demned. The  dividing  Hne  apparently  comes  at  a  figure  which  is 
about  150  B.  coli  per  liter  of  water.  The  whole  subject  of  B.  coli 
in  water,  the  methods  of  its  determination,  and  the  interpretation 
of  its  results  is  one  which  is  now  going  through  a  series  of  evolu- 
tionary  changes.      The   reader   is   therefore    referred    to   current 


I070  FRESH-WATER   BIOLOGY 

scientific  bacteriological  literature  and  especially  to  the  papers 
which  appear  in  the  American  Journal  of  PubHc  Health. 

Numbers  of  Bacteria  in  Water.  There  are  two  general  methods 
used  for  determining  the  numbers  of  bacteria  in  water.  By  the 
first  method  nutrient  gelatine  is  used  as  the  culture  medium  and 
the  period  of  incubation  is  48  hours  at  20°  C.  According  to  the 
second  the  media  is  nutrient  agar  and  the  period  of  incubation  is 
24  hours  at  37°  C.  Both  of  these  methods  are  useful  but  the  gela- 
tine method  has  been  used  more  than  the  other.  Neither  method 
gives  absolute  results;  the  figures  are  relative  in  both  cases. 

The  numbers  of  bacteria  as  determined  by  the  gelatine  count 
vary  all  the  way  from  less  than  100  in  relatively  clean  waters  to 
many  thousands  in  waters  which  are  dirty  and  polluted.  For 
drinking  purposes  it  is  generally  considered  that  the  number  of 
bacteria  determined  by  this  method  should  be  less  than  100  per  cc. 
The  numbers  of  bacteria  in  streams  vary  greatly  according  to  the 
rainfall.  Very  heavy  rains  wash  the  surface  of  the  ground  and 
increase  the  numbers  of  bacteria  in  the  drainage  water.  The  sew- 
age of  cities  contains  anywhere  from  a  few  hundred  thousand  to 
several  milhon  bacteria  per  cc.  These  bacteria  are  of  many  sorts, 
but  most  of  them  are  saprophytic  in  character  and  in  water  which 
contains  organic  matter,  even  in  small  amounts,  they  are  likely  to 
multiply  enormously  in  the  course  of  a  day  or  two.  Hence  bac- 
terial counts  mean  nothing  unless  the  samples  are  examined  im- 
mediately after  collection.  They  also  mean  Httle  unless  the 
bacteriologist  has  a  knowledge  of  the  character  of  the  waters. 

Removal  of  Bacteria  from  Water.  The  best  method  of  removing 
bacteria  from,  water  is  the  process  of  filtration.  There  are  two 
general  methods  in  use  at  the  present  time,  slow  sand  filtration  and 
mechanical  filtration.  In  the  former  process  the  water  is  filtered 
slowly  downward  through  a  bed  of  sand  at  such  a  rate  that  the  water 
above  the  sand  descends  ten  to  twenty  feet  in  the  course  of  a  day. 
By  sedimentation  within  the  pores  of  the  sand  bed  and  by  the 
adhesion  of  the  bacteria  to  the  sand  grains  at  or  just  below  the 
surface  of  the  filter  the  bacteria  are  removed  from  the  water.  The 
process  is  partly  physical,  partly  biological.  The  method  is  capable 
of  removing  upwards  of  99  per  cent  of  bacteria  from  moderately 


TECHNICAL  AND   SANITARY   PROBLEMS  107 1 

polluted  waters  and  experience  has  shown  that  the  waters  are 
thereby  rendered  entirely  safe  for  drinking. 

By  the  mechanical  system  of  filtration  the  water  is  first  coagu- 
lated by  the  use  of  chemicals  and  then  filtered  rapidly  through  a 
small  bed  of  relatively  coarse  sand  at  rates  which  are  20  and  40 
times  as  great  as  in  the  case  of  slow  sand  filtration.  This  process  is 
likewise  effective  in  the  removal  of  bacteria.  The  choice  of  the 
two  systems  depends  upon  the  amount  of  turbidity  and  color  of  the 
water  and  upon  its  hardness  and  upon  various  local  conditions  of 
an  engineering  character. 

After  water  has  been  filtered  it  must  be  stored  in  the  dark;  other- 
wise algae  and  other  microscopic  organisms  are  likely  to  develop  and 
become  troublesome. 

Bacteria  in  water  may  be  killed  by  the  use  of  liquid  chlorine, 
bleaching  powder,  ozone,  and  similar  substances.  These  are  poison- 
ing processes.  The  quantities  of  chemicals  used  are  so  small  that 
they  may  be  used  with  entire  safety  but  it  is  necessary  that  the 
chemicals  be  thoroughly  and  quickly  mixed  with  water  in  order  to 
assure  efficient  sterilization.  These  processes  are  especially  valuable 
in  cases  of  emergency  and  are  not  to  be  regarded  as  substitutes 
for  filtration.  Swimming  pools  should  be  disinfected  regularly  in 
order  to  prevent  the  transfer  of  pathogenic  bacteria  from  person  to 
person. 

Sewage  may  be  treated  in  various  ways  to  remo\e  bacteria  and 
other  objectionable  substances.  The  processes  used  arc  screening, 
sedimentation,  chemical  precipitation,  intermittent  sand  filtration, 
contact  beds,  trickling  filters,  and  disinfection.  There  are  many 
biological  problems  involved  in  these  processes  and  especially  in 
intermittent  sand  filters  and  trickUng  filters.  Bacteria  play  an 
important  part  in  the  disintegration  and  ultimate  absorption  of 
putrescible  organic  matter  while  in  trickling  filters  worms  and 
various  larvae  assist  in  the  process. 

Tastes  and  Odors  in  Water  Supplies.  Water  supplies  derived 
from  surface  sources  and  stored  in  reservoirs  frequently  develop 
tastes  and  odors  that  are  very  unpleasant.  These  are  largel>-  due 
to  the  growth  of  algae  and  other  microscopic  organisms.  The  matter 
is  one  of  very  considerable  importance  to  waterworks  superintend- 


I072  FRESH-WATER   BIOLOGY 

ents,  and  much  attention  has  been  given  to  the  study  of  these 
growths  during  recent  years.  This  study  has  resulted  in  success- 
ful measures  for  destroying  the  organisms  by  the  use  of  chemicals 
and  for  removing  the  organisms  and  the  odors  produced  by  them 
by  aeration  and  filtration.  Very  Httle  success,  however,  has  been 
achieved  in  preventing  the  organisms  from  growing. 

Chemically  pure  water  is  free  from  taste  and  odor.  Water  con- 
taining certain  substances,  as  for  example  sugar  or  salt,  may  have 
a  decided  taste  but  no  odor.  On  the  other  hand  water  may  con- 
tain substances,  hke  vanilla,  that  have  a  strong  odor  but  no  taste. 
The  two  senses,  though  distinct,  are  closely  related  to  each  other. 
Most  of  the  bad  tastes  observed  in  drinking  waters  are  due  to 
organisms  that  produce  odors  rather  than  tastes. 

Most  surface  waters  contain  some  organic  matter  and  have  a 
vegetable  or  earthy  odor.  When  decomposing  organic  matter  is 
present  the  odors  may  be  foul  and  disagreeable.  These  odors  may 
be  classified  in  three  general  groups:  —  (i)  those  caused  by  organic 
matter  other  than  living  organisms;  (2)  those  caused  by  the  de- 
composition of  organic  matter;  and  (3)  those  caused  by  living 
organisms. 

Observation  of  Odor.  The  odor  of  cold  water  is  best  observed  by 
shaking  a  partly  filled  bottle  of  the  water  and  immediately  remov- 
ing the  stopper  and  applying  the  nose.  The  odor  of  hot  water  is  ob- 
tained by  heating  a  portion  of  it  in  a  tall  beaker  covered  with  a  watch 
glass  to  a  point  just  short  of  boiling.  When  sufficiently  cooled 
the  cover  is  slipped  aside  and  the  observation  quickly  made.  The 
intensity  of  odors  is  commonly  indicated  by  numbers  as  follows:  — 
o,  no  odor;  i,  a  very  faint  odor  that  would  not  be  ordinarily  de- 
tected by  a  person  drinking  the  water;  2,  a  faint  odor  that  might 
be  detected  by  the  consumer  but  that  would  not  attract  any  spe- 
cial attention;  3,  a  distinct  odor  that  would  be  readily  detected; 

4,  a  decided  odor,  strong  enough  to  make  the  water  unpalatable^ 

5,  a  very  strong  odor  that  would  make  the  water  unfit  for  use. 
The  character  of  the  odor  is  usually  indicated  by  a  letter  which 
stands  for  a  descriptive  adjective.  For  purposes  of  record  the  two 
are  combined.  Thus  3f  indicates  a  distinct  fishy  odor;  2v,  a  faint 
vegetable  odor;    4m,   a   decided  moldy  odor.      Heating  usually 


TECHNICAL    AND    SANITARY    PRUBLKMS  1073 

intensifies  an  odor.     In  water  analysis  it  is  common  to  report  the 
odor  of  both  hot  and  cold  water. 

Cause  of  Odors.  The  odors  are  caused  by  aromatic  oils  that  are 
produced  during  the  growth  of  the  microscopic  organisms.  After 
disintegration  the  oily  substances  are  scattered  through  the  water. 
In  many  instances  the  oils  are  characteristic  of  the  organisms  and 
the  presence  of  organisms  in  water  can  sometimes  be  determined 
merely  by  the  odor.  They  cannot  always  be  thus  recognized, 
however,  for  the  quality  of  an  odor  changes  with  its  intensity.  Cer- 
tain organisms  present  in  small  numbers  im[)art  to  the  water  an 
odor  that  might  be  termed  aromatic,  Ijut  when  the  same.(jrganisms 
are  present  in  larger  numbers  the  odor  might  be  more  properly  de- 
scribed as  fishy.  The  amount  of  oily  matter  required  to  produce  a 
noticeable  odor  is  very  small.  The  oily  substance  that  gives 
Synura  its  odor  is  recognizable  when  diluted  to  the  extent  of  one 
part  in  twenty-five  million  parts  of  water.  This  is  not  surpris- 
ing, however,  as  the  oil  of  peppermint  can  be  recognized  in  a 
dilution  of  one  part  in  fifty  million  parts  of  water.  The  odors 
of  organisms  are  intensified  by  heating,  by  mechanical  agitation, 
by  a  change  in  the  density  of  the  water,  by  pressure,  and  by  any 
other  cause  that  tends  to  rupture  the  cell  walls  and  liberate  the  oil 
globules. 

The  following  table  gives  the  natural  odor  of  a  number  t)f  the 
common  microscopic  organisms.  For  convenience  the\-  ma\'  be 
grouped  around  three  general  terms,  aromatic,  grass)-,  and  lishy. 
The  aromatic  odors  are  due  chiefly  to  diatoms,  one  of  the  strongest 
being  that  produced  by  Asterionella.  Some  of  the  green  algae 
produce  sweetish,  grassy  odors,  and  this  is  even  more  true  of  the 
blue-green  algae.  Ambacna  produce  an  odor  that  varies  greatly 
according  to  its  dilution,  and  various  epithets  have  been  applied  to 
it.  The  fishy  odors  are  the  most  disagreeable  of  any  obser\e(l  in 
drinking  water,  and  that  produced  by  Uroi^lemi  is  perliaps  the  worst. 
The  water  that  contains  this  organism  in  large  numbers  may  ha\-e 
an  odor  resembling  that  of  cod  liver  oil.  The  odor  of  Synum  is 
almost  as  bad  and  even  more  common.  When  organisms  decay 
moldy  or  musty  odors  may  be  produced.  Hut  these  odors  of  de- 
composition are  less  characteristic  than  the  odors  of  growth.     Some 


1074 


FRESH-WATER   BIOLOGY 


of  the  blue-green  algae  have  odors  suggestive  of  the  pig  pen,  doubt- 
less because  of  their  high  nitrogen  content. 


Group 

Organism 

Natural  Odor 

Aromatic 

DiATOMACEAE 

Odor 

Asterionella 

Aromatic  —  geranium  —  fishy 

Cyclotella 

Faintly  aromatic 

Diatoma 

Faintly  aromatic 

Meridion 

Aromatic 

Tabellaria 

Aromatic. 

Protozoa 

Cryptomonas 

Candied  violets 

MaUomonas 

Aromatic  —  violets  —  fishy 

Grassy 

Cyanophyceae 

Odor 

Anabaena 

Grassy  and  moldy  —  green-corn  —  nas- 
turtiums, etc. 

Rivularia 

Grassy  and  moldy 

Clathrocystis 

Sweet,  grassy 

Coelosphaerium 

Sweet,  grassy 

Aphanizomenon 

Grassy 

Fishy 

Chlorophyceae 

Odor 

Volvox 

Fishy 

Eudorina 

Faintly  fishy 

Pandorina 

Faintly  fishy 

Dictyosphaerium 

Faintly  fishy 

Protozoa 

Uroglena 

Fishy  and  oily 

Synura 

Ripe  cucumbers  —  bitter  and  spicy  taste 

Dinobryon 

Fishy,  Hke  rockweed 

- 

Bursaria 

Irish  moss  —  salt  marsh  —  fishy 

Peridinium 

Fishy,  like  clam-shells 

Glenodinium 

Fishy 

Prevention  of  Growths  of  Algae.  Various  means  have  been  used 
to  prevent  the  growth  of  algae  in  reservoirs  and  standpipes.  Some 
of  these,  such  as  the  exclusion  of  sunlight,  are  successful  but  most 
of  them  afford  only  a  partial  remedy. 

Soil  Stripping  of  Reserooir  Sites.  The  removal  of  the  vegetation 
and  top-soil  from  the  ground  that  forms  the  floor  of  a  reservoir 
tends  to  reduce  the  amount  of  the  organic  and  mineral  matter 
available  for  the  food  supply  of  the  organisms  and  thus  tends  to 
diminish  their  number.  In  a  number  of  instances,  notably  the 
reservoirs  that  supply  the  city  of  Boston,  the  soil  has  been  carefully 
removed  from  the  reservoir  sites  before  the  reservoirs  were  filled. 
This  has  tended  to  reduce  the  growths  of  algae  during  the  first  few 


TECHNICAL   AND   SANITARY    PROBLKMS  1075 

years  after  construction,  but  it  has  been  found  t  at  the  effect  of 
this  "soil  stripping"  is  not  always  permanently  successful  and  that 
in  the  course  of  a  few  years  heavy  growths  of  organisms  have  s(jme- 
times  occurred.  Where  the  reservoir  sites  are  not  thus  cleaned 
growths  of  algae  are  likely  to  be  heavy  during  the  first  few  \'ears 
after  construction,  diminishing,  however,  withtime.  The  benefits 
from  soil  stripping  occur  chiefly  during  the  first  few  years  after  con- 
struction. Whether  or  not  there  is  economy  in  removing  the  soil 
from  the  bottom  of  the  reservoir  depends  upon  local  conditions. 
Often  it  is  advisable.  In  some  cases  it  will  be  found  cheaper  not 
to  strip  the  reservoir  bottom  but  to  apply  the  money  that  would 
be  thus  expended  towards  a  filter  plant. 

Swamp  Drainage.  The  presence  of  swamps  on  a  catchment  area 
tends  to  foster  the  growth  of  algae  and  similar  organisms.  If  these 
are  located  above  a  reservoir  they  may  seed  the  reservoir  and  thus 
increase  the  number  of  organisms  likely  to  be  found  there.  The 
quality  of  the  water  may  be  improved  in  some  instances  by  draining 
the  swamps,  thus  diminishing  the  chances  of  the  reservoir  becoming 
seeded  and  decreasing  the  amount  of  organic  food  supply  in  the 
water.  When  reservoirs  are  constructed  it  not  infrequently  happens 
that  pools  are  left  with  no  outlet.  Organisms  may  develop  rapidly 
in  such  pools  and  be  washed  into  the  reservoir  after  a  rain.  So  far 
as  possible  reservoirs  should  be  self-draining. 

Elimination  of  Shallow  Flowage.  In  the  construction  of  reservoirs 
efforts  should  be  made  to  reduce  the  area  over  which  the  water 
stands  with  a  depth  of  less  than  ten  feet.  For  in  these  areas  of 
shallow  flowage  aquatic  plants  are  hkely  to  become  seated  and  may 
serve  as  a  nidus  for  various  organisms  that  ultimately  become 
scattered  through  the  reservoir  and  give  trouble.  Cases  occur 
where  it  is  wise  to  strip  the  soil  from  the  areas  of  shallow  flow- 
age  without  attempting  to  strip  the  soil  from  the  entire  reservoir 
bottom. 

Prevention  of  Pollution.  Like  other  plants  the  algae  in  water 
grow  best  when  fertilized.  Nitrogen,  potash,  phosphates,  and  sim- 
ilar substances  stimulate  their  growth.  Polluted  waters  are.  there- 
fore, more  likely  to  develop  objectional  growths  of  algae  than  the 
same  waters   unpolluted.     The  ehmination   of  pollution   from   a 


1076  FRESH-WATER   BIOLOGY 

catchment  area  is  desirable  not  only  for  sanitary  reasons  but  also 
for  lessening  the  growths  of  algae. 

Aeration.  One  of  the  elements  of  food  supply  required  by  algae 
is  carbonic  acid,  which  is  present  to  some  extent  in  all  surface 
waters  but  is  likely  to  be  especially  abundant  in  swampy  and  pol- 
luted waters,  and  wherever  organic  matter  is  undergoing  decay. 
The  stagnant  water  at  the  bottom  of  a  reservoir,  for  example,  usu- 
ally contains  large  amounts  of  carbonic  acid.  The  amounts  of 
carbonic  acid  may  be  considerably  in  excess  of  saturation,  so  that 
when  the  water  is  exposed  to  the  air  the  gas  escapes.  Thus  the 
process  of  aeration  tends  to  reduce  the  likelihood  of  the  occurrence 
of  heavy  growths  of  algae.  Aeration  also  tends  to  reduce  the  odors 
of  the  water  as  the  exposure  of  the  water  to  the  air  gives  opportunity 
for  the  escape  or  volatilization  of  the  essential  oils.  Sometimes 
natural  conditions  of  aeration  exist  and  are  very  beneficial,  when 
water  flows  rapidly  over  the  rocky  bed  of  a  stream. 

Chemical  Treatment.  With  our  present  knowledge  little  can  be 
done  in  the  way  of  treating  the  water  chemically  to  prevent  the 
growth  of  algae.  It  is  possible  that  the  appKcation  of  lime  to  reduce 
the  free  carbonic  acid  in  the  water  would  be  of  some  benefit  but 
this  has  never  been  practically  used.  Chemical  treatment  has  been 
successful  in  destroying  organisms  as  referred  to  below. 

Exclusion  of  Light.  The  exclusion  of  Hght  from  a  reservoir  is 
an  effective  remedy  in  preventing  the  growth  of  algae.  This  can- 
not be  done  in  large  reservoirs  but  in  small  reservoirs  and  in  stand- 
pipes  it  has  proved  very  successful.  In  cases  where  ground  water 
that  contained  large  amounts  of  plant  food  has  been  exposed  in 
open  reservoirs  algae  growths  have  been  very  troublesome,  and  it 
has  been  found  that  covering  the  reservoir  or  standpipe  in  which 
the  water  is  stored  completely  prevents  the  trouble.  It  has 
become  an  axiom,  therefore,  among  waterworks  men  that  ground 
waters  should  not  be  stored  in  the  light. 

Methods  of  Killing  Algae.  Various  methods  have  been  suggested 
for  killing  algae  in  reservoirs,  such  as  copper  sulphate,  bleaching 
powder,  ozone,  and  creosote.  Of  these  copper  sulphate  has  proved 
to  be  by  far  the  most  effective.  Quantities  as  small  as  one  part  in 
one  million  by  weight,  and  sometimes  even  smaller  quantities,  have 


TECHNICAL   AND   SANTTAin'    PROHMCMS  1077 

been  found  sufficient  to  destroy  the  algae.  The  amount  require<i 
depends  upon  the  kind  of  organisms  present,  and  the  amount  and 
character  of  the  other  organic  matter.  Copper  sulphate  is  applied 
to  a  reservoir  by  putting  crystals  of  the  salt  in  a  gunnysack,  or  coarse 
bag,  and  dragging  it  around  the  reservoir  after  a  boat,  letting  it 
dissolve  in  the  water  as  it  will.  Preferably  this  should  be  done 
while  the  wind  is  blowing,  and  when  the  water  is  in  a  state  of  some 
agitation,  so  as  to  obtain  a  rapid  dissemination  of  the  solution 
through  the  water  of  the  reservoir.  Unless  care  is  exercised  in  this 
regard  there  is  danger  that  fish  may  be  killed,  and  in  any  case  there 
is  always  danger  that  some  fish  may  be  killed.  The  method,  there- 
fore, is  one  that  should  not  be  used  by  one  whose  experience  and 
judgment  is  insufficient. 

The  copper  sulphate  treatment  is  not  always  entirely  successful. 
Sometimes  after  one  kind  of  an  organism  has  been  destroyed  by 
its  use  some  other  organism  will  appear  and  be  more  troublesome 
than  the  first.  A  single  treatment  of  a  reservoir  with  copper  sul- 
phate therefore  does  not  always  suffice,  and  when  a  second  dose  is 
required  it  is  usually  necessary  to  use  larger  quantities  than  the 
first  time. 

Purification  of  Water  Containing  Algae.  Water  that  contains  algae 
may  be  purified  by  filtration,  though  the  ordinar\'  processes  may 
require  some  modification,  depending  upon  the  number  and  char- 
acter of  the  organisms  present.  One  of  the  essential  elements  of 
successful  filtration  is  that  the  water  shall  always  contain  a  sufficient 
quantity  of  oxygen  throughout  the  process.  Aeration,  therefore, 
may  be  necessary  before  or  after  filtration  or  both.  It  may  be 
accomplished  by  spraying  the  water  into  the  air  so  that  it  falls  in 
drops,  or  by  exposing  it  in  thin  films  as  it  passes  over  a  weir  with  a 
considerable  fall  through  the  air.  Generally  speaking  an  exposure 
from  one  to  two  seconds  is  necessary  and  sufficient. 

As  an  illustration  of  successful  purification  of  a  water  heavily 
laden  with  algae  maybe  mentioned  the  old  Ludlow  supply  of  Spring- 
field, Massachusetts,  which  during  the  summer  contained  very 
heavy  growths  of  Anahaena.  The  method  employed  was  inter- 
mittent sand  filtration,  similar  to  that  commonly  used  for  the  treat- 
ment of  sewage.     The  water  was  first  aerated  and  allowed  to  spread 


1078 


FRESH-WATER    BIOLOGY 


over  the  sand  filter,  which  was  built  without  cover  as  it  was  used 
only  during  warm  weather.  After  rapid  percolation  through  the 
sand  it  was  collected  in  well  ventilated  under-drains.  After  the 
water  had  passed  through  the  sand  the  beds  were  allowed  to  stand 
exposed  to  the  air  so  that  they  themselves  became  well  aerated. 
This  method  almost  completely  did  away  with  the  obnoxious  odors 
that  had  previously  existed  in  the  water  supply  of  the  city.  In  this 
instance  the  part  played  by  aeration  was  very  important  as  experi- 
ments had  shown  that  the  water  could  not  have  been  filtered  satis- 
factorily by  the  ordinary  processes  of  slow  sand  filtration. 

Mechanical  filtration  is  also  sometimes  employed  for  the  treat- 
ment of  algae  laden  water.  Used  in  connection  with  aeration  this 
method  may  prove  reasonably  satisfactory,  but  special  care  must  be 
given  to  maintaining  conditions  of  aeration  throughout  the  process. 
Sand  filters  are  capable  of  satisfactorily  removing  the  algae  and 
their  accompanying  tastes  and  odors  if  the  growths  are  not  too 
heavy. 

The  presence  of  algae  in  water  tends  to  clog  both  sand  filters  and 
mechanical  filters  to  an  unusual  extent  and  increases  the  loss  of 
head,  and,  therefore,  shortens  the  period  of  service  and  in  general 
increases  the  cost  of  filtration.  Where  water  is  stored  before 
filtration,  or  where  it  passes  through  settHng  basins  copper  sul- 
phate is  sometimes  used  as  an  auxihary  process  antecedent  to 
filtration. 

Self -Purification  of  Streams.  Various  microscopic  organisms 
play  an  important  part  in  the  self -purification  of  streams.  It  has 
long  been  known  that  rivers  polluted  by  sewage  and  other  waste 
substances  regain  their  purity  to  a  considerable  extent  during  their 
subsequent  flow.  Various  influences  combine  to  bring  about  this 
result,  such  as  the  natural  death  of  pathogenic  bacteria  in  an  un- 
favorable environment,  the  effect  of  sunHght,  sedimentation  of 
suspended  matter,  oxidation  of  organic  matter  brought  about  with 
the  assistance  of  bacteria,  and,  what  is  of  interest  here,  by  the  effect 
of  microscopic  organisms.  The  cycle  of  changes  by  which  nitroge- 
nous matter  is  broken  down  by  bacterial  action  and  by  which  the 
bacteria  are  destroyed  by  protozoa  and  other  larger  organisms, 
the  protozoa  being  devoured  by  rotifers  and  Crustacea,  and  these  in 


TECHNICAL  AND   SANITARY   PROBLEMS  1079 

turn  being  devoured  by  fish,  is  a  biological  phenomenon  of  great 
practical  importance.  In  this  way  natural  streams  succeed  in 
cleansing  themselves  so  that  waters  once  foul  become  clear  and 
attractive  in  appearance. 

An  excellent  illustration  of  these  biological  changes  is  the  Genesee 
river  below  the  city  of  Rochester.  This  river  now  receives  practi- 
cally all  of  the  sewage  of  the  city  at  a  point  about  six  miles  dislant 
from  Lake  Ontario.  Below  this  point  the  river  receives  few  acces- 
sions. Studies  made  during  the  summer  of  191 2  showed  that  the 
effect  of  the  discharge  of  the  sewage  into  the  river  was  to  increase 
the  number  of  bacteria  and  reduce  the  number  of  green  algae.  Im- 
mediately below  the  sewer  there  was  a  further  increase  in  bacteria 
and  a  reduction  of  the  dissolved  oxygen  in  the  water.  A  mile  or 
two  down  stream  the  bacteria  began  to  decrease  and  protozoa  in- 
creased. At  the  mouth  of  the  river  the  rotifers  disappeared  but 
Crustacea  were  found  in  abundance  in  the  lake  water  around  the 
river  mouth.  Beyond  one-quarter  of  a  mile  from  the  river  mouth, 
however,  the  Crustacea  also  showed  a  noticeable  decrease.  The 
chemical  changes  that  accompanied  these  biological  conditions  were 
equally  interesting.  Below  the  entrance  of  the  sewage  the  dissolved 
oxygen  in  the  water  almost  disappeared  but  later  increased.  As  the 
dissolved  oxygen  decreased  the  carbonic  acid  in  the  water  increased. 
At  the  river  mouth  there  was  an  under  run  of  the  lake  water  back 
into  the  river  due  to  the  lower  temperature  of  the  water  in  the 
lake. 

Algae  also  assist  in  self  purification  of  streams  and  lakes  by  liber- 
ating dissolved  oxygen.  Sometimes  the  growth  of  algae  is  so  rapid 
and  the  quantity  of  oxygen  produced  is  so  large  that  supersatu ra- 
tion occurs.  This  commonly  takes  place  in  lakes  in  the  region  of 
the  thermocHne,  as  Birge  and  Juday  have  well  shown.  How  great 
a  factor  this  oxygen  production  may  be  is  probabl}'  not  yet  realized 
by  sanitarians  to  its  full  extent. 

Microscopic  organisms  in  streams  are  also  useful  in  removing 
the  effects  of  pollution  by  manufacturing  wastes.  On  the  other 
hand  some  kinds  of  trade  wastes  are  of  such  a  character  that  they 
tend  to  destroy  microscopic  life;  such  are  acid  (^r  strongly  alkaline 
wastes,  and  wastes  containing  arsenic,  copper,  and  other  poisonous 


lo8o  FRESH-WATER   BIOLOGY 

substances.  Even  the  wastes  containing  inert  suspended  matter 
may  interfere  with  microscopic  Hfe  along  the  shores  by  smothering 
the  tiny  vegetable  and  animal  cells.  Oily  wastes,  such  as  the 
wastes  from  gas  works,  may  produce  films  upon  the  surface  of  a 
stream;  they  then  interfere  with  the  absorption  of  oxygen  by  the 
water  from  the  air  and  thus  exert  a  prejudicial  influence  on  the 
natural  agencies  of  purification.  It  is  for  these  reasons  that  the 
discharge  of  trade  wastes  into  streams  is  a  matter  that  is  seriously 
in  need  of  regulation.  The  wastes  from  manufacturing  estabhsh- 
ments  are  often  more  objectionable  even  than  domestic  sewage. 
Perhaps  the  worst  conditions  arise  when  streams  are  polluted  both 
with  domestic  sewage  and  with  trade  wastes. 

Identification  of  the  Source  of  Water.  Another  practical  applica- 
tion of  the  microscopical  examination  of  water  is  that  of  determin- 
ing the  origin  of  certain  waters.  One  of  the  studies  made  in  con- 
nection with  the  celebrated  Chicago  drainage  canal  case  was  a 
series  of  microscopical  examinations  of  water  from  Lake  Michigan 
down  the  Ilhnois  and  Mississippi  rivers  to  St.  Louis.  It  was  found 
that  certain  varieties  of  organisms  were  present  in  the  water  of 
Lake  Michigan  that  could  not  be  found  in  any  of  the  tributary 
streams,  and  the  argument  was  made  that  as  these  same  organisms 
were  found  in  the  water  supply  of  St.  Louis  taken  from  the  Missis- 
sippi river  they  must  have  been  derived  from  Lake  Michigan, 
showing  that  some  of  the  water  supplied  to  St.  Louis  came  from  Lake 
Michigan  through  the  Chicago  drainage  canal  and  the  rivers  men- 
tioned. 

The  studies  made  at  Rochester  in  191 2  showed  that  the  water 
near  the  surface  of  Lake  Ontario  contained  various  microscopic 
organisms  that  could  be  readily  identified  but  that  these  were  absent 
from  the  lower  strata.  Serial  studies  made  at  the  shore  of  the  lake 
sometimes  showed  the  presence  of  these  organisms  but  at  certain 
times  they  were  absent.  The  inference  was  that  on  these  days  the 
water  at  the  shore  was  that  which  had  been  drawn  shoreward  from 
the  deep  strata.  This  finding  corroborated  the  temperature  obser- 
vations and  the  wind  records,  and  proved  that  the  effect  of  a  strong 
off-shore  wind  was  to  blow  the  surface  water  away  from  the  shore 
and  draw  in  the  cold  deep  water  from  the  lake. 


TECHNICAL  AND   SANITARY   PROBLEMS  io8t 

Ground  waters  normally  do  not  contain  microscopic  organisms, 
and  when  these  are  found  in  ground  waters  a  natural  inference  is 
that  a  ground  water  has  been  contaminated  with  surface  water. 
Thus  the  microscopical  examination  of  ground  water  is  sometimes 
useful  in  determining  questions  of  pollution. 

Organisms  in  Pipes  of  Water  Systems.  When  surface  water 
which  contains  algae  and  other  microscopic  organisms  is  allowed  lo 
flow  through  pipes,  as  in  the  distribution  systems  of  public  water 
supplies,  it  frequently  happens  that  the  pipes  become  more  or  less 
choked  with  what  is  popularly  called  pipe-moss.  Sometimes  this 
pipe-moss  acquires  a  thickness  of  several  inches  and  forms  a  mat 
upon  the  inside  of  the  pipes  which  materially  reduces  their  carrying 
capacity.  The  organisms  which  give  trouble  of  this  character 
are  chiefly  the  Polyzoa,  Plumatella,  Pahidicelhu  and  PectinaUlla, 
Fresh-water  sponges  are  also  found  in  pipes  and  masonry  aqueducts. 
Snails,  worms,  and  various  Crustacea  may  be  found  associated  with 
these  moss  growths.  Dr.  Thresh  of  London  has  described  the 
occurrence  of  fresh-water  mussels  in  a  thirty-six  inch  pipe  which 
attained  such  a  growth  that  the  bore  was  reduced  to  nine  inches. 

It  is  evident  that  the  pipe  dwelling  organisms  depend  upon  the 
plankton  for  their  food  supply.  The  above-mentioned  growtlis 
do  not  occur  in  pipes  which  carry  water  which  has  been  filtered  or 
ground  water,  which  contains  no  microscopic  organisms. 

There  is  another  organism  sometimes  found  in  ground  waters 
which  contain  salts  of  iron  and  magnesia,  namely  Crefwthrix. 
There  are  three  distinct  varieties  of  this  organism.  One  of  these 
deposits  manganese  in  its  gelatinous  sheath,  another  deposits  iron, 
while  the  other  deposits  alumina.  All  of  them  grow  best  in  waters 
somewhat  deficient  in  dissolved  oxygen.  Crcnothrix  grows  on 
the  walls  of  the  pipes  in  tufts  of  filaments.  The  filaments  become 
attached  and  are  found  in  the  water  discharged  from  the  faucets. 
The  iron  which  impregnates  the  gelatinous  sheaths  that  surround  the 
cells  causes  trouble  in  laundries.  Clothes  washed  in  such  water 
acquire  rusty  stains  difficult  to  remove.  Crcnothrix  is  sometimes 
found  associated  with  the  pipe-moss  above  mentioned. 

Pipe-moss  may  be  removed  from  a  distribution  system  of  a  water 
supply  by  flushing,  but  the  best  practice  is  to  pre\ent  the  growth? 


lo82  FRESH-WATER   BIOLOGY 

from  forming  by  using  filtered  water  instead  of  water  laden  with 
plankton. 

Plankton  and  Fish  Life.  The  occurrence  of  plankton  in  natural 
waters  has  a  definite  and  direct  bearing  upon  the  occurrence  of 
fish  fife.  Algae  and  protozoa  and  such  organisms  play  an  important 
part  in  the  cycle  of  changes  which  extend  from  the  decomposition 
of  organic  matter  by  bacteria  to  the  food  supply  of  man.  This 
cycle  may  be  followed  through  the  several  elements  of  organic 
matter,  namely,  nitrogen,  carbon,  sulphur,  and  phosphorus.  The 
proteid  products  of  metaboHsm  are  consumed  by  bacteria;  bacteria 
are  eaten  by  protozoa  and  the  nitrate  formed  by  bacterial  action  in 
the  presence  of  oxygen  is  utiHzed  as  food  by  algae;  algae  and  proto- 
zoa are  consumed  by  rotifers  and  Crustacea  and  these  latter  form 
the  basis  of  the  food  of  many  fish.  Some  fish  are  provided  with 
special  mechanisms  for  straining  the  plankton  from  the  water,  a 
notable  instance  of  this  being  the  menhaden,  a  salt-water  fish 
which  swims  with  its  mouth  open.  The  water  enters  through  the 
mouth  and  passes  out  through  the  gills,  while  the  organisms  that 
are  thus  removed  are  carried  to  the  stomach.  The  late  Professor 
Peck  showed  by  experiments  at  Woods  Hole  that  the  abundance 
and  size  of  the  menhaden  are  closely  related  to  the  abundance  of 
plankton.  Similarly  oysters  have  been  shown  to  be  dependent 
upon  the  occurrence  of  diatoms  in  the  waters  which  flow  over  the 
oyster  beds.  Experiments  made  by  the  writer  in  the  Great  South 
Bay,  Long  Island,  showed  that  the  best  oyster  beds  were  located 
near  mud  flats  where  diatom  hfe  abounded. 

Intimately  connected  with  the  occurrence  of  the  plankton  and 
the  bacteria  associated  with  decomposition  of  organic  matter  is 
the  presence  or  absence  of  dissolved  oxygen  and  carbonic  acid  in 
the  water  of  lakes  at  different  depths,  and  fluctuations  in  the  occur- 
rence of  these  gases  profoundly  affect  fish  Hfe.  If  the  amount  of 
organic  matter  at  the  bottom  of  a  lake  or  pond  is  large  the  water 
below  the  thermocHne  may  lose  most  of  its  oxygen  during  periods 
of  stagnation.  It  is  impossible  for  fish  to  five  under  such  conditions, 
so  that  lakes  and  ponds  which  undergo  stagnation  are  not  Hkely  to 
contain  such  fish  as  naturally  seek  the  colder  water  found  only  at 
great  depths  during  the  summer.     Thus  it  is  seen  that  plankton 


TECHNICAL  AND   SANITARY    PROBLEMS  1083 

studies  and  determinations  of  the  amount  of  oxygen  and  carbonic 
acid  in  stagnation  may  be  a  valuable  guide  to  a  fish  commission  in 
determining  the  advisability  of  stocking  certain  lakes  with  certain 
fish.  The  study  of  limnology  is  a  matter  of  great  practical  impor- 
tance to  the  human  race. 


INDEX 


All  technical  terms  and  all  scientific  names  are  included,  but  only  major  references  to 
each  are  given.  Important  cross  references  are  grouped  together  after  other  entries  under  a 
given  term.     All  figures  refer  to  text  pages. 

Specific  names  are  printed  in  italics  and  follow  in  alphabetic  order  the  name  of  the  genus 
to  which  the  species  belong;  the  generic  name  is  printed  in  italics  only  when  it  occurs  exclu- 
sively in  a  binomial  combination  and  no  reference  is  made  to  the  genus  alone. 


Abedus,  933 

Abothrium,  431;  crassum,  431 

Acanthiidae,  933 

Acanthocephala,  16,  365,  416,  506-510,  542- 
551;  key,  545-551;  lemnisci,  543,  life 
history,  544,  proboscis,  542,  p.-  sheath, 
543,  references,  552;  see  Gordiacea;  Nema- 
toda  (Parasitic);  Parasitic  Roundworms 

Acanthocephalus,  547;  ranae,  547 

Acanthochasmidae,  391 

Acanthochasmus  coronarium,  391 

Acanthocirrus,  445 

Acanthocystis,  236;  chaetophora,  236 

Acantholeberis,  710;  curvirostris,  710 

Acella,  981 

Ace  tabula,  425 

Achnanthaceae,  130 

Achnanthes,  130;  exilis,  130 

Achromadora,  490;  minima,  490 

Acilius,  941 

Acineta,  300;  fluviatilis,  300 

Acinetactis,  244;   mirabilis,  244 

Acmostomum  crenulatum,  361,  364 

Acoleidae,  447 

Acoleus,  447;  armatus,  447 

Acrobeles,  495 

Acrodactyla,  396 

Acrolichanus,  396;  lintoni,  396,  petdosa,  396 

Acroloxus,  98s 

Acroperus,  718,  angustatus,  719,  harpae,  719 

Actinastrum,  159;   hantzschii,  159 

Actinobdella,  655;  annectens,  655,  inequian- 
nulata,  655 

Actinobolus,  271;  radians,  271 

Actinolaimus,  485;  radiatus,  485 

Actinolophus,  234;  minutus,  234 

Actinomonas,  243;   vernalis,  243 

Actinophrys,  234;  sol,  217,  234 

Actinopoda,  234 

Actinosphaerium,  234;   eichhornii,  213,  234 

Acuaria,  526;  ardeae,  527,  triaenucha,  526 

Acuariinae,  526 

Acyclus,  611;  inquietus,  611 

Adaptations  of  aquatic  animals,  1022 


Adineta,  619;  vaga,  619 

Aeolosoma,  638;  hcmprichi,  638,  Unebrarum, 
638 

Aeolosomatidae,  638 

Aerobes,  obligatory;   sec  Bacteria 

Aeronemum,  164;   polymorphum,  164 

Aeschna  (imago),  925,  (nymph),  930 

Agabetes  (adult),  942 

Agabus  (adult),  941 

Agamodistomum,  411;  apodis,  411 

Agamodistomum  stage  of  Cercaria  rubra,  420 

Agamomermis,  520 

Agamonema,  520;  capsiilaria,  521,  pap'd- 
ligerum,  521,  piscium,  521 

Age  series  of  ponds,  49 

Akinete,  118 

Alaimus,  499;  simplex,  499 

Alasmidonta,  1005;  areola,  1007,  caJceola, 
1006,  marginala,  1006,  undiilata,  ioo<i 

Alasmidonta  s.  s.,  1006 

Albertia,  589;   intrusor,  5S9 

Albia,  867;  stationis,  S67 

Alexia,  978;  selifer,  978  , 

Algae,  13;  methods  of  killing.  1076,  preven- 
tion of  growths,  1074,  purification  of  water 
containing,  1077;  see  .\lgae,  Blue-Cirecn; 
Algae,    Fresh-Water,   excl.   of    Bluc-(irecn 

Algae,  Blue-Green  (Cyanophyceae).  Frcsh- 
Water,  100-114;  color,  102,  cyanophycin 
granules,  102,  heterocysts,  103.  key,  104- 
114,  phycocyanin,  102,  117,  references,  114, 
thermal  springs,  life  of,  loi,  vacuoles.  103, 
"water-bloom,"  114;  see  .Mgae;  .Mgac. 
Fresh-Water,  excl.  of  Blue-Green 

Algae,  Fresh-Water,  excl.  of  BIue-Grccn.  115- 
177;  abundance,  121,  akinete,  118.  an- 
theridium,  iiy,  antherozoid,  119.  aplano- 
spores,  118,  centric  forms,  12^,  i  hromato- 
phores,  116.  cultures,  123,  and  mediums  of, 
124,  diatomin.  117,  disc-shaped  chroma- 
tophores,  116.  filamentous,  121.  forms,  115, 
gametes,  119,  key,  125-177.  life  history,  122, 
occurrence,  122,  oogonium,  119.  o»isporc, 
119,  palmella  condition,  115,  phycocyanin, 


108  = 


io86 


INDEX 


117,  phycoerythrin,  117,  phycophaein,  117, 
pyrenoid,  116,  references,  177,  reproduc- 
tion, physiology  of,  120,  zoosporangium, 
119,  zoospores,  118;  see  Algae;  Algae,  Blue- 
Green;  Bacillariaceae;  Chlorophyceae;  Pha- 
eophyceae;  Rhodophyceae 

AUassostoma,  387;  magnum,  387,  parvun,  387 

AUocreadiidae,  394 

AUocreadiinae,  394 

Allocreadium,  395;    commune,  395,  lobatum, 

395 
AUoeocoela,  354 
Alona,  722;    affinis,  723,  costata,  723,  guttata, 

721,  722,  intermedia,  724,  monacantha,  722, 

quadrangularis,  723,  rectangula,  723,  tenui- 

caudis,  720 
Alonella,  724,  734;  dadayi,  736,  dentifera,  735, 

diaphana,  721,  735,  exigua,  737,  excisa,  737, 

globulosa,  735,  karua,  724,  734,  nana,  736, 

rostrata,  736,  sculpta,  735 
Alonopsis,  719;  aureola,  719,  elongata,  719 
Amabilia,  448;   lamelligera,  448 
Amabiliidae,  448 
Ambly plana  cockerelli,  360 
Ambloplitis  rupestris,  1030 
Ameletus  (imago),  920,  (nymph),  922 
Ammonia  in  natural  waters,  39 
Amnicola,  989;    cincinnatiensis,  989,  limosa, 

989 
AmnicoUdae,  989 
Amnicolinae,  989 
Amoeba,  219;    guttula,  220,  /jmax,  220,  />ro- 

/eM5,  219,  radiosa,  220,  striata,  220,  rerri^- 

co^a,  220 
Amoebea,  219 
Amoebidae,  219 

Amoeboid  protozoa;  see  Sarcodina 
Amoebotaenia,  445;   cuneata,  445 
Amorgius,  934 

Amphiagrion  (imago),  923,  (nymph),  928 
Amphibia,  see  Batrachia 
Amphibious  plants,  see  Plants,  amphibious 
Amphids.  466 

Amphig3''ra,  986;   alahamensis,  986 
Amphileptus,  275;   gutta,  275,  meleagris,  294 
Amphilina,  430 

Amphimonas,  250;   glohosa,  250 
Amphipoda,  829,  842;  see  Malacostraca 
Amphiprora,  130 
Amphiproraceae,  130 
Amphisia,  288 

Amphistoma  grande,  386,  subtriquetrum,  386 
Amphistomata,  385 
Amphistome    cercariae,  413 
Amphitrema,  232;  flavum,  232,  wrightianum, 

232 
Amphizoa  (adult),  940,  (larva),  943 
Amphizoidae,  940 
Amphora,  128;   ovalis,  128 
AmpuUaria,  987;  paludosa,  987 


AmpuUariidae,  987 

Amygdalonaias,  1014 

Anabaena,  no;  circinalis,  110,  jios-aquae,  no 

Anaerobes,   facultative   and  obligatory;    see 
Bacteria 

Anaerobic  respiration,  38 

Anapodidae,  570,  601;  jee  Rotatoria 

Anapus,  601;   ovalis,  601 

Anarthra,  591;   aptera,  591 

Anax,  925,  930 

Anchistropus,  730;   minor,  730 

Anculosa,  994,  praerosa,  994 

Ancyhdae,  985 

Ancylostoma  duodenale,  513,  521 

Ancylus,  985;    diaphanus,  985,  mittallii,  985, 
rivularis,  985 

Ancylus  s.  s.,  985 

Ancyracanthus  cystidicola,  527 

Ancyrocephalus,  375 

Ancyronyx,  942 

Angiostoma,  521;   nigrovenosum,  521 

Angiostomidae,  521 

Angitrema,  992 

Anguillulidae,  521 

Animal  communities;    see  Communities,  ani- 
mal 

Animalcules,  moss;  see  Bryozoa 
wheel;  see  Rotatoria 

Animals,  aquatic,  food  relations  of,  53,  54 

Anisonema,  257;   acinus,  257 

Anistoptera,  924,  929 

Ankistrodesmus,  155 

Annelida;   see  Hirudinea 

Anodonta,  1002;   grandis,  1002 

Anodontinae,  looi 

Anodontoides,  1003;  ferussaciana,  1003 

Anomalagrion  (imago),  924,  (nymph),  929 

Anomopoda  (adult),  694 

Anomotaenia,  446;   constricta,  446 

Anonchus,  502;   monhystera,  502 

Anopheles,  944 

Anoplocephalidae,  444 

Anortha  gracilis,  334 

Anostraca,  666 

Antheridium,  119 

Antherozoid,  119 

Anthophysa,  248;  vegetans,  248 

Anuraea,  601;   brevispina,  601,  cochlearis,  601 

Anuraeidae,  571,  601 

Aorchis,  385;  extensus,  385 

Aphanizomenon,  in;  jlos-aquae,  in 

Aphai.ocapsa,  106;   grevillei,  106 

Aphanochaete,  169 

Aphanolaimus,  498;   spiriferus,  498 

Aphanothece,  104;   microscopica,  104 

Aphelenchus,  483;   microlaimus,  483 

Aphrothoracida,  234 

Apiocystis,  147;   brauniana,  147 

Aplanospore,  118 

Aplexa,  985;   hypnorum,  985 


INDEX 


1087 


!\plop^5urf         43;  filum,  443 

A.pocra(ocj  Cr^'  S43 

Apodina,J  30 

Apparatu\^  and  Methods,  61 ;  references,  88,  8<.) 

Apsilidae,  v  1 1 

Apsilus,  61  r^"   bucinedax,  611 

Aptogonum,  137;   bailcyi,  137 

Apus,  671;    aeq/alis,  663,  671,  longicaudalus, 

672,  lucasanus,  672,  ncivbcrryi,  671 
Aquatic    animals,    birds,    earthworms,    etc.; 
5ee    Animals,     BiiHs,     Earthworms,     etc., 
aquatic 
Arachnida,  17 
Arcella,    221;     dentata,    222,    dlscoidcs,    222, 

vulgaris,  222 
Arcellidae,  220 
Archer inia  boltoni,  144 
Archigetes,  430 

Archilestes  (imago),  923,  (nymph),  928 
Arcidens,  1003;   conjragosa,  1003 
Argia  (imago),  923,  (nymph),  928 
Argulidae,  786-788;   key,  787,  788;  see  Copc- 

poda;   Siphonostomata 
Argulus,  787;    amcricanus,  787,  appendiculo- 
sus,  787,  catostomi,  787,  ingens,  788,  lepldo- 
stei,  788,  maculosus,   787,    stizostethi,    788, 
versicolor,  787,  788 
xArhythmorhynchus,  550;    brevis,  550,  pumili- 
rostris,  551,  irichocephalus,  550,  uncinalus, 
5  50 
Arkansia,  1004;  wheeleri,  1004 
Armiger,  984 
Arrhenurinae,  863 
Arrhenurus,  863;   albator,  S6s,forpicatus,  863, 

globator,  863,  macidator,  863 
Arlemia  salina,  668 
Arthrodesmus,  141;   convergens,  141 
Arthropoda,  17 
Arthrospira,  108;  jenneri,  108 
Ascaridae,  531 

Ascaris,  531;  ardeae,  532,  cylindrica,  531, 
entomelas,  531,  hclicina,  532,  lanceolata,  531, 
longa,  531,  lumbricoides,  512,  microcephala, 
532,  mucronata,  532,  nigrovenosa,  531, 
/^ewj/a,  531,  serpentulus,  532,  sulcata,  531. 
tenuicollis,  531 
Ascaroidea,  531 
Ascoglena,  252 

Ascomorpha,  607;   ecaudis,  607 
Asellidae,  841 

Asellus,  841;  communis,  841 
Aspidisca,  291;   costata,  291 
Aspidobranchia,  994 
Aspidocotylea,  379 
Aspidogaster,  380;   conchicola,  380 
Aspidogastridae,  379 
Asplanchna,  607;  herrickii,  582,  607,  priodouUi, 

607 
Asplanchnidae,  571,  607 
Asplanchnina,  607 


.Asphmchnopus,  607;    myrnuUo,  »>o7 

Assimeiiia,  yS6;   californica,  986 

.\ssimcniidae,  yH6 

Association,  cocfliticnt  of,  54 

Assulina,  230;   minor,  230,  5fmiMWMm,  230 

.\stacus,  846 

Astasia,  254;   tricliophora,  254 

.\stasidae,  253 

.Vstcrionclla,  133;   Kracillima,  133 

Asteromeycnia,    311;     plumosa,    312,     r<kfi^- 

spiiulala,  31  2 
.\symphyl()dora,  larva  of,  423 
Atractidcs,  874;   spinipes,  874 
.\tractonema,  254:   lorluosa,  254 
Atrochus,  611;   tcntaculalus,  611 
Alurinae,  864 

\lurus,  866;   mirabilis,  866,  scaber,  866 
Alyidae,  845 

.\ul.)phorus,  639;  furcalus,  639,  ruj^wj,  639 
Auricula,  978;    pelluccns,  978 
Auriculidae,  977 
Auriculinae,  977 

Auridistomum,  397;   clielydrae,  397 
Auxospores,  125 

Awerinzewia,  227;   cycloslomala,  227 
Axonopsis,  866;   complanata,  866 
Azygia,  392;  /mcm,  392,  sebago,  371,  trreticolU, 

392 
Azygiidae,  392 

Bacillariaceae  (diatoms),  125-134;  key,  125- 
134;  5ee  Algae,  Fresh-Water,  excl.  of  BIuc- 
Green 

Bacteria,  13,  90-99;  aerobes,  obligatory,  93, 
anaerobes,  facultative  and  obligatory,  93, 
94,  bacillus  coli  as  index  of  contamination, 
1069,  classification,  90,  forms,  91,  metachro- 
matic granules,  92,  microorganism,  94, 
movement,  92,  number,  94,  in  natural 
waters,  96,  1070,  references,  99,  spores,  92, 
structure,  91 

Baetis  (imago),  921,  (nymph),  922 

Baetisca  (imago),  919.  (nymph),  921 

Baileya,  176 

Balla'dina,  28S 

Bangia,  177;   atro- purpurea,  177 

Bartonius,  849 

Basiacschna  (imago).  925.  (nymph).  930 

Bastiana,  497;   cxilis,  497 

Bathymermis.  505 

Batrachia  (Amphibia).  iojS.  1029:  refer- 
ences. 1066;   stf  W-rtebrala,  a<iuatic 

Batrachospcrmum,  176:    grabussonirmf,  176 

Bdellodrilus.  644;  iUuminatus.  644.  ihj/u- 
bitis,  644.  philadclphicus,  644,  puhhcrrimus, 
644 

Bdelloida.  576,  619 

Beetles,  acjuatic;   sec  Colcoptcra;  Insccta 

Belostoma.  934 

Beloslomatidae,  933 


io88 


INDEX 


f 


Benacus,  894,  934;  eggs,  896 

Berosus,  939 

Bicosoeca,  245;  lepteca,  245 

Bidens  beckii,  182 

Bidessus  (adult),  940 

Bikoecidae,  245 

Binuclearia,  163;  tetrana,  163 

Biology,  Fresh- Water,  9;  climate  vs.,  9,  dis- 
persal, 13,  diversity,  12,  fauna  relicta,  10,  in- 
vestigators, II,  journals  on,  20,  man  the 
modifying  agent,  11,  origin,  10,  references 
(general),  18-20,  seasonal  succession,  10, 
stations,  12,  stratification  of  organisms,  10, 
types,  13,  uniformity,  13,  variety,  11;  see 
References  for  specific  references 

Biomyxa,  232;  vagans,  232 

Bipalidae,  360 

Birds,  aquatic,  1024-1026;  references,  1066; 
see  Vertebrata 

Bithynis,  845 

Black-flies,  aquatic;  see  Insecta;  Simuliidae 

Bladder-worms,  427 

Blasturus  (imago).  920,  (nymph),  921 

Blauneria,  979;  heterodita,  979 

Blepharisma,  283;   lateritia,  283 

Blepharoceridae,  943 

Blue-Green  Algae;  see  .\lgae,  Blue-Green 

Boleosoma  nigrum,  1057 

Bolting  cloth,  specimens  in,  7;   see  Plankton 

Bopyridae,  842 

Bosmina,  706;  longirostris ,  706,  longispina, 
707,  obtiisirostris,  707 

Bosminidae,  706 

Bosminopsis,  707;   deitersi,  707 

Bothria,  425 

Bothriocephalus,  431;  latus,  432,  433 

Bothriomonus,  433;   sturionis,  433 

Bothromesostoma,  351;  personatum,  351 

Bothrostoma,  281 

Botrydiopsis,  156;   eriensis,  156 

Botrydium,  172;   granulatum,  172 

Botryococcus,  149;   hraunii,  149 

Bottle,  water-,  80 

Bottom  materials,  24;  collecting,  70,  differen- 
tiation, 25,  distribution  of  life,  35,  muck,  26, 
terriginous,  26,  45 

Boyeria  (imago),  925,  (nymph),  930 

Brachionidae,  605 

Brachionus,  605;  angular  is,  605,  bakeri,  579, 
mollis,  605,  pala,  605,  punctatus,  605,  quad- 
ratus,  605 

Brachycera  (larva),  946 

Brachycoeliinae,  400 

Brachycoelium  hospitale,  400 

Branchinecta,  667;  coloradensis,  667,  lin- 
dahli,  668,  packardi,  667,  paludosa,  662,  667 

Branchinectidae,  667 

Branchinella,  670;   gissleri,  668,  670 

Branchiobdella,  644;  americana,  644,  tetro- 
donta,  644 


Branchionidae,  570  i 

Branch! ura,  786-788;  see  Argulidae;     jpepoda 

Brasenia,  193;   peltata,  188  o 

Brebissonia,  128 

Brychius,  938 

Bryozoa  (moss  animalcules),  17,  947-956; 
appearance,  947,  habitat,  951,  key,  951-955, 
methods  of  study,  950,  occurrence,  949, 
polyzoa,  947,  references,  955,  956,  stato- 
blast,  950 

BucephaUdae,  379 

Bucephalus,  379;   polymorphus,  412,  pusillus, 

379 
Buenoa,  934 

Bugs,  aquaac  (water) ;   see  Hemiptera 
Bulbochaete,  167;   mirabilis,  167 
Bulimnaea,  980 
Bullella,  1007 

BuUinula,  225;  indica,  225 
Bumilleria,  164;   sicula,  164 
Bunodera,  388,  396,  398;   luciopercae,  396 
Bunoderuiae,  396 
Bunops,  712;  serricaudata,  712 
Bursa,  476,  514 
Bursaria,  285;  truncatella,  285 
Bythinia,  989;  tentaculata,  989 
Bythininae,  989 

"Cabbage-snake,"  534 

Cabomba,  182 

Caecidotea,  842 

Caecincola,  391,  4CX3;   parvulus,  400 

Caenis  (imago),  920,  (nymph),  922 

Caenomorpha,  285;   medusula,  285 

Caddisflies  (Trichoptera) ;  see  Insecta;  Tri- 
choptera 

Calamoceratidae,  936 

Calceolus,  277;  cypripediiim,  277 

Caligidae,  783;  see  Copepoda 

Callibaetis  (imago),  921,  (nymph),  922 

Callidina,  619;   angusticollis ,  619 

CalocyUndrus,  138 

Calopteryx  (imago),  922,  (nymph),  891,  928 

Calothrix,  113;   thermalis,  113 

Calyptomera,  689 

Calyptorhynchia,  352,  361 

Calyptotricha,  282;   inhaesa,  282 

Camallanidae,  528 

Camallanus,  528;  ancylodirus,  5x2,  529, 
lacustris,  517.  S18,  oxycephalus,  529,  trispi- 
nosus,  529 

Cambarellus,  848;  shiifeldti,  848 

Cambarincola  macrodonia,  644 

Cambarus,  847;  affi,7iis,  848,  bartoni,  847,  849, 
blandingi,  848,  diogenes,  850,  extrdneus,  849, 
gracilis,  847,  hamidaius,  849,  immunis,  849, 
limosus,  848,  pellucidus,  848,  propinquus, 
849,  rusiicus,  849,  simulans,  847,  virilis,  849 

Campascus,  229;   cornutus,  229 

Campeloma,  988;  subsolida,  988 


INDEX 


1089 


Camj/iSurus  (imago),  91 8,  (nymph),  921 

Campipcercus,  718;  macrurus,  718,  rccliros- 
tris,  7\8 

Campylc\iiscus,  130;   cribrosiis,  130 

Candona,  v823;  acuminata,  826,  Candida,  827, 
crogmani,  824,  Jabacformis,  826,  parallcla, 
825,  recticai:da,  826,  reflexa,  824,  sigmoides, 
825,  Simpson!,  825 

Candoninae,  809,  823 

Canthocamptus,  7  So;  hiemalis,  781,  idaho- 
cnsis,  781,  illinoisensis,  781,  minutus,  782, 
northumbricus,  782,  staphylinoides,  781, 
staphylinus,  781 

Canthyria,  looi 

Capillaria,  535;   ransomia,  535 

Carbon  dioxide  in  water,  39;   ^ee  Water 

Carchesium,  294;   polypinum,  294 

Carinifex,  984  ;   newberryi,  984 

Carteria,  144,  265;   obliisa,  144 

Carterius,  313;  latitenta,  314,  lenospcrma,  315, 
tubisperma,  314 

Carunculina,  loii 

Carychium,  977;   exiguum,  977 

Caryophyllaeidae,  430 

Caryophyllaeus,  430 

Castrada  hofmanni,  351 

Catatropis,  383;  filaynentis,  383 

Catenula,  334;   lemnae,  334 

Catenulidae,  334,  361 

Cathypna,  595;   /zow,  595 

Calostomus  commersoni,  1040;  nigricans,  1054 

Celithemis  (imago),  926,  927,  (nymph),  932 

Centrifuge,  84 

Centropagidae,  755 

Centroptilum  (imago),  921,  (nymph),  922 

Centropyxis,  222;   acideata,  222 

Centrorhynchidae,  549 

Centrorhynchus,  549;   spinosus,  549 

Centrovarium,  401;   lobotes,  401 

Cephalobus,  495;  sub-elongatus ,  495 

Cephalogonimus,  402;  americanus,  402, 
vesicaudus,  402 

Cephalosiphon,  617;   limnias,  617 

Cephalothamnium,  247;   caespitosiim,  247 

Ceratium,  270;   hirundinella,  270 

Ceratodrilus  thysanosomus,  644 

Ceratoneis,  130,  134;   crcM5,  134 

Ceratophyllum,  178,  180,  182;   demersum,  193 

Ceratopogoniae  of  Chironomidae,  945 

Cercaria,  371,  372,  411;  as  plankton  organ- 
ism, 372;  agilis,  415.  anchoroidcs,  422, 
ascoidea  (Gymnocephala),  415,  biflcxa,  420, 
bilineata,  411,  brevicaeca,  417,  cary/,  416, 
clausii,  414,  crenata,  417,  dendritica,  418, 
diaphana,  418,  diaslropha,  414,  doulhilti, 
422,  fasciolae  hepaticae,  415.  fiabeUiJormis 
(tetracotyle  form),  424.  glandulosa,  418, 
gorgonocephala,  373,  414.  gracillima,  423. 
hemilophura,  419,  hyalocauda,  413,  inhab- 
ilis,    413,  isocotylea,  417,   konadcnsis,  412, 


Uptacantha,  416,  lurania  (Cilcnmercaria^, 
413,  macrocerca,  421,  tnrgalura.  416,  mirro- 
pharynx,  418,  minuta,  415,  mirabUis,  422, 
pdlucida,  412,  platyura,  419,  polyadena,  418, 
piychocfieilus,    424,    racemosa,    419,    rrflexa, 

415,  421,  rubra,  420,  Agamodistomum  stage 
of,  420,  tardigrada  (RhopalcKcrca),  421, 
trigonura,  419,  trisolrnala,  420,  trixohis,  421, 
tubtristoma,  423,  urbanrnsis,  412,  -urightii, 
422;  5fe  Ccrcariac;  Ccrcariucum;  Para- 
sitic Flatworms;  Trcmatoda 

Cercariae,  amphistumt,  413,  cotylocercous, 
419,  cystocercous,  421,  distomc,  414.  echi- 
nostome,  420,  furcoccrcous,  422,  gastcros- 
tomous,  412,  gymnoccphalous,  415,  holo- 
stome,  423,   leptoccrcac,  415,   megalurous, 

416,  microcercous,  419,  microcwtylac.  416, 
monostome,  412,  ornatae,  419,  polya- 
denous,  416,  prostomatous,  412,  rhahdcxoe- 
lous,  412,  rhopalocercous,  421,  sctiferous, 
423,  stylet,  416;  5fc  Cercaria;  Cercariaeum; 
Parasitic  Flatworms;  Trematoda 

Cercariaeum,  423;  Itelicis,  423,  ra/fanj,  423; 
j^e  Cercaria;  Cercariae;  Parasitic  Flat- 
worms;  Trematoda 

Cercobodo,  244 

Cercomonadidae,  244 

Cercomonas,  244;  longicaudata,  244 

Cercorchis,  394 

Ceriodaphnia,  700;  acanthina,  701,  cornuta, 
700,  consors,  702,  lacustris,  701,  laticaudala, 
702,  megalops,  701,  pidchflla,  702,  quad- 
rangula,  702,  reticulata,  700,  rigaudi,  7cx>, 
rotunda,  703,  scilula,  702 

Cestoda,  Fresh- Water,  15,  365.  369.  424-453: 
acetabula,  425,  bladder-worms  (cysticcrci). 
427,  bothria,  425,  ciliated  larva.  427, 
cysticerci,  427,  key,  429-451.  life  history, 
427,  onchosphere,  427.  pleroccrcoid,  427, 
proglottids,  424,  references,  452,  453. 
reproductive  organs,  426,  rostellum,  424, 
scolex,  424,  s.  str.,  430,  strobila,  424,  struc- 
ture, 424;  see  Parasitic  Flatworms;  Para- 
sitic Worms 

Cestodaria,  369,  429:  ^^^  Cestoda 

Cestodes,  monozootic.  429 

Chaenia,  272;   teres,  272 

Chaetarthria,  939 

Chaetogaster,  638;  diaphanus,  638.  limnaei, 
638 

Chaetomorpha,  165 

Chaetonotidac,  626 

Chactonotus,  626;  acanthodfs,  627,  acan- 
thophorus,  629,  brevispinosus,  627,  enormis, 
630,  formostis,  627.  larus,  627.  longispi- 
nosus,  628,  maximus,  621,  623.  626.  oftonu- 
rius,  628.  jim/7/5,  626,  spinifcr,  629,  5A«««- 
losus,  629 

Chaetopeltis,  171 

Chaetophora,  lOS;    pisiformis,  16S 


logo 


INDEX 


Chaetophoraceae,  i68 

Chaetophoreae,  i68 

Chaetopoda  (earthworms),  aquatic,  i6,  632- 

645;  see  Oligochaeta 
Chaetosphaeridium,  170;   pringsheimii,  170 
Chaeturina,  630;   capricomia,  630 
Chalarothoraca,  235 
Chamaesiphonaceae,  107 
Chamaesiphon,  107;   incrustans,  107 
Chantransia,  176;   chalybea,  176 
Chara,  174;   coronata,  174,  fragilis,  174 
Characeae,  172 
Characetum,  196 
Characiopsis,  158 
Characium,  158;   longipes,  158 
Charales,  172 
Chareae,  174 

Chauliodes  (adult),  935,  (larva),  936 
Cheiracanlhiis  horridiis,  53°,  socialis,  530 
Chilodon,  276;   cucidlulus,  276 
Chilodonopsis,  276;   crenula,  276 
Chilomonas,  261;   Paramecium,  261 
Chirocephalidae,  668 
Chironomidae,  914,  945;  Ceratopogoniae  of, 

945 
Chironomus  (lar\'a),  945,  in  part,  945 
Chirotonetes   (imago),   920,    (nymph),   922 
Chlamydomonas,  143,  i44.  265;  ohioensis,  144 

pulvisculus,  265 
Chlamydophora,  234 
Chlamydotheca,    811;     azteka,    811,    herricki, 

811,  mexicana,  812 
Chlorangium,    147,    266;     sientorinum,    266 

stentorum,  147 
Chlorella,  153 
Chlorellaceae,  153 
Chlorobotrys,  151;   regular  is,  151 
Chlorochytrium,  157;   lemnae,  157 
Choanoflagellata,  257 
Choanotaenia,  446;     infundibulum,    446,    po- 

rosa,  447 
Chodatella,  155 

Chondracanthidae,  784;    see  Copepoda 
Chordata,  18 
Chordodes,  537,  538;    morgani,  538,  occiden- 

talis,  538 
Choroterpes  (imago),  920,  (nymph),  921 
Chlorococcum,  156;   infusionum,  156 
Chloroflagellida,  264 
Chlorogonium,  143;   euchlorum,  143 
Chloropeltis,  252;   hispidiila,  252 
Chlorophyceae,    117,    134;   key,    134-174;   sec 

Algae,  Fresh-Water,  excl.  of  Blue-Green 
Chlorosphaera,  158;   lacustris,  158 
Chlorosphaeraceae,  158 
Chlorotylium,  166;   caiaraclarum-,  166 
Chromadora,  490;   minor,  490 
Chromagrion  (imago),  923,  (nymph),  928 
Chromatophores  of  algae,  116 
Chromulina,  260 


Chronogaster,  493;   gracilis,  493 
Chroococcaceae,  104 
Chroococcus,  106;  giganteus,  106 
Chroolepideae,  170 
Chrysoflagellida,  259 
ChrysomeUdae  (adult),  937,  (larva),  943 
Chrysops  (larva),  946 
Chrysopyxis,  263;   urceolata,  263 
Chydoridae,  716 
Chydorinae,  717 

Chydorus,  730;  barroisi,  733,  hicornutus,  731, 
faviformis,  731,  gibbiis,  731,  globosus,  730, 
hybridus,  733-.  latus,  732,  ovalis,  733,  piger, 
732,  poppei,  734,  rugulosus,  731,  sphaericus, 
732 
Cilia,  238,  239;  see  Infusoria 
Ciliata,  271 

Cilia te  protozoa;   see  Infusoria 
Cincinnatia,  989 

Cinetochilum,  283;  margaritaceum,  283 
Circulation  of  water  in  lakes,  27;   epilimnion, 
28,  hypolimnion,  28,  38,  thermocline,  28,  38, 
waves  and  their  action,  28 
Cirolanidae,  841 
Cirolanides  texensis,  841 

Cladocera  (Water  Fleas),  Fresh-Water,  676- 
740;   digestive  tract,  681,  distribution,  687, 
key,   689-739,   method  of  study,   688,  oc- 
currence, 685,  references,   739-740,  repro- 
duction,   683,    shell,    679,    structure,    677; 
see  Crustacea 
Cladocopa,  806 
Cladomonas,  261 
Cladophora,  166;   glomeraia,  166 
Cladophoraceae,  165 
Cladorchiniinae,  3S6 
Clappia,  990;   clappia,  990 
Clathrocystis,  106;   aeruginosa,  106 
Clathrulina,  236;   elegans,  236 
Climacia  (adult),  935,  (larva),  935 
Climacostomum,  285 
Climate  and  fresh-water  life,  9 
Clinostomum,  408;   marginatum,  408 
Clock  pump,  80 

Cloeon  (imago),  921,  (nymph),  922 
Clonorchis  sinensis,  393-> 
Closterium,  137;  moniliferum  var.  concavum, 

137 
Clostonema,  255;  socialis,  255 
Coccogoneae,  104 
Coccomonas,  266 
CocconeiJaceae,  129 
Cocconeis,  129;   pediculus,  129 
Cocconema,  129;   lanceolatutn,  129 
Cochleare,  597;   turbo,  597 
Cochliopa,  990;   riograndensis,  990 
Cochhopodium,  221;   bilimbosum,  221 
Codonocladium,  259;   umbellattim,  259 
Codonoeca,  245;   inclinata,  245 
Codosiga,  259;  botrytis,  259 


INDEX 


109 1 


Coela:rf .  *ceae,  158 

Coelastrum,  159;  sphaericum,  159 

Coelenttrata,  15,  301,  316;  see  Hydrozoa 

Coelhelm"nthes,  16;  see  Annelida 

Coelosphav  rium,  105;  kutzingianum,  105, 
106 

Colacium,  25. :  steinii,  251 

Coleochaetacea,%  171 

Coleochaete,  171,  scutla,  171 

Coleoptera  (beetles),  904-909;  key,  917, 
adults,  937-942,  larvae,  943.  whirligig 
beetles,  906;  see  Ini.'^cta 

Coleps,  271;   hirtus,  271 

Collecting,  methods  of;  see  Methods  of  Col- 
lecting 

Collodictyon,  250 

Collyriclidae,  383 

CoUyriclum,  383;  colei,  384 

Coloburus,  920 

Colorus,  597;  grallator,  597 

Colpidium,  278;   striatum,  278 

Colpoda,  278;  campyla,  278 

Coluridae,  568,  59s 

Colurus,  597;  grallator,  597 

Colymbetes,  942 

Communities,  animal,  51;  adaptations,  1022, 
associations,  57,  balance,  54,  classification, 
55,  consocies,  56,  creek,  58,  formations,  57, 
lake,  58,  mores  56,  rapids,  52,  river,  58, 
strata,  56,  stream,  57 

Conchostraca,  672 

Conditions  of  Existence;  see  Existence,  Con- 
ditions of 

Condylostoma,  284;  patens,  284 

Cone  dredge,  68 

Confervales,  160 

Congeria,  1018;  leucophaeata,  1018 

Conjugales,  134 

Conjugation  in  Infusoria,  242,  in  Mastigo- 
phora,  242,  in  Sarcodina,  217 

Conochiloides,  617,  natans,  617 

Conochilus,  617;  unicornis,  617 

Contamination,  bacillus  coli  as  index  of,  1069 

Contracoecum,  533;  adunca,  533*  spiculi- 
gerum,  533 

Copelatus  (adult),  942 

Copepoda,  Fresh- Water,  741-789;  develop- 
ment, 745,  distribution,  741,  746,  vertical, 
749,  keys,  755-782,  784-786,  787-788,  meth- 
ods of  study,  753,  754.  occurrence,  745.  ref- 
erences, 788-789,  structure,  742,  vertical 
distribution,  749;  5<?e  Argulidae;  Crustacea; 
Ergasilidae;  Gnathostomata;  Siphonosto- 
mata 

Copeus,  591;   pachyurus,  556,  565.  S9i 

Coptotomus  (adult),  942;  interrogates  (adult), 
938,  (larva),  909 

Corallobothrium,  439 

Cordulegaster  (imago),  924,  (nymph),  930 

Cordulia  (imago),  926,  (nymph),  931 


Cordylophora,  319,  320,  321;  colony,  318;  la- 
CHstris,  321;   see  Hydrozoa 

Corethra  (larva),  945 

Corethrella  (larva),  944 

Corixidae,  934 

Corona,  554 

Corycia,  221;  flava,  221 

Corydalis  (adult),  935,  (larva),  936 

Corynoneura  (larva),  945 

Corynosoma,  549 

Corythion,  232;   dubium,  232 

Coscinodiscaceae,  126 

Coscinodiscus,  126;   apiculatus,  12G 

Cosmarium,  138,  140;   bolrylis,  140 

Cosmocladium,  150;  saxonicum,  140 

Cothurnia,  297,  plcctostyla,  297 

Cottus  ictalops,  1037 

Cotylaapis,  380;   cokcri,  380,  insignis,  380 

Cotylocercous  cercariae,  419 

Cotylogaster,  381;   occidentalis,  381 

Crabs,  828;   see  Malacostraca 

Crangonyx,  843 

Craspedacusta,  318,  322;  kawaii,  322,  sowerbyi, 
322;  see  Hydrozoa 

Crawfishes,  828;   see  Malacostraca 

Crayfishes,  828;   see  Malacostraca 

Creniphilus  (adult),  940 

Crenodonta,  996 

Crepidostomum,  395;  cornutum,  395 

Cricotopus  (larva),  945 

Cristatella  idae,  955,  lacustris,  955.  mucedo, 
947,  955,  ophidea,  955 

Crucigenia,  159;   apiculata,  159 

Crustacea,  17;  jrr  CUidocera;  Copepoda;  Ma- 
lacostraca; Ostracoda;  Phyllopoda 

Crustacea,  Higher;   see  Malacostraca 

Cryptodifflugia,  22S;   oviformis,  228 

Cryptoglena,  253;   pigra,  253 

Cryptogoniminae,  397 

Cryptogonimus,  381,  391.  398;   chyli,  39S 

Cryptomonas,  261;   ovata,  261 

Cr>'ptonchus,  492;   nudus,  492 

Ctedoctema.  282;   acanthocrypta,  282 

Ctenopoda,  689 

Cucullanidae,  529 

CucuUanus,  528,  530;  cliicllarius.  530.  clegans, 

517 
Cucurbitella.  225;   mcspUiformis,  225 
Culex  (larva),  944 
Culicidae  (larva),  944 
Currents  in  water,  influence  of,  28 
Cyanophyceac;   sec  Algae,  Blue-Green 
Cyanophycin  granules,  102 
Cyathocephalinac.  433 
Cyathocephalus,  433:   truncatus,  433 
Cyathocotyle,  409 
Cyathomonas,  260;   truncala,  260 
Cybister  (adult),  941 
Cyclanura,  253;   orbiculata,  253 
Cycle  of  matter,  207 


1092 


INDEX 


Cyclidium,  282;   glaucoma,  282 

Cyclocoelidae,  382 

Cyclocoelum,  382;  mutabile,  382 

Cyclocypridinae,  813 

Cyclocypris,  819;  forbesi,  822,  laevis,  822 

Cyclonexis,  263;  annularis,  263 

Cyclophyllidea,  439 

Cyclopidae,  774 

Cyclops,  774;  nauplius  of,  744,  second  stage 
of,  744;  aequoreus,  780,  albidus,  777,  attr, 
775,  bicolor,  780,  bicuspidaius,  776,  fim- 
briatus,  780,  Juscus,  778,  leuckarti,  777, 
modestus,  778,  phaleratus,  779,  prasinus, 
779,  serrulatus,  779,  strenuus,  776,  tenuis, 
TJT,  varicans,  779,  liridis,  775 

Cyclorchida,  444 

Cyclorhapha  (larva),  946 

Cyclotella,  126;  compta,  126 

Cyclothrix,  859 

Cyclustera,  445;  capilo,  445 

Cylinders,  plankton,  73 

Cylindrocapsa,  165;  involuta,  165 

Cylindrocapsaceae,  165 

Cylindrocystis,  137;  diplospora,  137 

Cylindrospermum,  iii;  stagnqle,  iii 

Cylindrotaenia,  450;   americana,  450 

Cymatopleura,  131;   apiculata,  131 

Cymbella,  129;  cuspidata,  129 

Cymbellaceae,  128 

Cymbiodyta  (adult),  939 

Cyphoderia,  229;  ampulla,  229,  var.  /»a/>i/- 
/a/a,  229 

Cypria,  819;  dentifera  (Cypria),  820,  exsculpta 
(Cypria),  820,  inequivalva  (Physocypria), 
822,  mons  (Cypria),  821,  obesa  (Cypris), 
821,  opthalmica  (Cypria),  821,  pustiilosa 
(Physocypria),  821 

Cyprididae,  807 
Cypridinae,  810,  813 
Cypridopsinae,  807 
Cypridopsis,  807;   vidua,  807 
Cyprinotus,  814;    americanus   (Cypris),   816, 
burlingtonensis    (Cypris),    816,   crena    (Cy- 
pris),   817,    dentata,    796,    (Cypris),    816, 
incongruens   (Cypris),   815,  pellucida   (Cy- 
pris), 815 
Cypris,    813,    817;     altissima    (Cypris),    817, 
americanus     (Cyprinotus),     816,     burling- 
tonensis (Cyprinotus),  816,  crena  (Cyprino- 
tus), 817,  dentata  (Cyprinotus),  816,  Juscata 
(Cypris),    818,   grandis    (Paracypris) ,    819, 
incongruens     (Cyprinotus),    815,    pellucida 
(Cyprinotus),  815,  perelegans  (Paracypris), 
c^i9,    pubera    (Eurycypris),    814,    reticulata 
(Cypris),   818,   testudinaria   (Cypris),   818, 
virens,  792,  (Cypris),  817 
Cy^jrogenia,  1015;  irrorata,  1015 
Cyprois,  809;  marginata,  809 
Cyrena,  1018;  carolinensis,  1018 
Cyrcnella,  1019;  floridana,  1019 


Cyrenellidae,  1019 

Cyrenidae,  1018 

Cyrtolophosis,  282;  mucicola,  282 

Cyrtonia,  599;  tuba,  599 

Cysticerci,  427 

Cysticercoid,  451 

Cysticercus,  451;  fasciolaris,  447 

Cystidicola,  527;  farionis,  527,  serrata,  527, 

stigmatura,  527 
Cystocercous  cercariae,  421 
Cytheridae,  806 
Cytholaimus,  489;  truncatus,  489 

Dacnitis,  528,  52P 

Dacnitoides,  530;   cotylophora,  530 

Dactylococcus,  155;   infusionum,  155 

Dactylothece,  150;   braunii,  150 

Dadaya,  737;  macrops,  737 

Dallasia,  279;  frontata,  279 

Dalyellia,  340;  armigera,  346,  articulata,  345, 
bilineata,  361,  363,  blodgetti,  343,  dodgei,  342, 
eastmani,  342,  fairchildi,  343,  inermis,  341, 
marginatum,  361,  363,  mohicana,  345,  rheesi, 
341,  343,  344,  rochesteriana,  341,  rossi,  345, 
347,  sillimani,  347,  viridis,  346 

Dalyellidae,  340,  361 

Damselflies  (Odonata),  aquatic;  nymphs, 
891;  see  Insecta;  Odonata 

Daphnia,  694;  arcuata,  696,  cucullata,  696, 
longispina,  677,  696,  697,  var.  hyalina,  697, 
var.  longiremis,  697,  magna,  694,  psittacea, 

695,  pulex,  695,  var.  clathrata,  695,  var.  cur- 
virostris,  695,  var.  minnehaha,  695,  var. 
obtusa,  69s,  var.  pulicaria,  695,  retrocurva, 

696,  var.  breviceps,  696 
Daphnidae,  694 

Darwinulidae,  807;   stevensoni,  807 
Dascyllidae,  942;    (larva),  943 
Dasydytes,  630;  saltitans,  630 
Dasydytidae,  630 
Dasymetra,  406;   conferta,  406 
Davainea,  441;  anatina,  441 
Davaineidae,  441 

Debarya,  142;  glyptosperma,  142 
Decapoda,  829,  844;  see  Malacostraca 
Dendrocoelum,   354,  361,  364;  lacteum,  354, 

364,  sp.,  364 
Dendrocometes,  298;  paradoxus,  298 
Dendromonas,  247;   virgaria,  247 
Dendrosoma,  298;   radians,  298 
Denticula,  132;   inflata,  132 
Derepyxis,  264;   amorpha,  264 
Dero,  640;   limosa,  640,  obtusa,  640,  perrieri, 

640 
Deropristis,  391;  hispida,  392 
Derostoma  elongatum,  361,  363 
Derostomum,  348 
Desmarella  irregularis,  259 
Desmidiaceae,  134 
Desmidium,  136;  schwartzii,  136 


INDEX 


1093 


Desmonema,  112;  wrangelii,  112 

Desmopachria  (adult),  941 

Desmothoraca,  236 

Detracia,  979 

Dexiotricha,  280;   plagia,  280 

Diamesa  (larva),  945 

Diaphanosoma,  690;  hrachyurum,  691, 
leuchtcnbergianum,  691 

Diaptomus,  756;  alberqiicrquensis,  771,  asli- 
landi,  765,  asymmetricHS,  769,  bakrri,  770, 
birgei,  758,  clavipes,  760,  coloradensis,  759, 
conipedatus,  767,  dorsalis,  769,  ciseni,  765, 
Jranciscanus,  766,  judayi,  762,  Icplopiis, 
760,  lintoni,  761,  minutus,  764,  mississip- 
piensis,  757,  novamexicanus,  771,  nudiis, 
772,  oregonensis,  757,  pallidus,  758,  />z/r- 
Pureus,  772,  reighardi,  757,  saltillintis,  768, 
sanguineus,  767,  shoshone,  763,  sicilis,  763, 
siciloides,  773,  signicauda,  773,  spalulo- 
crenatus,  766,  stagnalis,  768,  tcnuicaicdatus, 
762,  trybomi,  761,  tyrelli,  759,  wardi,  764, 
washingtonensis,  770 

Diaschiza,  593;   hoodii,  593 

Diatoma,  131;   elongatum,  131 

Diatomaceae,  131 

Diatoms  (Bacillariaceae) ;  5e(?  Algae,  Fresh- 
Water,  excl.  of  Blue-Green;  Bacillaria- 
ceae 

[Dibothrium]  cordiceps,  432 

Dichelestidae,  784;  5ce  Copepoda 

Dichothrix,  113;   interrupta,  113 

Dicrocoeliidae,  407 

Dicrocoelium,  407;   dendriticum,  408 

Dictyocystis,  148 

Dictyosphaerium,  149;   pulchellum,  149 

Dictyosphaeropsis,  150;   pdatina,  150 

Didinium,  272;   nasutiim,  272 

Didymops  (imago),  925,  (nymph),  930;  //«/- 
?jerf,  926,  transversa,  892 

Differentiator,  508,  509 

Difflugia  224;  acuminata,  225,  corona,  224, 
constricta,  224,  /efte^,  224,  lobostoma,  224, 
pyriformis,  225,  urceolala,  224 

Digenea,  379 

Diglena,  589;  forcipata,  589,  rostrata,  589 

Digononta,  619 

Dilepididae,  444 

Dilepis,  444;    transfuga,  444,  unilateral  is,  444 

Dileptus,  275;  gii'a^,  275 

Dimorophococcus,  148;   lunatus,  148 

Dina,  659;  anoculata,  659,  fervida,  660,  wf- 
crostoma,  659,  />an'a,  659 

Dinamoeba,  219;   mirabilis,  219 

Dineutes  (adult),  937 

Dinobryon,  264;  sertularia,  264 

Dinocharidae,  569,  597 

Dinocharis,  597;   pocillum,  597 

Dinoflagellida,  269 

Dinomonas,  248;   wrax,  248 

Dinops,  607 


Dioctophyme,  523;  renale,  523 

Dioctophymidae,  523 

Dioicocestus,  448;  paronai,  448 

Diorchis,  443;  afuminata,  443,  americana,  443 

Diphyllolxjlhriidae,  431 

Diphyllolxjthriinac,  432 

Diphyllolwthrium,  432;  latum.  432 

Diplax,  593;   videns,  593 

Diplobothrium,  378;   armatum,  378 

Diplocardia,  643 

Diplochlamys,  220;  fragilis,  220,  timida,  221 

Diplodiscus,  387;    tempcraltis,  3S7,  413 

I)ipl()discinacr3S7 

Diplodontinac,  86 1 

Diplodontus,  861;   drspiciens,  861 

Diplogaster,  488;  y?r/or,  488 

Diplogonoporus,  433;   grandis,  433,  434 

Diplois,  593;  daviesiae,  593 

Diplophallus,  448;    polymorphus,  448 

Diplophrys,  233:   archeri,  2,\}, 

Diploposthc,  446;   larvis,  447 

Diplostomulum,  411,  424;    cuticola,  411,  ro/- 

w»5,  411 
Dip  nets,  67 

Diplera  (two-winged  flies),  aquatic,  909-916, 
9i7i  943~946;  black-flies  (Simuliidae), 
913,  key,  917,  943-946,  larvae,  917,  midges 
(Chironomidac),  914,  wing  venation,  910, 
916;  5cr  Chironomidae,  Insecta,  Simuliidae 
Dipylidiidae,  440 
Discodrilidae,  644 

Disease  germs,  water  as  conveyor  of,  1068, 
transmission  of,  1068 

Dispersal  of  fresh-water  life  (biology),  13 

Dispharagus,  526,  ardeae,  527 

Distemma,  589;   seligcrum,  589 

Distigma,  254;    proteus,  254 

Disloma  dendriticum,  408.  hflieis,  423,  lancr- 
olatum,  40S,  oricola,  408.  polyorchis,  397, 
vagans,  423,  var labile,  406;  see  Dislomum 

Distomata,  388 

Distome  cercariae,  414 

Dislomum  aspersum,  391,  centra ppcndictdalum, 
411,  flexum,  391,  auriculatum,  396,  dupli- 
catum,  421,  nodulosum,  396;  see  Disloma 

Distribution  of  life,  35 

Distyla,  593;  inermis,  593.  ohioensis,  593 

Diurella,  595;  stdcata,  595,  /icrrt,  562,  595 

Diversity  of  fresh-water  life  (biology),  12 

Dixidae  (larvae),  944 

Dobson  flies  (Sialididac) ;  j^-r  Insecta,  Ncuro- 
tera,  Sialididae 

Docidium,  139;   hactdum,  139 

Dolichodorus,  484;   heterocephaliis,  484 

Donacia  (larva),  943 

Dormancy,  43 

Dorocordulia  (imago),  926,  (nymph),  931 

Dor>laimus,  485;  fecundus.  485,  labyrin- 
thostomus,  485 

Dosilia,  311;   palmfri,  311,  pluttwsa,  311 


I094 


INDEX 


Dracunculidae,  523 

Dragonflies  (Odonata),  aquatic;    see  Insecta 

and  Odonata 
Drainage  of  swamps,  1075 
Draparnaldia,  169;  plumosa,  169 
Dredge,  cone,  68,  pyramid,  71,  triangle,  71 
Dreissensiidae,  1018 
Drepanidotaenia,  442;   fasciata,  451,  lanceo- 

lata,  442 
Drepanothrix,  710;  dentata,  710 
Dromogomphus  (imago),  924,  (nymph),  930 
Dromus,  1012;  dromus,  1012 
Drunella  (imago),  920,  (nymph),  922 
Dryops  (adult),  942 
Dunhevedia,  725;  crassa,   725,   serraia,    726, 

se  tiger  a,  725 
Dwarf  plankton,  6;  see  Plankton 
Dysnomia,  1009 

Dytiscidae  (adults),  940,  (larvae),  943 
Dytiscus  (adult),  908,  941 

Earthworms     (Chaetopoda),      aquatic;      see 

Chaetopoda  and  Oligochaeta 
Echinochasminae,  391 
Echinocotyle,  442;  rosseteri,  442 
Echinodermata,  15 
Echinopharyphium,  391 
Echinorhynchus,  547;  gigas,  542,  salvelini,  548, 

thecatus,  548 
Echinostoma,  391;  spinulosum,  391 
Echinostome  cercariae,  420 
Echinostomidae,  390 
Eclipidrilus,  643;  asymmetricus,  64s,  frigidus, 

643,  palustris,  643 
Ectoprocta,  951 
Eiseniella  (Helodrilus),  643;   tetraedus  (Helo- 

drilus),  643,  forma  pupa  (Helodrilus),  643 
Elakatothrix,  152;  viridis,  152 
Elliptio,  icxx> 
Elmis  (adult),  942 
Elodea,  191,  192 
Elvirea,  248;  cionae,  248 
Emea  rubra,  457,  458 
Enallagma     (imago),     923,     (nymph),     928; 

antennatum  (nymph),  928 
Enchelys,  273;  pupa,  273 
Enchytraeidae,  642 
Enchytraeus,  642 
Encyonema,  129;  auerwddii,  129 
Endoprocta,  951 
Endosphaera,  157;  biennis,  157 
Enteromorpha,  161;  intestinalis,  161 
Entocythere,  806;  cambaria,  806 
Entosiphon,  257;  sidcatus,  257 
Eosphora,  591;  digitata,  591 
Ephemera  (imago),  918,  (nymph),  921 
Ephemerella  (imago),  920,  (nymph),  922 
Ephemerida     (mayflies),    aquatic,    885-888, 

917,918-922;  keys:  917;  imagos,  918-921; 

nymphs,  921-922;  see  Insecta 


Ephydatia,  307,  309,  314;   crateriformis,  311, 

everetti,  311,  fluvaitilis,  309,  japonica,  310, 

leidyi,  951,  millsii,  309,  miilleri,  309,  310. 

robusta,  310,  subdivisa,  309,  subtilis,  310 
Epiaeschna  (imago),  925,  (nymph),  930 
Epicordulia  (imago),  926,  (nymph),  931 
Epilimnion,  28 
Epiphragma  fascipennis,  912 
Epipyxis,  263;  ulricidus,  263 
Epischura,  755;  lacustris,  756,  nevadensis,  756 
Epision,  449 
Epistome,  948 

Epistylis,  295;  flavicans,  295 
Epithemia,  134;  turgida,  134 
Epithemiaceae,  133 
Eremosphaera,  153;  viridis,  153 
Eretmia,  603;   trithrix,  603 
ErgasiUdae,    783-786;     key,    784-876;     see 

Copepoda  and  Siphonostomata 
Ergasilus,    783;    caeruleus,  785,   centrarchida- 

rum,    785,    chautauquaensis,   786,  funduli, 

784,  labracis,  785,  versicolor,  786 
Eschaneustyla,  288;  brachyiona,  288 
Estheria,  673;   belfragei,  674,  calif ornica,  674, 

compleximanus,  674,  digueti,  674,  mexicana, 

675,  morsei,  664,  675,  newcombii,  674,  selosa, 

675 
Etheostoma  caeruleum,  1047 
Ethmolaimus,  491;   americanus,  491 
Euastrum,  140;   elegans,  140 
Eubranchipus,  668;    bundyi,  670,  dadayi,  669, 

gelidus,  669,  holmani,  668,  670,  ornatiis,  669, 

serratus,  670,  vernalis,  668 
Euchlanidae,  568,  593 
Euchlanis,  595;  macrura,  595 
Eucrangonyx,  843 

Eudorina,  146,  267;  elegans,  146,  267 
Euglena,  251;  spirogyra,  251,  viridis,  251 
Euglenida,  251 
Euglenidae,  251 
Euglypha,  230;   alveolaia,  231,  brachiata,  231, 

ciliata,   231,   compressa,   231,   cristata,   230, 

mucronata,  230 
Euglyphidae,  228 
Euichthydina,  624 
Eulamelhbranchia,  994 

Eulimnadia,  673;    agassizii,  673,  texana,  673 
Eumermis,  505 
Eunotia,  134;  pectinalis,  134 
Eupera,  1019;  singleyi,  1019 
Euplotes,  291;  charon,  291,  patella,  291 
Euryalona,  720;   occidentalis,  720 
Eurycaelon,  992;  anthonyi,  992 
Eurycercinae,  716 
Eurycercus,  716;  lamellatus,  717 
Eurycypris,  814;  pubera  (Cypris),  814 
Eurynia,  ion 

Eurytemora,  750;  affinis,  756 
Eustrongylus  papillosus,  523 
Euthyplocia  (imago),  918,  (nymph),  921 


INDEX 


1095 


Eutreptia,  252;  viriois,  252 

Excentrosphaera,  i:^;   viridis,  153 

Existence,  conditior  -of,  21-60;  bottom  mate- 
rials, 24,  different  -tion  in  bottom  material, 
25,  distrib'ition  of  life,  35,  in  lakes,  23,  in 
Lake  Michigan,  35,  dormancy,  43,  mutk 
bottons,  26,  references,  60,  terriginous  bot- 
toms, 26 

Eylaidae,  860 

Eylais,  860;   extendens,  860 

Fairy  shrimps;  see  Phyllopoda 

Fasciola,  389;   hepalica,  389 

Fasciolidae,  389 

Fasciolinae,  389 

Fascioloides,  389;   magna,  389 

Fasciolopsis,  389 

Fauna  relicta,  10 

Faxonius,  848 

Ferrissia,  985 

Filaria,  524;  amphiutnae,  524,  ardeariim,  524, 
cingula,  525,  cistudinis,  524,  hcliciniis  (Pcle- 
citus),  524,  nilida,  524,  physalura,  525, 
solitaria,  521,  524,  stigmatura,  527,  triae- 
nucha,  526,  wymani,  524 

Filariidae,  524 

Filarioidea,  523 

Filaroides,  522;   mustelarum,  522 

Filicollis,  548,  551;  analis,  S49,  botulus,  549,  551 

Fimbraria,  449;   plicata,  449 

Fimbriariidae,  449 

Fishes,  Fresh-Water,  1029-1065;  adapt- 
ations, 1039,  adjustment  to  biological  en- 
vironment, 1055,  to  current,  1053,  to  light, 
1054,  to  temperature,  1050,  dispersal,  1037, 
enemies  of,  106 1,  homes,  1042,  migration, 
1040,  nests,  1043,  number,  1033,  origin, 
1032,  103s,  of  adapted  faunas,  1064, 
plankton  and  fish  life,  1082,  references, 
1066,  secondary  sexual  characters,  1047;  see 
Vertebrata 

Fish-flies  (Sialididae);  see  Insecta,  Neurop- 
tera,  Sialididae 

Fish  life,  plankton  and,  1082 

Flagella,  238 

Flagellate  protozoa;  see  Mastigophora 

Flatworms  (Platyhelminthes),  15;  free-liv- 
ing; see  Nemertina  and  Turbellaria;  para- 
sitic; see  Parasitic  Flatworms 

Fleas,  aquatic;  see  Cladocera 

Flexiphyllum,  274;   elongatiim,  274 

Flies;     black;     see   Insecta   and   Simuliidae; 
damsel,  dragon;    see  Insecta  and  Odonata; 
fish;     see   Insecta    and    Neuroptera;    two- 
winged;  see  Diptera  and  Insecta 
Florideae,  175 
Floscularia,  609;  campanulata,  561.  609,  cdcn- 

tata,  609,  proboscidea,  609,  iiniloba,  609 
Floscularida,  572,  609 
Flosculariidae,  572,  609 


Flowing  waters,  2 

Fluctuations  in  numl>ers  of  organisms,  54 

Flukes;   see  Trcmatoda 

Fluminicola,  991;   nutlalliana,  991 

Food  relations  of  aquatic  animals,  53,  54 

Foraminifcra,  2^2 

Fordycc  pump,  79 

Fragilaria,  132;   crototicnsis,  132 

Fragilariaceae,  132 

Franceia,  155 

Frederkella  sultana,  952     « 

Free-living  flatworms;  sec  Ncmcrlcans  and 
Turbellaria 

Free-living  nematodes;  see  Ncmatoda,  free- 
living 

Free-living  Roundworms;  sec  Nematoda,  free- 
living 

Fresh-water  algae,  biology,  life,  etc.;  see  Al- 
gae, Biology,  Life,  etc..  Fresh-water 

Frontipoda,  868;   musculus,  868 

Frontonia,  280;     Iciicas,  280 

Funiculus,  948 

Furcocercous  cercariae,  422 

Furcularia,  589;    forficula,  589.  longisela,  589 

Fusconaia,  997 

Fyke  nets,  63 

Gadinia,  980;   reticulata,    9S0 

Gadiniidae,  980 

Galba,  982 

Galerucclla  (larva),  943 

Gametes,  1 19 

Gammaridae,  842 

Gammarus,  843;  limnaeus,  843 

Gases,  dissolved  in  water,  36,  distribution,  37. 
solubility,  37 

Gasterostomata,  379 

Gasterostomous  cercariae,  412 

Gasterostomum,  379 

Gastropoda,  970,  977:  •^«*<'  Mollusca 

Gastropodidac,  570,  603 

Gastropus,  603 ;  hyptopus,  603,  siylifer,  599,  (>o.\ 

Gastrostyla,  289;   steinii,  289 

Gastrotricha,  fresh-water,  16,  621-631:  dis- 
tribution, 624,  excretory  organs,  623.  key, 
624-630,  locomotion,  622,  references,  631, 
structure,  621 

Geminella.  163 

Genicularia,  135;   spirolarnia,  135 

Geoplana  nigrofusca,  360,  slolli,  360 

Geoplanidae.  360 

Gerda,  292;   sigmoiJes,  292 

Gerridae,  933 

Gigantorhynchus  hirudinaceus,  542 

("lillia,  991:   dltilis,  991 

Gill  nets,  64 

Glass,  water.  87 

Glaucoma,  280;   sdntUlans,  2S0 

Glebula,  1017;   rotundata,  1017 

Glenocercaria,  413 


1096 


INDEX 


Glenodinium,  270;  pulvisculus,  270 

Gloeocapsa,  106;   polydermatica,  106 

Gloeocystis,  150;   vesiculosus,  150 

Gloeotaenium,  152;   loilelsbergerianum,  152 

Gloeothece,  104;  confluens,  104 

Gloeotrichia,  114;   pisum,  114 

Glossiphonia,  651;  complanata,  652,  fusca, 
652,  heterodita,  652,  nepheloidea,  651, 
stagnalis,  651 

Glossiphonidae,  651 

Glypthelmiiis,  404;   quieta,  404 

Gnathobdellae,  656 

Gnathostoma,  530;  horridum,  530,  sociale,  530 

Gnathostomata,  755-782;  key,  755-782;  see 
Copepoda 

Gnathostomidae,  530 

Golenkinia,  154;  radiata,  154 

Gomphaeschna  (imago),  925 

Gomphonema,  129;   acuminatum,  129 

Gomphonemaceae,  129 

Gomphosphaeria,  105;   aponina,  105 

Gomphus  (imago),  924,  (nymph),  930 

Gonatonema,  143;  ventricosum,  143 

Gonatozygon,  135;   raljsii,  135 

Gonidea,  1002;   angulata,  1002 

Gordiacea,  16,  365,  506-510,  535-542;  devel- 
opment, 536,  key,  537-542,  references,  551, 
552;  see  Acanthocephala,  Nematoda  (Para- 
sitic), Parasitic  Roundworms 

Gordius,  539;  alascensis,  539,  densareolatus, 
540,  541,  leidyi,  541,  lineatus,  540,  541, 
longareolatus,  540,  plaiycephalus,  541,  542, 
puerilis,  538,  villoti,  540,  541 

Gorgodera,  399;   minima,  399 

Gorgoderidae,  398 

Gorgoderina,  399;   attenuata,  399 

Gorgoderinae,  398,  421 

Goniobasis,  993;   virginica,  993 

Gonium,  145,  266;  pectorale,  145,  266,  so- 
ciale, 266 

Graphoderes  (adult),  941 

Grapple,  68 

Graptoleberis,  724;  testudinaria,  724 

Grimaldina,  711;   brazzai,  711 

Gromia,  233;  fluviatilis,  233,  terricola,  233 

Gryporhynchus,  445,451;  cheilancristrotus,  445 

Gundlachia,  986;  meekiana,  986 

Gymnamoebida,  219 

Gymnocephala,  415 

Gymnocephalous  cercariae,  415 

Gymnodinium,  270;  fuscum,  270 

Gymnolaemata,  951 

Gymnomera,  738 

Gymnostomina,  271 

Gymnozyga,  135;  brebissonii,  135 

Gyratricidae,  353 

Gyratrix  hermaphroditus,  353 

Gyraulus,  983;  s.  s.,  983 

Gyretes  (adult),  938 

Gyrinidae  (adults),  937,  (larvae),  943 


Gyrinus  (adult),  937 
Gyrocoelia,  447 
Gyrodactylidae,  374 
Gyrodactylus,  374 
Gyrotoma,  993;  demissum,  993 

Habrophlebia  (irdago),  920,  (nymph),  921 
Haemopis,   657;    grandis,  658,  lateralis,  658, 

marmoratis,  658,  plumbeus,  658 
Haemotococcus,  266 
Hagenius  (imago),  924,  (nymph),  929 
Hair  snakes;  see  Gordiacea 
Hairworms;   sec  Gordiacea 
Halipegus,  408;  occidualis,  408 
Hallplidae  (adults),  938,  (larvae),  943 
HaUplus  (adult),  938,  (larva),  907,  943 
Halteria,  286;   grandinella,  286 
Hapalosiphon,  113;   hibernicus,  113 
Haplobothriinae,  432 
Haplobothrium,  432;  globuliforme,  432 
Haplonema,  526;  immutatum,  526 
Haplopoda,  739 
Haplotaxidae,  642 
Haplotaxis  emis sarins,  642 
Harpacticidae,  780 
Harringia,  607;   eupoda,  607 
Hassallius,  392 
Hasstilesia,  409;   tricolor,  409 
Hastatella,  292;  radians,  292 
Hedruris,  528;  androphora,  528,  siredonis,  528 
Heleopera,  227;  picta,  227,  rosea,  227 
Heliozoa  213,  234 
Helisoma,  982;  s.  s.,  982 
Helminthes,  365;  see  Parasitic  Worms 
Helochares  (adult),  939 
Helocombus  (adult),  939 
Helocordulia  (imago),  926,  (nymph),  931 
Helodrilus  (Eiseniella),  643;    tetraedrus,  643, 

forma  pupa,  643 
Helophorus  (adult),  939 
Hemerobiidae   (dobson  and  fish  flies),   898- 

899;  (adults),  934;  5ee  Insecta  and  Neurop- 

tera 
Hemiciplostyla,  287 
Hemidium,  269 

Hemilastena,  1007;   ambigua,  1007 
Hemiptera  (water  bugs),  aquatic  and  semi- 
aquatic,  893-896,  917,  933-934;    key,  917, 

933-934;   see  Insecta 
Hemistomidae,  409 
Hemistomum,  410;    (l$irva),  424;    craterum, 

410,  denticulatum,  411 
Hemiurus,  392 

Heptagenia  (imago),  919,  (nymph),  921 
Herpetocypridinae,  810 
Herpetocypris,   811;    barbatus,   812,  reptans, 

812,  testudinaria,  813 
Heronimidae,  384 
Heronimus,  384;  chelydrae,  384 
Eerpohdella  punctata,  659^ 


INDEX 


1097 


Herpobdellidae,  659 

Herposteiron,  169;   confervicola,  169 

Hetaerina  (imago),  923,  (nymph),  928 

Heterakidae,  532 

Heter  anther  a  graminea,  191 

Heterocheilidae,  533 

Heterocysts,  103 

Heteromastigida,  248 

Heteromastigidae,  246 

Heteromeyenia,  312,  314;  argyrosperma,  313, 
re  pens,  313,  ryderi,  312 

Heteromita,  249;   ovata,  249 

Heteronema,  256;   acus,  256 

Heterophrys,  235;   myriopoda,  235 

Helerostomum  echinatiim,  411 

Heterotricha,  283 

Hexagenia  (imago),  918,  (nymph),  921;  bi- 
lineata,  887 

Hexamita,  250;   inflata,  250 

Hexotricha,  277;   globosa,  277 

Hibernacula,  192,  949 

Hippuetis,  983 

Hirmidium,  259;  inane,  259 

Hirudinea  (leeches),  Fresh-water,  16,  646-660; 
key,  651-660,  methods  of  study,  651,  ne- 
phridia,  648,  occurrence,  649,  references, 
660,  reproduction,  647,  650 

Hirudinidae,  656 

Hiriido  medicinalis,  657 

Histrio,  290;   erethisticus,  290 

Histriobalantidium,  281 

Holopedidae,  693 

Holopedium,  693;  amazonicum,  693,  gib- 
berum,  693 

Holophrya,  272 

Holosticha,  288;  vernalis,  288 

Holostomata,  409 

Holostome  cercariae,  423 

Holostomum,  410;  niiidum,  410 

Holotricha,  271 

Hormidium,  162;  nitenz,  172 

Hormospora,  163;   mutabilis,  163 

Homostyla,  287;  elliptica,  287 

Hormogoneae,  107 

Hormotila,  148;   mucigena,  148 

Host,  intermediate,  371,  primary,  372,  second- 
ary, 372 

Ilyalella  knickerbockeri,  843 
I  Hyalodiscus,  219;   riibicundus,  219 

'  Ilyalolampe  fenestrata,  235 

Hyalosphenia,  223;  cuneata,  223,  elegans,  223, 
papilio,  223 

Hyalotheca,  135;  dissiliens,  135 

Hydaticus  (adult),  941 

Hydatina,  599;  senta,  599 

Hydatinidae,  569,  599 

Hydatinina,  599 

Hydra,  316-322;  development,  317,  habitat, 
318,  key,  320-322,  methods,  319,  structure, 
316;    corala,  321,  fusca,  321,  grisea,  320, 


oligaclis,  320,  321,  pallida,  321,  polypus,  321, 

viridis,  320,  viridissima,  320,  vulgaris,  320; 

see  Hydrozoa 
Hydracarina  (water-mites).  Fresh-water,   17, 

851-875;    development,  855,  key,  859-874, 

methods   of   study,    857,    occurrence,    851, 

references,  875,  structure,  852 
Hydrachna,  860;   gcographica,  860 
Hydrachnidae,  860 
Hydracna,  938 
Hydrobaenus  (larva),  945 
Jlydrobius  (adult),  940 
Hydrocampa,  903 
Hydrocharis  (adult),  940 
Hydrochus  (adult),  939 
Hydrocirius,  933 

Hydrocoleum,  109;   homocotrichum,  109 
Hydrodictyaceae,  160 
Hydrodictyon,  160;   rrticulaium,  160 
Hydrogen  sulphide  in  streams,  39 
Hydrography,  i ;  see  Limnology,  Oceanology, 

Rheology 
Hydromermis,  505 
Hydrometridae,  933 
Hydrophilidae  (adult),  938,  (larva),  943 
Hydrophilus,  940 
Hydro porus  (larva),  941,  (larva  and  pupa), 

908 
Hydropsychidae,  937 
Hydroptilidae,  936 
Hydrosphere,  i 
Hydrovatus  (adult),  941 
Hydrozoa,  Fresh-water,  316-322;    key,  320- 

322,    medusae,    318,    references,   322;    see 

Hydra 
Hydryphantes,  862;  ruber,  862 
Hydryphantidae,  S60 
Hydryphantinae,  861 
Hygrobates,  874;  longipalpis,  874 
Hygrobatidae,  863 
Hygrobatinae,  873 
Hymenolepididae,  441 
Hymenolepis,  442;  compressa,  442,  fusus,  442, 

megalops,  442 
Hymenostoma,  281 
Hypolimnion,  28,  38 
Hypotricha,  286 
Hysterophora,  3^,:?,,  361 
Hysterothylacium,  534;  brachyurum,  534 
Ilystrichis  papillosus,  52s 

Ichthydiidae,  624 

Ichthydium,    624;     podura,    624,    sulcatum, 

625 
Ichthyobdellidae,  655 
Ichthyonema,  523;   cylindraccum,  524 
Idiogencs,  441 
Ileoncma,  271;  dispar,  271 
Ilybiosoma  (adult),  941 
Ilybius  (adult),  941 


logS 


INDEX 


Ilyocryptus,  712;  acutifrons,  7i3»  halyi,  713. 
longiremis,  713,  sordidiis,  712,  spinifer,  713 

Ilyocypris,  809;   bradyi,  810,  gi6io,  809 

Ilyodrilus,  641 

Ilyodromus,  810;   pedinatus,  810 

Incrustation  on  aquatic  plants,  185;  car- 
bonate of  lime,   187,  gelatinous  covering, 

187 

Ineffigiata,  149 

Infusoria  (Ciliate  Protozoa),  Fresh- water,  14, 
238-243,  271-300;  cilia,  238,  239,  ciliate 
protozoa,  238,  conjugation,  242,  key, 
271-300,  methods  of  study,  242,  physiolog- 
ical processes,  241,  references,  300,  repro- 
duction, 241,  structure,.  239;  see  Protozoa 

Insecta,  aquatic,  17,  876-946;  adaptation  to 
water,  876,  of  larvae  to  aquatic  life,  878 
keys,  917-946;  of  adults,  934-935.  937-942 
of  imagos,  918-921,  922-927;  of  larvae, 
917,  935-936,  943-946;  of  nymphs,  921-922, 
928-932;  recognition  of  characters,  880 
references,  946,  wing  venation,  916;  see 
Coleoptera,  Diptera,  Ephemerida,  Hemip- 
tera,  Lepidoptera,  Neuroptera,  Odonata, 
Plecoptera,  Trichoptera 

Intermediate  host;   see  Host 

Investigators  in  Fresh- Water  Biology,  1 1 

lo,  992;  spinosa,  992 

Iota,  482;   octangulare,  482 

Ironus,  486;  americanns,  486 

Ischnura  (imago),  924,  (nymph),  929;  verti- 
calis,  893 

Isopoda,  829,  841;  see  Malacostraca 

Jaws  (trophi)  of  rotatoria,  559 
Jensenia,  348;   pinguis,  348 
Journals  on  Fresh- Water  Biology,  20 

Kerona,  287;   pediculus,  287 

Keys  to  Fresh- Water  Biology;  Algae,  Blue- 
Green  (Cyanophyceae),  104-114,  Algae, 
excl.  of  Blue-Green,  125-177,  Acanthoceph- 
ala,  545-551,  Animalcules,  587-619,  951- 
955,  Argulidae,  787-788,  Bacillariaceae, 
125-134,  Bryozoa,  951-955,  Chlorophyceae, 
134-174,  Cestoda,  429-451,  Cladocera,  689- 
739,  Copepoda,  755-782,  784-786,  787-788, 
Coleoptera,  937-943,  Diptera,  943-946, 
Ephemerida,  918-922,  Ergasihdae,  784-786, 
Gastrotricha,  624-630,  Gnathostomata, 
755-782,  Gordiacea,  537-542,  Hemiptera, 
933-934,  Hirudinea,  651-660,  Hydra,  320- 
322,  Hydracarina,  859-874,  Hydrozoa, 
320-322,  Infusoria,  271-300,  Insecta,  917- 
946,  Mollusca,  977-1020,  Malacostraca, 
841-850,  Mastigophora,  243-270,  Nema- 
toda,  Free-Living,  482-505,  Nematoda, 
Parasitic,  520-535,  Neuroptera,  934-936, 
Odonata,  922-932,  Oligochaeta,  638-644, 
Ostracoda,    806-827,    Phaeophyceae,    174- 


175,  Porifera,  306-315,  Protozoa,  219-236, 
243-300,  Phyllopoda,  666-675,  Rhodo- 
phyceae,  175-177,  Rotatoria,  587-619, 
Sarcodina,  219-236,  Trichoptera,  936-937. 
Trematoda,  374-424,  Turbellaria,  333-364 

Kirchneriella,  151;  obesa,  152 

Koenikea,  865;  concava,  865 

Krendowskija,  863;   ovata,  863 

Kurzia,  718;  latissima,  718 

Labidestes  siculus,  1036 
Laccohius  (adult),  939 
Laccophilus  (adult),  940 
Lacinularia,  617;  socialis,  561,  575,  617 
Lacrymaria,  274;   olor,  274 
Ladona  (imago),  927,  (nymph),  932 
Laevapex,  985 

Lagenophrys,  297;  vaginocola,  297 
Lagerheimia,  154;   genevensis,  154 
Lakes,  2,  4,  5;  age  series,  49,  circulation  of 
water  in,  27,  conditions  of  existence  in,  23, 
in  Lake  Michigan,  35,  epilimnion,  28,  hypo- 
limnion,  28,  38,  thermocUne,  28,  38,  waves 
and  their  action,  28 
Lamellibranchia,  970,  994;  see  Mollusca 

Lamprothamnus,  174 

LampsiUnae,  1007 

Lampsilis,    1009;     ovata,    loio,    recta,    loii, 
texasensis,  loii;   s.  s.,  loio 

Land  planarians;  see  Turbellaria 

Lanthus  (imago),  924,  (nymph),  929 

Lanx,  986;   newberryi,  986 

Lara  (adult),  942 

Lasmigona,  1005 

Lastena,  1002;  lata,  1002 

Lateriporus,  444 

Lathonura,  716;  rectirostris,  716 

Latona,  689 ;  parviremis,  690,  setifera,  690 

Latonopsis,    691;    fasciculata,    692;    occiden- 
talis,  691 

Lebertia,  867;    dubia,  867,  tau-insignita,  867 

Lebertiinae,  867 

Lechriorchis,  407;   elongatus,  407,  primus,  407 

Lecithophora,  340,  361 

Lecquereusia,  222;   epistomium,  223,  modesta, 
222,  spiralis,  223 

Leeches;   see  Hurudinea 

Lemanea,  175;   lorulosa,  175 

Lembadion,  281:   bullinum,  281 

Lemna,  178;  minor,  192 

Lemnisci,  543 

Lepidoderma,  625;   concinnum,     626,     rhom- 
boides,  625,  squamatum,  625 

Lepidoptera  (moths),  903,  917;   see  Insecta 

Lepidurus,  671;    bilobatus,  671,  couesii,  671, 
glacialis,  671,  lemmoni,  671 

Lepocinclis,  253 

Lepodermatidae,  402 

Lepomis  megalotis,  103 1 

Leptidae  (larvae),  946 


INDEX 


1099 


Leptoceridae,  936 

Leptodora,  739;   kindtii,  739 

Leptodoridae,  739 

Leptomonas,  246 

Leptophlebia  (imago),  919,  (nymph),  921 

Leptorhynchus  dentifer,  736 

Leptozosma,  135;  catenulata,  135 

Lepyrium,  994;   showalteri,  994 

Lcrnacidae,  7 84;   see  Copepoda 

Lernaeopodidae,  784;   see  Copepoda 

Lestes  (imago),  923,  (nymph),  891,  928 

Leuceruthrus,  392,  407;   micro ptcri,  392 

Leucochloridium,  409,  423 

Leucophrys,  278;   patula,  278 

Leucorhinia  (imago),  927,  (nymph),  932 

Leydigia,  721;  acanthocercoides,  721,  quadran- 
gular is,  721 

Libellula  (imago),  927,  (nymph),  931,  932 

Lieberkiihnia,  233;  wageneri,  233 

Life,  distribution  of,  35;  see  Existence,  con- 
ditions of 

Life,  Fresh-water;   see  Biology,  Fresh-water 

Light,  intensity  of,  32,  penetration  in  water  of, 
29,  30,  vs.  migration,  31 

Ligula,  431 

Ligulinae,  431 

Limnadia,     673;     americana,    673,    coriacea, 

673 
Limnadiidae,  673 
Limnebius  (adult),  939 
Limnesia,  87c;  histrionica,  870 
Limnesiopsis,  869;   anomala,  869 
Limnetic  region,  4 
Limnetidae,  672 
Limnetis,  672;    brevifrons,  672,  gouldii,  672, 

gracilicornis,  672,  mucronatiis,  762 
Limnias,  615;   ceratophylli,  615 
Limnicy there,  806;    illinoisensis ,  807,  reticu- 
lata, 806 
Limtiocalanus  macrurus,  774 
Limnochares,  859;   aquaticus,  859 
Limnocharidae,  859 
Limnocnida,  322;    indica,  322,  rhodesia,  322, 

tanganyicae,  322;   see  Hydrozoa 
Limnodrilus,  641;  claparedianiis,  641,  gracilis 

641 
Limnology,  i;    lakes,  2,  4,  5,  limnetic  region, 

4,   Httoral  region,   4,   ponds,    2,   pools,   3, 

shore  zone,  3 
Limnomermis,  505 
LimnophiUdae,  936,  937 
Limnoplankton,  6;   see  Plankton 
Lionotopsis,  275;   anser,  275 
Lionotus,  276;  wrzesniowskii,  276 
Lioplax,  988;  subcarinala,  988 
Liporhynchia,  340,  361 
Liriola,  980 
Lissoflagellata,  243 

Lithasia,  992;  armigera,  992,  geniculata,  992 
Littoral  region,  4 


Liltoridina,  990;   monroensis,  990 

L<jp)h()phure,  947 

LophopHs  cristiiilinus,  954 

Loricalina,  591 

Loxocephalus,  2H0;   granulosus,  280 

Ixjxodes,  274;   rostrum,  274 

Loxogcncs,  400;   arcanum,  400 

L()xoi)h>lium,  27s;  rostralum,  275 

Lucius  vcrmiculatus,  103 1 

Luml)rii  illiis,  i'y\2;   ruiUus,  642 

Lun\l)riiulidac,  642 

Lumbriculus,  ^42;    inconstans,  642 

Lutrochus  (adult),  942 

Lycastoides  alticola,  632 

Lychnothamnus,  174 

Lymnaca,  980;  auricularia,  981.  columella. 
gSi,  haldcmani,  981,  megasoma,  980,  obrussa, 
982,  palustris,  981,  stagnalis,  980,  utahensis 
981,  s.  s.,  980 

Lymnaeidae,  980 

Lyngbya,  108;   major,  108 

Lyngbyeae,  107 

Lyogyrinac,  991 

Lyogyrus,  99 1 ;    pupoidt  us,  c)gi 

Lysianassidae,  842 

Lythoglyphinae,  990 

Macrobdella,  65(1;   decora,  656,  seslertia.  656 

Macromia  (imago),  925,  (nymph),  930 

Macronychus  (adult),  942 

Macrostominae,  338 

Macrostomum,  33S;  appendiculatum,  338, 
hystrix,  338,  scnsitivum,  339 

Macrothricidac,  708 

Macrothrix,  713;  horysthrnica,  715,  eUgans, 
715,  hirsuticontis,  714,  laticornis,  714,  mon- 
tana,  714,  rosea,  715,  ttnuicornis,  715 

Malacostraca  (Higher  Crustacea),  828-850; 
cave  species,  837,  development.  832,  habi- 
tat, 83s,  key,  841-850.  mcthtxi  of  study, 
840,  occurrence,  828,  references.  850,  struc- 
ture, 830;   see  Crustacea 

Mallomonas,  260 

Mammals,  a(iuatir,  1022-1024:  references, 
io6'>;    srr  \\Ttcl)rata 

Man  the  modifying  agent  in  fresh-water  life, 
1 1 

Manayunkia  speciosa,  632 

Mancasellus.  841 

Margaritana,  995;    margaritiiera,  995 

Margarilanidae,  995 

Marionina  jorlnsac,  642 

Marl  and  marl  lakes,  aquatic  plants  factors 
in  ft)rmation  of.  207 

Marshia.  7S0;  aibuqurrqurnsis,  780,  brevkau- 
data,  780 

Mastax.  55S.  560 

Mastigamoeba.  243:   lotigi/ilum,  3a\ 

Mastigophora  (Flagellate  Trotuzoa).  Fresh- 
water, 14,  238-270,  300:  conjugation,  342, 


IIOO 


INDEX 


flagella,    238,   key,    243-270,   methods   of 
study,   242,  pseudopodia,  238,  physiologi- 
cal processes,  241,  references,  300.  repro- 
duction, 241,  structure,  238;  see  Protozoa 
Mastogloia,  128;  smithii,  128 
Matter,  cycle  of,  207 
Matus  (adult),  942 

Mayflies,  aquatic;  see  Ephemerida;  Insecta 
Mazocraes,  375 
Meadow,  aquatic,  197 
Medionidus,  1015;  conradicus,  1015 
Mediorhynchus,  549 
Medusae  of  Hydrozoa,  318 
Megadistomvun,  392 

Megalotrocha,  617;  alboflavicans,  611,  617 
Megalurous  cercariae,  416 
Megarhinus  (larva),  944 
Melampinae,  978 
Melampus,  978;  hidentata,  979,  bulloides,  979. 

hemphilli,  979,  Uneatus,  978;  s.  s.,  978 
Melicerta,  615;  ringens,  57s,  615 
Mehcertida,  574,  611 
Melicertidae,  615 
Melosira,  126;  varians,  126 
Melosiraceae,  126 
Menoidium,  255;  pellucidum,  255 
Meridion,  132;  constrictum,  132 
Meridionaceae,  132 
Merismopedia,  105;  elegans,  105 
Mermis,  505 

Mermithidae,  503,  510,  534 
Meromyaria,  515 
Mesenchytraeus,  642 
Mesocarpeae,  142 
Mesocestoides,  440 
Mesocestoididae,  440 
Mesodinium,  272;  pvlex,  272 
Mesomermis,  503;  virginiana,  503 
Mesostoma,  352;    ehrenbergii,  352,  patter soni, 

361,  362,  vividatum,  350,  viviparum,  350 
Mesostomatini,  351 

Mesotaenium,  138;  endlicherianum,  138 
Mesothemis  (imago),  927,  (nymph),  931 
MetaboUsm,  temperature  vs.,  33 
Metanema,  257 
Metastrongylinae,  522 

Methods  of  Collecting,  61-85;  bottom,  70,  by 
pyramid  dredge,  71,  by  runner  net,  70,  by 
triangle  dredge,  71;  fish,  61,  by  fyke  net, 
63,  by  gill  net,  64,  by  net,  61-66,  by  seine, 
61,  by  trammel,  62,  by  trap,  65,  by  turtle 
net,  66;  invertebrates,  in  littoral  vegetation, 
67,  by  Birge  net,  68.  by  cone  dredge,  68,  by 
dip  net,  67,  by  grapple,  68,  by  plankton 
pump,  70;  in  open  water,  quaUtative,  72, 
by  plankton  cyUnders,  73,  by  townet,  72; 
in  open  water,  quantitative.  74.  by  clock 
pvunp,  80,  by  closable  plankton  net,  77, 
78,  by  plankton  pump,  78,  by  quantita- 
tive plankton  net,  74,  by  thresher  tank- 


pump,  80,  by  water-bottle,  80;   references, 
88-89;  special  methods,  85 
Methods   of   Photographing,    86-88;    under- 
water,  86,  by   screen,   86,  through  water 
glass,  87;  references,  88-89 
Metopidia,  597;   ehrenbergii,  597 
Metopus,  284;  sigmoides,  284 
Metorchis,  393;   complexus,  393 
Metriocnemus  (larva),  945 
Meyeninae,  308 

Micrasterias,  140;  papillifera,  140 
Micrathyria  (imago).  927 
Microcercous  cercariae,  419 
Microchlamys,  221;  patella,  221 
Microcodides,  609;  robustus,  609 
Microcodon,  609;  claviis,  609 
Microcoleus,  109;  delicatulus,  109 
Microcotylae,  cercariae,  416 
Microcotyle,  375 
Microcotylidae,  375 
Microcystis,  105 

Microdina,  619;   paradoxa,  577,  619 
Microdinidae,  619 
Microdonidae,  609 
Microgromia,  233;  socialis,  233 
Microhydra,  318,  319,  322;   ryderi,  322;   see 

Hydrozoa 
Microlaimus,  491;  fluviatilis,  491 
Microorganism,  anaerobic,  94 
Microphalhnae,  401 
Microphallus,  401;   opaciis,  370,  401 
Microspora,  164;  amaena,  164 
Microstomidae,  337 
Microstominae,  337 
Microstomum,  337;    caudatum,  338,  lineare, 

337,  philadelphicum,  361,  variable,  361 
Microthamnion,  170;   kiitzingianum,  170 
Microthorax,  283;  sulcatus,  283 
Micro-trichoptera,  901 
Mideopsis,  865;   orbicularis,  865 
Midges;  see  Chironomidae;  Insecta 
Migrations,  daily  depth,  32,  light  vs.,  31 
Mimodistomum,  392 
Miracidium,  371 

Mischococcus,  148;  confervicola,  148 
Mochlonyx  (larva),  944 

Moina,    703;     affi,nis,     70S,    brachiata,^   704, 
flagellata,    705,    macrocopa,    705,    micrura, 
704,  paradoxa,  705,  rectirostris,  705 
Moinodaphnia,  703;    alabamensis,  703,  in<ic- 

leayii,  703 
Molannidae,  936 

MoUusca,  Fresh  and  Brackish-water,  18,  957- 
1020;  classification,  970,  collection  and 
preparation  of  specimens,  960,  distribution, 
959,  jaws  and  lingual  membrane,  968,  key, 
977-1020,  measurement  and  descriptive 
terms,  969,  radula,  973,  references,  1020; 
see  Gastropoda;  Lamellibranchia 
Monadida,  243 


INDEX 


I  lOI 


Monas,  246;  fluida,  246 

Monhystera,  soo;  seniiens,  500 

Monocilia,  164 

Monogenea,  374 

Monogononta,  587 

Mononchus,  486;  major,  486 

Monopisthocotylea,  374 

Monopylephorus,  641 

Monopylidium,  446 

Monosiga,  258;   ovata,  258 

Monospilus,  738;   dispar,  738 

Monostoma,   382;     affi,ne,   382,    amitiri,   382, 

aspersum,  2,^2,  f aba,  384,  incommodum,  382, 

molle,    397,    mutabile,    382,   ornatum,    382, 

spatulatum,  382 
Monostomata,  382 
Monostome  cercariae,  412 
Monostomum,  382 
Monostroma,  161;   bullosum,  161 
Monostyla,  595;   lunaris,  595 
Monozooic  cestodes,  429 
Moss    animalcules;    see    Animalcules;    Bry- 

ozoa 
Moths,  aquatic;  see  Insecta;  Lepidoptera 
Mougeotia,  138,  143 
Musculium,  1019;  partumeium,  1019 
Mycoideaceae,  171 
Myosyringata,  522 
Myriophyllum  spicatum,  182 
Mysidacea,  829;  see  Malacostraca 
Mysidacea,  844 
Mysis  relicta,  844 
Myxonema,  168;  hibricum,  168 
Myxophyceae;  see  Algae,  Blue-Green 

Naias  flexilis,  191,  major,  193 

Naididae,  638 

Naidium,  640;  osborni,  640 

Nais,  639;   communis,  639,  elingiiis,  639 

Najadicola,  872;  ingens,  872 

Nannoplankton,    6,    7,    84;     centrifuge,    84, 

Sedgewick-Rafter  sand  filter,  83,  study,  84, 

(quantitative),  83;  ^ec  Plankton 
Nannothemis  (imago),  926,  (nymph),  932 
Nasiaeschna  (imago),  925,  (nymph),  930 
Nassula,  276;  ornata,  276 
Natural  waters,  bacteria  in,  96 
Naucoridae,  933 
Nauplius  of  Cyclops,  744 
Navicula,  128;  rhynchocephala,  128 
Naviculaceae,  127 
Nebela,  226;   collaris,    226,    dentisioma,    227, 

flabellum,  226,  lageniformis,  226 
Necator  americanus,  512,  521 
Nehallennia  (imago),  923,  (nymph),  928 
Nelumbo,  181 
Nemathelminthes    (roundworms),     15,    So<'s 

see     Acanthocephala;    Gordiacea;    Nema- 

toda 
Nematocera  (larva),  943 


Nrinattxla  (frce-livinR  and  parasitic  round- 
worms), 1- rrsh-Wulcr  i*',,  j^s;  ice  Nana- 
ti)da,  Itli-  Livins:  \emal(Kla.  Parasitic 

Nemaloda,  1-rec  LivinK.  4  5t«  So.s:  amphid*. 
466,  bursa,  47r»,  tulicula,  46.}.  development, 
464,  digestive  system,  467,  di.stribution,  46a, 
esophagus,  468,  excretory  orjcan  (ntulle), 
470,  formula,  481,  habitatn,  459,  kc>-,  482- 
505,  locomotion,  470.  methods  of  »tudy, 
478,  numlKT,  4r)0,  occurrence,  460,  refer- 
ences, 505,  rctictte,  470,  roundworms.  459, 
sexual  organs,  471,  spicula,  475,  structure, 
461,  462,  threadworms,  459;  see  NemA- 
loda 

Ncmatoda,  Parasitic,  506-510;  510-SJS; 
bursa,  514,  development,  516,  csophaini&. 
513.  key,  520-535,  life  histor>-.  517.  519, 
movement,  511,  oral  apparatus,  513,  refer- 
ences, 551-552,  reproductive  system,  516. 
structure,  511,  tail,  514.  threadworms  511; 
^ff  Acanthocephala;   Gordiacea;   Nematoda 

Nematoideum  integumenti  lumbruuli  limosi, 
521 

Nematomorpha,  510 

Nematotaenia,  450;  dispar,  450 

Nematotaeniidae,  449 

Nemertina  (Xemerteans),  Fresh- Water,  15, 
454~458;  development,  457,  habitats.  454. 
occurrence,  457,  references,  458,  struc- 
ture, 455 

Neoechinorhynchidae,  545 

Neoechinorhynchus,  545;  cylindrattu.  546. 
emydis,  546,  gradlisentis,  545,  ttntUui,  546 

Neomermis,  503 

Neoplanorbis,  986;  tantiUus,  986 

Nepa,  934 

Nephdopsis  obscura,  659 

Ncphrocytium,  152;   agardhianum,  152 

Nepidae,  934 

Nereis  limnicola,  63.' 

Neritidae,  994 

Xeritina.  994;   redivata,  994 

Nerthriidac,  933 

Net  plankton,  6 

Netrium,  138:  latnrlhsum,  138 

Nets,  61;  Birge.  68.  care  of.  66,  closahlc 
plaiUtton,  77.  dip,  67.  errors  of  plankton,  78, 
fyke,  63,  gill,  64,  cjuantitative  plankton.  74. 
runner,  70.  tow,  72,  trammel,  63,  turtle.  66 

Neumania.  871;   spinipes,  S71 

Neurocordulia  (imago),  926 

Xeuroj^tera  (dobson.  fish  and  sponirilU  flies), 
Fresh-Water,  8tj7-89y:  keys,  (adults).  934* 
935,  (lar\ae),  917.  935-9J6;  see  Ilcracn>- 
biidae;  Insocta;  Sialididac 

Xiphargus,  843 

Nitella.  173 

Xitelleae,  l^^ 

Nitzschia,  130:  linearis,  13c,  sturionis,  374 

NiLzschiaceae,  ijo 


II02 


INDEX 


Nodularia,  iii 

Nostoc,  no;  commune,  no 

Nostoceae,  no 

Nostochopsis,  113;  lobata,  113 

Notaspis,  874 

Noteus,  605;   quadricornis,  605 

Notholca,  603;  longispina,  603 

Notocotylidae,  382 

Notocotylus,  383;   quinqueserialis,  383 

Notodromas,  808;   monacha,  798,  808 

Notommata,  591;   aurita,  591,  torulosia,  591, 

truncata,  556,  591 
Notommatida,  587 
Notommatidae,  587 
Notommatina,  587 
Notonecta,  934 
Notonectidae,  934 
Notops,  601;   brachionus,  601,  davulatns,  601, 

pelagicus,  601 
Notopsidae,  569,  599 
Notosolenus,  257;  orbicularis,  257 
Notostraca,  671 
Nuclearia,  233;  simplex,  233 
Nudocotyle  novicia,  383 
Nuphar,  193 
Nupharetum,  196 
Nylandera,  171;  tentaculata,  171 
Nymphula,  903 

Obliquaria,  1014;  reflexa,  1014 

Obovaria,  1012;  ellipsis,  1013,  retusa,  1013; 
s.  s.,  1013 

Oceanology,  i ;  pelagic  region,  4 

Ochromonas,  260 

Octhebius  (adult),  938 

Octobothrium  sagiltatiim,  375 

Octocotylidae,  375 

Octotrocha,  615;  speciosa,  615 

Odonata  (damselflies,  dragonflies),  Fresh- 
Water,  889-893,  917,  922-932;  damselfly 
nymphs,  89 1 ,  keys,  917;  dragonflies  (images) , 
922-927,  (nymphs),  928-932;  see  Insecta 

Odontalona,  720 

Odontidium,  132;  mutabile,  132,  tabellaria,  132 

Odontoceridae,  936 

Odors,  cause  of,  1073,  observation  of,  1072 

Oecistes,  615;   brevis,  615 

Oedogoniaceae,  167 

Oedogonium,  167;  crenulato-costatum,  167 

Oikomonas,  244;  steinii,  244 

Oligobdella  biannulala,  654 

OHgochaeta  (earthworms),  Fresh-Water,  633- 
64s;  biology,  63s,  excretory  organs,  633, 
key,  638-644,  locomotion,  636,  methods  of 
study,  636,  occurrence,  632,  references, 
645,  reproduction,  634,  structure,  633;  see 
Chaetopoda 

Oligorchis,  441 

Olisthanella,  349;  caeca,  S49 

OHsthanellini,  349 


Oncholaimellus,  487;  heterurus,  487 

Oncholaimus,  487,  punclatus,  487 

Onchosphere,  427 

Onychodromopsis  flexilis,  289 

Onychodromus,  289;  grandis,  289 

Onychonema,  136;   laeve,  136 

Onychopoda,  738 

Oocardium,  141;  stratum,  141 

Oocystis,  151;  solilaria,  151 

Oogonium,  119 

Oospore,  119 

Open-water  collecting;  see  Methods  of  Collect- 
ing 

Opercularia,  295;   plicatilis,  295 

Ophidonais,  639;  serpentina,  639 

Ophiocytium,  157;  cochleare,  157 

Ophiogomphus  (imago),  924,  (nymph),  929 

Ophiotaenia,  438;  filaroides,  425,  438,  grandis, 
439,  lonnbergii,  438,  perspicua,  439 

Ophridinopsis,  296 

Ophrydium,  296;  eichhornii,  296 

Ophryocotyle,  441;   Proteus,  441 

Ophryoglena,  278;   atra,  278 

Ophryoxus,  708;  gracilis,  708 

Opisthodon,  276 

Opisthorchiidae,  393 

Opisthorchis,  393;  pseudofelineus,  393 

Opisthotricha,  289 

Opistomum,  340 

Organisms,  water;  effect  of  pressure,  34,  en- 
vironment, 9,  fluctuations,  54 

Orchestiidae,  843 

Oribatidae,  874 

Ornatae,  cercariae,  419 

Orthocladius  (larva),  945 

Orthorrhapha  (larva),  943 

Orthosira,  126;   orichalcea,  126 

Oscillatoria,  108;  limosa,  108,  prolifica,  108 

Oscillatoriceae,  107 

Osphranticum  labronectum,  774 

Ostracoda,  790-827;  development,  797,  dis- 
tribution, 801,  genital  organs,  795,  key, 
806-827,  methods  of  study,  803,  occur- 
rence, 799,  references,  827,  structure,  791; 
see  Crustacea 

Ovatella,  979 

Oxus,  868;   ovalis,  868,  strigatus,  868 

Oxytricha,  289;  pellionella,  289 

Oxyurella,  720,  722;    longicaudis,  721,  tenui- 

caudis,  720 
Oxyuridae,  533 
Oxyuris  dubia,  533 

Pachydiplax    (imago),    927,    (nymph),    932; 

longipennis,  890 
Palaemon,  845;  ohionis,  845 
Palaemonetes,   845;    exilipes,   845,  paludosa, 

84s,  vulgaris,  845 
Palaemonias  ganteri,  845 
Palaemonidae,  845 


INDEX 


1 103 


Palmella,  150 

Palmella  condition,  115 

Palmellaceae,  147 

Palmellococcus,  153 

Palmodactylon,  148 

Palmodictyon,  149;   viridis,  149 

Paludestrina,  989;   nickliniana,  989 

Paludicella  ehrenbergii,  952 

Paludicola,  354 

Pamphagus,  228;  hyaliniis,  228,  mutabilis,  228 

Pandorina,  145,  267;   niorum,  145,  267 

Panisus,  862,  cataphraclus,  862 

Pantala  (imago),  927,  (nymph),  932 

Paracandona,  823;   euplectella,  823 

Paracypris,  817;  grandis  (Cypris),  819,  perele- 
gans  (Cypris),  819 

Paragonimus,  390;  kellicotii,  390,  westcr- 
manli,  390 

Paragordius,  539;  varius,  539,  embryo  of,  536 

Paralonella,  734 

Paramermis,  505 

Paramoecium,  281;   caudatum,  281 

Paramphistoma  cervis,  413 

Paramphistomidae,  385 

Paramphistominae,  385 

Paranais,  639;  liloralis,  639 

Paraponyx,  903 

Paraptera,  1017;   gracilis,  1017 

Parasitic  Copepoda,  782-788;  see  Argulidae; 
Copepoda;  Ergasilidae;  Siphonostomata 

Parasitic  Flatworms,  365-453;  adaptability, 
366,  external,  367,  methods  of  study,  368, 
number,  365,  period  of  free  existence,  366; 
see  Cestoda;  Parasitic  Worms;  Trematoda 

Parasitic  Roundworms,  506-552;  differen- 
tiator, 508,  references,  551,  technic,  507; 
5ee  Acanthocephala;  Gordiacea;  Nematoda, 
Parasitic;   Parasitic  Worms 

Parasitic  Worms,  365-369,  452;  adaptations, 
365,  external,  367,  methods  of  study,  368, 
period  of  free  existence,  366,  references, 
452;  see  Acanthocephala;  Cestoda;  Gordi- 
acea; Nematoda,  Parasitic;  Parasitic  Flat- 
worms;  Parasitic  Roundworms;  Trema- 
toda 

Parmulina,  221;  cyalhus,  221 

Parnidae  (adults).  942,  (larvae),  943 

Parophryoxus,  708;   tubulatus,  708 

Pectinatella,  954;  magnifica,  948,  954 

Pectinibranchiata,  986 

Pedalion,  613;   niirum,  613 

Pedalionidae,  613 

Pedetes,  613;  sallator,  613 

Pediastrum,  160;   boryanum,  160 

Pedipes,  978;  unisidcatus,  97S 

Pedinocoris,  933 

Pegias,  1003;  fabula,  1003; 

Pegosomum,  391 

Pelagic  region,  4 

Peleciius  helicinus,  524 


Pelogonidae,  933 

Pelomyxa,  219;  caroliiunsis,     219,    paiustris, 

219 
Pelonomus  (adult),  942 
IV'lurempis  (larva),  944 
Peltodytes  (adult),  938,  (larva),  943 
I'cnium,  138;   cucurbitinum,  138 
I'entagcnia  (imago),  918,  (nymph),  921 
I'cranema,  255;   irichophonim,  255 
Peranemidac,  255 
i'eridinium,  270;   tabtilatum,  270 
I'erispira,  273;   strephosoma,  273 
I'erithcmis  (imago),  926,  (nymjih),  931 
Peritricha,  291 
Perla,  883 

Petalomonas,  256;   plcurosigma,  25t'i 
Phacus,    253;    longicaudus,    253,   plmronectes, 

253 
Phaenocora,  348;   agassizi,  348 
Phaeophyceae,    174-175;    key,    174-175;    see 

Algae,  Fresh-Water,  excl.  of  Blue-Green 
Phagocata,  359;   gracilis,  359 
Phalansterium,  25S;   digitatum,  258 
Phanerogams,  aquatic,  198 
Phascolodon,  277 
Phialonema  cyclostomum,  256 
Philhydrus  (adult),  940 

Philobdella,  657;  fioridana,  657,  gracile,  657 
Philodina,  619;   brycci,  sn,  619,  roseola,  619 
Philodinidae,  619 
Philopotamidae,  936 
Phormidium,  108;  subfuscum,  108 
Photographing,     Methods     of,     86-88;      see 

Methods  of  Photographing 
Photography,  under-water,  86;    see  Methods 

of  Photographing 
Photokinesis,  328 
Phragmitetum,  196 

Phreoryctes  {Ilaploiaxis  emissarius),  642 
Phryganea,  902 
I'hryganeidae,  936,  937 
I'hryganella,  227;  hcmisphacrica,  228,  nidtdus, 

22^ 

Phycochromophyceae;  see  .\lgae,  Blue-Gn-en 

Phycoerythrin,  117 

Phycophacin,  117 

Phylactolaemata,  952 

Phyllodistomum,  399;  dmcriidnum,  399,  fo- 
lium, 414,  421 

Phyllomitus,  248;   amylophagtis,  248 

Phyllopoda  (fairy  shrimps),  661-675;  col- 
lecting, 666,  development,  664.  key,  666- 
675,  occurrence.  661.  665.  references.  675, 
structure,  662;  see  Crustacea 

Phyllosiphon,  172:   afisari,  172 

Physa,  985;  i?,vri;ia.  985 

Physaloptera,  526;  constricta,  526,  conUirta, 
526 

Physidae.  984 

Physiography,  22 


1 104 


INDEX 


I 


Physocypria,  819;  inequivalva  (Cypria),  822, 
puslulosa  (Cypria),  821 

Physomonas,  247;   elongata,  247 

Phytia,  978 

Phytoflagellata,  259 

Phytomastigida,  249 

Phytomastigophora,  259 

Pierosoma,  983 

Pilea,  1009 

Pimephales  notatus,  1048 

Pinnularia,  127;   viridis,  127 

Piona,  873;   constricla,  873,  rn}a^  873 

Pionacercus  leuckarti,  853 

Pioninae,  870 

Pipette,  piston,  82 

Piscicola  punctata,  655 

Pisidium,  1019;   virginicum,  1019 

Piston  pipette,  82 

Pithophora,  166;   kewensis,  166 

Placobdella,  652;  hollensis,  654,  montifera, 
652,  parasitica,  653,  pedicidata,  653,  pha- 
lera,  654,  picta,  653,  rugosa,  654;   s.  str.,  653 

Placocephalus  kewense,  360 

Placocista,  231;  spinosa,  231 

Plagiola,  1013;  elegans,  1014,  securis,  1014; 
s.  s.,  1014 

Plagioporus,  394;   serotinus,  394 

Plagiopyxis,  225;   callida,  226,  labiata,  226 

Plagiorchiidae,  402 

Plagiorchiinae,  403 

Plagiorchis,  404,  proximiis,  404 

Plagiostoma  (?)  planum,  361,  364 

Planaria,  355;  agilis,  357,  doroiocephala,  357, 
foremanii,  355,  fuliginosus,  359,  gonoceph- 
ala,  356,  liguhris,  355,  maculata,  356,  wor- 
gani,  358,  simplex,  358,  simplissima,  355, 
truncata,  358,  unionicola,  358,  w/a/a,  358 

Planarians;  5ee  Turbellaria 

Planariidae,  354 

Planktology,  6 

Plankton,  4,  6,  character  of  organism,  7, 
dwarf,  6,  fish  life  and,  1082,  Umnoplank- 
ton,  6,  nannoplankton,  6,  7,  quantitative 
study,  81,  by  piston  pipette,  82,  quantity, 
47,  48,  Sedgewick-Rafter  cell,  82,  size,  7, 
specimens  shown  in  bolting  cloth,  7;  see 
Nannoplankton 

Plankton  pump,  70,  78;  cylinders,  73, 
quantitative  plankton  net,  74,  quanti- 
tative closable  plankton  net,  77 

Planktonema,  163,  164;  laulerbornii,  164 

Planorbella,  983 

Planorbidae,  982 

Planorbinae,  982 

Planorbis,  982;    antrosus,  982,  campanulalus, 

983,  crista,   984,   cultratus,   983,   glahratus, 
982,  hirsutus,  983,  opercularis,  983,  parvus, 

984,  trivolvis,  983;   s.  s.,  982 
Planorbula,  984 

Plant  societies,  succession  of,  197 


Plants,  amphibious,  183;  succession  of  so- 
cieties, 197 

Plants,  aquatic,  179,  180;  distribution,  194, 
factors  in  formation  of  marl  and  marl  lakes, 
207,  floating,  178,  groups,  197,  growing  in 
soil,  202,  203,  hibernacula  (winter  buds), 
192,  incrustation,  mineral,  185,  carbonate 
of  lime,  186,  gelatinous,  187,  leaves,  180, 
submerged,  182,  phanerogams,  198,  refer- 
ences, 209,  reproduction,  by  runners,  189, 
by  pollination  under  water,  189,  stomata  on 
submerged  leaves,  184,  submerged  leaves, 
182,  succession  of  societies,  197,  zones,  196; 
see  Vegetation,  Larger  (Higher) 

Plants,  water;   see  Plants,  aquatic 

Plathemis  (imago),  927,  (nymph),  932 

Platoum,  228;   parvum,  228 

Platycola,  297;   decumhens,  297 

Platycopa,  806 

Platydorina,  145,  268;   caiidata,  145,  268 

Platyhelminthes  (Flatworms);  see  Cestoda; 
Flatworms;  Nemertina;  Trematoda;  Tur- 
bellaria 

Platytrichotus,  288;   opislhoboliis,  288 

Plea,  934 

Plecoptera  (stoneflies),  882-885,  917."  nymphs, 
883 ;  see  Insecta 

Plectanocotyle,  375 

Plectonema,  in;  wollei,  in 

Plectus,  492;   tubifer,  492 

Pleodorina,  146,  268;  calif  or  nica,  268,  illi- 
noisensis,  146,  268 

Pleorchis,  397;  mollis,  397 

Plerocercoid,  427,  451 

Plethobasus,  1000 

Pleurobema,  999;    aesophus,  1000,  claxa,  999 

Pleurocera,   993;     canaliculatum,   993,   plena, 

993 

Pleuroceratidae,  991 

Pleurococcaceae,  152 

Pleurococcus,  152;  vulgaris,  152 

Pleurogenetinae,  400 

Pleuromonas,  249;  jaculans,  249 

Pleuronema,  281;  chrysalis,  281 

Pleurosigma,  127;  allenualum,  127 

Pleurotaeniopsis,  13S;  tiirgidus,  138 

Pleurotaenium,  138,  139;  nodulosum,  139 

Pleurotricha,  289;  lanceolata,  289 

Pleurotrocha,  589;  grandis,  589 

Pleuroxalonella,  734 

Pleuroxus,  726;  acutirostris,  736,  aduncus, 
729,  denticulaius,  728,  gracilis,  727,  hamu- 
latus,  728,  hastalus,  727,  procurvatus,  726, 
striatus,  725,  727,  trigoncllus,  729,  truncatus, 
727,  uncinatus,  726,  iinidens,  727 

Ploesoma,  603;  hudsoni,  603,  lenticulare,  603, 
truncal  urn-,  603 

Ploesomidae,  570,  ^03 

Plumatella,  952;  art'husa,  953,  polymorpha. 
953,  princeps,  953,  punctata,  954 


INDEX 


no: 


Pncumatophilus,  406;   lariabilis,  40G 
Pneumobites,    403;     breviplexus,    403,    longi- 

plexus,  403 
Pneumonoeces,  403;   coloradensis,  403 
Podocopa,  806 
Podophrya,  298;  fixa,  298 
Pollination  under  water,  189 
Pollution,  prevention  of,  1075 
Polyadenous  cercariae,  416 
Polyartemiella,  666;   hanscni,  66(->,judayi,  667 
Polyartemiidae,  666 
Polyarthra,  591;  platypicra,  591 
Polycelis,  359;   coronata,  359 
Polycentropidae,  937 
Polychaeta,  632 
Polychaetus,  599;  collinsii,  599 
Polycotyle,  410;  ornala,  410 
Polycystididae,  353 

Polycystis,  353;   gaelti,  353,  rooscvcili,  353 
Polymitarcys    (imago),    918,    (nymph),    921; 

alba,  888 
Polymorphus,  548;  minutus,  548 
Polyopisthocotylea,  375 
Polyphemidae,  738 
Polyphemus,  738;  pediculus,  738 
Polyrhytis,  981 

Polystoma,  376;  inlcgerrimum,  376 
Polystomidae,  375 

Polystomoides,  376;   coronatum,  376,  hassalli, 
376,     megacotyle,     377,     microcolyle,     377, 
opaciim,  378,  oblongum,  377,  orbicidare,  377 
Polytoma,  265;  uvella,  265 
Polyzoa;  see  Bryozoa 
Pomatiopsinae,  991 
Pomatiopsis,  991;  lapidaria,  991 
Pompholiginae,  984 
Pompholyx,  611,  984;   complanta,  611,  ejfusa, 

984 
Pompholyxophrys,  235;   punicea,  235 
Pomphorhynchus,  551 
Ponds,  2;  age  series,  49 
Pontigulasia,  225;  spcctabilis,  225 
Pontoporeia,  842;  hoyi,  842 
Pools,  3 

Porifera  (sponges),  Fresh-Water,  15,  301-315; 
collecting,   304,   development,  303,   habits, 
302,  key,  306-315,  methods  of  study,  305, 
references,  315,  structure,  301 
Porphyridium,  106 

Potamanthus  (imago),  919,  (nymph),  921 
Potamobiidae,  846 
Potamobius,  846;    aslacus,  846,  gambcli,  846, 

troivbridgci,  846 
Potamocypris,  808;  smaragdina,  808 
Potamogeton,  181;  crispus,  189,  192,  dcnsus, 
185,    heterophyllus,    183,    195,   lucens,    193, 
nutans,     182,     pcctinatus,     182,     185,     191. 
perfoliatus,  181,  191,  192,  robbinsii,  191 
Potamogetonetum,  196 
Potamopyrgus,  990;  coronalus,  990 


Pottsiella  creda,  951 

Prasiola,  161;  crispa,  161 

Prawns,  828;  see  Malacostraca 

Pressodon,  1006 

Pressure  in  water,  34;  cflecl  ujxin  organisms, 
34 

Primary  host;  sec  Host,  primar>' 

I'rismatulaimus,  499;  stenurus,  499 

I'rislina,  640;  Jlagellum,  640,  iongiseta,  var. 
leidyi,  640 

Proales,  589;  sordida,  589,  tigrida,  589, 
werncckii,  ^55,  589 

Problems,  Technical  and  Sanitary,  1067- 
1083;  algae,  methods  of  killing,  1076,  pre- 
vention of  growths  of,  1074.  purification  of 
water  containing,  1077;  bacteria,  in  water, 
1070,  bacillus  coli  as  index  of  contami- 
nation, 1069;  disease,  transmission  of,  1067, 
water  as  conveyor  of  germs,  1068;  drainage 
of  swamps,  1075;  odors,  cause  of,  1073, 
observation  of,  1072;  organisms  in  pipes 
of  water  systems,  1081;  plankton  and  fish 
life,  1082;  prevention  of  pollution,  107s: 
soil  stripping  of  reservoir  sites,  1074; 
streams  and  self-purification,  107.S;  water, 
identification  of  source  of,  1080,  tastes  and 
odors  in,  107 1 

Probopyrus,  842;  pandalicola,  842 

Proboscis,  542;  sheath,  543 

Proglottids,  424 

Progomphus  (imago),  924,  (nymph),  929 

Proptera,  1016;  alata,  1016 

Prorhynchidae,  339 

Prorhynchus,  339;   applanatits,  340,  stagnalis, 

339 
Prorodon,  274;   ovum,  274 
Prosthogoniminae,  402 
Prosthogonimus,  402 
Prostoma  marginatum,  363 
Prostomatous  cercariae,  412 
Prosostomata,  379 

Protenes,  394;  leptus,  394,  angustus,  394 
Protenteron,  401;   diaphanum,  401 
Proteocephalidae,  434 
Proteocephalus,  434;  ambloplitis,  436.  exiguus, 

437,    macrocephaJus,    435,    pcrplexus,    435, 

pinguis,  437.  Pusillus,  437.  singularis,  435 
Proteomyxa,  233 

Proterosjwngia,  25S;   hatckeli,  258 
Protoclepsis  occidcntalis,  654 
Protococcaceae,  156 
Protococcales,  1 43 
Protosiphon,  156;  botryoides,  156 
Protozoa,  14,  210-300;   see  Infusoria;    Masti- 

gophora;   Sarcodina 
Psamathiomyia  (lar\a),  945 
Psephenus  (adult),  942 
Pseudalona,  718 

PseudcKlirtlugia,  229;  gradlis,  229 
Pseudoccistcs,  617;  rotifer,  617 


iio6 


INDEX 


Pseudomermis,  505 

Pseudoon,  1013 

Pseudophyllidea,  430;  larvae  of,  450 

Pseudo-pleurococcus,  153;  vulgaris,  153 

Pseudopodia,  238 

Pseudosida,  692;  bidentata,  692 

Pseudosuccinea,  981 

Pseudulvella  americana,  171 

Psilonemateae,  107 

Psorophora  (larva),  944 

Psychodidae  (larvae),  945 

Psychomyiidae,  937 

Pterodina,  611;  casca,  611,  patina,  611 

Pterodinidae,  611 

Pterodrilus,   644;    alcicornus,    644,  distichus, 

644 
Pteronarcys  dorsata,  884 
Pterosygna,  1005 
Ptychobothriidae,  430 
Ptychobranchus,  1012;  phaseolus,  1012 
Ptychopteridae  (larvae),  944 
Pulmonata,  977 
Pump;   plankton,  70,  78,  clock,  80,  Fordyce, 

79,  thresher-tank,  80 
Purification  of  water  containing  algae,  1077 
PyraUdae,  903 
Pyramid  dredge,  71 
Pyrenoid,  116 

Pyrgulopsis,  990;  nevadensis,  990 
Pyxicola,  297;  carleri,  297 
Pyxidicula,  222;  cymbalum,  222 
Pyxidium,  293;  ramosum,  293 

Quadrula,  995;    cylindrica,  996,  lachrymosa, 

997,  plicata,  996,  pusttdosa,  997,  undata,  997; 

s.  s.,  996 
Quadrulella,  226;  symmetrica,  226 
Qualitative   methods  of   collecting,    72;    see 

Methods  of  Collecting 
Quantitative  plankton  net,  74 
Quantitative  study;    of  nannoplankton,   83; 

see  Nannoplankton;  of  net  plankton,  81; 

see  Plankton 

Radiofilum,  163;  flavescens,  163 

Radiosphaera,  156 

Radix,  981 

Radula,  973 

Ramosonema,  247;  laxum,  247 

Ranatra,  934 

Rangia,  1020;  cuneata,  1020 

Rangiidae,  1020 

Ranunculus    aquatilis,    182,    183,    191.    i93, 

201 
Raphidiophrys,  235;  elegans,  235,  viridis,  235 
Rattenkonigcercarien,  414 
RattuUdae,  568,  595 
Rattulus,   595 ;    cylindricus,  595.  lalus,   595, 

longiseta,  595 
Redia,  371 


References  on  Fresh-Water  Biology,  18-20; 
Acanthocephala,  551-552,  Algae,  Blue- 
Green  (Cyanophyceae),  114,  Algae,  excl.  of 
Blue-Green,  177,  Amphibia  (Batrachia), 
1066,  Animalcules,  620,  955-956,  Appa- 
ratus and  Methods,  88-89,  Bacteria,  99, 
Batrachia  (Amphibia),  1066,  Birds,  1066, 
Bryozoa,  955-956,  Cestoda,  452-453, 
Cladocera,  739-740,  Copepoda,  788-789, 
Crustacea,  Higher  (Malacostraca),  850, 
Cyanophyceae  (Algae,  Blue-Green),  114, 
Existence,  Conditions  of,  60,  Fishes,  1066, 
Gastrotricha,  631,  Gordiacea,  551-552, 
Hirudinea,  660,  Hydra,  322,  Hydracarina, 
875,  Hydrozoa,  322,  Infusoria,  300,  Insecta, 
946,  Malacostraca,  850,  Mammals,  1066, 
Mastigophora,  300,  MoUusca,  1020,  Nema- 
toda,  Free-Living,  505,  Nematoda,  Para- 
sitic, 551-552,  Nemertina  (Nemerteans), 
458,  OUgochaeta,  645,  Ostracoda,  827, 
Parasitic  Worms,  452,  551,  Plants,  Higher 
(Larger),  209,  Phyllopoda,  675,  Porifera, 
315,  Protozoa,  236-237,  300,  Reptiles,  1066, 
Rotatoria,  620,  Sarcodina,  236-237,  Trema- 
toda,  452-453,  Turbellaria,  364,  Vegetation, 
Larger  (Higher),  209,  Vertebrata,  1066; 
see  Investigators  in  Fresh-Water  Biology; 
Journals  on  Fresh-Water  Biology 

Renette,  470 

Renifer,  405;  ellipticus,  405,  elongatus,  407, 
mcgasorchis,  407,  variabilis,  406 

Reniferinae,  405 

Reproduction,  physiology  of,  120;  see  also 
the  specific  subjects 

Reptiles,  Fresh-Water,  1026-1028;  references 
1066;  see  Vertebrata 

Reservoir  sites,  soil  stripping  of,  1074,  Pre- 
vention of  algae  growths  in,  1074 

Rhabditis,  493;  cylindrica,  493 

Rhabdocoela,  333 

Rhabdocoelida,  333,  361 

Rhabdocoelous  cercariae,  412 

Rhabdolaimus,  494;  minor,  494 

Rhabdonema  nigrovenosum,  521 

Rhabdostyla,  293;  vernalis,  293 

Rhadinorhynchus,  550 

Rhantus  (adult),  942 

Rheology,  i;  evolution  of  stream,  5 

Rhinops,  599;  vitrea,  565,  599 

Rhipidendron,  262;  splendidum,  262 

Rhipidoglossa,  994 

Rhizoclonium,  166;  hieroglyphicum,  166 

Rhizodrilus,  641;  lacteus,  641 

Rhizomastigidae,  243 

Rhizopoda,  219 

Rhizosolenia,  127;  eriensis,  127 

Rhizosoleniaceae,  127 

Rhodophyceae,  175-177;  key,  i75-i77;  see 
Algae,  Fresh- Water,  excl.  of  Blue-Green 

Rhoicosphenia,  129;  curvata,  129 


INDEX 


1 107 


Rhopalocerca  tardigrada,  421 

Rhopalocercous  cercariae,  421 

Rhyacophilidae,  936 

Rhyncheta,  299 

Rhynchobdellae,  651 

Rhynchodemidae,  360 

Rhynchodemus  alrocyaneus,  360,  sylvaticus,  360 

Rhynchomesostoma,  349;  rostralum,  349 

Rhynchomonas,  246;  nasida,  246 

Rhynchoprobolus  papiilosus,  361,  363 

Rhynchoscolex,  337;  simplex,  337,  vcjdovski, 
S37 

Rhynchotalona,  724;  falcaia,  724 

Rhyphidae  (larvae),  945 

Rhythms  of  fresh-water  organisms,  43;  daily 
depth  migrations  vs.,  43 

Rhyzota,  574 

Richteriella,  154;  botryoides,  154,  globosa,  154 

Rivularia,  114;  minutula,  114 

Rivulariaceae,  113 

Rostellum,  424 

Rotatoria  (wheel  animalcules),  Fresh-Water, 
16,  553-620;  body,  554,  corona,  554,  557, 
the  chief  organ  of  locomotion,  562,  cosmo- 
poUtan  characteristics,  578,  development, 
582,  eggs,  580,  excretory  organs,  560,  foot, 
554,  jaws  (trophi),  558,  559.  key,  587-619, 
mastax,  558,  560,  methods  of  study,  583, 
minute  males,  580,  nervous  system,  563, 
Notommatidae  as  example,  555,  occurrence, 
554,  references,  620,  relationships,  586, 
reproduction,  564,  species  (perennial),  581, 
(summer),  581,  (winter),  581,  structure,  554, 
579,  trophi,  558,  559,  variations  of  type 
among  Anapodidae,  570,  Anuraedae,  571, 
Asplanchnidae,  571,  Bdelloida,  576,  Branch- 
ionidae,  570,  Coluridae,  568,  Dinocharidae, 
569,  Euchlanidae,  568,  Floscularida,  572, 
Flosculariidae,  572,  Gastropodidae,  570, 
Hydatinidae,  569,  Melicertida,  574,  Notom- 
matidae, 566,  Notopsidae,  569,  Ploe- 
somidae,  570,  Rattulidae,  568,  Rhizota, 
574,  Salpinidae,  567,  Seisonacea,  577,  578, 
Synchaetidae,  566 

Rotifer,  619;  citriniis,  619,  nepiunius,  619 

Rotifera;  see  Rotatoria 

Rotundaria,  999;  lubercidata,  999 

Roundworms  (Nemathelminthes),  Fresh- 
Water,  15;  free-living;  see  Nematoda, 
Free-Living;  parasitic;  ^ee  Acanthoccph- 
ala;  Gordiacea;  Nematoda,  Parasitic; 
Parasitic  Roundworms;    Parasitic  Worms 

Rugifera,  1006 

Sagiltaria  chinensis,  183,  natans,  183 
Salpina,  593;  spinigera,  593 
Salpingoeca,  258;  convallaria,  258 
Salpinidae,  567,  593 

Sanitary  Problems,  Technical  and.  1067- 
1083;  see  Problems,  Technical  and  Sanitary 


Sajjrophilus,  279;  agitans,  279 

Sarcodina  (amoeboid  protozoa),  14,  210-237; 
conjugation,  217,  food,  212,  215,  habitats, 
211,  key,  219-236,  mclal)<)lism,  216,  meth- 
ods of  study,  218,  references,  236-237, 
reproduction,  216,  shells,  214,  structure, 
211;  see  Protozoa 

Sayella,  979 

Scalenaria,  1008 

Scai)lit)leberis,  Gyy;  aurita,  699,  mturonata,  699 

Scaridium,  597;  longuandutn,  597 

Scencdesmus,  159;  quddricauda,  159 

Sciadium,  158;  arbuscuia,  158 

Siirpetum,  196 

Schistocephalus,  432 

Schislosomatidae,  409 

Schistotaenia,  448;  macrorhyncha,  448 

Schizamphistominae,  387 

Schizocanthum,  141;  armalum,  141 

Schizocerca,  605;  dkersuornis,  605 

Schizochlamys,  150;  gelatinosa,  150 

Schizomeris,  162;  Icibleinii,  163 

Schizonema,  128 

Schizomycctes;  sec  Bacteria 

Schizothrix,  109;  rubella,  109 

Schizophyceae;  see  Algae.  Blue-Green 

Schmardaella,  638;  Jilijormis,  638 

Scolex,  424 

Scotinosphaera,  157;  paradoxa,  157 

Scuds,  828;  sec  Malacostraca 

Scutopterus  (adult),  941 

Scyphidia,  292;  j'romentellii,  292 

Scytonema.  112;  mirabile,  112 

Scytonemaceac,  1 1 1 

Seasonal  succession  of  fresh-water  life  (biol- 
ogy), 10 

Seasonal  temperature  changes.  33 

Secondary  host;  see  Host,  secondary 

Sedgewick-Rafter  cell,  82,  sand  filler,  &i 

Segmentina,  984;  armigera,  984 

Seines,  61 

Seison  anmdatus.  578 

Seisonacea.  577,  578 

Selenastrum.  159;  gracile,  159 

Sepedon.  913 

Sericostomatidae,  936,  937 

Serphus.  933 

Setiferous  cercariae.  423 

Shore  zone,  3 

Shrimps,  828;  sec  Malacostraca 

Shrimps.  fair>-;    see  Crustacea;   Phyllopoda 

Sialididae  (siMmgilla  flics).  S97-S9S;  adults. 
935;  sec  Insecta;  Neuroptera 

Sialis  (adult).  935.  (larva).  935;   injunuita,  898 

Sida,  689;  cryslallina,  689 

Sididae,  689 

Simocephalus.  698;  exspinoitu,  698.  serru- 
lalus,  699.  irluJus,  698 

Simuliidae  (black-flics).  9x3;  lar\'ac,  946;  sef 
Diptera;  Insecta 


iio8 


INDEX 


Siphlurus  (imago),  920,  (nymph),  922 

Siphonales,  172 

Siphonaria,  979;  alternata,  979,  peltoides,  980; 

_  s.  s.,  979 
Siphonariidae,  979 
Siphonostomata   (Parasitic  Copepoda),   782- 

788;   structure,  783;   see  Argulidae;    Cope- 
poda; Ergasilidae 
Sisyra  (adult),  934,  (larva),  899,  935 
Slavina,  639;  appendiculata,  639 
Solenophrya,  299;  per  a,  299 
Somatochlora  (imago),  926,  (nymph),  931 
Somatogyrus,  991;  subglobosus,  991 
Sorastrum,  159;  spinulosum,  159 
Sow-bugs,  828;  see  Malacostraca 
Sparganophilus,    643;     benhami,    643,    eiseni, 

643,  smithi,  643 
Sparganum,    434;     mansoni,    433,    434,    pro- 

liferum,  434,  sebago,  434 
Spathidium,  273;  spathula,  273 
Sperchon,  870;  glandulosus,  870 
Sperchoninae,  869 

Sphaerella,  144;  nivalis,  144,  pluvialis,  144 
Sphaeriidae,  1018 
Sphaerium,  1018;  simile,  1018 
Sphaerocystis,  151;  schraeteri,  151 
Sphaerophrya,  299;  magna,  299 
Sphaeroplea,  165;  annulina,  165 
Sphaeropleaceae,  165 
Sphaerostoma,  408 
Sphaerozosma,  136;    pulchriim  var.  inflatum, 

136,  verlebralum,  136 
Sphenoderia,    229;    dentata,    229,  lenia,    230, 

macrolepis,  230 
Sphenomonas,  254;  quadrangular  is,  254 
Sphyranura,  378;  osleri,  378 
Spicula,  475 

Spilophora,  489;  canadensis,  489 
Spinitectus,  527;  gracilis,  527 
Spirocypris,  813;    passaica,  813,  tuberculala, 

814 
Spirogyra,  142;  crassa,  142 
Spiromonas,  249;  angusta,  249 
Spironoura,  533;   affine,  533,  gracile,  533 
Spirostomum,  284;   ambiguum,  184 
Spirotaenia,  137;  minuta,  137 
Spirulina,  107;  major,  107 
Spiruridae,  525 
Spirurinae,  525 
Spiruroidea,  525 
Spondylomorum,    144,    267;     quarternarium, 

144,  267 
Spondylosium,  136;  papillatum,  136 
Sponges;  see  Porifera 
Spongilla,  306,  311;  aspinosa,  306,  baileyi,  311, 

Jragilis,    307,    igloviformis,    307,    lacustris, 

306,    novae-terrae,    307,    paupercula,    306, 

wagneri,  308 
Spongilla-flies,    897;   ^ec   Hemerobiidae;    In- 

secta;  Neuroptera 


Spongomonas,  262;  discus,  262 

Sporadoporus,  862;  invalvaris,  862 

Spores  of  bacteria,  92;  ^ee  Bacteria 

Sporocyst,  371 

Sporozoa,  14 

Stagnicola,  981 

Stations,  fresh- water  biology,  12 

Statoblast,  949 

Staurastrum,  139;  crenulatum,  139 

Staurogenia,  160 

Stauroneis,  128;  anceps,  128 

Stauroptera,  127 

Stenelmis  (adult),  942 

Stenostomum,  334;  agile,  336,  coluber,  337, 
grande,  336,  leucops,  335,  speciosum,  335, 
ienuicauda,  336 

Stentor,  285;  coeruleus,  285,  polymorphus,  285 

Stephanoceros,  611;  eichhornii,  611 

Stephanodiscus,  127;  niagareoe,  127 

Stephanoprora,  391;  gilberti,  391 

Stephanops,  597;  intermedins,  597 

Stephanosphaera,  145,  266;  pluvialis,  145, 
266 

Stichococcus,  152;  bacillaris,  152 

Stichorchis,  386,  subtriquetrus,  386 

Stichostemma  asensoriatum,  457,  rubrum,  455, 
458 

Stichotricha,  287;  secunda,  287 

Stigonema,  112;  minutum,  112,  ocellatum,  112 

Stigonemaceae,  112 

Stomata  on  submerged  leaves,  184 

Stoneflies;  ^ee  Insecta;  Plecoptera 

Stratification  of  aquatic  organisms,  10 

Stratiomyiidae  (larvae),  946 

Streams;  bottom  materials,  24,  bottoms, 
differentiation  in,  25,  current  strength,  23, 
evolution,  5,  hydrogen  sulphide,  39,  rate 
of  flow,  27,  self-purification,  1078,  tem- 
perature of  water,  32 

Streblocerus,  709;  pygmaeus,  709,  serricau- 
datus,  709 

Strephobasis,  993 

Streptocephalidae,  670 

Streptocephalus,  670;  floridanus,  670,  sealii, 
670,  texanus,  670 

Strigea,  410;  cornu,  410 

Strobila,  424 

Strombidium,  286;  claparedii,  286 

Strongyleae,  522 

Strongylidae,  522 

Strongylinae,  522 

Strongyloidea,  522 

Strongyloides  stercoralis,  521 

Strongylostoma,  350;  gonocephalum,  350, 
radiatum,  350 

Strongylus,  522;  auricularis,  523 

Strophitus,  looi;  edentulus,  looi 

Stygonectes,  843 

Stylaria,  639;  fossularis,  639,  lacustris,  635, 
639 


INDEX 


IIOQ 


Stylet  cercariae,  416 

Stylobryon,  245;  petiolatum,  245 

Stylohedra,  297 

Stylonychia,  290;  nolophora,  290 

Styphlodora,  405;  bascaniensis,  405 

Submerged  leaves,  182;  stomata  on,  184 

Suctoria,  298 

Surirella,  131 

Surirellaceae,  130 

Sutroa,  642;  alpestris,  642,  roslrala,  642 

Sympetrum  (imago),  927,  (nymph),  932 

Swamp,  3,  5,  59;  drainage  of,  1075 

Symphynota,   1004;    complanata,   1005,  com- 

pressa,  1004,  coslata,  1005;   s.  s.,  1004 
Symploca,  109;  liicifuga,  109 
Synchaeta,    591;     bdtica,    591,   stylata,    591, 

tremula,  591 
Synchaetidae,  591;  see  Rotatoria 
Synechococcus,  105;  aeruginosus,  105 
Synedra,  132;  salina,  132 
Synplecta  pendula,  528 
Synura,  262;  uvella,  262 

Tabanidae  (larvae),  946 

Tabanus  (larva),  946 

Tabellaria,  133;  fenestrata,  133 

Tabellariaceae,  133 

Tachopteryx  (nymph),  929,  930 

Tachysoma,  290;  parvistyla,  290 

Taenia,  440,  447;  crassicollis,  44'j,filum,  442, 
pulchella,  450,  scolopendra,  449 

Taeniidae,  447 

Taenioglossa,  986 

Tanaognathus,  864;  spinipes,  864 

Tanaorhamphus,  547;  lotigirostris,  547 

Tank-pump,  80 

Tanypus  carneus,  914,  (larva),  945 

Tany tarsus  (larva),  945 

Tapeworms,  15;  see  Cestoda;  Parasitic  Flat- 
worms;   Parasitic  Worms 

Taphrocampa,  589;  annulosa,  589 

Tardigrada,  17 

Tatria,  449;  biremis,  449 

Technical  and  Sanitary  Problems,  1067-1083; 
see  Problems,  Technical  and  Sanitary 

Telmatodrilus,  641;  mcgregori,  641,  vejdovskyi, 
641 

Telorchinae,  393 

Telorchis,  394;  medius,  394 

Temperature  of  water,  32;  and  metabolism, 
33,  in  streams,  32,  reaction  of  animals,  34, 
seasonal  changes,  33 

Tentaculata,  17;  see  Bryozoa 

Teratocephalus,  496;  cornutus,  496 

Terricola,  359 

Terriginous  bottom,  26,  45 

Testacea,  220 

Tetmemorus,  138;  granulalus,  138 

Tetrabothriidae,  440 

Tetrabothrius,  440;  macrocephalus,  440 


retracoccus,  149 

Tctrucotylc,  411;  typica,  411 

Tetracotyle  form,  424 

Tclracyclus,  133;  lacustrii,  135 

Tetradesmus,  160;  wiscomiensis,  160 

Tctruedron,  155;  enormt,  155 

Tetniguneuria  (imago),  926,  (nymph),  931 

Tetramastix,  613;  opolimsis,  613 

Tetramitus,  251;  lariabilis,  251 

Tctra[X'dia,  105 

Tctraphyllidc-a,  434 

Tctraselmis,  2G4;  limtiftis,  264 

Tctraspora,  147;  cxplanala,  147 

Tetrasporaccac,  146 

Tclrastnnma  aquarium  dulcium,  457;  see 
Nemcrtina 

Tctrastrum,  160 

Thalassomyia,  94s 

Thallasironus,  486 

Thamnoccphalus,  670;  platyurus,  670 

Thelaziidae,  527 

Thermal  springs,  life  of,  101 

ThermocHne,  28 

Theliderma,  997 

Thermonectes  (adult),  941 

Thorea,  175;  ramosissima,  175 

Threadworms;  sec  Xt-maloda,  Parasitic 

Thresher  tank-pump,  80 

Throscinus  (adult),  942 

Thuricola,  296;  valvata,  296 

Thuricolopsis,  296 

Thyas,  861;  venusta,  861 

Tintinnidium,  286;  fluviatUis,  2S6 

Tintinnus,  286 

Tiphys,  873;  liliaceus,  873 

Tipulidae  (larvae),  944     « 

Tolypclla,  173;  nidifua,  173 

Tolypothrix,  112;  lanata,  112 

Torquis,  984 

Torrenticola,  864;  anomala,  864 

Tow  net,  72 

Trachclius,  275;  ovum,  275 

TrdchelobdeUa  I'ii-ida,  655 

Trachelmonas,  252:  hispUia,  252,  hgrmUa, 
252,  voh'ocina,  232 

Trachclophyllum,  273:  tachyblaslum,  273 

Tralia,  978;   mysotis,  979,  pusilla,  978 

Tramca  (imago).  927.  (nymph).  93a 

Trammel  net,  62 

Transmission,  disease,  1067 

Traps.  65 

Trcmatoda  (flukes),  Fresh-Watcr.  15.  36s. 
369-424,  452-453:  ccrcaria.  37«.  .^72.  as 
plankton  organism,  372,  dcprct-  of  infection, 
373,  development.  37 >.  intormi-diatc  host, 
371,  key,  374-424.  miracidium.  37'.  primary 
host,  372,  rcdia,  37 >.  references.  45^-453. 
sporocyst,  371,  structure.  369.  370;  see  Para- 
sitic piatworms;   Parasitic  Worms 

Trentipohlia,  170;  viaitwi,  170 


mo 


INDEX 


Trentonia,  265;  flagellata,  265 
Trepomonas,  249;  agilis,  249 
Triaenophorinae,  433 
Triaenophorus,  433 
Triangle  dredge,  71 

Triarthra,  613;    brachiaia,  613,  longiseta,  613 
Tribonema,  164;  minor,  164 
Trichinella  spiralis,  534 
Trichinellidae,  534 
Trichocephaloides,  444 
Trichoda,  279;  pura,  279 
Trichodina,  291;  pediculus,  291 
Trichogaster,  286 
Trichomastix,  250 
Trichophoreae,  113 
Trichophrya,  299;  sinuosa,  299 
Trichoptera  (caddisflies) ,  Fresh- Water,  900- 
903,  917.  936-937;  cases,  900,  key,  936-937. 
pupa,  902;  see  Insecta 
Tricorythus  (nymph),  922 
Trichosotna  contortum,  513 
Trichostomina,  277 
Trichostrongylidae,  522 
Trichostrongylinae,  522 
Trichostrongylus,  522;  fiberius,  522 
Trichosyringata,  534 
Trichurinae,  534 
Trichuris,  534;  opaca,  534 
Tricladida,  333,  354,  361 

Trilobus,  501;  longus,  501 

Trinema,  231;  camplanatum,  231,  enchelys, 
232,  lineare,  232 

Triophthaknus,  589;  dorsualis,  589 

Triphylus,  599;  lacustris,  599 

Triploceras,  139;  gracile,  139 

Tripyla,  498;  lata,  498 

Tristomidae,  374 

Tritigonia,  998;  tuberculata,  99S 

Trochehninthes,  16 

Trochiscia,  154;  vestilus,  154 

Trochosphaera,  613;  solstitialis,  613 

Trochosphaeridae,  613 

Trochospongilla,  308;  horrida,  308,  leidyi,  308 

Troglotrematidae,  390 

Tropidiscus,  983 

Tropidoscyphus,  254,  257 

Tropistemus  (adult),  940 

Truncilla,  1008;  foliata,  1009,  personata,  1009, 
sulcata,  1008,  triquetra,  1008;   s.  s.,  1008 

Tryonia,  989;  clathrata,  989 

Trypanorhyncha,  434,  450 

Tubefla,  313;  pennsylvanica,  313 

Tubifex,  642;  miiltisetosus,  641,  642,  tubifex, 
641,  642 

Tubificidae,  640 

Tulotoma,  988;  magnifica,  988 

Tuomeya,  176;  fluviatalis,  176 

Turbellaria  (free-living  flatworms),  Fresh- 
Water,  15,  323-364;  cultures,  331,  digestive 
apparatus,  325,  habitat,  329,  key,  333-364. 


land  planarians,  330,  methods  of  study, 
331,  movement,  325,  photokinesis,  328, 
references,  364,  reproduction,  326,  respon- 
siveness to  stimuh,  328 

Turbidity  of  fresh  water,  29,  36 

Turtle  nets,  66 

Two-winged  flies;  see  Diptera;  Insecta 

Tylenchus,  483;  devastatrix,  483,  dipsaci,  483 

Types  of  fresh-water  hfe,  13 

Typhlocypris,  823;  delawarensis,  824,  peircei, 
823 

Typhloplana,  350;  viridata,  350 

Typhloplanid  from  Canandaigua  Lake,  361, 
362;  from  Irondequoit,  361,  362 

Typhloplanidae,  348,  361 

Typhloplanini,  349 

Tyrrellia,  869;  circularis,  869 

Ulothrix,  162;  zonata,  162 

Ulothrichaceae,  161 

Ulvaceae,  160 

Ulvella,  171;  americana,  171 

Under- water  photography,  86;    see  Methods 

of  Photographing 
Uniformity  of  fresh-water  life  (biology),  13 
Unio,  1000;   crassidens,  1000,  spinosus,  looi, 

tetralasmus,  looi,  uniomerus,  looi 
Unionicola  (non-parasitic  species),  871 
Unionicola  (parasitic  species),  872;  crassipes, 

872 
Unionidae,  995 
Unioninae,  995 
Univalve,  957;  see  Mollusca 
Uranotaenia  (larva),  944 
Urceolaria,  292 

Urceolopsis,  256;  sabulosa,  256 
Urceolus,  256;  cycloslomum,  256 
Urnatella  gracilis,  951 
Umula,  299 

Urocentnmi,  277;  turbo,  277 
Uroglena,  261;  americana,  261 
Uroleptus,  288;  musculus,  288 
Uronema,  279;  marinum,  279 
Urosoma,  290 

Urostyla,  287;   grandis,  287,  trichogaster,  287 
Urotricha,  273;  farcta,  273 
Utricularia,  188;  infiata,  188,  minor,  188 

Vacuoles,  103 

Vaginarieae,  109 

•Vaginicola,  296;  kptosoma,  296 

VaUisneria,  181,  190;  spiralis,  181,  185,  189, 

190 
Valvata,  988;  tricarinata,  988 
Valvatidae,  988 
Vampyrella,  234;  lateritia,  234 
Vanheurckia,  128;  rhomboides,  128 
Variety  of  fresh-water  life  (biology),  11 
Vaucheria,  172;  re  pens,  172 
Vegetation,  amount,  50 


INDEX 


IIII 


Vegetation,    Larger    (Higher),    Fresh-Water, 

178-209;    cycle  of  matter,   207,  evolution, 

198,  references,  209,  zones,  196;   see  Plants, 

aquatic 
Veliidae,  933 
Venation,  wing,  916;    of  stonctlics,  916;    see 

Insecta 
Vertebrata,    1021-1066;     adaptations,    1022, 

references,  1066;  see  Amphibia  (Batrachia); 

Birds;  Fishes;  Mammals;  Reptiles 
Viviparidae,  987 
Viviparus,  9S7;  interlcxtus,  987 
Volvocaceae,  143 
Volvox,  146,  269;    aureus,  2G9,  globalor,  269, 

perglobator,  269,  spennatosphara,  269 
Vortex,  340 

Vortex  (?)  cavicolens,  361,  363 
Vorticella,  293;  campanula,  293 

Wardius,  386;  zibet hicus,  386 

Water;  acid  or  alkaline  characteristics  of,  40, 
ammonia  in,  39,  bacteria  found  in  natural, 
96,  number  in,  96,  1070,  biological  con- 
ditions in,  46,  carbon  dioxide  in,  39, 
chemical  factors,  36,  circulation,  27,  irf 
lakes,  27,  conveyor  of  disease,  1068,  current 
strength  in  streams,  23,  daily  depth  migra- 
tions, 32,  43,  density,  22,  distribution  of 
gases,  37,  of  life,  35,  expansion  in  freezing, 

21,  gases  dissolved  in,  36,  general  solvent, 

22,  identification  of  source  of,  1080,  index 
of  suitability,  46,  influence  of  currents  in, 
28,  odors  in,  107 1,  1072,  oxygen  content, 
37,  penetration  of  light,  29,  30,  physical 
conditions  of,  22,  physical  environment  of 
organisms  in,  9,  pressure  in,  34,  quantity 
of  life  in,  46,  of  plankton  in,  47,  48,  reser- 
voirs, purification  of,  1074,  1076,  1077, 
rhythms  of  organisms,  43,  seasonal  changes, 
33,  solubility  of  gases  in,  37,  tastes  in,  107  1, 
temperature,  32,  in  streams,  32,  terriginous 
bottom,  45,  thermal  properties,  21,  tur- 
bidity, 29,  36 

Water  Biology,  Fresh-;    sec  Biology,   Fresh- 
Water 
"Water-bloom,"  100 
Water  bodies,  physical  features  of,  8 
Water  bottle,  80 


Water  glass,  87 

Water  Life,  Fresh-;  see  Biology,  Fresh-Water 
Water  organisms,  physical  environment  of,  9 
Water    plants    and    vegetation;     srr    IMants, 

acjuatic;    \'egetation,  a(|uatic 
Water  supplier,  tastes  antl  <Klors  in,  1071 
Water  systems,  organisms  in  piix-s  of,  loHi 
Waters,  flowing,  2 
Waves  and  their  action,  28 
Wheel  animalcules;  see  Rotatoria 
Whirligig  beetles,  906;  see  Coleoplcra;  Insecta 
Wilsonema,  495 
Wing  venation.  916 
Winter  buds  (hibernacula),  192 
Wlassicsia,  711;  kinistinemis,  711 
Wollea,  no;  saccala,  no 
Worms,  earth;   see  Chactopoda;   Oligochacta 
Worms,  free-living;    see  Nemaloda;    Nemer- 

tina  (Nemerteans);  Turbcllaria 
Worms,  parasitic;   see  Acanthcnephala;    Ce»- 

toda;     Gordiacea;     Nematoda,    Parasitic; 

Parasitic  Worms;  Trematoda 
Wyeomyia  (larva),  944 

Xanthidium,  141;  J'asciculaium,  141 
Xiphidiocercariae,  416 
Xystonotus,  865:  as  per,  865 

Zannichellia,  189;    repens,  185,  palustris,  190 

Zeugorchis,  407;  aequatus,  407 

Zoethamnium,  294;  adatnsi,  294 

Zone,  shore,  3 

Zones  of  vegetation,  196;  characctum,  196, 
nupharetum,  196,  phragmitelum.  196, 
potamogetonetum,  196,  scirjx'tum.  196 

Zoochlorella,  153 

Zooccium,  948 

Zoophytes,  301 

Zoosporangium,  119 

Zoospores,  1 18 

Zostcra  nana,  1S5 

Zygnema,  142 

Zygncmaceae,  141 

Zygnemeae,  142 

Zygocotyle,  388;  ceratosa,  388 

Zygocotylinae.  38S 

Zygoptera  (imago),  922,  (nymph),  928 

Zygospore,  119 


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